Commercial poultry nutritio
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Dr. Waqas Nawaz

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PMAS Arid agriculture university rawalpindi, Pakistan

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Commercial poultry nutritio Commercial poultry nutritio Document Transcript

  • COMMERCIAL POULTRY NUTRITIONTHIRD EDITIONbySTEVEN LEESON, Ph.D.Professor of Animal NutritionandJOHN D. SUMMERS, Ph.D.Professor EmeritusDepartment of Animal and Poultry ScienceUniversity of GuelphGuelph, Ontario, CanadaPUBLISHED BYUNIVERSITY BOOKSP. O. Box 1326Guelph, Ontario, CanadaN1H 6N8Nottingham University PressManor Farm, Church Lane,Thrumpton, Nottingham,NG11 0AX, England
  • Commercial Poultry Nutrition, Third EditionUniversity BooksP.O. Box 1326Guelph, Ontario©2005 University BooksAll rights reserved. No part of this publication may be reproducd, stored in a retrieval system,or transmitted in any form by electronic, mechanical, photocopying or photographing orotherwise, without the prior written permission of the publisher.Canadian cataloguing in publication data1. Poultry - Feeding and Nutrition 2. Birds 3. NutritionI Leeson, Steven, 1948, II Summers, John D. 1929.ISBN 0-9695600-5-2Digitally reprinted in 2008 from:All rights reserved. No part of this publicationmay be reproduced in any material form(including photocopying or storing in anymedium by electronic means and whether or nottransiently or incidentally to some other use ofthis publication) without the written permissionof the copyright holder except in accordance withthe provisions of the Copyright, Designs andPatents Act 1988. Applications for the copyrightholder’s written permission to reproduce any partof this publication should be addressed to the publishers.British Library Cataloguing in Publication DataCommercial Poultry Nutrition, Third EditionI. Leeson, S., Summers, J.D.ISBN 978-1-904761-78-5DisclaimerEvery reasonable effort has been made to ensure that the material in this book is true, correct, complete and appropriate at thetime of writing. Nevertheless, the publishers and authors do not accept responsibility for any omission or error, or for any injury,damage, loss or financial consequences arising from the use of the book.
  • PREFACEThe first edition of this book was published in 1991, while the second edition followed in1997. It has been an interesting exercise to follow the development of poultry production overthis time, and to encapsulate ideas of associated changes in nutrition and feeding management.For example, in 1991, the emphasis in broiler nutrition was on maximizing growth rate,together with the new approach of considering breast meat yield. In 1997, the concept ofcompensatory growth was emphasized, as a necessary management tool to control metabolicdisorders. In the intervening eight years, poultry geneticists have obviously reduced theincidence of these disorders, and so we are once again considering rapid growth throughoutthe entire grow-out period. It is such evolving circumstances within the industry that dictatethe need for periodic reappraisal of our feeding programs.We have changed the layout of the book to accommodate a two-column presentation ofmaterial. In response to reader requests, we have also included commercial data on the nutrientrequirements of layers, broilers and turkeys. This data is taken from Management Guidesavailable in early 2004. We realize that such information changes as bird genetics change.The reader should always source the latest information available on a specific breed, from thebreeding company, and use this information, rather than that presented in this book as themost accurate assessment of nutrients for a specific strain.Many of the ideas in this book are based on work carried out in the Department of Animaland Poultry Science at the University of Guelph. In this regard, we are indebted to the manysponsors of our research program, and in particular, the on-going support of the OntarioMinistry of Agriculture and Food, Guelph, Ontario.Once again, we are indebted to the corporate sponsors of this book. Their names appear inthe front covers, while their company logos are displayed on the back cover. Their generoussupport allows us to subsidize the cost of this book, and in so doing, hopefully allows us toreach a wider audience.Special thanks to Laurie Parr for her conscientious effort in typing the original version of thebook, and to Ford Papple of Papple Graphics for his assistance and ideas with the layout anddesign. Thanks to Linda Caston for again proof reading numerous versions of the book, andher attention to detail is much appreciated. Also thanks to Greg Hargreave, Baiada Poultryfor agreeing to proof read the final version. Greg’s constant reminder of the importance ofbrown-egg layers is much appreciated.Steven Leeson and John SummersGuelph, 2005PREFACEThe first edition of this book was published in 1991, while the second edition followed in1997. It has been an interesting exercise to follow the development of poultry production overthis time, and to encapsulate ideas of associated changes in nutrition and feeding management.For example, in 1991, the emphasis in broiler nutrition was on maximizing growth rate,together with the new approach of considering breast meat yield. In 1997, the concept ofcompensatory growth was emphasized, as a necessary management tool to control metabolicdisorders. In the intervening eight years, poultry geneticists have obviously reduced theincidence of these disorders, and so we are once again considering rapid growth throughoutthe entire grow-out period. It is such evolving circumstances within the industry that dictatethe need for periodic reappraisal of our feeding programs.We have changed the layout of the book to accommodate a two-column presentation ofmaterial. In response to reader requests, we have also included commercial data on the nutrientrequirements of layers, broilers and turkeys. This data is taken from Management Guidesavailable in early 2004. We realize that such information changes as bird genetics change.The reader should always source the latest information available on a specific breed, from thebreeding company, and use this information, rather than that presented in this book as themost accurate assessment of nutrients for a specific strain.Many of the ideas in this book are based on work carried out in the Department of Animaland Poultry Science at the University of Guelph. In this regard, we are indebted to the manysponsors of our research program, and in particular, the on-going support of the OntarioMinistry of Agriculture and Food, Guelph, Ontario.Once again, we are indebted to the corporate sponsors of this book. Their names appear inthe front covers, while their company logos are displayed on the back cover. Their generoussupport allows us to subsidize the cost of this book, and in so doing, hopefully allows us toreach a wider audience.Special thanks to Laurie Parr for her conscientious effort in typing the original version of thebook, and to Ford Papple of Papple Graphics for his assistance and ideas with the layout anddesign. Thanks to Linda Caston for again proof reading numerous versions of the book, andher attention to detail is much appreciated. Also thanks to Greg Hargreave, Baiada Poultryfor agreeing to proof read the final version. Greg’s constant reminder of the importance ofbrown-egg layers is much appreciated.Steven Leeson and John SummersGuelph, 2005
  • SPONSORSWe are indebted to the following companies for their financial support which allowed us to subsidizethe cost of this publication.ADM Animal Health Nutrition4666 Faries Pkwy.DecaturIL 62526U.S.A.Alltech Inc.3031 Catnip Hill PikeNicholasville, KY40356 U.S.A.Danisco Animal Nutrition411 E. GanoSt. LouisMO 63147U.S.A.DSM Nutrition Products Inc.45 Waterview BlvdPursippanyNJ 07054-1298U.S.A.Hyline InternationalP.O. Box 65190West Des Moines, IA 50265U.S.A.Novus International Inc.530 Maryville Centre Dr.St. Louis, MO63141 U.S.A.Provimi Holding B.V.Veerlaan 17-23NL-3072 AN RotterdamTHE NETHERLANDSVetech Laboratories Inc.131 Malcolm RoadGuelph, OntarioN1K 1A8 CANADAThe publishers of the original version of this book are indebted to the following companies for theirfinancial support which allowed them to subsidize the cost of the original publication.
  • TABLE OF CONTENTSCHAPTER 1 GLOBAL POULTRY PRODUCTIONCHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATIONCHAPTER 3 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSCHAPTER 4 FEEDING PROGRAMS FOR LAYING HENSCHAPTER 5 FEEDING PROGRAMS FOR BROILER CHICKENSCHAPTER 6 FEEDING PROGRAMS FOR BROILER BREEDERSCHAPTER 7 FEEDING PROGRAMS FOR TURKEYSCHAPTER 8 FEEDING PROGRAMS FOR DUCKS AND GEESECHAPTER 9 FEEDING PROGRAMS FOR GAME BIRDS, RATITESAND PET BIRDSAPPENDIX - INGREDIENT COMPOSITION DATAINDEX
  • 1SECTION 1.1World Animal ProductionGLOBAL POULTRYPRODUCTION 11.1 World animal production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Poultry meat production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.3 Egg production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.4 Future considerations for poultry production . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.5 Global feed production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Production of most farm animal specieshas increased over the last 10 years,and predictions are for this trend tocontinue in the near future. Poultry hasseen the greatest increase in productionand again, this trend will likely continue. Bothpoultry meat and eggs are well positioned tomeet demands for increased supply fromour growing world population. Predictionof world populations is always subject toadjustment, but it seems as though we willhave around 7 billion people to feed by2008. However, an obvious trend occurringis that this population is quickly aging andalso living in urban settings of ever increasingsize. Today almost 2% of the world’s pop-ulation live in the 10 largest cities in the world,and by 2008, we will likely have 20 cities withpopulations in excess of 10 million people.These large urban populations obviouslyrely almost 100% on food supply from ruralareas. Traditionally such rural food supplyhas been grown adjacent to the urban pop-ulations, but this situation is becomingincreasingly more difficult as these urbanpopulations reach 10-15 million. Nationaland international movement of feed andfood will become critical to feeding these largeexpanding populations. The population inthe developed world is predicted to changelittle in the next 10 years, and so virtually allgrowth will be in developing countries, andespecially in Africa and Asia. With its unpre-dictable weather patterns, Africa has alwayshad difficulty feeding its growing population,and with increased urbanization, this situa-tion will only deteriorate.In all countries, there is an aging of thepopulation, and it is predicted that theproportion of people 60 years of age, willdouble in the next 30 years. The purchasingpower of many such individuals may not beadequate to sustain their usual diet supply.Up to now, and in the near future, we havebeen able to meet increased demands for foodthrough a combination of increased supplycoupled with improved production effi-ciency. Such improvements in efficiency ofproduction will allow us to gradually upgradethe general nutritional status of the worldpopulation as a whole and it is evident thatPageCHAPTER1.1 World Animal Production
  • 2 CHAPTER 1GLOBAL POULTRY PRODUCTIONSECTION 1.1World Animal Productionthe poultry industry is playing a major role in thisimportant development. In the past, we have hadto face criticism of the energy used in animalproduction and especially from the point of viewof the inefficiency of consuming animal vs. veg-etable protein. Of the total energy used by mostdeveloped countries, less than 4% is used for foodproduction. During this food production, by farthe greatest quantities of energy are used duringprocessing and household preparation to meet thestringent demands of the consumer. Consequently,of the 4% of energy used by the agrifood business,only 18% (or 0.7% of total energy needs) is actu-ally used in primary animal production. Increasedhuman consumption of vegetable proteins as analternative to meat and eggs has failed to mate-rialize, essentially due to excessive energy use nec-essary during manufacture, which is the same crit-icism originally aimed at animal production.The production of synthetic meat analogues is thusvery energy intensive, and their limited impact overthe last decade attests to problems witheconomic viability and/or consumer acceptance.With the economy of many third world countriesimproving, there appears to be increased demandfor animal products and especially poultry meatand eggs.In developed countries, the current concernsregarding meat and eggs are not lack of supply,but rather wholesomeness and food safety. Theconcern about genetic modification of plants andanimals quickly evolved in Europe, such thatcurrently their use is not allowed in foodproduction. Many plant species such as corn andsoybean meal are now routinely geneticallymodified and used as ingredients in diets forpoultry and other animals in many countries.Concern about using animal proteins in dietsfor farm animals also arose in Europe followingthe outbreak of BSE in the mid 1990’s. Europeansare still uncertain about the health status of theirruminant animals, and the ban on using productssuch as meat meal continues. While it ispossible to formulate diets without meat meals,it is more expensive, and does add a majorfinancial burden on most animal industries sincethey have to find alternative means of disposal ofwaste by-products.It is impossible to produce meat or eggsthat are guaranteed to be free of pathogens. Anon-tolerance scenario for organisms such assalmonella is untenable, and any such regulationsare unrealistic. Certainly there will be increasedemphasis on pathogen reduction, and both thepoultry meat and egg industries have madesignificant progress with programs such asHACCP at processing plants, feed mills andpoultry farms. Feed is one potential route of entryfor pathogens into meat and eggs, and so for-mulation will have to be modified, or alternateadditives used, to try to reduce pathogen loadof feed to acceptable levels of tolerance. Feedprocessing is now viewed with an aim topathogen control, in addition to concerns aboutfeed intake and bird growth. There will undoubt-edly be reduced emphasis on antibiotic growthpromoters as are now commonly used in broilerand turkey production and this situation adds evenmore demand on feed pathogen control programs.On a more positive note, the production ofso-called designer foods continues to increase;with the best example being omega-3 enrichedeggs. It is simple to modify the fat-solublenutrient profile of meat and eggs, and so therewill be an increased demand, within nichemarkets, for food products modified in relationto improved human nutrition.
  • 3CHAPTER 1GLOBAL POULTRY PRODUCTIONSECTION 1.2Poultry meat productionThe broiler chicken industry has shownunparalleled growth over the last 30years, although there are now signs of amaturing market in many countries. Theindustry is relatively easy to establish and whilethere are regional differences, production systemsin most countries are modeled in a similarmanner. Because of the increased growth poten-tial in modern strains of broiler, it is now realizedthat some degree of environmental control isessential. Such systems can be full environ-mental control through to curtain sided housesin tropical countries. Even with the latter, cheapertype housing, it seems essential to ensure adequateair movement and so tunnel ventilation hasbecome popular over the last 10 years. Optimumgrowth rate cannot be achieved much beyond therange of 15-30ºC and so the ventilation systemsare designed to hopefully maintain the birds’environment within this temperature range.Chicken is usually the least expensive meatin most countries and consequently it is first orsecond for per capita consumption. This com-petitive situation has occurred due to continuedimprovements in efficiency of production that oftennecessitate acceptance of new ideas and inno-vations by poultry producers and agribusiness.On the other hand, production systems for com-peting meat products have shown little changeover the last two decades. Interestingly, theswine industry is now starting to use ‘poultry’models in production systems.Much of the success of the chicken meatindustry relates to development of new consumerproducts, largely because of continued advancesin further processing. The most successful singleproduct is undoubtedly the ‘chicken nugget’, nowfeatured by most fast food and retail outlets. Overthe last 10 years, some 30,000 non-chickenfast-food outlets in North America have addedchicken products to their menu, and duringspecial advertising campaigns, chicken productscan be the leading sales item over suchconventional products as hamburgers. So-called ‘fast-food’ stores are increasing in numberin Europe, in Asia and in South America, andthis will likely lead to increased demand forchicken. In addition to developing new uses forconventional parts of the chicken and turkeycarcass, the industry has also been successful indeveloping technology to use its own ‘by-products’ and then finding markets for these(or vice versa). The demand for chicken wingsand chicken feet together with mechanicallydeboned meat exemplify these types of products.In addition to increasing overall poultry meatconsumption, these products also lead toimproved overall efficiency of production andhelp maintain the economic advantage seenwith poultry meat.Poultry meat is also ideally suited in terms ofmeeting demands for leaner meat by healthconscious consumers. There has been consid-erable publicity over the last few years con-cerning the relative fat content of various meats,yet the fact remains that when comparisons areconducted on comparable products, poultrymeat is the leanest product. Comparison of ahighly trimmed steak or pork chop vs. a wholebroiler carcass certainly reduces the advantageusually seen with poultry. However, the validcomparison is trimmed steak vs. poultry breastfillet, in which case the poultry product is by farthe leanest. Broiler chicken and especiallyturkey are therefore ideal products for segmentsof the food industry wishing to provide low-fatmeals. Poultry meat also has the almost uniqueadvantage of not being discriminated against dueto religious or cultural beliefs, making poultry prod-ucts popular with airlines, hotels, institutions, etc.1.2 Poultry Meat Production
  • 4 CHAPTER 1GLOBAL POULTRY PRODUCTIONSECTION 1.3Egg productionThe poultry meat industry has come underrecent scrutiny regarding the use of growthpromoters in the feed. When these are removedfrom diets, broilers most frequently developnecrotic enteritis and coccidiosis, and so theirmain mode of action seems to be control overclostridial infection. When growth promoters arenot used in the feed, then alternate strategies suchas competitive exclusion, water acidification, man-Table 1.1 Poultry meat production(million tonnes)1993 2005World 48 80North America 15 25S. America 6 12Europe 10 13Asia 14 22Table 1.2 Broiler meat production(million tonnes)1993 2005World 41 68North America 13 21S. America 5.5 11.5Europe 9 10.5Asia 12 20Table 1.3 Turkey meat production(million tonnes)1993 2005World 4 5.5North America 2 3S. America 0.1 0.3Europe 1.5 1.8Asia 0.1 0.2Table 1.4 Egg production(million tonnes)1993 2005World 38 57North America 6 8S. America 2.5 3.4Europe 10 10Asia 18 321.3 Egg ProductionThe egg industry is enjoying increasedproduction as consumers become moreeducated about the nutritive value ofeggs and as more eggs are processed. The mis-information from the 1980’s regarding therelationship between cholesterol intake andblood cholesterol levels has been superceded bypertinent information detailing the relevantcontribution of various dietary nutrients to serumnan-oligossaccharides and pro- and prebioticsare often considered. Ironically, while growthpromoters are often banned as feed additives, analternative strategy is to use them as watermedication. Table 1.1 shows total poultry meatproduction worldwide, and in major producingareas, whileTables 1.2 and 1.3 show the break-down for broiler and turkey meat production.cholesterol in humans. Eggs are relatively inex-pensive per unit of protein and energycontained in yolk and albumen, and so eggconsumption continues to increase in developingcountries.The egg industry produces either brown- orwhite-shelled eggs. While white eggs predom-inate in North America, consumers in many
  • 5CHAPTER 1GLOBAL POULTRY PRODUCTIONSECTION 1.4Future considerations for poultry production5countries demand a brown egg. Unfortunately,such demand is based on the naive view thatbrown-shelled eggs are more nutritious or whole-some. In developing countries, this myth iscompounded with the demand for a highlypigmented yolk, and both of those factors addto the cost of production. North America has alsoseen great success in production of designer eggs,since some 5% of shell eggs are now enrichedwith nutrients such as omega-3 fatty acids andvitamin E. This profitable segment of the eggindustry has not merely displaced demand fornormal eggs, but rather has created a genuineincreased demand for eggs and egg products.In North America, the most dynamic segmentof the egg industry relates to processing andfurther processing of eggs, paralleling thesuccess seen in the poultry meat industry. By 2008,it is estimated that at least 50% of eggs in NorthAmerica will be processed in some way orexpressed in an alternate way, only 50% ofeggs will be marketed in the shell. Expansion ofegg processing is raising new challenges to pro-duction, where for instance egg mass is much moreimportant than egg size per se, and where shellquality is of lesser importance. It is likely thatthe white-egg strains will be developed for theprocessing industry, while brown-shelled strainswill be selected for characteristics importantfor the shell egg market. Disposal of the end-of-lay bird is becoming more difficult in manyregions and so it seems important to develop newfood products from this potentially valuableresource. Converting spent fowl into animal feedingredients and especially for layer feed seemsa very shortsighted approach in terms of consumerperception. Table 1.4 shows global and region-al egg production.1.4 Future Considerations for Poultry NutritionOver the last 20 years, developments inpoultry nutrition have paralleled, ormade possible, increased productivityof the various poultry industries. As productionconditions and goals have changed, we have beenable to revise our estimates of nutrient require-ments. Greater variation in production goals hasimposed some degree of complication tofeeding programs, because ‘global’ recom-mendations are now often not applicable. Thefuture emphasis in poultry nutrition must bethe development of life-cycle feeding programsfor various classes of birds, rather than consid-eration of individual diets in isolation.Unfortunately, there is still a dearth of researchinformation that views recommendationswithin the context of an overall program. Withthe sophistication we have today in our productionsystems, birds seldom fully recover frominappropriate nutrient intake at any time intheir production cycle.Because feed still represents 60 – 70% of thecost of production of most poultry products,there is a continual need to evaluate new ordifferent sources of ingredients and to continu-ally re-examine the more common ingredients.A yearly review of the published research dataindicates that ingredient evaluation occupies themajor portion of practical poultry nutritionresearch, and feed manufacturers should beaware of the potential of such new ingredients.Often, so-called new ingredients are not new inthe sense of being novel to poultry feeding perse, rather they have not been as seriously con-sidered in a particular geographical location. A
  • 6 CHAPTER 1GLOBAL POULTRY PRODUCTIONSECTION 1.4Future considerations for poultry productionTable 1.5 Bird numbers (millions)1993 2006BROILERSWorld 30,700 46,000North America 8,500 13,000South America 3,700 7,500Europe 6,600 6,600Asia 9,700 18,000TURKEYSWorld 580 700North America 300 320South America 20 40Europe 230 280Asia 25 30LAYERSWorld 3,800 5,500North America 480 600South America 300 350Europe 770 750Asia 1,850 3,500good example is the consideration of wheat asan ingredient in many areas of North America,whereas wheat has been a standard in othercountries for 20-30 years. Under such conditions,feed manufacturers are encouraged to take a moreglobal perspective on ingredient evaluation,because, for example, if wheat can be usedsuccessfully in Europe with strain A of broiler, inall likelihood it will be appropriate in anothercountry assuming comparable conditions.Nutritionists must now have first-hand knowledgeof production techniques to ensure that allconditions are comparable, as failure to do sois undoubtedly the reason for problems thatperiodically occur with such ‘new’ ingredients.In this context, justification of ingredient max/minconstraints used during formulation is becomingmore critical. As previously mentioned, thegoals in many production situations varycommensurate with consumer demand for endproducts and/or manipulation of bird manage-ment. As such, nutritionists are now faced withan array of alternate programs dependent uponsuch specific, and often specialized, needs.The best example of this trend is nutritional mod-ification aimed at manipulating meat or eggcomposition. Changing the proportion ofenergy:protein or amino acids or limiting feed intakeduring specific grow-out periods is known toinfluence fat deposition in the carcass. Likewise,choice of ingredients may well influence egg com-position in relation to needs to improve humanhealth. It is likely that nutritionists will be facedwith increasing pressure from their customers,in terms of diets and programs aimed at meet-ing such market niches. In these situations,knowledge of ingredient profile and compatibilitywithin a diet and feeding program become evenmore critical. A more holistic approach in the devel-opment of feeding programs will allow the poul-try industry to pursue its goals of increased pro-duction, improved efficiency and increasedspecialization. It is hoped that thematerial provided in the following chapters willgive the reader a background in developingsuch programs. Table 1.5 shows the expected num-ber of birds that we will likely have to feed by 2006.
  • 7CHAPTER 1GLOBAL POULTRY PRODUCTIONSECTION 1.5Global feed production7The poultry industry accounts for 20–40%of animal feed use in most countries,and this proportion is invariably increas-ing over time. Table 1.6 shows estimates offeed production for broilers, turkeys, layers andassociated breeders.As a generalization, the numbers shown inTable1.6 can be multiplied by 0.6 for an estimate ofcereal needs and by 0.3 for needs of ingredientssuch as soybean meal. The feed industry willundoubtedly become more regulated and becomepart of any tracking initiatives introduced foreggs or meat. Regulation concerning the use andreconciliation for most drugs is now mandatoryin many countries, through such programs asHACCP. Undoubtedly the cost of such extraregulation and control will be passed on to thepoultry industry and eventually to the consumer.1.5 Global Feed ProductionTable 1.6 2006 Feed production (million tonnes)Broiler Turkey TotalBroiler Turkey Pullet LayerBreeder Breeder PoultryWorld 184 15 28 2.8 30 192 452North America 52 4.2 7.9 0.8 8.4 54 127South America 30 2.4 4.6 0.5 4.9 31 73Europe 26 2.1 4.0 0.4 4.3 28 65Asia 72 5.9 11.0 1.0 11.7 75 177
  • 89INGREDIENTEVALUATION ANDDIET FORMULATION22.1 Description of Ingredients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111. Corn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112. Wheat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153. Milo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194. Barley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215. Rice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236. Wheat by-products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257. Bakery meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288. Rice by-products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299. Soybean meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3110. Soybeans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3511. Canola meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3712. Corn gluten meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4013. Cottonseed meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4214. Flaxseed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4415. Meat meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4716. Poultry by-product meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5017. Feather meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5218. Fish meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5419. Fats and oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57OTHER INGREDIENTS20. Oats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6521. Rye . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6522. Triticale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6623. Molasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6624. Dehydrated alfalfa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6725. Full-fat canola seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6726. Groundnut (peanut) meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6727. Peas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6828. Safflower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6829. Sesame meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6830. Lupins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6831. Blood meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6832. Sources of calcium, phosphorus and sodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6933. Trace minerals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7134. Synthetic amino acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74PageCHAPTER
  • 10 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION2.2 Ingredient testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77a. Bulk density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77b. Proximate analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78c. Amino acid analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79d. Metabolizable energy (AME or TME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80e. Near infra-red analysis (NIRA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80f. Urease testing of soybeans and soybean meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82g. Protein solubility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82h. Protein and amino acid dye-binding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83i. Fish meal gizzard erosion factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83j. Sorghum tannins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84k. Gossypol in eggs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84l. Fat assays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84m. Hulls in rice by-products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85n. Mineral solubility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 852.3 Feed additives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86a. Pellet binders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86b. Anticoccidials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86c. Antibiotics, growth promoters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88d. Antifungal agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90e. Probiotics and prebiotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91f. Yeast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92g. Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92h. Pigments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96i. Flavoring agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96j. Worming compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97k. Odor control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 972.4 Feed toxins and contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98a. Mycotoxins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98b. Plant toxins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99c. Autointoxication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106d. Bacterial toxins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106e. Chemotherapeutic drugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107f. Toxic seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
  • 11CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients11CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION2.5 Feed manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110a. Vitamin-mineral premixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110b. Vitamin stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112c. Pelleting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112d. Expanding, extrusion and thermal cooking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1132.6 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115a. Water intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115b. Water output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117c. Water balance and dehydration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117d. Drinking water temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118e. Water restriction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118f. Water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119g. General management considerations with water . . . . . . . . . . . . . . . . . . . . . . . . . . . 121Corn has become the standard againstwhich other cereals, cereal by-prod-ucts and other energy-yielding ingre-dients are compared. In most poultry diets,corn will be the major contributor of metab-olizable energy. World production is around600 m tonnes of which 240 m tonnes are pro-duced by the U.S.A. Although China is theworld’s second largest producer at around 100m tonnes, Brazil at 40 m tonnes, is the sec-ond largest world exporter. The feed indus-try usually uses the equivalent of U.S.A.grade #2. As grade number increases, bulkdensity declines and there are greater per-missible levels of damaged kernels and for-eign matter allowed in the sample. Corn grade#2 should contain no more than 5% damagedkernels and 3% foreign material. Whiledamaged kernels are unlikely to affect its ener-gy value, foreign material is likely to reduceits energy value and hence monetary value.Broken kernels are also potential sites for moldinfestation.The energy value of corn is contributedby the starchy endosperm, which is composedmainly of amylopectin, and the germ, whichcontains most of the oil. Most corn samplescontain 3 – 4% oil, although newer varietiesare now available which contain up to 6 –8% oil, and so contribute proportionallymore energy. These high-oil corn varietiesalso contain 2 – 3% more protein, and pro-portionally more essential amino acids. Theprotein in corn is mainly as prolamin (zein)and as such, its amino acid profile is not idealfor poultry. This balance of amino acids, andtheir availability, must be seriously consid-ered when low protein diets are formulated,because under these conditions the cornprolamin can contribute up to 50 – 60% ofthe diet protein. Corn is also quite high in2.1 Description of Ingredients1. CornOther Names: MaizeNutritional Characteristics:
  • SECTION 2.1Description of ingredients12 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONthe yellow/orange pigments, usually containingaround 5 ppm xanthophylls and 0.5 ppmcarotenes. These pigments ensure that corn-fedbirds will have a high degree of pigments in theirbody fat and in egg yolks.While #2 grade is the standard for animal feeds,lower grades are often available due to adversegrowing, harvesting or storage conditions.Dependent upon the reason for lower grade, thefeeding value of corn usually declines withincrease in grade number. Table 2.1 shows themetabolizable energy value of corn necessarilyharvested at various stages of maturity due toadverse late-season growing conditions.Corn Moisture at 100 kernel wt at AMEn (kcal/kg) atdescription harvest (%) 10% moisture (g) 85% dry matterVery immature 53 17 3014Immature 45 22 3102Immature 39 24 3155Mature 31 26 3313The energy value of corn declines by 10 – 15kcal/kg for each 1 lb reduction in bushel weightbelow the standard of 56 lb/bushel. However, theselower bushel weight samples show no consistentpattern with protein or levels of most aminoacids, although there is an indication of loss ofmethionine content with the immature samples.Another potential problem with handlingimmature, high-moisture corn is that the dryingconditions must necessarily be harsher, or moreprolonged in order to reduce moisture level to anacceptable 15%. Excessive or prolonged heatingcauses caramelization of corn which then has acharacteristic smell and appearance, and there isconcern that lysine will be less available becauseof Maillard Reaction with available carbohydrates.As detailed in subsequent ingredients thereis processing of corn that yields products suchas gluten meal and corn oil. However, in NorthAmerica well over 95% of corn is used foranimal feeds.There is some debate regarding the ideal sizeof ground corn particles for various classes ofpoultry. Within reason, the finer the grind, thebetter the pellet quality, while in mash diets, toofine a grind can lead to partial feed refusal.Table 2.2 indicates guidelines for expecteddistribution of particle sizes of corn ground to be‘fine’ vs. ‘coarse’. There seems to be somebenefits in terms of AMEn of using a finer grindfor birds up to 3 weeks of age, while a coarsegrind is better for birds >21 d of age.Depending upon the growing season andstorage conditions, molds and associated myco-toxins can be a problem. Aflatoxin contaminationis common with insect damaged corn grown inhot humid areas, and there is little that can bedone to rectify the horrendous consequences ofhigh levels of this mycotoxin. There is an indicationof aluminosilicates partially alleviating theeffects of more moderate levels of aflatoxin. Ifaflatoxin is even suspected as being a prob-lem, corn samples should be screened prior toTable 2.1 Corn maturity and energy value
  • 13CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients13blending and mixing. Zearalenone is anothermycotoxin that periodically occurs in corn.Because the toxin ties up vitamin D3, skeletal andeggshell problems can occur. With moderatelevels of contamination, water-soluble D3 via thedrinking water has proven beneficial.Mold growth can be a serious problem in cornthat is transported for any length of time.Damaged kernels and foreign material aregoing to reduce the economic value of corn.However, Dale and co-workers at Georgia suggestthe energy value of these contaminants is littledifferent from whole corn. Broken kernels werejust 200 kcal/kg lower than the AMEn of corn,while foreign material tested 600 kcal/kg lowerthan corn. Therefore having #4 grade corn with10% damaged kernels and 5% foreign materi-al vs 5% and 3% respectively for #2 grade,relates to a reduction of just 25 kcal/kg for this#4 vs #2 grade corn.If corn is to be fed in mash diets, then thereseems to be an advantage to grind to as uniforma particle size as possible, (0.7 – 0.9 mm). Thissize is often referred to as ‘medium’ grind. Birdsfed fine or coarse-ground corn seem to exhibitlower digestibility values. Corn presents someproblems to the manufacture of pelleted diets,and often good pellet durability in diets containing30% corn can only be obtained by inclusionof pellet-binders.With corn shipped at 16% moisture and sub-jected to 25ºC during shipping, mold growthoften occurs. One solution to the problem is toadd organic acids to the corn during loading forshipments. However, it must be remembered thatwhile organic acids will kill molds, andprevent re-infestation, they have no effect on anymycotoxins already produced.Particle size Grind(microns) Fine Coarse<150 5 <1300 11 2450 16 3600 17 3850 22 41000 16 41500 10 52000 1 102500 <1 24>3000 <1 44Table 2.2 Particle size distribution of corn (%)
  • SECTION 2.1Description of ingredients14 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONDry Matter 85.0 Methionine 0.20Crude Protein 8.5 Methionine + Cystine 0.31Metabolizable Energy: Lysine 0.20(kcal/kg) 3330 Tryptophan 0.10(MJ/kg) 13.80 Threonine 0.41Calcium 0.01 Arginine 0.39Av. Phosphorus 0.13Sodium 0.05 Dig Methionine 0.18Chloride 0.05 Dig Meth + Cys 0.27Potassium 0.38 Dig Lysine 0.16Selenium (ppm) 0.04 Dig Tryptophan 0.07Fat 3.8 Dig Threonine 0.33Linoleic acid 1.9 Dig Arginine 0.35Crude Fiber 2.5Nutrient Profile: (%)Bulk Density:Formulation Constraints:kg/m3 lb/ft3 lb/bushelWhole kernels #2 696 42.2 54#4 632 38.3 49Ground corn 642 40.0 51Corn screenings 475 30.1 39Bird age Min. Max. Comments0-4 wk - 60% Usually no problems with upper limits. From 0-7d, birdsmay not digest as well as adult birds.4-18 wk - 70%Adult layer - 70% Higher levels cause more problems with pellet durability.Moisture CP Fat Ca/P AA’s OtherAll deliveries Wkly 6 mos 12 mos 12 mos Molds – mycotoxins, AME,12 mos11 Assay to be conducted within 30 d of yearly harvest.QA Schedule:
  • 15CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients2. WheatNutritional Characteristics:Wheat is commonly used in many coun-tries as the major energy source in poultry diets.There is often confusion regarding the exacttype of wheat being used, because wheats aredescribed in a number of different ways.Traditionally wheats were described as being win-ter or spring varieties and these were usually grownin different regions because of prevailing cli-mate and soil conditions. Wheats are sometimesalso referred to as white or red, depending uponseed coat color, and finally there is the classifi-cation of hard vs soft. In the past, most winterwheats were white and soft, while spring wheatswere hard and red. In terms of feeding value, themain criterion is whether wheat is soft or hard,because this will have an effect on composition,and especially on protein. Because of developmentsin plant breeding, the seed color and time of plant-ing can now be more variable. Hard wheats havea greater proportion of protein associated with thestarch and so contain more protein that is also high-er in lysine. The proteins in hard wheat areuseful in bread making, while the soft wheats aremore useful in manufacture of cookies andcakes. Durum wheat used in manufacture of pastais a very hard wheat. The physical hardness ofthese wheats is due to the strong binding betweenstarch and the more abundant protein.Varietal differences based on ‘hard’ vs ‘soft’varieties seem to have inconsistent effects on AMEand amino acid digestibility. A more consistentvarietal effect is seen when genes from rye aretranslocated into wheat ostensibly to improvebaking characteristics. These translocated wheatvarieties (often termed 1B → 1R) have 10%lower amino acid digestibility and in the case oflysine, the differences may be as much as 18%in favor of the non-translocated varieties.As with corn, the grading system for wheatrelates to bulk density and the proportion ofbroken grains and foreign material. For #2grade there is a maximum allowable inclusionof 5% foreign material and broken kernels.Feed grade wheat can have over 20% broken ker-nels and foreign material.The composition of wheat is usually morevariable than that of other cereals. Even withinthe hard wheats, protein level can vary from 10to 18%, and this may relate to varietal differencesand variance in growing conditions. Most hardwheats will not have to be dried after harvest,although drying conditions and moisturecontent of wheat at harvest appear to havelittle effect on feeding value. Environmentaltemperature during growing seems to have a majoreffect on wheat nitrogen content, and althoughhigh temperature can result in 100% increase innitrogen level, the relative proportion of both lysineand starch tend to be decreased.Depending upon the growing region, frostdamaged or sprouted wheat is sometimes avail-able to the feed industry. Frost damage effectivelystops starch synthesis, and so kernels are small andshrunken. While 100 kernel weight should bearound 27 g, with severe frost damage, this canbe reduced to 14 – 16 g. As expected, themetabolizable energy level of this damagedwheat is reduced and under these conditions, thereis a very good correlation between bulk densityand metabolizable energy. For non-frosted wheat,however, there does not seem to be the same rela-tionship between energy level and density.Wheat will sometimes sprout in the field.Sprouted wheat would probably be rejected
  • SECTION 2.1Description of ingredients16 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION16simply based on appearance, although researchdata suggests that metabolizable energy level isonly reduced by 3 - 5%. There are no problemsin feeding sprouted wheat, as long as it has beendried to 14% moisture, and can beeconomical if discounted accordingly. Wheat con-taminated with ‘rust’ however seems to moreseriously affect feeding value, and metabolizableenergy value can be reduced by up to 25%.While wheats are much higher in proteincontent compared to corn, and provide onlyslightly less energy, there are some potentialproblems from feeding much more than 30% ina diet, especially for young birds. Wheatcontains about 5 – 8% of pentosans, whichcan cause problems with digesta viscosity,leading to reduced overall diet digestibility andalso wet manure. The major pentosancomponents are arabinoxylans, which are linkedto other cell wall constituents, and these are ableto adsorb up to 10 times their weight in water.Unfortunately, birds do not produce adequatequantities of xylanase enzymes, and so thesepolymers increase the viscosity of the digesta. The10 - 15% reduction in ME of wheats seen withmost young birds (<10 d age) likely relates to theirinability to handle these pentosans. Variabilityin pentosan content of wheats per se likelyaccounts for most of the variability of results seenin wheat feeding studies, together with ourinability to predict feeding value based onsimple proximate analyses. These adverse effectson digesta viscosity seem to decrease withincreased storage time for wheats. Problems withdigesta viscosity can be controlled to someextent by limiting the quantity of wheat used,especially for young birds, and/or by usingexogenous xylanase enzymes (see Section 2.3 g).Wheats also contain -amylase inhibitors.Although these inhibitors have not been fullyidentified, they are thought to be albuminproteins found predominantly in the endosperm.These inhibitors can apparently be destroyed bythe relatively mild temperatures employedduring pelleting. Compared to corn, wheat is alsovery low in levels of available biotin. Whereasit is sometimes difficult to induce signs of biotindeficiency in birds fed corn diets devoid ofsynthetic biotin, problems soon develop if wheatis the major cereal. While newly hatched chickshave liver biotin levels of around 3,000 ng/g, thisnumber declines to 600 ng/g within 14 d in thewheat fed bird. Adding just 50 µg biotin/kg dietalmost doubles the liver biotin reserve, while adding300 µg/kg brings levels back to that seen in theday-old chick. There is also concern that wheatcauses a higher incidence of necrotic enteritisin broiler chicks. It seems as though wheatprovides a more suitable medium for the pro-liferation of certain pathogenic bacteria. Theproblem is most severe when wheat is finelyground, and incidence of necrotic enteritis canbe tempered by grinding wheat through a rollermill rather than a hammer mill. Fine grindingof wheat can also cause beak impaction inyoung birds. The proteins in wheat tend to be‘sticky’, and so adhere to the beak and mouthlining of the bird. Severe beak impaction tendsto reduce feeding activity, increase feeddeposited in open bell drinkers, and provides amedium in the mouth region that is ideal forbacterial and fungal growth. These problems canbe resolved by coarse grinding of wheat.Using wheat in diets for meat birds doeshowever improve pellet durability. The sameproteins that enhance the baking characteristicsof hard wheats, also help to bind ingredientsduring pelleting. Adding 25% wheat to adiet has the same effect as including a pellet binderin diets that are difficult to pellet.
  • 17CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients17INGREDIENT EVALUATION AND DIET FORMULATIONOne advantage of wheat, is that it can be fed aswhole grain to birds after 10 – 14 d of age.Offering whole wheat and a balancer feed withadequate minerals and vitamins provides a veryeconomical way for farmers to utilize home-grownwheat. In recent studies we offered broilers aconventional three diet program, or after 7 d ofage, a choice between whole wheat andcrumbled broiler starter through to 49 d. From7 – 21 d, male broilers voluntarily consumed about15% of their ration as wheat, while from 21 – 35d and 35 – 49 d this increased to 34% and41% respectively. Table 2.3 shows performancedata of these birds. Body weight was onlyslightly depressed, although carcass weight wassignificantly reduced and breast yield wasreduced by about 10%. The free-choice wheatsystem did however show a saving of 10% in feedcost per kg liveweight gain although feed costper kg of breast meat was not different. Anotheradvantage claimed for feeding whole wheat tobroilers is greater control over coccidiosis.Whole wheat feeding stimulates gizzard andgastric motility and the enhanced activitywithin this acidic environment is thought toreduce oocyte viability.Potential Problems:Wheats contain variable quantities of xylan,which is poorly digested and results in wetviscous excreta together with poor digestibility.As detailed in section 2.3g, this problem can beovercome by using synthetic xylanase enzymes.Feeding much more than 30% wheat can leadto beak/mouth impaction that can reduce feed-ing activity. Such material building-up in the mouthcan be a site for mold and mycotoxin develop-ment. This problem can be resolved by grindingwheat more coarsely. With wheat as the majorcereal, there is need for greater levels of sup-plemental biotin, since biotin availability inwheat has been reported to be as low as 0 – 15%.Diet Body Wt Feed:Gain Protein Energy Carcass Wt49d (g) Intake Intake (g)(g/kg Bwt) (kcal/kg Bwt)Control 3030 1.93 370 6044 2230bFree-choice wheat 2920 1.99 364 6106 2135aTable 2.3 Broiler performance with free-choice wheatAdapted from Leeson and Caston, 1993
  • SECTION 2.1Description of ingredients18 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONDry Matter 87.0 Methionine 0.20Crude Protein 12 - 15 Methionine + Cystine 0.41Metabolizable Energy: Lysine 0.49(kcal/kg) 3150 Tryptophan 0.21(MJ/kg) 13.18 Threonine 0.42Calcium 0.05 Arginine 0.72Av. Phosphorus 0.20Sodium 0.09 Dig Methionine 0.16Chloride 0.08 Dig Meth + Cys 0.33Potassium 0.52 Dig Lysine 0.40Selenium (ppm) 0.50 Dig Tryptophan 0.17Fat 1.5 Dig Threonine 0.32Linoleic acid 0.50 Dig Arginine 0.56Crude Fiber 2.70Nutrient Profile: (%)kg/m3 lb/ft3lb/bushelWhole kernels #2 738 46 57Feed grade 645 41 50Ground wheat 530 33 42Bulk Density:Bird age Min. Max. Comments0-4 wk 15% 20 (40)1% Minimum constraint used if improved pelletquality desired.4-18 wk 15% 25 (50)%Adult layer 15% 25 (60)% Maximum value in parenthesis if a syntheticxylanase used.Formulation Constraints:1Higher inclusion level with enzymes.Moisture CP Fat Ca/P AA’s OtherAll deliveries Wkly 6 mos 12 mos 12 mos Xylan, AME each 12 mos1QA Schedule:1 Assay to be conducted within 30 d of yearly harvest.
  • 19CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients3. MiloOther Names: sorghum, kaffir cornNutritional Characteristics:In many characteristics, milo is almost com-parable to corn in feeding value. There seem tobe more varietal differences with sorghum,although on average, its energy value will be slight-ly less than that of corn. For those not wantingany marked degree of pigmentation of eggs orskin, milo offers the best high energy alternativeto corn.The feeding value of milo is essentially 95 – 96%that of corn, although in many markets it ispriced at less than this. The starch in milo isintimately associated with the protein, and thisleads to slightly reduced digestibility, especiallyin the absence of any heat processing. Themajor concern with milo, is the content oftannins, which are a group of polyphenolshaving the property of combining with variousproteins. Birds fed tannins therefore exhibitreduced growth rate and in some instancesincreased incidence and severity of skeletaldisorders. Hydrolyzable tannins are charac-terized by having a gallic acid unit combined byester linkages to a central glucose moiety.Condensed tannins on the other hand are basedon flavan-3-ols (catechin). Because tannins inmilo are essentially condensed tannins, studiesinvolving tannic acid (hydrolyzable) as a sourceof tannin may be of questionable value. The tan-nins are located in the outer seed coat and theunderlying testa layer. Generally, the darker theseed coat, the higher the tannin content, althoughthe tannins in the testa layer may be more indica-tive of general tannin content in the milo.So-called bird resistant milos are usuallyvery high in tannin, and are characterized by adarker seed coat color. These higher levels oftannin can result in up to 10% reduction ofdry matter and amino acid digestibility. Thereis a good correlation between tannin content andAMEn, and as a generalization the followingformula can be used:AMEn = 3900 – 500 (% tannin), kcal/kg.Tannins are most detrimental when fed toyoung birds, and especially when proteincontent of the diet is marginal. For example, it isusually recommended that milo with more than1% tannin not be used for turkeys under 8 weeksof age. The relationship between tannins and dietprotein or amino acids is not clear. Certainly feed-ing more protein or higher levels of certain aminoacids seems to temper any growth retardation. Thefact that methionine supplementation can over-come detrimental effects of tannins on growth rate,without alleviating problems with digestibility, sug-gests that birds can compensate for inferiordigestibility by increasing their feed intake.Tannins also seem to increase the incidence of legproblems, especially in broiler chickens. The exactmechanism is unknown, although because bonemineral content is little affected, it is assumed torelate to derangement in the development of theorganic matrix, especially in the region of the growthplate. There seems no advantage to increasing sup-plemental levels of any minerals or vitaminswhen high-tannin milos are necessarily used.
  • SECTION 2.1Description of ingredients20 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONVarious mechanisms have been tried toreduce the level or effect of tannins in milo.Unfortunately, most of these processes involvewet chemical treatment, which although quitesimple, are expensive when re-drying of themilo is considered. Water treatment (25% withpropionic acid for 10 d) has been shown toimprove protein and energy availability by up to10%. Alkali treatment seems the most effectivemeans of reducing tannin levels, and productssuch as potassium and sodium hydroxide haveboth been used. Adding non-ionic polymers, suchas polyethylene glycol also seems to be beneficial,while the problem of impaired bone developmentcan be partially corrected by adding up to 0.8%available phosphorus to the diet of young birds.Potential Problems:The major potential problem is tannin con-tent and so this antinutrient should be assayedroutinely. As described in section 2.2 j, seed coatcolor of milo can be used to give an indicationof tannin content.Dry Matter 85.0 Methionine 0.12Crude Protein 9.0 Methionine + Cystine 0.29Metabolizable Energy: Lysine 0.31(kcal/kg) 3250 Tryptophan 0.09(MJ/kg) 13.60 Threonine 0.32Calcium 0.05 Arginine 0.40Av. Phosphorus 0.14Sodium 0.05 Dig Methionine 0.09Chloride 0.07 Dig Meth + Cys 0.24Potassium 0.32 Dig Lysine 0.23Selenium (ppm) 0.04 Dig Tryptophan 0.06Fat 2.50 Dig Threonine 0.24Linoleic acid 1.00 Dig Arginine 0.28Crude Fiber 2.70Nutrient Profile: (%)kg/m3 lb/ft3 lb/bushelWhole seed 560 35.0 44.8Ground seed 545 34.0 43.5Bulk Density:
  • 21CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients4. BarleyNutritional Characteristics:Barley is a cereal with medium content of bothenergy and protein, and while it can be used inpoultry feeds, most is used in swine diets. Youngbirds are less able to digest barley, althoughthis may be a consequence of ß-glucan content,and so this effect may relate to variety andgrowing conditions. The protein content ofbarley is usually around 11 – 12%, although muchhigher levels to 14 – 16% are sometimes encoun-tered. These high-protein varieties are oftenlittle changed in content of essential aminoacids. The lysine content of barley, within therange of 10 – 14% CP, is described by the equa-tion 0.13 +0.024 x %CP. The metabolizable ener-gy level of barley is correlated with bulk densi-ty, and there is a strong negative correlationwith fiber.Barley contains moderate levels of trypsininhibitor, whose mode of action relates to seques-tering of arginine, although by far the majorproblem with barley is content of ß-glucan.Most varieties of barley will contain 4 – 7% ß-glucan, although with dry growingconditions that involve rapid maturation and earlyharvest, the content can increase to 12 – 15%.As previously described for wheat, the mainproblem of these ß-glucans is the bird’s inabilityto digest the structure, resulting in the formationof a more viscous digesta. This increased viscosityslows the rate of mixing with digestive enzymesand also adversely affects the transport of digest-ed nutrients to the absorptive mucosal surface.The rate of diffusion to the intestinal microvilliis a function of the thickness of the unstirred bound-ary layer, and this increases with increaseddigesta viscosity. Motility of the digesta will alsoindirectly affect the thickness of the unstirredboundary layer, which will also affect rate of absorp-tion of all nutrients. The adverse effect of ß-glucanis most pronounced with nutrients such as fatsand fat-soluble compounds. Adding syntheticß-glucanase enzymes to diets containing morethan 15 – 20% barley seems to resolve many ofBird age Min. Max. Comments0-4 wk - 40% Maximum inclusion level necessarily reduced with4-18 wk - 50% high tannin samples, especially for young birds (20% max).Adult layer - 40%Formulation Constraints:Moisture CP Fat Ca/P AA’s OtherTannin, AME – each 12 mos or moreAll deliveries Wkly 6 mos 12 mos 12 mos often if seed color variable.AME after harvest.QA Schedule:
  • SECTION 2.1Description of ingredients22 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONthese problems, the usual outward sign of whichis wet litter. Unfortunately, the description ofexogenous enzymes is not standardized, asneither is the standard for units of efficacy, andso it is often difficult to compare products on thebasis of the concentration of specific enzymes.Early studies show that any product shouldprovide at least 120 units ß-glucanase/kg diet.Enzymes seem to be less efficacious as thebirds get older. Our studies show slight improve-ment in energy value of high ß-glucan barley whenenzymes are used in diets for adult birds, and thatsome enzymes actually cause reduction in energyvalue when used with low ß-glucan barley.With this low ß-glucan barley, the addition ofß-glucanase enzymes actually caused birds tobe in severe negative nitrogen balance for the 3d duration of the balance study. For younger birdshowever, the efficacy of ß-glucanase enzymesis well established and many nutritionistsconsider barley plus enzymes as being equiva-lent in feeding value to wheat. These values canbe used as a basis for economic evaluation ofenzymes. While ß-glucans are most oftenregarded as being problematic to birds, there seemsto be one advantage to their inclusion in the diet.Feeding ß-glucans reduces blood cholesterol inbirds, and this likely positive effect is reversed byuse of synthetic ß-glucanases. The mode ofaction of ß-glucans may well be simply viasequestering of fats and bile acids in the digesta.Barley can be used in choice-feedingstudies, as previously described for wheat. Dueto the physical structure of the kernel however,with its sharp spinets, birds are often reluctantto consume whole barley grain. Turkeys atleast seem to readily eat whole barley in achoice-feeding situation after 50 d of age.Potential Problems:The moderate level of energy usually limitsthe inclusion of barley in most poultry diets.Additionally, the level of ß-glucan can beproblematic in terms of poor performance andwet litter/manure. Synthetic enzymes can be usedto overcome most of the problems.Dry Matter 85.0 Methionine 0.21Crude Protein 11.5 Methionine + Cystine 0.42Metabolizable Energy: Lysine 0.39(kcal/kg) 2780 Tryptophan 0.19(MJ/kg) 11.63 Threonine 0.40Calcium 0.10 Arginine 0.51Av. Phosphorus 0.20 Dig Methionine 0.16Sodium 0.08 Dig Meth + Cys 0.32Chloride 0.18 Dig Lysine 0.31Potassium 0.48 Dig Tryptophan 0.15Selenium (ppm) 0.30 Dig Threonine 0.29Fat 2.10 Dig Arginine 0.41Linoleic acid 0.80Crude Fiber 7.50Nutrient Profile: (%)
  • 23CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients5. RiceNutritional Characteristics:Almost without exception, rice is grown forhuman consumption, although periodically inrice growing areas, samples unfit for humanconsumption, or damaged samples are availablefor animal feeding. Rice is a relatively poor qual-ity ingredient for poultry, containing only 7 – 8% CP and providing just 2600 – 2700 kcalME/kg. Rice does contain high levels of trypsininhibitor that will be destroyed at normal pelletingtemperatures. As detailed in the next section oncereal by-products, rice bran and rice polishingsare more commonly used in poultry feeds thanis rice grain itself.Potential Problems:Because most feed sources will have beengraded as unfit for human consumption, then thereason for rejection should be ascertained.Mold growth and mycotoxin (aflatoxin)contamination are often the basis for such grading.kg/m3 lb/ft3 lb/bushelWhole barley 674 42 53.8Ground barley 417 26 33.3Bird age Min. Max. Comments0-4 wk - 10 (30)%1ß-glucan content usually4-18 wk - 15 (40)% dictates maximum inclusion levelAdult layer - 15 (30)%Bulk Density:Formulation Constraints:1 with ß-glucanase enzymeMoisture CP Fat Ca/P AA’s OtherAll deliveries Wkly 6 mos 12 mos 12 mosAMEn1 12 mos; ß-glucan, bulkdensity-monthly since correlateswith AMEQA Schedule:1 within 30 d of yearly harvest.
  • SECTION 2.1Description of ingredients24 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONDry Matter 85.0 Methionine 0.12Crude Protein 7.3 Methionine + Cystine 0.23Metabolizable Energy: Lysine 0.22(kcal/kg) 2680 Tryptophan 0.11(MJ/kg) 11.21 Threonine 0.34Calcium 0.04 Arginine 0.62Av. Phosphorus 0.13Sodium 0.03 Dig Methionine 0.09Chloride 0.28 Dig Meth + Cys 0.15Potassium 0.34 Dig Lysine 0.17Selenium (ppm) 0.17 Dig Tryptophan 0.07Fat 1.70 Dig Threonine 0.27Linoleic acid 0.60 Dig Arginine 0.50Crude Fiber 10.00Nutrient Profile: (%)kg/m3 lb/ft3 lb/bushelWhole kernels 722 45 57.6Ground rice 626 39 49.9Bulk Density:Formulation Constraints:QA Schedule:Bird age Min. Max. Comments0-4 wk - 15% Maximum constraints due to low energy.4-18 wk - 25%Adult layer - 20%Moisture CP Fat Ca/P AA’s OtherAll deliveries 1 mos 1 mos 12 mos 12 mos AME11 within 30 d of yearly harvest.
  • 25CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsDuring the processes of cleaning wheat andsubsequent manufacture of flour, up to 40%by weight is classified as by-product material. Thereis considerable variation in the classificationand description of these by-products, and greatcare must be taken when formulating withwheat by-products in different countries.Traditionally there were three major by-products,namely wheat bran, wheat shorts and wheat mid-dlings. Bran is the outer husk, and so is very highin fiber and rarely used in poultry diets.Unfortunately, in many countries the term wheatbran is used to describe wheat middlings. A checkon crude fiber level of wheat by-products isnecessary to ensure correct terminology. The finermaterial removed during bran extraction, was tra-ditionally termed wheat shorts. As wheat isground through a series of grinders of decreas-ing size, middlings are produced, most of whichis extracted as flour. Wheat middlings are the majorby-product from the final extraction of flour.In the U.S.A., the term red-dog was sometimesused to describe the very fine material extract-ed from ‘red’ wheats, and was similar to shorts.Today most by-products are combined at the flourmills, and commonly called wheat shorts. Theonly other by-product produced in reasonablequantity is wheat screenings, which as its nameimplies, is material removed during initial clean-ing and separation. If screenings are composedmainly of broken wheat kernels, then their nutri-tive value is little different to wheat.Wheat by-products such as shorts can containvery high levels of ‘natural’ phytase enzyme. Whenmore than 15% shorts are used in a diet thisendogenous enzyme can be greater than levelsof commercial phytase added to the diet, and soinfluence assay results. While endogenousphytase levels are high, it is questionable if thisenzyme is beneficial to the bird at the pH of theproventriculus or small intestine.Wheat shorts: Shorts are the major by-prod-uct of flour manufacture and since they are usu-ally a composite of various fractions, nutrient pro-file can be variable. The major difference willbe in the quantity of bran included in the mate-rial, and so this directly influences its energy value.If wheat shorts contain much more than 5% crudefiber, it is an indication of a greater proportionof bran-type residues. Dale (1996) suggeststhat the metabolizable energy value of wheat by-product is directly proportional to its fibercontent, and that ME can be described as:3182 – 161 x % crude fiber (kcal/kg)With an average fiber value of 5%, ME isaround 2370 kcal/kg. However, it is commonto see a range of 3 to 10% CF depending uponflour manufacturing procedures, which equatesto a range of ME values of from 1570 to 2700kcal/kg. Measuring crude fiber level of wheatby-products is obviously important in qualityassurance programs. As described previously withwheat, most by-products will contain xylan,6. Wheat by-productsOther Names: wheat shorts, wheat middlings, wheat bran, wheat millrun,wheat screeningsNutritional Characteristics:
  • SECTION 2.1Description of ingredients26 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONand so xylanase enzyme is advisable if inclusionlevels are >15% for young birds or > 30% for birdsafter 4 weeks of age.Wheat bran:The main characteristics are highfiber, low bulk density and low metabolizableenergy. Bran is however, quite high in protein,and amino acid profile is comparable to that seenin whole wheat. Bran has been claimed to havea growth promoting effect for birds which is notdirectly related to any contribution of fiber to thediet. Such growth promotion is possibly derivedfrom modification of the gut microflora. Theenergy value of bran may be improved by up to10% by simple steam pelleting, while the avail-ability of phosphorus is increased by up to 20%under similar conditions. Bran would only beconsidered where limits to growth rate arerequired, and where physical feed intake is nota problem. High bran diets promote excessivemanure wetness, and transportation costs ofbran diets are increased in proportion to thereduced bulk density of the diet.Wheat screenings: Wheat screenings are aby-product of the cleaning and grading of wheatthat itself is usually destined for humanconsumption. The product is therefore availablein most countries that have significant wheatproduction. In addition to broken and crackedwheat kernels, screenings will also contain wildoats and buckwheat as well as weed seeds andother contaminants. The higher grades (#1 or #2)contain significant proportions of wheat, and sotheir nutrient profile is very similar to that of wheat.The weed seeds, depending upon variety, maybe of some nutritional value. Since certainweed seeds produce a feed-refusal type reactionin layers, only the highest grades should beconsidered for high producing stock. The weedseeds can pose problems to arable farms that usemanure from birds fed coarsely ground dietscontaining screenings, since some of the weedseeds can pass undamaged through thedigestive tract. The level of screenings used infinisher diets of meat birds should also beseverely limited, since breakage of the gut dur-ing processing leads to fine particles of black weedseeds adhering to the fat pads of the bird– such birds are easily recognized and oftencondemned due to fecal contamination. Number1 and 2 grade screenings can be used up to 40%of the diet for broilers and layers.Potential Problems:The fiber content will directly influenceenergy value. With wheat screenings there willlikely be some weed seeds present, and these maycause feed refusal.
  • 27CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsShorts Screening Bran Shorts Screenings BranDry Matter 90 90 90 Methionine 0.21 0.21 0.10Crude Protein 15 15 16 Meth + Cyst 0.40 0.42 0.20Metabolizable Energy: Lysine 0.61 0.53 0.60(kcal/kg) 2200 3000 1580 Tryptophan 0.21 0.20 0.31(MJ/kg) 9.20 12.55 6.61 Threonine 0.50 0.42 0.34Calcium 0.07 0.05 0.10 Arginine 0.80 0.60 0.85Av. Phosphorus 0.30 0.20 0.65Sodium 0.07 0.08 0.06 Dig Methionine 0.16 0.15 0.08Chloride 0.10 0.05 0.20 Dig Meth + Cys 0.30 0.32 0.15Potassium 0.84 0.55 1.20 Dig Lysine 0.48 0.39 0.42Selenium (ppm) 0.80 0.57 0.92 Dig Tryptophan 0.15 0.15 0.24Fat 4.0 4.1 4.5 Dig Threonine 0.41 0.31 0.28Linoleic acid 1.6 0.7 1.7 Dig Arginine 0.71 0.52 0.79Crude Fiber 5.0 3.0 12.0kg/m3 lb/ft3 lb/bushelWheat bran 193 12 15.4Wheat shorts 480 30 38.4Wheat screenings 740 46 58.9Bird age Min. Max. CommentsShorts, and 0-4 wk 10% 20%Minimum if pellet durability an issueScreenings 4-18 wk 30%Adult layer 30%Bran 4 wk+ 10% Energy will be the limiting factorMoisture CP Fat Ca/P AA’s OtherAll deliveries Wkly 6 mos 12 mos 12 mos Crude fiber on all deliveries.AMEn yearlyNutrient Profile: (%)Bulk Density:Formulation Constraints:QA Schedule:
  • SECTION 2.1Description of ingredients28 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONBakery meal is a by-product from a range offood processing industries. In order to ensure con-sistent composition, individual products must beblended or the supplier large enough to provideadequate quantities from a single manufactur-ing process. The most common by-products comefrom bread and pasta manufacture, as well as cook-ies and snack foods. By-products from snack foodscan be quite high in salt and fat. Bakery mealis often derived from pre-cooked products andso digestibility is often higher than for the orig-inal starch components.Fillers are sometimes used to improve flowcharacteristics of high-fat bakery meals. The most-common fillers are soybean hulls and limestonewhich influence nutritive value accordingly.The metabolizable energy value of bakery mealcan be described as:4000–(100x%fiber+25x%ash)kcal/kg with4% fiber and 3% ash, ME becomes 3525 kcal/kgPotential Problems:Quality control programs must ensureconsistent levels of sodium, fiber and ash.Dry Matter 90.0 Methionine 0.21Crude Protein 10.5 Methionine + Cystine 0.40Metabolizable Energy: Lysine 0.29(kcal/kg) 3500 Tryptophan 0.13(MJ/kg) 14.6 Threonine 0.30Calcium 0.05 Arginine 0.50Av. Phosphorus 0.13Sodium 0.50 Dig Methionine 0.18Chloride 0.48 Dig Meth + Cys 0.34Potassium 0.62 Dig Lysine 0.19Selenium (ppm) 0.30 Dig Tryptophan 0.08Fat 9.5 Dig Threonine 0.21Linoleic acid 3.0 Dig Arginine 0.40Crude Fiber 2.5Nutrient Profile: (%)Bulk Density:kg/m3 lb/ft3 lb/bushel353 22.0 28.07. Bakery mealOther Names: Cookie meal, bread mealNutritional Characteristics:
  • 29CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsRice by-products are the result of dehullingand cleaning of brown rice, necessary for the pro-duction of white rice as a human food. Rice by-products are one of the most common cereal by-products available to the feed industry, withworld production estimated at around 45 mtonnes. The by-product of preparing white rice,yields a product called rice bran, which itself iscomposed of about 30% by weight of rice pol-ishings and 70% true bran. In some regions, thetwo products are separated, being termed pol-ishings and bran. Alternatively, the mixture is some-times called rice bran, whereas in other areas themixture may be called rice pollards. The polishingsare very high in fat content and low in fiber whilethe true bran is low in fat and high in fiber. Theproportions of polishings and true bran in amixed product will therefore have a major effecton its nutritive value. In the following discussion,rice bran refers to the mixture of polishings andbran. The composition of any sample of mixedrice bran can be calculated based on levels offat vs fiber.Because of a high oil content (6 – 10%)rice bran is very susceptible to oxidative rancidity.Raw bran held at moderate temperatures for10 – 12 weeks can be expected to contain 75 – 80%of its fat as free fatty acids, which are themselvesmore prone to rancidity. Rice bran should bestabilized with products such as ethoxyquin.Higher levels of ethoxyquin give greater protectionagainst rancidity although economical levelsappear to be around 250 ppm. Rice bran canalso be stabilized by heat treatment. Extrusionat 130ºC greatly reduces chances of rancidity, andof the development of free fatty acids.When high levels of raw rice bran are used( 40%) there is often growth depression and reduc-tion in feed efficiency, likely associated with thepresence of trypsin inhibitor and high levels ofphytic acid. The trypsin inhibitor, which seemsto be a relatively low molecular weight structure,is destroyed by moist heat, although phytic acidis immune to this process. The phosphoruscontent of rice bran is assumed to be only 10%Bird age Min. Max. Comments0-4 wk 10% Concern over sodium content4-18 wk 15%Adult layer 15%Moisture CP Fat Ca/P AA’s OtherAll deliveries 1 mos 1 mos 6 mos 12 mos Na content of all samples if snack foodspart of bakery mealFormulation Constraints:QA Schedule:8. Rice by-productsOther Names: Rice bran, rice polishings, rice pollardsNutritional Characteristics:
  • SECTION 2.1Description of ingredients30 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONavailable for very young birds. However, phos-phorus availability may increase with age, andif this happens, it could create an imbalance ofcalcium:phosphorus. This latter effect is suggestedas the reason for improved growth response inolder birds fed rice bran when extra calcium isadded to the diet. Phytase enzyme can be usedto advantage in diets containing > 15% ricebran. Because of the potential for high fiber content, use of rice bran may be improved withaddition of exogenous arabinoxylanase enzymes.Potential Problems:Rice bran should be stabilized with anantioxidant if storage at the mill is to be longerthan a few weeks. Heating is advisable if youngbirds (< 3 weeks) are fed > 10% rice bran, to limitadverse effects of trypsin inhibitor.Bran Polishing Bran PolishingDry Matter 90.0 90.0 Methionine 0.29 0.21Crude Protein 13.0 11.0 Methionine + Cystine 0.30 0.52Metabolizable Energy: Lysine 0.51 0.50(kcal/kg) 1900 2750 Tryptophan 0.18 0.12(MJ/kg) 7.95 11.52 Threonine 0.38 0.32Calcium 0.06 0.06 Arginine 0.52 0.61Av. Phosphorus 0.80 0.18Sodium 0.10 0.10 Dig Methionine 0.15 0.16Chloride 0.17 0.17 Dig Meth + Cys 0.22 0.24Potassium 1.30 1.17 Dig Lysine 0.39 0.41Selenium (ppm) 0.19 0.17 Dig Tryptophan 0.13 0.08Fat 5.0 15.0 Dig Threonine 0.28 0.25Linoleic acid 3.4 6.2 Dig Arginine 0.40 0.48Crude Fiber 12.0 2.5kg/m3 lb/ft3 lb/bushelRice bran 417 26 33Rice polishings 480 30 38Bird age Min. Max. Comments0-4 wk 10% Fat rancidity the major concern4-8 wk 20% High phytate contentAdult 25%Nutrient Profile: (%)Bulk Density:Formulation Constraints:
  • 31CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsSoybean meal has become the worldwidestandard against which other protein sources arecompared. Its amino acid profile is excellent formost types of poultry, and when combined withcorn or sorghum, methionine is usually theonly limiting amino acid.The protein level in soybean meal can bevariable, and this may be a reflection of seedvariety and/or processing conditions involved infat extraction. Traditionally the higher proteinmeals are produced from de-hulled beans,whereas the lower protein (44% CP) mealsinvariably contain the seed hulls, and are high-er in fiber and lower in metabolizable energy.There is some variation in seed type used and thiscan affect protein and fat content, which arenegatively correlated. Whereas fat content of theseed is dictated early in seed development,protein is deposited through to the end ofmaturity, and therefore growing and harvestingconditions tend to have more of an effect onprotein content of the seed. For soybeanprocessors, about 65% of the value of soybeansis attributed to their protein content, and 35%to the oil. In recent years, there have been anumber of ‘new’ varieties introduced, and someof these are produced by genetic engineering.At this time (2004) there are no new GMOproducts modified in terms of enhancednutrient profile or reduced anti-nutritionalcontent. Current GMO soybeans are modifiedfor agronomic reasons, and there is no indicationthat they have different feeding value. In the future,there seems great potential for reduction in con-tent of anti-nutrients within GMO soybeans.Soybeans have to be heat-treated in order toinactivate various anti-nutrients. During processing,soybeans are dehulled (about 4% by weight) andthen cracked prior to conditioning at 70ºC. Thehot cracked beans are then flaked to about 0.25mm thickness to enhance oil extraction by a sol-vent, which is usually hexane. Hexane must beremoved from the meal because it is a highlycombustible material and a potent carcinogen.Problems occurring during processing that resultin residual hexane in the meal are usuallynoticed by severe and sudden liver failure in birds.Soybean meals tend to be very dusty, and in mashdiets, soy is responsible for some of the dust foundin controlled environment poultry houses.Soybean meal is also notorious for its poor flowcharacteristics and for bridging in storage bins.Addition of products such as bentonite clays, evenat levels as low as 2.5 kg/tonne, can greatly improvethe flow characteristics of soybean meal.Moisture CP Fat Ca/P AA’s OtherAll deliveries monthly All deliveries 6 mos 12 mos Fiber for all deliveriesQA Schedule:9. Soybean mealOther Names: High protein SBMNutritional Characteristics:
  • SECTION 2.1Description of ingredients32 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSoybeans contain a number of natural toxinsfor poultry, the most problematic being trypsininhibitor. As with most types of beans, thetrypsin inhibitors will disrupt protein digestion,and their presence is characterized bycompensatory hypertrophy of the pancreas.Apart from reduced growth rate and eggproduction, presence of inhibitors is thereforediagnosed by a 50-100% increase in size of thepancreas. Fortunately, the heat treatmentemployed during processing is usuallyadequate to destroy trypsin inhibitors and otherless important toxins such as hemaglutinins(lectins). In developing countries, trypsininhibitor levels are sometimes controlled byfermentation or germinating beans, where after48 hrs of treatment, protein digestibility is almostequivalent to that seen in conventionally heatedbeans. Trypsin inhibitor levels are usually‘assayed’ indirectly by measuring urease activityin processed soybean meal. Urease is of littleconsequence to the bird, although the heat-sensitivity characteristics of urease are similar tothose of trypsin inhibitors, and urease levelsare much easier to measure. Residual urease insoybean meal has therefore become the standardin quality control programs. Urease is assessedin terms of change in pH during the assay,where acceptance values range between 0.05 and0.15. Higher values mean there is still residualurease (trypsin inhibitor) and so the test isuseful to indicate undercooked meal. However,while low values mean that the proteases havebeen destroyed, there is no indication ofpotential overcooking, which can destroy lysineand reduce ME value. For this reason other testsare sometimes used. A fairly easy test to accom-plish is protein solubility in potassium hydroxide.Dale and co-workers at the University of Georgiahave shown a good correlation between theamount of protein soluble in 2% KOH, andchick growth, determined in a bioassay. Heatingtends to make the protein less soluble, and so highvalues suggest undercooking, while low values meanovercooking. Values of 85% solubility indicateunder-processing and 70% mean the samplehas been over-processed. The assay is influencedby particle size of soybean meal and time ofreaction, and so these must be standardizedwithin a laboratory. As soybean meal is heated,its color changes and again this can be used inquality control programs. Simply measuring colorin a Hunterlab Color Spectrophotometer canindicate degree of cooking. Degrees of ‘lightness’,‘redness’ and ‘yellowness’ can be measuredsince these change with cooking temperature andtime. Again it is important to control particle sizeduring this assay.Discussion about soybean meal qualityinvariably involves the significance of trypsininhibitor relative to other antinutrients. It isoften claimed that only about 50% of the growthdepression resulting from consumption of under-heated soybean meal is due to active trypsininhibitor. The other antinutrients of importanceare isoflavones, lectins and oligosaccharides.Lectins are antinutritional glycoproteins thatbind to the intestinal epithelium resulting inimpaired brush border function. Such ‘thickening’of the epithelium results in reduced efficiencyof absorption. There are strains of soybeansthat contain no lectins, and so studying their feed-ing value provides some information on impor-tance or not of lectins. Feeding uncookedlectin-free soybean meal produces greaterbroiler growth than does feeding regular uncookedsoybean. However, the growth is still less thanusing trypsin inhibitor-free soybeans. Thesedata support the concept that lectins are muchless important than are trypsin inhibitors inassessing nutritive value of soybean meal.
  • 33CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsWhile undercooking of soybean meal is themost common result of incorrect processing, over-heating sometimes occurs. It seems as thoughlysine availability is most affected by over-cooking of soybeans, since addition of other aminoacids rarely corrects growth depression seenin birds fed such meals. When soybeans are over-cooked, KOH protein solubility declines. Usingdata from Dale and co-workers, it seems asthough problems of using overheated soybeanmeal can be resolved by adding 0.5 kg L-LysineHCl/tonne feed for each 10% reduction inprotein solubility below a value of 70%.Over the last few years there has beengrowing concern about some of the less digestiblecarbohydrates in soybean meal. The -galacto-side family of oligosaccharides cause a reduc-tion in metabolizable energy with reduced fiberdigestion and quicker digesta transit time. Birdsdo not have an -1:6 galactosidase enzyme in theintestinal mucosa. Apart from reduced digestibil-ity, there is concern about theconsistency of excreta and its involvement in foot-pad lesions in both young turkeys and broilerbreeders. Soybean meal usually contains about6% sucrose, 1% raffinose and 5% stachyose, allof which are poorly digested by the bird. Addingraffinose and stachyose to isolated soybeanprotein to mimic levels seen in soybean meal,causes a significant reduction in metabolizableenergy. These problems limit the diet inclusionlevel of soybean meal, especially in turkeyprestarters. The solution to the problem relatesto change in soybean processing conditions oruse of exogenous feed enzymes. Extractingsoybeans with ethanol, rather than hexane,removes most of the oligosaccharides. Themetabolizable energy value of soybean mealextracted from low oligosaccharide varieties ofsoybeans is increased by about 200 kcal/kg.There are now some galactosidase enzymeproducts available which are designedspecifically to aid digestion of vegetable proteinsand presumably these help in digestion ofproducts such as raffinose and stachyose.Potential Problems:In most feeding situations, the main concernis usually processing conditions and knowl-edge of urease index or protein solubility.Soybean meal is also very high in potassium. Inregions where animal proteins are not used,then necessarily high levels of soybean meal canlead to enteritis, wet litter, and food pad lesions.
  • SECTION 2.1Description of ingredients34 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONDry Matter 90.0 Methionine 0.72Crude Protein 48.0 Methionine + Cystine 1.51Metabolizable Energy: Lysine 3.22(kcal/kg) 2550 Tryptophan 0.71(MJ/kg) 10.67 Threonine 1.96Calcium 0.20 Arginine 3.60Av. Phosphorus 0.37Sodium 0.05 Dig Methionine 0.64Chloride 0.05 Dig Meth + Cys 1.27Potassium 2.55 Dig Lysine 2.87Selenium (ppm) 0.11 Dig Tryptophan 0.53Fat 0.5 Dig Threonine 1.75Linoleic acid 0.3 Dig Arginine 3.20Crude Fiber 3.0kg/m3 lb/ft3 lb/bushel640 40 51.5Bulk Density:Nutrient Profile: (%)Formulation Constraints:QA Schedule:Bird age Min. Max. Comments0-4 wk 30% Higher levels may lead to wet litter due to high K intake4-8 wk 30%Adult 30%Moisture CP Fat Ca/P AA’s OtherAll deliveries All deliveries 6 mos 12 mos 12 mos Urease or KOH solubilityeach 6 mos, AMEn each 12 mos
  • 35CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients10. SoybeansOther Names: Full-fat soybeansNutritional Characteristics:Soybeans provide an excellent source ofboth energy and protein for poultry. As with anyingredient, their usage rate depends uponeconomics, although in the case of soybeans sucheconomics relate to the relative price ofsoybean meal and of supplemental fats. Soybeanscontain about 38% crude protein, and around20% oil.Comparable to the manufacture of soybeanmeal, soybeans must be heat processed in someway to destroy the trypsin inhibitors and toimprove overall protein digestibility. Feeding rawsoybeans or improperly processed soybeanswill cause poor growth rate or reduced eggproduction and egg size. If processing conditionsare suspect, the birds’ pancreas should beexamined, because if trypsin inhibitors are stillpresent pancreas size can be expected to increaseby 50-100%. While processed beans should beperiodically tested for trypsin inhibitor or ureaselevels, a simple on-going test is to taste thebeans. Under-heated beans have a character-istic ‘nutty’ taste, while over-heated beans havea much darker color and a burnt taste. Theproblem with overheating is potential destruc-tion of lysine and other heat-sensitive amino acids.Heat-treated soybeans can be easily groundin a hammer mill, even though they are high infat, and the ground product is a relatively free-flowing material. Because of the high oilcontent, ground beans should not be stored forany length of time due to potential for oxidativerancidity. However, it is important that beans bewell ground because it is necessary to release fatfrom the plant cells in order to aid digestion.Coarsely ground beans have lower fat digestibil-ity than do more finely ground material. Heatingbeans by whatever means usually results inconsiderable ‘shrinkage’ which is mainly due toloss of water. In many situations, shrinkagewill be up to 7%, but of this, less than 1% willbe real loss of dry matter.Recently there has been growing interestin processing beans through extruders orexpanders. The heat necessary to destroy trypsininhibitors and other hemagglutinins found in rawbeans is dependent upon exposure time, and sohigh temperatures for a shorter time period areas effective as lower temperatures for longertimes. Because both expanders and extrudersare fast throughput, the beans have a relativelyshort dwell time in the conditioning chamber.Consequently, slightly higher temperatures arenecessary, and depending upon design, suchmachines are best operated at 140-155ºC.Again, the effectiveness of expanding andextrusion can be measured by tests for urease andavailable lysine content.Potential Problems:Under-heating of soybeans is detected as ahigh urease or KOH protein solubility. If broilerfinisher diets contain > 30% soybeans, thentheir body fat will become less saturated and moreprone to oxidative rancidity. This latter problemcan be resolved to some extent by using higherlevels of vitamin E (75-100 IU/kg).
  • SECTION 2.1Description of ingredients36 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONDry Matter 90.0 Methionine 0.49Crude Protein 38.0 Methionine + Cystine 1.12Metabolizable Energy: Lysine 2.41(kcal/kg) 3880 Tryptophan 0.49(MJ/kg) 16.23 Threonine 1.53Calcium 0.15 Arginine 2.74Av. Phosphorus 0.28Sodium 0.05 Dig Methionine 0.41Chloride 0.04 Dig Meth + Cys 0.93Potassium 1.50 Dig Lysine 2.00Selenium (ppm) 0.10 Dig Tryptophan 0.39Fat 20.0 Dig Threonine 1.27Linoleic acid 9.0 Dig Arginine 2.31Crude Fiber 2.0Nutrient Profile: (%)Bulk Density:Formulation Constraints:QA Schedule:kg/m3 lb/ft3 lb/bushel750 47 60Bird age Min. Max. Comments0-4 wk 15 In broiler finisher diets, > 30%may cause ‘oily’ fat depots.4-8 wk 20Adult 30Moisture CP Fat Ca/P AA’s OtherAll deliveries 1 mos 1 mos 6 mos 12 mos Monthly analyses forurease or KOH solubility
  • 37CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients11. Canola mealNutritional Characteristics:Canola is a widely grown crop in westernCanada and production is increasing in other partsof the world. Production has been influencedby the marked increase in the demand forcanola oil as well as the ability of this highprotein oilseed to grow in northern climateswhere the short growing season is not suitablefor the production of soybeans.While canola was derived from varieties ofrapeseed, its composition has been alteredthrough genetic selection. The level of goitrogensand erucic acid, two of the more detrimental con-stituents of the original rapeseed cultivars, havebeen markedly reduced. Erucic acid levels arenow negligible while goitrogen levels are downto less than 20 µg/g and these levels are lowenough to be of little or no problem to poultry.Varieties containing such levels of toxins areclassified as canola and are often referred to as‘double zero varieties’.Canola still has enough goitrogen activity toresult in measurable increases in thyroid weight,although this does not appear to be a problemaffecting the performance of poultry. The tanninlevels in canola can also be relatively high,with up to 3% for some cultivars. Again, researchhas shown that the canola tannins have littleinfluence in the utilization of the protein indiets containing appreciable levels of the meal.Canola meal also contains significantquantities (1.5%) of sinapine. While thiscompound poses no problem to most classes ofpoultry, a significant percent of brown egg layersproduce eggs with a fishy and offensive odourwhen fed canola sinapines. One of the endproducts of the degradation of sinapine in theintestinal tract is trimethylamine and it is this com-pound, which is involved in the production offishy- flavored eggs. A small proportion oftoday’s brown egg laying birds lack the ability toproduce trimethylamine oxidase which effectivelybreaks down the compound and so the intacttrimethylamine is deposited into the egg. Even1% sinapine in canola can result in off-flavoredeggs. It should be pointed out that brown eggsproduced by broiler breeders, are not affectedby canola sinapines.While canola meal has been accepted by thefeed industry as a high quality feedstuff forpoultry, there continues to be isolated reports ofincreased leg problems with broilers and turkeys,smaller egg size with layers and in some cases,reports of increased liver hemorrhages when dietscontain significant amounts of canola meal.There are several reports which suggest thatincreased leg problems resulting from feedingcanola may be due to its having a differentmineral balance than does soybean meal. Theaddition of dietary K, Na and in some cases Clhave, under certain conditions, altered birdperformance. Canola is also high in phyticacid and so there is speculation that the high levelof this compound may be sequestering zincand this affects bone development. The smalleregg size reported with canola meal diets seemsto be a direct result of lower feed intake. Canolameal levels should therefore be limited in dietsfor very young laying hens, or at least until feedintake plateaus at acceptable levels.Within the past few years, there have beenreports suggesting that high levels of sulfur in canolameal may be responsible for some of the legproblems and reduced feed intake noted withcanola meal diets. Canola meal contains 1.4% sul-fur while soybean meal contains around 0.44%.
  • SECTION 2.1Description of ingredients38 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONUp to 75% of the sulfur in soybean meal iscontributed by the sulfur amino acids com-pared to around only 20% for canola meal.High levels of dietary sulfur have been report-ed to complex intestinal calcium and lead toincreased calcium excretion.This could explainthe reports suggesting low availability of calci-um in canola meal, and so possibly contributeto more leg problems. While lower weightgain has periodically been reported with canoladiets, it is usually noted that feed:gain ratios arelittle affected. This situation suggests that the reduc-tion in gain was not the result of reducednutrient availability but rather a direct effecton appetite, resulting in reduced feed intake.Recent work demonstrates quite clearly that a soy-bean meal diet containing the same level of sul-fur as that in canola diets results in comparableweight gain and feed intake in young broilers (Table2.4). In this study, the unsupplemented canoladiet contained 0.46% sulfur while the soy dietcontained 0.14%. Adding sulfur to the soy-bean meal diet resulted in a decrease in weightgain. The level of sulfur in the unsupplementedcanola diet (0.46%) lies part way between thelevels found in the 0.26 and 0.39% sulfur sup-plemented soybean meal diet. Weight gain forthe unsupplemented canola meal diet was 424g while the average for the two soybean meal dietswas 426 g. Higher dietary calcium levels par-tially overcame the growth depressing effect ofhigh dietary sulfur thus demonstrating the neg-ative effect of sulfur on calcium retention.Protein Suppl. S Total S Calcium Weightsource (%) (%) level (%) gain (g)- .46 .37 424Canola meal .26 .72 .37 371- .46 1.32 560.26 .72 1.32 481- .14 .37 525.13 .27 .37 519.26 .40 .37 479.39 .53 .37 373Soybean meal - .14 1.32 635.13 .27 1.32 598.26 .40 1.32 559.39 .53 1.32 451Table 2.4 Interaction of sulfur and calcium in canola andsoybean meal diets
  • 39CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsIn view of the reductions in appetite and cal-cium retention resulting from high dietary sul-fur levels, these need to be closely monitored ifsubstantial levels of canola meal are used. Highlevels of methionine or sulphate salts, alongwith ingredients with significant amounts ofsulfur, such as phosphate supplements, can addconsiderable sulfur to a diet. Some sources ofwater can also be high in sulfur. Broilers cantolerate dietary sulfur levels of up to around 0.5%without any effect on performance while layinghens can handle even higher levels. There arereports which suggest that part of the responseto increased levels of dietary sulfur is due to itsinfluence in dietary acid-base balance. WhileMongin, in his original work, suggested consideringNa, K, and Cl in the dietary acid-base balanceequation, S, being a strong anion, should also beconsidered in this equation if > 8% canolameal is used in poultry diets.Potential Problems:Canola meal contains less lysine than doessoybean meal but slightly more sulfur amino acidsper unit of dietary protein. It is also lower inenergy than is soybean meal. Levels of up to 8%canola meal can be used in laying diets withoutany adverse effects on performance althoughegg size may be reduced by up to 1 g. Energycontent is the factor that usually limits inclusionlevel. Levels of toxic goitrogens should be assayedperiodically, together with tannins. Canola mealshould not be fed to brown egg layers.Dry Matter 90.0 Methionine 0.69Crude Protein 37.5 Methionine + Cystine 1.3Metabolizable Energy: Lysine 2.21(kcal/kg) 2000 Tryptophan 0.50(MJ/kg) 8.37 Threonine 1.72Calcium 0.65 Arginine 2.18Av. Phosphorus 0.45Sodium 0.09 Dig Methionine 0.61Chloride 0.05 Dig Meth + Cys 1.08Potassium 1.45 Dig Lysine 1.76Selenium (ppm) 0.90 Dig Tryptophan 0.38Fat 1.5 Dig Threonine 1.30Linoleic acid 0.5 Dig Arginine 1.92Crude Fiber 12.0Nutrient Profile: (%)kg/m3 lb/ft3 lb/bushel625 39 50Bulk Density:
  • SECTION 2.1Description of ingredients40 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION12. Corn gluten mealNutritional Characteristics:Corn gluten meal contains around 60% CPand is a by-product of wet milling of corn, mostof which is for manufacture of high-fructosecorn syrup. Being high in protein, it is often com-pared to animal protein ingredients during for-mulation. The protein is merely a concentrationof the original corn protein component broughtabout by removal of the starch in the endosperm.There are, in fact, two products often manufacturedduring wet milling, the alternate being corngluten feed which contains only 20% CP, due todilution with various hull material. In certainregions of the world, the two products are mere-ly called ‘corn gluten’ and so this must be dif-ferentiated based on protein content. Corngluten meal is very deficient in lysine, althoughwith appropriate use of synthetic lysine sources,the product is very attractive where high nutri-ent density is required. Gluten meal is alsovery high in xanthophylls pigments (up to 300mg/g) and is a very common ingredient wherethere is a need to pigment poultry products.Potential Problems:Periodically corn gluten feed (20% CP) is inad-vertently formulated as corn gluten meal (60%CP). Using much more than 10% corn glutenmeal will produce a visible increase in pigmen-tation of broilers and egg yolks.Bird age Min. Max. Comments0-4 wk 5% Potential problems with tannins,4-8 wk 8%low energy and high sulfur.Adult 8%Not for brown egg layers.Formulation Constraints:QA Schedule:Moisture CP Fat Ca/P AA’s OtherAll deliveries 6 mos 12 mos 12 mos 12 mos Tannins, sulfur and goitrogenseach 6 mos.
  • 41CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsDry Matter 90.0 Methionine 1.61Crude Protein 60.0 Methionine + Cystine 2.52Metabolizable Energy: Lysine 0.90(kcal/kg) 3750 Tryptophan 0.30(MJ/kg) 15.70 Threonine 1.70Calcium 0.10 Arginine 2.20Av. Phosphorus 0.21Sodium 0.10 Dig Methionine 1.44Chloride 0.06 Dig Meth + Cys 2.22Potassium 0.04 Dig Lysine 0.81Selenium (ppm) 0.30 Dig Tryptophan 0.21Fat 2.51 Dig Threonine 1.58Linoleic acid 1.22 Dig Arginine 2.07Crude Fiber 2.48Nutrient Profile: (%)Bulk Density:Formulation Constraints:QA Schedule:kg/m3 lb/ft3 lb/bushel578 36 46.1Bird age Min. Max. Comments0-4 wk 15% Pigmentations increases with4-8 wk 20% > 10% inclusion.8 wk+ 20%Moisture CP Fat Ca/P AA’s OtherAll deliveries 3 mos 6 mos 6 mos 12 mos -
  • SECTION 2.1Description of ingredients42 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION13. Cottonseed mealNutritional Characteristics:Cottonseed meal is not usually consideredin diets for poultry, although for obvious economicreasons it is often used in cottonseed producingareas. A high fiber content and potential con-tamination with gossypol are the major causesfor concern. Gossypol is a yellow polyphenolicpigment found in the cottonseed ‘gland’. In mostmeals, the total gossypol content will be around1%, although of this, only about 0.1% will befree gossypol. The remaining bound gossypol isfairly inert, although binding can have occurredwith lysine during processing, making both thegossypol and the lysine unavailable to the bird.So-called ‘glandless’ varieties of cottonseed arevirtually free of gossypol.Birds can tolerate fairly high levels ofgossypol before there are general problemswith performance although at much lowerlevels there can be discoloration of the yolkand albumen in eggs. Characteristically thegossypol causes a green-brown-blackdiscoloration in the yolk depending upongossypol levels, and the duration of egg storage.As egg storage time increases, the discolorationintensifies, especially at cool temperatures (5ºC)where there is more rapid change in yolk pH.Gossypol does complex with iron, and thisactivity can be used to effectively detoxify the meal.Adding iron at a 1:1 ratio in relation to freegossypol greatly increases the dietary inclusionrate possible in broiler diets and also the levelat which free gossypol becomes a problem withlaying hens. Because most cottonseed samplescontain around 0.1% free gossypol, detoxifica-tion can be accomplished by adding 0.5 kgferrous sulphate/tonne feed. With addition of iron,broilers can withstand up to 200 ppm freegossypol, and layers up to 30 ppm free gossypolwithout any adverse effects.If cottonseed meal contains any residualoil, then cyclopropenoid fatty acids may contributeto egg discoloration. These fatty acids aredeposited in the vitelline membrane, and alterits permeability to iron that is normally found onlyin the yolk. This leached iron complexes withconalbumin in the albumen producing acharacteristic pink color. Addition of iron saltsdoes not prevent this albumen discoloration, andthe only preventative measure is to use cottonseedmeals with very low residual fat content.Potential Problems:Yolk discoloration is the main concern, andso ideally, cottonseed meal should not be usedfor laying hens or breeders. The lysine in cotton-seed is particularly prone to destruction due tooverheating of meals during processing.
  • 43CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsDry Matter 90 Methionine 0.49Crude Protein 41.0 Methionine + Cystine 1.11Metabolizable Energy: Lysine 1.67(kcal/kg) 2350 Tryptophan 0.50(MJ/kg) 9.83 Threonine 1.31Calcium 0.15 Arginine 4.56Av. Phosphorus 0.45Sodium 0.05 Dig Methionine 0.35Chloride 0.03 Dig Meth + Cys 0.75Potassium 1.10 Dig Lysine 1.18Selenium (ppm) 0.06 Dig Tryptophan 0.35Fat 0.50 Dig Threonine 0.90Linoleic acid 0.21 Dig Arginine 3.68Crude Fiber 14.50Nutrient Profile: (%)Bulk Density:Formulation Constraints:QA Schedule:kg/m3 lb/ft3 lb/bushel644 40.1 51.3Bird age Min. Max. Comments0-4 wk 10% Maximum levels dependent upon levels of free gossypol.Inadvisable for layers if alternative ingredients available.4-8 wk 15%8-18 wk 20%18 wk+ 10%Moisture CP Fat Ca/P AA’s OtherAll deliveries 6 mos 6 mos 12 mos 12 mos Gossypol 2-3 times each year
  • SECTION 2.1Description of ingredients44 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION14. FlaxseedOther Names: LinseedNutritional Characteristics:Flax is grown essentially for its oil content,although in Europe there is still some productionof special varieties for linen production. Fat-extracted flax, which is commonly called linseedmeal, has traditionally been used for ruminantfeeds. Over the last few years, there has beeninterest in feeding full-fat flaxseed to poultry,because of its contribution of linolenic acid. Flaxoil contains about 50% linolenic acid (18:3w3)which is the highest concentration of omega-3fatty acids within vegetable oils. It has recent-ly been shown that 18:3w3, and its desaturationproducts docosahexaenoic acid and eicos-apentaenoic acid are important in human health,and especially for those individuals at risk fromchronic heart disease. Government agencies inmany countries now recognize the importanceof linolenic acid in human health, suggesting theneed to increase average daily intake, andespecially intake in relation to that of linoleic acid.Feeding flaxseeds to poultry results in directincorporation of linolenic acid into poultrymeat and also into eggs. Feeding laying hens 10%flax results in a 10-fold increase in egg yolklinolenic acid content and eating two suchmodified eggs each day provides adults with mostof their daily recommended allowance oflinolenic acid. For each 1% of flaxseed addedto a layer diet, there will be a +40 mg increasein total omega-3 fatty acids per egg. Likewise,in broilers, each 1% flaxseed addition willincrease total omega-3 fats in the carcass by +2%of total fat. Feeding layers 8% flaxseed will resultin an egg with about 320 mg total omega-3fatty acids. For broiler chickens, there is no needto feed flaxseed for the entire grow-out period.Feeding 10% flaxseed to broilers for only the last14 d of grow-out, results in significant incorporationof omega-3 fatty acids in the meat. With cookedbreast + skin there is an increase in omega-3 con-tent from 150 675 mg/100 g cooked product.Linolenic acid enriched eggs and poultry meatare therefore an attractive alternative to con-sumption of oily fish. Linolenic acid is essentiallyresponsible for the characteristic smell of ‘fish oils’and undoubtedly flax oil does have a ‘paint-type’smell. There is some concern about the taste andsmell of linolenic acid-enriched poultry meat andthis topic needs more careful study with controlledtaste panel work. There is often discussionabout the need to grind flaxseed. The seeds arevery small, and for birds with an ‘immature’gizzard it seems likely that some seeds willpass directly through the bird. Flaxseeds are quitedifficult to grind, and are usually mixed 50:50with ground corn before passing through ahammer mill. Perhaps the greatest benefit togrinding is seen with mash diets. Table 2.5shows digestible amino acid values, determinedwith adult roosters for whole and ground flaxseed.These digestibility values were determinedusing the force-feeding method, and so the birdis fed only the flaxseed, which is a novelsituation to the bird. Over time gizzardactivity may increase and so digestibility ofwhole seeds may improve. Using a classicalAMEnbioassay, we have shown a consistent increasein AMEn of flaxseed when diets are steamcrumbled (Table 2.6).
  • 45CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsTable 2.5 Amino acid digestibilityof flaxseed (%)FlaxseedWhole GroundMethionine 68 85Cystine 68 87Lysine 72 88Threonine 65 82Tryptophan 85 95Arginine 71 92Isoleucine 66 86Valine 65 84Leucine 67 87Courtesy Novus Int.Table 2.6 Effect of steam crumblingon AMEn of flaxseed (kcal/kg)Bird Type Mash SteamCrumbleBroiler chicken 3560 4580 +31%Rooster 3650 4280 +17%Laying hen 3330 4140 +24%Adapted from Gonzalez (2000) and Bean (2002)These assays were conducted at differenttimes and with different samples of flaxseed. Inanother study there was an 18% improvementin AMEn for layers when flaxseed was extruded.Conventional pelleting seems sufficient toweaken the seed structure so as to allow greaterdigestibility of amino acids and energy.With laying hens, there may be transitoryproblems with suddenly incorporating 8-10%flaxseed in the diet, usually manifested asreduced feed intake and/or wet sticky manure.These problems can usually be overcome bygradual introduction of flaxseed, using for ex -ample, 4% for one week, followed by 6% foranother week and then the final 8-10% inclusion.It usually takes 15-20 d in order for omega-3content of eggs to plateau at the desired level of300 mg/egg. With prolonged feeding there is oftengreater incidence of liver hemorrhage in layers,even though mortality is rarely affected. Suchhemorrhaging occurs even in the presence of100-250 IU vitamin E/kg diet, which is aregular addition to flax-based diets. Disruptionto liver function may become problematic ifother stressors occur.Potential Problems:Flaxseed should be introduced graduallywhen feeding young layers. Weekly incrementsusing 4-6 and 8-10% over 3 weeks are ideal to pre-vent feed refusal. Ground flaxseed is prone to oxida-tive rancidity, and so should be usedwithin 2-3 weeks of processing.There seem to beadvantages to steam pelleting diets contain-ingflaxseed. Flaxseed contains a number ofantinutrients including mucilage, trypsin inhibitor,cyanogenic glycosides and considerablequantities of phytic acid. The mucilage is main-ly pectin, found in the seed coat and can be 5-7%by weight. The mucilage undoubtedly con-tributes to more viscous excreta, and there issome evidence that ß-glucanase enzymes may beof some benefit, especially with young birds.Flaxseed may contain up to 50% of the level oftrypsin inhibitors found in soybeans, and this ispossibly the basis for response to heat treatmentand steam pelleting of flaxseed. The main glucosidesyield hydrocyanic acid upon hydrolysis, and thishas an adverse effect on many enzyme systemsinvolved in energy metabolism.
  • SECTION 2.1Description of ingredients46 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONDry Matter 90.0 Methionine 0.41Crude Protein 22.0 Methionine + Cystine 0.82Metabolizable Energy: Lysine 0.89(kcal/kg) 35001-42002Tryptophan 0.29(MJ/kg) 14.64–17.60 Threonine 0.82Calcium 0.25 Arginine 2.10Av. Phosphorus 0.17Sodium 0.08 Dig Methionine 0.281-0.352Chloride 0.05 Dig Meth + Cys 0.56-0.70Potassium 1.20 Dig Lysine 0.64-0.78Selenium (ppm) 0.11 Dig Tryptophan 0.25-0.27Fat 34.0 Dig Threonine 0.53-0.67Linoleic acid 5.2 Dig Arginine 1.49-1.93Crude Fiber 6.0Nutrient Profile: (%)Bulk Density:Formulation Constraints:1Mash; 2Pelletskg/m3lb/ft3lb/bushel700 43.5 55.7Bird age Min. Max. Comments0-4 wk 84-8 wk 8> 8 wk 10Gradual introduction suggestedto prevent feed refusal.Moisture CP Fat Ca/P AA’s OtherAll deliveries 6 mos 6 mos 12 mos 12 mos Fatty acid profile each 12 mos.QA Schedule:
  • 47CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients15. Meat mealOther names: Meat and bone mealNutritional Characteristics:Meat meal is a by-product of beef or swine pro-cessing, and this can be of variable composition.For each 1 tonne of meat prepared for human con-sumption, about 300 kg is discarded as inedibleproduct, and of this, about 200 kg is rendered intomeat meal. In the past, meat meal referred onlyto soft tissue products, while meat and bonemeal also contained variable quantities of bone.Today, meat meal most commonly refers to ani-mal by-products with bone where protein levelis around 50% and calcium and phosphorus areat 8% and 4% respectively. Because the miner-al comes essentially from bone, the calciumphosphorus ratio should be around 2:1 and devi-ations from this usually indicate adulterationwith other mineral sources.Variation in calcium and phosphorus contentis still problematic, and the potential for over-feeding phosphorus is a major reason for upperlimits of inclusion level. Meat meals usuallycontain about 12% fat and the best qualitymeals will be stabilized with antioxidants suchas ethoxyquin. Some of the variability incomposition is now being resolved by so-called‘blenders’ that source various meat mealproducts and mix these to produce moreconsistent meat meals.Meat meals are currently not used in Europebecause of the problems they have had with BSE(Bovine Spongiform Encephalopathy). It seemsas though conventional rendering treatmentsdo not inactivate the causative prions. However,pressure treatment to 30 psi (200 kPa) for about30 minutes during or after rendering seems todestroy prions. Parsons and co-workers at theUniversity of Illinois have shown that suchpressure treatment can reduce lysine digestibilityfrom 75% to 55% and cystine from 65% downto 30%. If extreme pressure treatment becomesstandard during rendering of meat meal, it willobviously be necessary to carefully re-evaluatenutrient availability.Recent evidence suggests that the metabolizableenergy content of meat meal, and other animalprotein by-products, is higher than the mostcommon estimates used in the past. In bioassays,ME values determined at inclusion levels of 5 –10%are much higher than those determined at moreclassical levels of 40 – 50% inclusion. The reasonfor the higher values is unclear, although it mayrelate to synergism between protein or fat sources,and these are maximized at low inclusion levels.Alternatively, with very high inclusion levels of meatmeal, the high calcium levels involved maycause problems with fat utilization due to soapformation, and so energy retention will be reduced.Another reason for change in energy value, is thatcommercial samples of meat meal today containless bone than occurred some 20 – 30 years ago.Dale suggests that the TMEn of meat meal frombeef is around 2,450 kcal/kg while that frompork is closer to 2,850 kcal/kg.Another concern with meat meal is microbialcontent, and especially the potential for con-tamination with salmonella. Due to increasingawareness and concern about microbial quality,surveys show that the incidence of contaminationhas declined, but remains at around 10%. Proteinblendsareathighestrisk,becauseobviouslyasinglecontaminated source can lead to spread ofsalmonella in various blended products. One meansof reducing microbial load is to treat freshlyprocessed meals with organic acids. In many stud-ies, it is shown that meals are virtually sterile when
  • SECTION 2.1Description of ingredients48 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONthey emerge from the cooking chambers, and thatproblems most often occur with recontamination.Certainly most feed ingredients contain salmonella,however, because of the relative proportion of meatmeals used in a diet, the actual chance ofcontamination for a single bird may, in fact,come from corn (Table 2.7).The relative risk to an individual bird is,therefore, claimed to be higher from cerealsbecause, even though they are not usuallycontaminated, their much higher inclusion levelresults in a greater potential risk. However,this type of argument is open to the real criticismthat meat meals are much more likely to con-taminate the feed, trucks, equipment etc., andthat salmonella numbers will likely increaseafter feed manufacture. Pelleted and extruded/expanded diets will have much lower microbialcounts than corresponding mash diets.Unfortunately, there is variability in nutrientavailability of conventionally rendered meatmeal, where lysine digestibility, for example, canvary from 70 to 88%. Such variability is nothighly correlated with simple in vitro assayssuch as pepsin digestibility and KOH solubility.Potential problems:Meat meal should contain no more than4% phosphorus and 8% calcium, since higherash content will reduce its energy value. Nutrientavailability is variable across suppliers, and soit is important to have adequate quality controlprocedures in place, and especially when thereis a change in supplier.SalmonellaDietRelativeContamination Risk Factor(%) (%)Corn 1 60 60Vegetable proteins 8 30 24Meat meals 10 5 50Table 2.7 Relative risk due to salmonella fromvarious ingredients
  • 49CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsDry Matter 90.0 Methionine 0.71Crude Protein 50.0 Methionine + Cystine 1.32Metabolizable Energy: Lysine 2.68(kcal/kg) 2450 - 2850 Tryptophan 0.36(MJ/kg) 10.25 - 11.92 Threonine 1.52Calcium 8.0 Arginine 3.50Av. Phosphorus 4.0Sodium 0.50 Dig Methionine 0.62Chloride 0.90 Dig Meth + Cys 0.95Potassium 1.25 Dig Lysine 2.09Selenium (ppm) 0.4 Dig Tryptophan 0.26Fat 11.5 Dig Threonine 1.17Linoleic acid 1.82 Dig Arginine 2.78Crude Fiber -Nutrient Profile: (%)kg/m3 lb/ft3 lb/bushel394 37 47.4Bulk Density:Formulation Constraints:QA Schedule:Bird age Min. Max. Comments0-4 wk 6% Main concern is4-8 wk 8% level of Ca and> 8 wk 8%P, and ashMoisture CP Fat Ca/P AA’s OtherAll deliveries Yearly Fatty acid profile yearly.Salmonella each 3 months.
  • SECTION 2.1Description of ingredients50 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONAs for meat meal, poultry by-product mealis produced essentially from waste generatedduring poultry meat processing. Because onlyone species is used, PBM should be a moreconsistent product than is meat meal, andcertainly calcium and phosphorus levels will belower. Variability in composition relates towhether or not feathers are added during processingor kept separate to produce feather meal. PBMand feathers are best treated using differentconditions, because feathers require moreextreme heat in order to hydrolyze the keratinproteins. PBM with feathers may thereforemean that either the feather proteins are under-cooked or that the offal proteins are overcooked.Overcooking usually results in a much darkercolored product. PBM contains more unsaturatedfats than does meat meal, and so if much morethan 0.5% fat remains in the finished product,it should be stabilized with an antioxidant.Because of problems of disposal of spentlayers, there is now some production of ‘spenthen meal’ which is essentially produced byrendering the whole body, including feathers. Suchspent hen meal contains around 11% fat and 20%ash, with 70% crude protein. Methionine,TSAA and lysine in such samples are around 1.2%,2.5% and 3.5% respectively, with digestibilityof methionine and lysine at 85%, while cystineis closer to 60% digestible. As with poultry by-product meal, the ME of spent hen meal isinfluenced by content of ash, fat and protein, witha mean value around 2,800 kcal/kg.There is also current interest in ensilingvarious poultry carcasses and/or poultry by-products prior to heat processing. Ensilingallows for more control over microbial con-tamination prior to processing, and allows the poten-tial to better utilize smaller quantities of poultrycarcasses on-farm or from sites more distant tothe PBM processing plant. Ensiling is also beingconsidered as a means of handling spent layersprior to production of PBM. Poultry carcasses oroffal do not contain sufficient fermentable car-bohydrate to allow lactic acid fermentationwhich will quickly reduce pH to about 4.2 andstabilize the product. These lactic acid produc-ing microbes can therefore be encouraged to pro-liferate by adding, for example, 10% molasses or10% dried whey to ground carcasses. Thesemixtures quickly stabilize at around pH 4.2 – 4.5,and can be held for 10 – 15d prior to manufac-ture of PBM. Carcasses from older birds may requireslightly higher levels of theses carbohydrates, andbecause of their inherently high fat content,may be mixed with products such as soybean mealin order to improve handling characteristics.Ensiled whole carcasses, as is now being producedwith spent fowl, may present problems withavailability of feather proteins for reasons outlinedpreviously in terms of ideal processing conditionsfor tissue versus feathers. In the future, thisproblem may be resolved by adding feather-degrading enzymes to the ensiling mixture.Potential problems:Nutritive value will be positively correlatedwith protein and fat content and negativelycorrelated with ash. Cystine content will givean indication if feathers were included duringprocessing, which will detract from amino aciddigestibility.16. Poultry by-product mealOther Names: Poultry Meal, PBM Nutritional Characteristics:
  • 51CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsDry Matter 90.0 Methionine 1.3Crude Protein 60.0 Methionine + Cystine 3.3Metabolizable Energy: Lysine 3.4(kcal/kg) 2950 Tryptophan 0.4(MJ/kg) 12.34 Threonine 2.2Calcium 3.60 Arginine 3.5Av. Phosphorus 2.10Sodium 0.36 Dig Methionine 1.1Chloride 0.40 Dig Meth + Cys 2.3Potassium 0.28 Dig Lysine 2.7Selenium (ppm) 0.90 Dig Tryptophan 0.3Fat 8.50 Dig Threonine 1.8Linoleic acid 2.50 Dig Arginine 3.0Crude Fiber 1.9Nutrient Profile: (%)Bulk Density:kg/m3 lb/ft3 lb/bushel578 36.0 46.1FormulationConstraints:Bird age Min. Max. Comments0-4 wk 8% No major concerns other4-8 wk 10% than fat stability> 8 wk 10%QA Schedule:Moisture CP Fat Ca/P AA’s OtherAll samples Weekly Weekly Weekly Yearly Digestible amino acids,including cystine, yearly
  • SECTION 2.1Description of ingredients52 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION17. Feather mealNutritional Characteristics:Feather meal can be an excellent source ofcrude protein where this is needed to meetregulatory requirements. However, its use is severe-ly limited by deficiencies of several amino acids,including methionine, lysine and histidine.Feather meal usually contains about 4.5 – 5.0%cystine, and this should be around 60% digestible.The energy value of feather meal is quite high,being around 3300 kcal ME/kg, and Dale andco-workers at the University of Georgia suggestsTMEn of feather meal is highly correlated withits fat content (2860 + 77 x % fat, kcal/kg).Variability in quality is undoubtedly related tocontrol over processing conditions. Feathers arepartially dried and then steam-treated to inducehydrolysis, and within reason, the higher thetemperature and/or longer the processing time,the better the chance of complete hydrolysis.Obviously extreme processing conditions will causedestruction of heat-labile amino acids such aslysine. As a generalization, the lower the pro-cessing and drying temperatures, the lower thelevel of cystine digestibility. Research has shownprocessing conditions to result in digestiblecystine levels as low as 45% with low cookingtemperature, to as high as 65% with highertemperatures for longer durations. Becausefeather meal is an important contributor toTSAA in the diet, the level of digestible cystineis a critical factor in evaluating nutritive value.High pressure, unless for a short duration,seems to reduce amino acid digestibility, and againthis is especially critical for cystine. Underextreme processing conditions it seems as thoughsulfur can be volatilized, likely as hydrogensulfide, and so another simple test for proteinquality, is total sulfur content. Sulfur levelshould be just over 2%, and any decline is like-ly a reflection of higher than normal processingtemperature, time and/or pressure, all of whichwill adversely affect amino acid digestibility.Feather meal also contains an amino acidcalled lanthionine, which is not normally foundin animal tissue. Total lanthionine levels can there-fore be used in assaying meat meal products forpotential contamination with feathers. Lanthioninecan occur as a breakdown product of cystine, andthere are some research results which indicatea very good correlation between high lanthio-nine levels and poor digestibility of most otheramino acids. In most feather meal samples,lanthionine levels should be at 20 – 30% of totalcystine levels. A potential problem in usinglanthionine assays in quality control programs,is that it is readily oxidized by performic acid,which is a common step used in preparation ofsamples for amino acid analysis and particularlywhere cystine levels are of interest.As with other animal proteins, there is currentinterest in alternate methods of processing.Treating feathers with enzyme mixtures that pre-sumably contain keratinase enzyme togetherwith NaOH has been shown to improve overallprotein digestibility and bird performance. Morerecently, it has been shown that a pre-fermenta-tion with bacteria such as Bacillus licheniformisfor 5 d at 50ºC, produces a feather lysate that iscomparable in feeding value to soybean meal whenamino acid balance is accounted for.Potential problems:Amino acid digestibility, and especiallycystine digestibility is greatly influenced byprocessing conditions. Monitoring total sulfurlevels may be a simple method of assessingconsistency of processing conditions.
  • 53CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsNutrient Profile: (%)Dry Matter 90.0 Methionine 0.60Crude Protein 85.0 Methionine + Cystine 6.10Metabolizable Energy: Lysine 1.72(kcal/kg) 3000 Tryptophan 0.60(MJ/kg) 12.55 Threonine 4.51Calcium 0.20 Arginine 6.42Av. Phosphorus 0.70Sodium 0.70 Dig Methionine 0.47Chloride 0.40 Dig Meth + Cys 2.85Potassium 0.30 Dig Lysine 1.10Selenium (ppm) 0.72 Dig Tryptophan 0.41Fat 2.50 Dig Threonine 3.15Linoleic acid 0.10 Dig Arginine 5.05Crude Fiber 1.50Bulk Density:kg/m3 lb/ft3 lb/bushel460 28.7 36.7Formulation Constraints:Bird age Min. Max. Comments0-4 wk 2% Amino acid4-8 wk 3% digestibility the> 8 wk 3% main concernQA Schedule:Moisture CP Fat Ca/P AA’s OtherAll deliveries Weekly Monthly 6 mos 6 mos Total sulfur each 3 months
  • SECTION 2.1Description of ingredients54 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONBecause of the decline in activities of mostfisheries directed at human consumption, fish mealsare now almost exclusively produced fromsmaller oily fish caught specifically for mealmanufacture. Menhaden and anchovy are themain fish species used for meal manufacture, withlesser quantities of herring meal produced inEurope. Fish meal is usually an excellent sourceof essential amino acids, while energy level islargely dependent upon residual oil content.Because of variable oil and protein content,expected ME value can be calculated basedon knowledge of their composition in the meal.ME (kcal/kg) = 3000 ± (Deviation in % fat x8600) ± (Deviation in % CP x 3900)Where standard fat content is 2%, and CP is 60%.Therefore, a 4% fat, 63% CP sample isexpected to have an ME of 3289 kcal/kg, whilea 1% fat, 58% CP sample will have ME closerto 2836 kcal/kg. The ash content of fishmeal willbe predominantly calcium and phosphorus andthe latter can be around 90% available, as isphosphorus from any quality animal protein.All fish meals should be stabilized withantioxidants. This is especially true for high oilcontent samples, but even with only 2%residual oil, there is good evidence to showreduced oxidation (in terms of production ofoxidation products and free fatty acids, as wellas reduced heat production) by adding 100ppm ethoxyquin during manufacture.Potential problems in feeding fish meal aretaint of both eggs and meat, and gizzard erosionin young birds. With inadequately heat-treatedfishmeal, especially from fresh water fish, thereis also the potential problem of excessivethiaminase activity. Depending upon geographicallocation, taint in eggs and meat can be detectedby consumers when birds are fed much more than4 – 5% fish meal. Problems of taint will bemore acute with high fat samples, and of course,the problems are most acute if fish oil per se is used.Even at levels as low as 2.5% fish meal, some brownegg birds produce tainted eggs which may be relat-ed to the trimethylamine content of fish meal, andthe genetic predisposition of certain birds failingto produce sufficient trimethylamine oxidase.Excess trimethylamine is shunted to the egg, pro-ducing a characteristic fishy taint (see also canolameal). The trimethylamine content of fish mealis around 50 – 60 mg/kg, and assuming a 2.5%inclusion level, and feed intake of such brown egglayers of 115 g/day, means that the bird is takingin about 0.2 mg/day. Each affected egg con-tains around 0.8 mg, and so, it is obvious that thediet contains sources of trimethylamine otherthan fish meal, or that there is microbial synthe-sis in the intestine.For young chicks, and especially the broil-er chicken, a major concern with feeding fish meal,is gizzard erosion. A proportion of chicks fedalmost any level of fish meal develop gizzardlesions, although there is a strong dose-response.Affected birds have signs ranging from smalllocalized cracks in the gizzard lining, throughto severe erosion and hemorrhage which ultimatelyleads to total destruction of the lining. Thethick lining is required for preventing degradingeffects of acid and pepsin produced by theproventriculus. Because of disrupted protein18. Fish mealOther names: Herring meal; White Fish meal; Menhaden mealNutritional Characteristics:
  • 55CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsdegradation, the affected birds show very slowgrowth rate. The condition is most common whenfish meal is included in the diet, althoughsimilar signs are seen with birds fed a high levelof copper (250 ppm) or vitamin K deficientdiets, or simply induced by starvation. Gizzarderosion was initially thought to be associated withhistamine levels in fish meal. Feeding histamineto birds simulates the condition, as does feed-ing a heated semi-purified diet containing his-tidine. Fish meals contain histamine, and followingmicrobial degradation during pre-cooking stor-age, bacteria possessing histidine decarboxy-lase will convert variable quantities from histi-dine to histamine. Histamine has the effect ofstimulating excessive acid production by theproventriculus, and it is this acid environmentthat initiates breakdown of the gizzard lining. Aproduct known as gizzerosine has beenisolated from fish meal, and this hashistamine-type properties in terms of stim-ulating acid secretion. Gizzerosine is formed byheating histidine and a protein during manufactureof fish meal. The most common components arelysine and histidine. Gizzerosine is almost 10xas potent as is histamine in stimulating proven-tricular acid production and some 300x morepotent in causing gizzard erosion. Currently theonly useful screening test is to feed high levels(25 – 50%) to young chicks and score the degreeof gizzard lesions (see ingredient quality controlSection 2.2 i).Because the mode of action of gizzerosineis via acid production and a change in gizzardpH, there have been attempts at adding buffersto prevent the problem. For example addingsodium bicarbonate has been reported to lessenthe severity of gizzard erosion. However,levels as high as 10 kg/tonne are required to changegizzard pH by only 0.3 units. Variable levels ofgizzerosine in fish meals likely relate topre-processing holding time and storagetemperature, and also to the time and temper-ature of the cooking and oil extraction procedures.Potential Problems:Taint of meat or eggs can occur with muchmore than 2% fish meal in the diet. Fish mealshould be stabilized with an antioxidant, and thisfactor is critical when residual fat contentexceeds 2%. With young chicks, gizzard erosionis a consequence of using poorly processed, orinadequately stored fish meal.
  • SECTION 2.1Description of ingredients56 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONDry Matter 90.0 Methionine 1.82Crude Protein 60.0 Methionine + Cystine 2.92Metabolizable Energy: Lysine 5.28(kcal/kg) 2750 Tryptophan 0.58(MJ/kg) 11.51 Threonine 3.01Calcium 6.50 Arginine 4.05Av. Phosphorus 3.50Sodium 0.47 Dig Methionine 1.62Chloride 0.55 Dig Meth + Cys 2.42Potassium 0.32 Dig Lysine 4.72Selenium (ppm) 1.85 Dig Tryptophan 0.48Fat 2.0 Dig Threonine 2.50Linoleic acid 0.3 Dig Arginine 3.62Crude Fiber 1.0Nutrient Profile: (%)Bulk Density:kg/m3 lb/ft3 lb/bushel674 42 53.8Formulation Constraints:Bird age Min. Max. Comments0-4 wk 8% Taint problems likely in most4-8 wk 10% markets at levels much in excess> 8 wk 10% of 2%QA Schedule:Moisture CP Fat Ca/P AA’s OtherAll deliveries Monthly 12 mos Fat oxidation, gizzerosineeach 6 mos.
  • 57CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients19. Fats and oilsNutritional Characteristics:Fats provide a concentrated source of energy,and so relatively small changes in inclusionlevels can have significant effects on diet ME. Mostfats are handled as liquids, and this meansheating of most fats and fat blends that containappreciable quantities of saturated fatty acids.Depending upon the demands for pelletdurability, 3 – 4% is the maximum level of fat thatcan be mixed with the other diet ingredients. Tothis, up to 2 – 3% can be added as a spray-oncoat to the formed pellet. Alternate technologyof spraying fat onto the hot pellet as it emergesfrom the pellet die means that much higherinclusions are possible since the hot pelletseems better able to adsorb the fat. Underthese conditions, there is concern for manufacturerswho demand extreme pellet durability, since fineswill already be treated with extra fat, prior to theirrecycling through the pellet mill.All fats and oils must be treated with anantioxidant which ideally should be added at thepoint of manufacture. Fats held in heated tanksat the mill must be protected from rancidity. Themore unsaturated a fat, the greater the chanceof rancidity. Fats also provide varying quantitiesof the essential nutrient linoleic acid. Unless adiet contains considerable quantities of corn, itmay be deficient in linoleic acid, because all dietsshould contain a minimum of 1%. A major prob-lem facing the industry at the moment is theincreasing use of restaurant grease in feed-gradefats. These greases are obviously of variablecomposition in terms of fatty acid profile andcontent of free fatty acids. Also, dependentupon the degree of heating that they have beensubjected to, these greases can contain significantquantities of undesirable break-down products.In order to ensure adequate levels of linole-ic acid, and to improve palatability and reducedustiness of diets, all diets require a minimumof 1% added fat, regardless of other economicor nutritional considerations. There is consid-erable information published on factors thatinfluence fat digestibility, but in most instances,this knowledge is not used during formulation.In large part variability is due to the fact thatdigestibility is not a static entity for any fat, butrather its utilization is variable with such factorsas bird age, fat composition and inclusion level.Unfortunately, these variables are difficult tofactor into formulation programs. Other concernsabout fats are their potential for rancidity and effecton carcass composition. Following are descrip-tions of the major types of fat used in the feedindustry. Table 2.8 summarizes the fatty acidprofile and ME of the most common fat sourcesused in poultry nutrition. An attempt has beenmade to predict fat ME based on bird age.19a. TallowTallow has traditionally been the principle fatsource used in poultry nutrition. However, over thelast 10 years, there has been less use of pure tallowand greater use of blended fats and oils. Tallow issolid at room temperature and this presents someproblems at the mill, especially when heated
  • SECTION 2.1Description of ingredients58 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONMetabolizableenergyFatM.I.U.5Fattyacidprofile(%)(kcal/kg)Ingredient1122%%12:014:016:018:016:118:118:218:319aTallow740080009824.025.024.00.543.02.00.519bPoultryfat820090009821.020.04.05.541.025.01.519cFishoil860090009918.021.04.015.017.24.43.0319dVegetableoil880092009910.513.01.00.531.050.02.019eCoconutoil7000800099150.0420.06.02.50.54.02.10.219fPalmoil720080009912.042.43.50.742.18.00.419gVegetablesoapstock780081009820.318.03.00.329.046.00.819hAnimal-Vegetableblend820086009822.121.015.00.432.026.00.619iRestaurantgrease810089009821.018.013.02.542.016.01.0Table2.8Nutrientcompositionoffatsandoils1MEforyoungbirdsupto3weeksofage;2MEforbirdsafter3weeksofage;3Contains25%unsaturatedfattyacids20:4;4Contains15%saturatedfattyacids10:0;5Moisture,impurities,unsaponifiables.
  • 59CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsfats are added to very cold ingredients originatingfrom unheated outside silos. Being highlysaturated, tallow is not well digested by youngchickens, although there is some evidence ofbetter utilization by young turkeys. The digestibil-ity of tallow can be greatly improved by theaddition of bile salts suggesting this to be alimiting feature of young chicks. However, theuse of such salts is not economical and soinclusion of pure tallow must be severelyrestricted in diets for birds less than 15 – 17 d of age.19b. Poultry FatThis fat source is ideal for most types and agesof poultry in terms of its fatty acid profile. Dueto its digestibility, consistent quality and residualflavor, it is in high demand by the pet foodindustry, and this unfortunately reduces itssupply to the poultry industry.As occurs with poul-try meal, there is a concern with integratedpoultry operations that fat-soluble contaminantsmay be continually cycled (and concentrated)through the birds. This can obviously be resolvedby breaking the cycle for a 1 or 2 bird cycle.19c. Fish OilThere is current interest in the use of fish oilsin diets for humans and animals, since its distinctivecomponent of long chain fatty acids is thoughtbeneficial for human health. Feeding moderatelevels of fish oils to broiler chickens has beenshown to increase the eicosapentaenoic acidcontent of meat. However, with dietary levels inexcess of 1%, distinct fish type odour is oftenpresent in both meat and eggs, which is duemainly to the contribution of the omega-3 fatty acids.19d. Vegetable OilA large range of vegetable oils is available asan energy source, although under most situations,competition with the human food industrymakes them uneconomic for animal feeds.Most vegetable oils provide around 8700 kcalME/kg and are ideal ingredients for very youngbirds. If these oils are attractively priced asfeed ingredients, then the reason(s) for refusal bythe human food industry should be ascertainede.g. contaminants.19e. Coconut OilCoconut oil is a rather unusual ingredient inthat it is a very saturated oil. Coconut oil is moresaturated than is tallow. It contains 50% ofsaturated fatty acids with chain length less than12:0. In many respects, it is at the opposite endof the spectrum to fish oil in terms of fatty acidprofile. There has been relatively little workconducted on the nutritional value of coconutoil, although due to its saturated fatty acid contentit will be less well digested, especially by youngbirds. However recent evidence suggests veryhigh digestibility by young birds of mediumchain triglycerides, such as C:8 and C:10 asfound in coconut oil. These medium length fattyacids do not need bile for emulsification orprior incorporation within a micelle prior toabsorption.19f. Palm OilPalm oil production is now only second tosoybean oil in world production. Palm oil isproduced from the pulpy flesh of the fruit, whilesmaller quantities of palm kernel oil are extractedfrom the small nuts held within the body of thefruit. Palm oil is highly saturated, and so will havelimited usefulness for very young birds. Also, soap-stocks produced from palm oil, because of theirfree fatty acid content, will be best suited for olderbirds. There is potential for using palm andcoconut oils as blends with more unsaturated oilsand soapstocks, so as to benefit from potentialfatty acid synergism.
  • SECTION 2.1Description of ingredients60 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION19g. Soapstock (Acidulated soapstock)As a by-product of the vegetable oil refiningindustry, soapstocks provide a good source ofenergy and essential fatty acids. Soapstockscan be quite high in free fatty acids, and sostabilization with an antioxidant is essential.Soapstocks may also be acidulated, and thismay pose problems with corrosion of metallicequipment. Some impurities may be added tosoapstocks as a means of pollution-freedisposal by refineries, and therefore qualitycontrol becomes more critical with theseproducts. Moisture level may also be high in somesamples, and this simple test is worthwhile foreconomic evaluation.19h. Animal-Vegetable Blend FatSome manufacturers mix animal and vegetablebased fats, to give so-called blended products.The vegetable source is usually soapstockmaterial. The blend has the advantage of allowingfor some synergism between saturated fattyacids of animal origin and unsaturates from thesoapstock. Animal-vegetable blends are there-fore ideally suited for most classes of poultrywithout the adverse problem of unduly increasingthe unsaturates in meat which can lead to increasedrate of oxidative rancidity (reduced shelf life).19i. Restaurant GreaseAn increasing proportion of feed fats isnow derived from cooking fats and oils, and thegeneric product is termed restaurant grease. Itsuse has increased mainly due to problems ofalternate disposal. Traditionally restaurantgreases were predominately tallow or lard basedproducts and this posed some problems incollection and transportation of the solidmaterial. In recent years, due to consumerconcerns about saturated fats, most major fast foodand restaurant chains have changed to hydro-genated vegetable cooking fats and oils. The fatsare hydrogenated to give them protection againsthigh-temperature cooking. Today, restaurantgreases contain higher levels of oleic acid, andmuch of this will be trans-oleate. Assuming therehas not been excessive heating, and that the greasehas been cleaned and contains a minimum ofimpurities, then the energy value will becomparable to that of poultry fat. Future use ofnon-fat ‘cooking fats’ will lead to considerablevariation in the nutrient profile of these products.19j. Conjugated Linoleic Acid (CLA)CLA is an isomer of conventional linoleic acid,but unlike linoleic, there are numerous healthbenefits claimed for CLA. It is claimed to helpcontrol glucose metabolism in diabetic mammals,and more importantly to prevent and/or controlthe growth of certain cancerous tumors. CLA isnormally found in dairy products, represent-ing around 0.3% of total fat. Turkey meat is alsohigh in CLA. Feeding CLA to layers results inbioaccumulation in the egg, much as for any fattyacid, and so there is potential for producing CLAenriched designer eggs. It seems as though theAMEn of CLA is comparable to that of linoleicacid, suggesting that the two fatty acids arecomparably metabolized.It is possible that CLA is not elongated as inlinoleic acid during metabolism and so this hasposed questions about adequacy of prostaglandinsynthesis, and hence immune function. Thereare some reports of altered lipid metabolism inembryos and young chicks from eggs hatched fromhens fed 1 g CLA daily. There is some discussionabout whether or not synthetic sources of CLAactually mimic the beneficial anti-cancerousproperties of ‘natural’ CLA found in dairyproducts.
  • 61CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsImportant Considerations:Fats and oils are probably the most problem-atic of all the ingredients used in poultry feeds.Theyrequire special handling and storage facilitiesand are prone to oxidation over time. Their fattyacid profile, the level of free fatty acids and degreeofhydrogenationcanallinfluencedigestibility. Unlikemost other ingredients, fat digestion can be agedependent, since young birds have reduced abil-ity to digest saturated and hydrogenated fats.a. Moisture, Impurities, UnsaponifiablesFeed grade fats will always contain somenon-fat material that is generally classified as M.I.U.(moisture, impurities and unsaponifiables).Because these impurities provide no energy orlittle energy, they act as diluents. A recentsurvey indicated M.I.U’s to range from 1 – 9%.Each 1% MIU means a loss in effective value ofthe fat by about $3 - $4/tonne, and moreimportantly, energy contribution will be lessthan expected. The major contaminants aremoisture and minerals. It seems as thoughmoisture can be quickly detected by Near InfraRed Analysis. Moisture and minerals also leadto increased peroxidation.b. Rancidity and OxidationThe feeding value of fats can obviously beaffected by oxidative rancidity that occurs priorto, or after feed preparation. Rancidity caninfluence the organoleptic qualities of fat, as wellas color and ‘texture’ and can cause destructionof other fat soluble nutrients, such as vitamins,both in the diet and the bird’s body stores.Oxidation is essentially a degradation process thatoccurs at the double-bond in the glyceridestructure. Because presence of double-bonds infersunsaturation, then naturally the more unsaturateda fat, the greater the chance of rancidity. Theinitial step is the formation of a fatty free radicalwhen hydrogen leaves the -methyl carbon inthe unsaturated group of the fat. The resultantfree radical then becomes very susceptible to attackby atmospheric oxygen (or mineral oxides) to formunstable peroxide free radicals. These peroxidefree radicals are themselves potent catalysts,and so the process becomes autocatalytic andrancidity can develop quickly. Breakdownproducts include ketones, aldehydes and shortchain fatty acids which give the fat its characteristic‘rancid’ odour. Animal fats develop a slightrancid odour when peroxide levels reach 20meq/kg while for vegetable oils problems startat around 80 meq/kg.Oxidative rancidity leads to a loss in energyvalue, together with the potential degradation ofthe bird’s lipid stores and reserves of fat-soluble vitamins. Fortunately we have somecontrol over these processes through the judicioususe of antioxidants. Most antioxidants essentiallyfunction as free radical acceptors – theseradical-antioxidant complexes are, however,stable and do not cause autocatalytic reactions.Their effectiveness, therefore, relies on adequatedispersion in the fat immediately after process-ing. As an additional safety factor, most diets willalso contain an antioxidant added via the premix.The Active Oxygen Method (AOM) is most com-monly used to indicate potential for rancidity. After20 h treatment with oxygen, quality fats shoulddevelop no more than 20 meq peroxides/kg.Time is a very important factor in the AOMtest, because peroxides can break down anddisappear with extended treatment. For thisreason, some labs will provide peroxide valuesat 0, 10 and 20 hr. A newer analytical techniqueis the Oil Stability Index (OSI). This is similar toAOM, but instead of measuring initial peroxideproducts, measures the accumulation of secondarybreakdown compounds. The assay is highly auto-mated and records the time necessary to producea given quantity of breakdown products such asshort chain volatile fatty acids.
  • SECTION 2.1Description of ingredients62 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONc. Fatty Acid ProfileFat composition will influence overall fatutilization because different components aredigested with varying efficiency. It is generallyrecognized that following digestion, micelleformation is an important prerequisite to absorp-tion. Micelles are complexes of bile salts, fattyacids, some monoglycerides and perhapsglycerol. The conjugation of bile salts withfatty acids is an essential prerequisite fortransportation to and absorption throughthe microvilli of the small intestine. Polarunsaturated fatty acids and monoglyceridesreadily form this important association. However,micelles themselves have the ability tosolubilize non-polar compounds such as satu-rated fatty acids. Fat absorption is, therefore,dependent upon there being an adequatesupply of bile salts and an appropriate balanceof unsaturates:saturates.Taking into account the balance of saturatedto unsaturated fatty acids can be used to advan-tage in designing fat blends. This type of synergisticeffect is best demonstrated using pure fatty acids(Table 2.9). In this study, the metabolizableenergy of the 50:50 mixture of the unsaturatedoleic acid with the saturated palmitic acid, is 5%higher than the expected value based on the meanvalue of 2710 kcal/kg. We therefore have a boostof 5% in available energy that likely comesfrom greater utilization of the palmitic acidbecause of the presence of the unsaturatedoleic acid.This type of synergism can, however, have aconfounding effect on some research results. Ifwe want to measure the digestibility of corn, itis possible to feed just corn for a short period oftime and conduct a balance study. For obviousreasons, it is impossible to feed only fats, and wehave to conduct studies involving graded fatadditions to a basal diet, with extrapolation ofresults to what would happen at the 100%feeding level. In these studies, we assume thedifference in digestibility between any two dietsis due solely to the fat added to the diet. If, becauseof synergism, the added fat improved digestibilityof basal diet components, then this ‘boost’ indigestibility is attributed to the fat and an erro-neously high value is projected. However, it canbe argued that this ‘boost’ to fat’s value occursnormally when fats are added to diets, and thatthese higher values more closely reflect thepractical value of fat in a poultry diet. We haveproposed this synergism to account for some ofthe so-called ‘extra-caloric’ effect of fat often seenin reported values, where metabolizableenergy can sometimes be higher thancorresponding gross energy values (whichtheoretically cannot occur). Table 2.10 showsresults from this type of study where corn oil wasassayed using different types of basal diet.Table 2.9 Metabolizable energy oflayer diets containing various fattyacids(Atteh and Leeson, 1985)Determined ExpectedME (kcal/kg)Oleic 2920Palmitic 250050:50 mixture 2850 (+5%) 2710
  • 63CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsWhen the basal diet contains saturated fattyacids, there is an apparent increase in the ME ofcorn oil. This effect is possibly due to the unsat-urates in corn oil aiding in utilization of the basaldiet saturates. However, because of methods ofdiet substitution and final ingredient MEcalculation, any such synergism is attributedto the test ingredient (corn oil).ME values of fats will therefore vary withinclusion level, although this effect will beinfluenced by degree of fat saturation. A ratioof 3:1, unsaturates:saturates is a good compro-mise for optimum fat digestibility for all ages ofbird. However, this ratio may not be the mosteconomical type of fat to use, because of theincreased cost of unsaturates relative to saturates.d. Level of Free Fatty Acids and FattyAcid HydrogenationConcern is often raised about the level of freefatty acids in a fat, because it is assumed theseare more prone to peroxidation. Acidulatedsoapstocks of various vegetable oils containthe highest levels of free fatty acids, which canreach 80 – 90% of the lipid material. For youngbirds there is an indication that absorption of fattyacids is highest in birds fed triglycerides ratherthan free fatty acids and this may relate to lessefficient micelle formation or simply to lessbile production. Wiseman and Salvadore (1991)demonstrated this effect in studying the MEvalue of tallow, palm oil and soy oil that containedvarious levels of free fatty acids (soapstock of therespective fat). Table 2.11 shows a summary ofthese results, indicating energy values for therespective fats containing the highest andlowest levels of free fatty acids used.Table 2.10 Variation in ME value ofcorn oil attributed to fatty acidsaturation of the basal dietBasal diet Corn oil ME(kcal/kg)Predominantly unsaturated 8390aPredominantly saturated 9380bCorn-soy diet 8510aTable 2.11 Effect of level of freefatty acid and bird age on fat MEvalue (kcal/kg)Age10 d 54 dTallow 13% FFA 7460 794095% FFA 4920 6830Palm 6% FFA 6690 780092% FFA 3570 6640Soy 14% FFA 9290 930068% FFA 8000 8480Adapted from Wiseman and Salvador (1991)These data suggest that free fatty acids are moreproblematic when the fat is predominantlysaturated and this is fed to young birds. Contraryto these results, others have shown comparableresults with broilers grown to market weightand fed tallows of varying free fatty acid content.Hydrogenation of fats becomes an issuewith the general use of these fats in restaurants,and the fact that restaurant grease is now acommon, and sometimes the major compo-nent of feed-grade fat blends. Hydrogenationresults in a high level of trans oleic acid (40 – 50%)and such vegetable oils have physical characteristicssimilar to those of lard. There seems to be noproblem in utilization of these hydrogenated fatsby poultry with ME values of restaurant greasesbeing comparable to those of vegetable oils. Thelong-term effect of birds eating trans fatty acidsis unknown at this time.
  • SECTION 2.1Description of ingredients64 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONe. Bird Age and Bird TypeYoung birds are less able to digest saturatedfats, and this concept has been known for sometime. With tallow, for example, palmitic aciddigestibility increases from 50 to 85% through14 to 56 d of age, which together with corre-sponding changes for other fatty acids means thattallow ME will increase by about 10% over thistime period.The reason why young birds are lessable to digest saturated fats is not well understood,although it may relate to less bile salt production,less efficient recirculation of bile salt or lessproduction of fatty acid binding protein.f. Soap FormationWhen fats have been digested, free fattyacids have the opportunity of reacting withother nutrients. One such possible associationis with minerals to form soaps that may or maynot be soluble. If insoluble soaps are formed, thereis the possibility that both the fatty acid and themineral will be unavailable to the bird. There issubstantial soap formation in the digesta ofbroiler chicks and this is most pronounced withsaturated fatty acids, and with increased levelsof diet minerals. Such increased soap productionis associated with reduced bone ash and bonecalcium content of broilers. Soap production seemsto be less of a problem with older birds. This isof importance to laying hens that are fed highlevels of calcium. In addition to calcium, otherminerals such as magnesium can form soaps withsaturated fatty acids. In older birds and some otheranimals, there is an indication that while soapsform in the upper digestive tract, they aresubsequently solubilized in the lower tract dueto changes in pH. Under these conditions boththe fatty acid and mineral are available to the bird.Control over digesta pH may, therefore, be animportant parameter for control over soapformation.g. Variable ME ValuesIt seems obvious that the use of a singlevalue for fat ME during formulation is a com-promise, considering the foregoing discussion onfactors such as inclusion level, bird age, soapformation etc. Table 2.8 gives different MEvalues for birds younger or older than 21 d, andthis in itself is a compromise. Following is anattempt to rationalize the major factors affectingME of a given fat, although it is realized that suchvariables are not easily incorporated within aformulation matrix (Table 2.12).Table 2.12 Factors affecting fat MEvaluesRelative fat ME28 d+ 100%Bird age: 7 - 28 d 95%1 – 7 d 88%(esp. for saturates)0 – 10% 102%Free fatty 10 – 20% 100%acids: 20 – 30% 96%30%+ 92%(esp. for saturates)1% 100%2% 100%Inclusion level: 3% 98%4% 96%5%+ 94%<1% 100%Calcium level: >1% 96%(esp. for birds <56 dof age)
  • 65CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsh. Trans Fatty AcidsTrans fatty acids are isomers of naturallyoccurring cis fatty acids. Trans fatty acids are oftenproduced by the process of hydrogenation, ascommonly occurs in production of margarine andother cooking fats. Hydrogenated (stabilized)soybean oil, which is a common component ofcooking oils, contains around 20% trans fatty acids.With increasing use of restaurant grease inanimal fats and fat blends, it seems inevitable thatfats used in the feed industry will contain higherproportions of trans fatty acids than occurred some20 years ago. It is thought that ‘overused’ fryingoil, that contains trans fatty acids as well asoxidized and polymerized materials, is harmfulto human health. These trans fatty acids can befound in human adipose tissue, and have beenassociated with immune dysfunction andunusual lipid metabolism in heart tissue. Thereis very little information available on the effectof trans fatty acids on health of broilers or layers.OTHER INGREDIENTS20. OatsOats are grown in cooler moist climatesalthough they are of minor importance on a glob-al scale, representing only about 1.5% of totalcereal production. Most oats are used for ani-mal feed, and about 85% of this quantity isused locally and there is little trade involved. Thehull represents about 20% of the grain by weight,and so this dictates the high fiber – low energycharacteristics of oats. The amino acid profileis however quite good, although there is somevariation in protein and amino acid levels dueto varietal and seasonal effects. The best predictorof the energy value of oats, is simply the crudefiber content which is negatively correlatedwith ME. Oat lipids are predominantly oleic andlinoleic acid, although a relatively high pro-portion of palmitic acid leads to a ‘harder’ fat beingdeposited it the bird’s carcass.As for other small grains, oats contain an appre-ciable quantity of ß-glucans, and these cause prob-lems with digesta and excreta viscosity. Most oatscontain about 3-7% ß-glucans and so withmoderate inclusion levels of oats in a poultry dietit may be advantageous to use supplemental ß-glucanase enzyme. There has been some inter-est in development of so-called naked oats,which are similar in composition to oat groats.Naked oats contain up to 17% CP with 0.68%lysine and 1% methionine plus cystine. The MEvalue is around 3200 kcal/kg, making theseoats comparable to wheat in most characteristics.As with regular oats, ß-glucans can still beproblematic and their adverse effect can beovercome with use of exogenous enzymes, andto a lesser extent antibiotics such as neomycin.Much of the phosphorus in naked oats is asphytic acid, and so availability is very low.There have been some reports of reducedskeletal integrity in birds fed naked oats unlessthis reduced phosphorus availability is takeninto account. There are reports of broilersperforming well with diets containing up to40% naked oats, and with layers, up to 50% hasbeen used successfully.21. RyeAlthough the nutrient content of rye is essen-tially similar to that of wheat and corn, itsfeeding value for poultry is poor due to thepresence of various antinutritional factors. Ryecontains a water insoluble fraction, which ifextracted, improves its feeding value. Various othertreatments such as water soaking, pelleting,irradiation and the dietary supplementation ofvarious antibiotics all help to improve the growthof chicks fed rye.
  • SECTION 2.1Description of ingredients66 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONOne of the most noticeable effects of feedingrye, other than reduced performance is theproduction of a very sticky and wet excreta.The sticky droppings are due to the pectin-likecomponentspresentinrye. Structuralarabinoxylans,present in rye endosperm cell walls, are respon-sible for creating the viscous digesta. Theseviscous products reduce the rate of diffusion ofother solutes in the digesta so affecting nutrientuptake from the gut. In recent years enzymepreparations have been developed that markedlyreduce the antinutritional factor and eliminate thewet-sticky fecal problem with rye based diets.22. TriticaleTriticale is a synthetic small grain cerealresulting from the intergeneric cross of wheat andrye. Its higher yield per acre, as compared to ryeor wheat, make it of agronomic interest in areasof the world not suitable for corn production.Numerous cultivars have been developed withprotein contents varying from 11 to 20% andamino acid balance comparable to wheat andsuperior to that of rye. Energy content is alsosimilar to that of wheat and superior to that ofrye. Like wheat, triticale has a significantphytase content and so is a better source ofavailable phosphorus than other cereals such ascorn or milo. There are reports of increasedenhancement of other dietary phosphorus withtriticale supplementation. The starch content oftriticale is as digestible as that of wheat andpresents no wet litter or sticky manure problem.Where triticale is available, high levels can be usedin poultry diets without any adverseproblems. Similar to wheat and rye it containslittle or no xanthophylls and with fine grinding canresult in beak impaction with young birds. Alsolike wheat its feeding value can be increased byappropriate enzyme supplementation of the diet.23. MolassesMolasses is a by-product of the sugar refiningindustry, where either sugar beet or sugar caneare used as raw materials. Because of a high watercontent and concomitantly low energy value, itis only used extensively in poultry diets in areasclose to sugar refineries. The molasses usuallyavailable for animal feeding is so called final orblackstrap molasses, which is the productremaining after most of the sugar has beenextracted for human consumption. Dependingupon local conditions, high-test and type A andB molasses are sometimes available. Thehigh-test product is basically unrefined caneor beet juice that has had its sugars inverted toprevent crystallization. Type A and B molassesare intermediate to final molasses. As expected,the energy level of molasses decreases as moreand more sugar is extracted. Molasses is usuallyquantitated with a Brix number, measured indegrees, and these numbers relate very closelyto the sucrose concentration in the product.Both cane and beet molasses contain about46 - 48% sugar.Although molasses contains relatively littleenergy and protein, it can be used to advantage tostimulate appetite and to reduce dustiness of feed.For example, feed intake is usually increased in birdssuch as young Leghorn pullets, if molasses ispoured directly onto feed in the feed trough. It isdoubtful that molasses improves ‘taste’ of feedunder these conditions, rather it presents a novelfeed texture to the bird. A major problem withmolasses is a very high potassium content, at 2.5– 3.5%, which has a laxative effect on birds.While most birds perform well on balanced dietscontainingupto2%molasses,inclusionlevelsmuchabove 4% will likely result in increased waterintake and increased manure wetness.
  • 67CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredients24. Dehydrated AlfalfaDehydrated alfalfa meal can be quite high inprotein (18 – 20%) although because theproduct is heated during drying, availability ofessential amino acids such as lysine is often 10to a 20% below expected values. Alfalfa isvery high in fiber content, and is most often addedto poultry diets as a source of xanthophylls forpigmentation, or as a source of so-calledunidentified growth factors.Alfalfa products should contain a minimumof 200,000 IU vitamin A activity per kg, althoughin most cases this will only be 70% available. Inorder to achieve intense yellow skin color inbroilers or egg yolk color of 10 on the Rochescale, diets should contain 5% alfalfa as one sourceof xanthophylls in the diet. Alfalfa levels muchin excess of 5% have only a moderate effect onpigmentation and so other natural or syntheticsources must be used to ensure consistentlyhigh levels of pigmentation. At high levels ofinclusion (20%) problems can arise due to thesaponins and phenolic acids normally presentin alfalfa. If alfalfa contains any appreciable moldcount, then estrogen level can be high. Fresh grassis thought by some nutritionists to contain anunidentified growth factor which is of particularsignificance to turkeys, although much of thisfactor is destroyed by the dehydrating process.Even so, many nutritionists still insist on adding1 – 2% dehydrated alfalfa to turkey feeds,especially pre-starter and starter diets. Theaddition of small quantities of alfalfa also imparta darker color to diets which helps mask any minorfluctuations in appearance due to regular changesin formulations. The quality of alfalfa productshas been improved considerably in recent yearsdue to the use of inert gas storage, pelleting andaddition of antioxidants.25. Full-fat Canola SeedsThe nutrient profile of canola seed makes it anideal ingredient for high nutrient dense diets.Periodically, grades unfit for oil extraction areavailable for animal feeding. Canola seed suffersfrom the same problems as described for canolameal, although obviously most harmful elementsare diluted by the high oil content. Seeds must beground adequately to ensure normal digestion, andthis is best accomplished by mixing with groundcorn prior to passing through a hammer mill.The oil provides considerable energy, and is an excel-lent source of linoleic acid. The ground seed is nottoo oily, and so provides a practical way of addingconsiderable quantities of fat to a diet. Due to earlyfrost damage, some samples of canola contain oilthat is contaminated with chlorophyll – while unac-ceptabletothehumanfoodindustry, thiscontaminantdoesnotseemtoposeanymajorproblemstopoultry.26. Groundnut (Peanut) MealThe peanut is an underground legume, andbecause of warm moist conditions in the soil, isvery susceptible to fungal growth with aspergilluscontamination being of most concern. Grownessentially for their oil, peanuts yield a solventextracted meal containing 0.5 – 1% fat with about47% protein. As with soybeans, peanuts con-tain a trypsin inhibitor that is destroyed by theheating imposed during oil extraction. Potentialaflatoxin contamination is the major problem withgroundnut meal. Being a potent carcinogen,aflatoxin causes rapid destruction of the liver, evenat moderate levels of inclusion. Peanut meal thatis contaminated with aflatoxin can be treated byammoniation which seems to remove up to95% of the toxin. Alternatively, products suchas sodium-calcium aluminosilicates can beadded to the diet containing contaminatedgroundnut because these minerals bind with afla-toxin preventing its absorption.
  • SECTION 2.1Description of ingredients68 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION27. PeasPeas are a medium energy-protein ingredientthat can be used effectively in poultry dietsdepending upon local economical conditions.The major limitation to using peas is low levelsof sulfur amino acids and moderate energylevel. With high-tannin peas, there may be anadvantage to some type of heat treatment,although such processing is of little value forregular pea varieties. Protein digestibility isreduced by about 6% for each 1% increase intannin content. Peas do have some of theircarbohydrate as oligosaccharides, and so enzymesystems being developed to improve the digestibil-ity of soybean meal may be of use with peas.Peameal is a very dense material and bulkdensity of the final diet should be taken intoconsideration for diets containing > 15% peas.28. SafflowerSafflower is grown mainly for its oil contentwhich, although variable, can be as high as40%. The residual meal contains in excess of 20%fiber and is referred to as undecorticated safflowermeal. It is possible to commercially remove alarge portion of the hull resulting in a mealcontaining 42 to 44% protein with a fibercontent of around 14%. This product is referredto as decorticated meal. Safflower meal is verydeficient in lysine, although with appropriate lysinesupplementation the protein quality of safflowermeal is similar to that of soybean meal. However,with the high fiber content the available energyis still relatively low and so its value does not equalthat of soybean meal. Where safflower meal isavailable, relatively large quantities can be usedin poultry diets if proper consideration is givento nutrient availability.29. Sesame MealSesame meal is very deficient in availablelysine, and this is sometimes used to advantagein formulating lysine-deficient diets for experi-mental reasons. Sesame also contains highlevels of phytic acid which can cause problemswith calcium metabolism leading to skeletaldisorders or poor eggshell quality. If dietscontain >10% sesame, then the diet should beformulated to contain an extra 0.2% calcium.30. LupinsLow alkaloid lupins are being increasinglyused as an alternative feedstuff for poultry incertain areas of the world. These new cultivars havebeen reported to contain low levels of the toxic alka-loids (less than .01%) normally found in wild vari-eties. Theselowalkaloidlupinseedsareoftenreferredto as sweet lupins and can vary in seed color.The high level of fiber in the seeds (up to 25%) resultsin low metabolizable energy values compared tosoybean meal. Mature lupin seeds contain little orno starch, the bulk of their carbohydrate beingoligosaccharides (sugars) and non-starch poly-saccharides. Many reports suggest that sweetlupins are comparable to soybeans in terms of pro-tein quality although they are much lower inmethionine and lysine. Their low oil content (6 to10%) and absence of antinutritive factors means thatthey can be inexpensively processed. Recentstudies have shown that dehulling lupins results ina marked increase in nutritive value. Also with prop-er dietary enzyme supplement the feeding value ofraw lupins is improved. Fine grinding also aidsdigestibility.31. Blood MealBlood meal is very high in crude protein, andwhile it is an excellent source of lysine, it is verydeficient in isoleucine and this imbalance needscorrecting if any substantial quantity is used ina diet. Blood meal is essentially the solids of theblood from processing plants, and consistsmainly of hemoglobin, cell membranes, cellu-lar electrolytes and a small quantity of lipid.
  • 69CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsHistorically, the level of blood meal used indiets has been severely limited, mainly becauseof problems of palatability, poor growth rateand abnormal feathering. All these problems relateto inherent amino acid balance and also to lowdigestibility induced by overheating of the bloodduring processing. With less harsh dryingtreatments, the amino acids are more stable, andthere are few problems with palatability. Ifblood meal is overheated, it has a muchdarker color, tending to be black rather thanreddish-brown. The amino acid balance ofblood meal can be ‘improved’ by combining itwith other ingredients. For example, a 50:50mixture of blood meal and hydrolyzed hairmeal gives a product with a reasonable aminoacid balance, and certainly a balance that ispreferable to either product alone. Such amixture may be used in least-cost formulation,whereas either ingredient is unlikely to be usedindependently because of amino acid balance.32. Sources of Calcium,Phosphorus and SodiumCalciumConstraints are not usually imposed on theseingredients because there should be fairlystringent constraints imposed on minimum andmaximum levels of calcium and phosphorus ina diet. There has been considerable controversyin the past concerning the relative potency oflimestone vs oyster shell as sources of calcium,especially for the laying hen. Perhaps of moreimportance than the source of calcium, isparticle size. Usually the larger the particlesize, the longer the particle will be retained inthe upper digestive tract. This means that thelarger particles of calcium are released moreslowly, and this may be important for thecontinuity of shell formation, especially in thedark period when birds are reluctant to eat.Oyster shell is a much more expensive ingredientthan limestone, but it offers the advantage of beingclearly visible in the diet to the egg producer andso there is less chance of omission during feedmanufacture. Birds also have some opportunityat diet self-selection if oyster shell is given, andthis may be of importance in maintainingoptimum calcium balance on egg-forming vs nonegg-forming days. There are current limitationson oystershell dredging in the Chesapeakeregion of the U.S.A., due to environmentalissues, and this may add to the discrepency inprice between oystershell and limestone.Limestone should be in as large a particle sizeas can be readily manipulated by the bird’sbeak. For laying hens, this means a fairly coarsecrumble consistency. There has been someconcern in recent years regarding the variabil-ity in solubility of limestone from various sources.This can easily be checked by measuring pHchanges when limestone is added to hydro-chloric acid at initial pH of 4.0. Obviously100% solubility is desirable, yet ideally thisshould be achieved over a prolonged period oftime which hopefully correlates with the slowrelease of calcium into the blood stream.Periodically, dolomitic limestone is offeredto the feed industry. Dolomitic limestonecontains at least 10% magnesium, and this com-plexes with calcium or competes withcalcium for absorption sites. The consequence offeeding dolomitic limestone is inducedcalcium deficiency, usually manifested by poor skele-tal growth or egg shell quality. The major user ofdolomitic limestone is the steel industry and so prob-lems with this ingredient seem to mirror the eco-nomic malaise in steel production. Dolomitic lime-stone should never be used in poultry diets.PhosphorusA considerable number of inorganicphosphorus sources are used around the world.
  • SECTION 2.1Description of ingredients70 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONMost naturally occurring phosphate sources areunavailable to the bird unless they are heat-treated during processing. As with limestone, thesolubility in HCl at pH 4 can be used as a meas-ure of quality. Insoluble phosphate sources areunlikely to be available to the bird –however solubility is not a guarantee of subse-quent availability. Solubility tests are thereforeonly useful in screening out insoluble sources. Testsfor biological availability are much more com-plex, because they necessarily require a chick bioas-say where growth and bone ash are measured.The phosphorus in most phosphate sourceswith the exception of soft phosphate, can beregarded as close to 100% available. Rockphosphate and Curaco phosphate are the majorexceptions because these sources may only be60 – 65% available to the bird. Anhydrousdicalcium phosphate is about 10% less availablethan the hydrated form, and this seems to relateto solubility. In this context, ingredients thatstimulate gastric secretion, and hence HClproduction, seem to result in improved utiliza-tion of the anhydrous form. Some rock phosphatescontain various contaminants of concern forpoultry. The most common of these is vanadium.At just 7 – 10 ppm of the diet, vanadium will causeloss in internal egg quality and hatchability. Atslightly higher levels (15 – 20 ppm), there is achange in the shell structure where the shell takeson a somewhat translucent appearance, andappears more brittle. Rock phosphates canalso contain as much as 1.5% fluorine. Becausefluorine can influence calcium metabolism,there are often regulations governing themaximum permissible levels in feed. Only de-fluorinated rock phosphates are recommendedalthough it must be remembered that thisproduct usually contains about 5% sodium.Most mineral sources are detrimental to thepelleting process because they create significantfriction at the pellet die. With phosphates,there is a distinct advantage to using rockphosphates rather than mono- or dicalciumphosphate in terms of pelleting efficiency, whereup to +10% throughput is achieved.Sodium SourcesMost diets will contain some added salt,usually in the form of sodium chloride. Whereiodine is not added as a separate ingredient, iodizedsalt must be used. In most countries the varioussalt forms are differentiated by color, withcommon salt being a natural white color andiodized salt being red. Cobalt iodized salt is oftenused in diets for swine and ruminants, and thiscan be used without any problems for poultry.This type of salt is usually colored blue. Becausehigh levels of sodium chloride can lead toincreased water intake, then a substitution ofsodium bicarbonate for a portion of this chloridesalt has been shown to be beneficial. Under thesecondition, up to 30% of the supplemental saltcan be substituted with sodium bicarbonatewithout loss in performance, and such birdsoften produce drier manure. For substitutions ofsodium bicarbonate for sodium chloride above30%, care must be taken to balance dietarychloride levels, since under commercial conditionsit is often difficult to add inexpensive sources ofchloride other than salt. Chloride contributedby ingredients such as choline chloride andlysine-HCl should be accommodated duringformulation. There is a trade-off when substitutingsodium bicarbonate for sodium chloride underheat-stress conditions. Birds will drink lesswhen NaHCO3 is used, and this is the reasonfor substitution. However, we really have toquestion this scenario, since higher levels of waterintake are correlated with survival under extremeheat stress conditions. Sources of calcium,phosphorus and sodium are given inTable 2.13.
  • 71CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsTable 2.13 Calcium, phosphorus and sodium sourcesIngredient % Ca % PLimestone 38.0 -Oyster shell 38.0 -Calcium carbonate 40.0 -Bone meal 26.0 13.0Monocalcium phosphate 17.0 25.0Dicalcium phosphate 21.0 20.0Tricalcium phosphate 23.0 19.0Defluorinated rock phosphate 34.0 19.0Curaco phosphate 35.0 16.0Phosphoric acid (75%) - 25.0Ingredient % Na % ClPlain salt 39.0 60.0Iodized salt 39.0 60.0 (I, 70 mg/kg)Cobalt iodized salt 39.0 60.0 (I, 70 mg/kg; Co, 40 mg/kg)Sodium bicarbonate 27.0 -33. Trace MineralsTrace minerals are available in a variety offorms, and periodically problems arise due to lackof knowledge of the composition, and/or stabilityof mineral salts. Most research into mineralavailability has been conducted with so-calledreagent-grade forms of minerals, which are verypure and of known composition and purity.Unfortunately, the feed industry cannot afford theluxury of such purity, and so obviously, feed gradeforms are used.One of the most important factors toascertain prior to formulation is the state ofhydration of a mineral. Many mineral formscontain ‘bound’ water which obviously dilutesthe effective mineral concentration. Forexample, hydrated cupric sulphate (whitecrystal) contains about 40% copper, whereas themore common pentahydrate (blue) contains26% copper. It should also be emphasizedthat the various processing conditions used inmanufacturing will likely influence mineralbioavailability. A combination of these twofactors can mean a substantially lower potencyof trace mineral sources relative to chemical stan-dard values (Table 2.14). For this reason, feedmanufacturers are encouraged to take great
  • SECTION 2.1Description of ingredients72 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONcare in ordering trace minerals based on valency,hydration and purity. All minerals sourcesshould be analyzed, on an ‘as is’ basis for the majormineral component.Because feed manufacturers are oftenconcerned about ‘space’ in the diet duringformulation, there is a trend towards makingvery concentrated mineral and vitaminpremixes. In considering concentration of min-eral sources, oxides appear attractive, since theyinvariably contain the highest mineral concen-tration. Oxides however, are potent oxidizingagents, and if stored with premixed vitaminsfor any length of time, can cause the destructionof vitamins that are susceptible to oxidation.Since oxides are generally less available than othermineral salts, they should not be used exclusivelyin mineral premixes.CobaltThe major source of cobalt is cobalt sulphateor cobalt carbonate. Both products are goodsources of cobalt, with the cobalt as sulphate beingslightly more available than in the carbonateform. Cobalt oxide has very low availability,and should not usually be considered duringformulation.CopperCopper oxide, sulphate and carbonate are usedby the feed industry. Copper oxide can be of verylow biological availability, especially with poorquality samples that contain significant amountsof metallic copper. Good quality copper oxide canbe considered as available as is copper sulphate.As previously mentioned, the degree of hydrationof copper sulphate must be specified.Table 2.14 Trace mineral sources1Cupric; 2Ferrous; 3FerricIngredient% ofmajormineraloxide 71.0Cobalt chloride 24.0sulphate 21.0carbonate 46.0oxide179.0Copper chloride 37.0sulphate 25.5carbonate 55.0oxide277.0Iron chloride334.0sulphate232.0carbonate240.0oxide 56.0Magnesiumcarbonate 30.0% ofIngredient majormineraloxide 77.0Manganesechloride 27.5sulphate 32.5carbonate 47.0oxide 78.0Zincchloride 48.0sulphate 36.0carbonate 52.0Seleniumsodium selenite 46.0sodium selenate 42.0Iodinepotassium iodine 77.0calcium iodate 65.0
  • 73CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsIronFerrous salts should be used in feed manu-facture. As with copper, the major contaminantcan be the metal itself, and this has a very lowbiological availability. Ferrous carbonate and fer-rous sulphate are the preferred forms of iron.Ferrous salts are prone to chemical change dur-ing storage, such that 10 – 20% of ferric salts canbe produced from original ferrous forms after 3–6 months storage at around 25ºC.MagnesiumMagnesium carbonate and oxide are bothavailable in feed grade form. The oxide can takeup both water and carbon dioxide when storedfor any length of time, and such activity obviouslyreduces the relative potency of magnesium.ManganeseThe major source of manganese used in thefeed industry is manganese oxide. Sulphateand carbonate sources both have higher biologicalavailability, yet these are usually uneconomicalto use. Manganese oxide has a biologicalavailability of 50 – 70%, yet this can be greatlyinfluenced by its major contaminant, namelymanganese dioxide. Manganese dioxide isonly 50% as bioavailable as is the oxide, and soan appreciable content of dioxide can lead to amarked reduction in effectiveness of manganeseoxide. Oxides should not contain more than 10%dioxides, and undoubtedly the range of availabilityquoted in research findings is usually areflection of dioxide contamination.ZincZinc oxide and zinc sulphate are the mostcommon forms of zinc used in the feedindustry. Zinc is often used as a catalyst invarious industrial processes, and unfortunately cat-alysts sometimes find their way into the feedindustry and are of low biological availability.Zinc sources can be contaminated withaluminum,leadandcadmium. Ifgoodqualitysourcesare considered, then zinc oxide and zinc sulphateappear to be of comparable biological availability.SeleniumSelenium is most often added to feeds assodium selenite or sodium selenate. The mostcommon naturally occurring form of seleniumis selenomethionine, and this seems to have a muchlower potency than either of the salt forms.There seems to be a greater availability ofselenium within low protein diets, althoughthis may be related to the fact that when birdsare growing at a slower rate, their absoluteselenium requirement is reduced. Seleniumavailability, from whatever source, is improvedwhen diets contain antioxidants.Selenite is more readily reduced to elementalselenium, and for this reason selenate is some-times preferred. Selenium metal is less availableand can form insoluble complexes with otherminerals. Whichever form of selenium is used,it must be remembered that the final diet inclusionsare extremely low in relation to the otherminerals, and so some degree of premixing isessential prior to incorporation in diets or premixes.IodineIf iodine is added to a mineral premix, ratherthan supplied with salt, then potassium iodideand calcium iodate are the preferred sources.Potassium iodide is very unstable and deterio-rates rapidly with moderate exposure to heat, lightand/or moisture. Calcium iodate is the mostcommon source of supplemental iodine.Mineral chelatesChelates are mixtures of mineral elementsbonded to some type of carrier such as anamino acid or polysaccharide. These carriers,or ligands, have the ability to bind the metal,
  • SECTION 2.1Description of ingredients74 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONusually by covalent bonding through aminogroups or oxygen. The formed chelate is usuallya ring structure with the divalent or multivalentmetal held strongly or weakly through two or morecovalent bonds. Iron in hemoglobin is theclassical example of a chelate. The covalent bond-ing is such that the chelate has no electrical charge.Chelated, or complexed minerals are usuallymuch more expensive than inorganic minerals,and so one expects improved bird perform-ance through either enhanced absorption orbetter utilization in some way. It is difficult torationalize the cost of chelated minerals basedsolely on improved absorption in the intestine.Even a 50% difference in absorption can be mosteconomically resolved by doubling the level ofinorganic mineral used. However, there arelimits to the level of any one mineral to beused, because of potential negative effects ofabsorption and utilization of other mineralsand other nutrients. The mineral availability fromsome inorganic sources can be very low. For exam-ple, the manganese in some samples of manganesesulfate has been reported at just 5%, and inthis instance a 20 fold increase in inclusionlevel, while correcting the potential manganeseabsorption problem, will likely have adverse effectson utilization of phosphorus, calcium and iron.Factors affecting the uptake of heme iron areoften used to support the concept of usingchelated minerals. There are a number of othertrace minerals, such as copper, manganese andphosphorus that can affect absorption of inorganiciron, while uptake of heme iron will be littleaffected. The uptake of chelated minerals is there-fore expected to be more consistent and lessaffected by adverse (or enhanced) environmentsin the gut lumen. Bioavailability of minerals fromchelates should also be consistent because ofstandardization during manufacture versus lessstandard conditions with some supplies ofinorganic salts. There are also claims of chelatedminerals being used more effectively at thecellular level following absorption. There are fewclassical supporting claims for these suppositions,and so enhanced performance of meat birds andlayers is discussed in terms of stimulation ofvarious biological processes by the mineraland/or that the chelated mineral enters certainpools with greater affinity or efficiency.Inorganic minerals are likely to contain tracequantities of heavy metals such as arsenic, leadand cadmium. Such levels of heavy metals arenot problematic to poultry, although the EEC hasrecently imposed limits of these metals inmineral premixes and complete feeds. While itis challenging to consistently achieve minimumlevels using conventional mineral salts, most chelat-ed minerals are very pure and usually containno heavy metals.Ultimately the choice of using inorganicversus chelated minerals is one of economics,which obviously relates to cost benefit. Such resultsmay vary depending upon the levels andspectrum of trace minerals used and the bioavail-ability to be expected from inorganic sources thatare available.34. Synthetic Amino AcidsSynthetic sources of methionine and lysineare now used routinely in poultry diets andtryptophan and threonine will likely be usedmore frequently as future prices decline. Inmost situations, the use of synthetic amino acids(Table 2.15) is an economic decision, and so theirprice tends to shadow that of soybean meal,which is the major protein (amino acid) sourceused world-wide. By the year 2010, lysine usein North America is estimated to be at 150,000tonnes while that for methionine will be around85,000 tonnes, of which the poultry industries use30 – 65%.
  • 75CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.1Description of ingredientsLysine is usually produced as the hydrochlo-ride salt, and consequently, the commercialproducts have 79% lysine activity on a weightbasis. Liquid lysine products are now also avail-able. In North America, lysine tends to be con-sidered a commodity, and as such its use isdirectly related to that of other ingredients. Ingeneral, there is greater L-lysine HCl usagewhen soybean meal price increases, or when cornprice declines. In Europe however, because ofinherently higher commodity prices, L-lysine HCltends to be used less as a commodity, and moreas a means of improving performance. Care mustbe taken therefore, in interpretation of costbenefit of lysine use in research results reportedfrom these two regions.Tryptophan is not usually a limiting aminoacid in most poultry diets, and so the move togreater synthetic tryptophan use comes from theswine industry. Tryptophan will become alimiting nutrient as crude protein levels of dietsare reduced, although currently its efficient useis somewhat hampered by complexity involvedin diet analysis. Tryptophan levels in ingredientsand feed are much more difficult to assay thanare the other common amino acids, and inpart, this situation leads to variability in researchresults aimed at quantitating response to tryptophan.This amino acid is most likely to be consideredwhen diets contain appreciable quantities of meator poultry by-product meal.Methionine is available in a number of formsand also as an analogue. Over the years there hasbeen considerable research into the potency anduse of these various sources. There are essentiallyfour different sources of methionine (Table 2.16).Table 2.15 Synthetic amino acidsCrudeAmino acid Relative proteinactivity equivalent(%)DL-Methionine 100 59Methionine hydroxy analogue (liquid) 88 0L-Lysine 100 120L-Lysine HCL 79 96L-Arginine 100 200L-Arginine HCL 83 166L-Tryptophan 100 86L-Threonine 100 74Glycine 100 117Glutamic acid 100 117
  • SECTION 2.1Description of ingredients76 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONDow Chemical was the first to produce pow-dered DL-methionine in commercial quantitiesin the 1940’s, while Monsanto introduced thecalcium salt of methionine hydroxy analogue in the1950’s. Since this time, the market has establisheddemand for both DL-methionine and the analogue,in both powdered and liquid forms.It has been known for some time that mostessential amino acids can be replaced by thecorresponding -keto acid (analogue). With theexception of lysine and threonine, which are notinvolved in transamination processes, it istherefore possible to replace amino acids withtheir keto acid-analogues. Presumably the birdproduces the corresponding amino acid bytransamination involving mainly non-essentialamino acids such as glutamic acid. Suchtransamination can occur in various tissues,and some bacteria in the intestine may alsosynthesize amino acids prior to absorption. Thequestion of relative potency of products such asliquid MHA (eg. Alimet®) often arises in selec-tion of methionine sources. Liquid MHA has avalue of 88% methionine based on normalchemical structure. Availability of this 88%value has then been shown to vary from 60 –100%. It seems inconceivable that any nutrientcould have such variable efficacy, and so one mustlook at experimental conditions and diet for-mulation in assessing such results. Potency ofMHA relates to variable uptake in the intes-tine, degradation in body tissues and/or degreeof elimination by the kidney. Another major vari-able in response to MHA under commercialconditions is ingredient methionine levels usedin formulation and diet specifications for methio-nine and cystine. There are usually logical reasonswhy nutritionists use different potency values. Thebottom line is cost per kg of meat/eggs produced,and the value of products such as MHA quick-ly establish themselves over time within anintegrated operation. In most situations MHA isused at 85-88% relative to DL-methionine.MethionineDL- Methionine hydroxyDL- methionine hydroxy analogue-methionine Na analogue CaCH3 CH3 CH3 CH3S S S SCH2 CH2 CH2 CH2CH2 CH2 CH2 CH2H-C-NH2 H-C-NH2 H-C-OH H-C-OHCOOH COONa+ COOH COOCa+Powder Liquid Liquid PowderTable 2.16 Methionine sources
  • 77CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.2Ingredient testingIngredients must be continuously moni-tored to ensure consistency of nutrientprofile and presence of potential contam-inants. The number and frequency of assays willdepend upon the class of ingredient, historicalresults of analysis and to some extent the seasonof the year. Ingredients from new suppliersshould be tested the most rigorously, andnumber and frequency of testing reduced onlywhen consistency of nutrient profile is established.Examples of the type and frequency of testing aregiven previously with the description of all themajor ingredients.The frequency of sampling will obviously varywith the significance of a particular ingredientin the feed. For example, where fish meal is usedextensively, and represents a significant pro-portion of dietary amino acids, then amino acidanalyses may be done more frequently, and it mayalso be advisable to screen more often forgizzard erosion factors. On the other hand, wherea history of consistent analyses is developed, thentesting can be less frequent.For assay results to be meaningful, ingredientsmust be sampled accurately. For bagged ingre-dients, at least 4 bags per tonne, to a maximumof 20 samples per delivery, should be taken, andthen these sub-samples pooled to give one or twosamples that are sent for assay. It is alwaysadvisable to retain a portion of this mixed sample,especially when assays are conducted by outsidelaboratories. For bulk ingredients, there shouldbe about 10 sub-samples taken from each truckor rail car load and again this mixed to give arepresentative composite for assay.There are a number of rapid tests availablefor evaluating ingredients. In some instances, thesetests are specific to certain ingredients and to spe-cific nutrients and/or antinutrients within aningredient. Alternatively, some tests are more gener-ic and can be applied across a number of ingre-dients. The decision to carry out any of these testsis based on significance of the ingredient inthe diet, and so the relative contribution of con-stituents under test. Developing historical dataon ingredients is also a useful way of deter-mining the need and frequency ofvarious testing procedures. The following testsor methodologies are assumed to be in additionto more extensive chemical testing that willroutinely be used for the most important nutrients.a. Bulk densityBulk density of individual cereals is correlatedwith energy value and protein content. In NorthAmerica, the usual measurement is bushelweight, while the common metric equivalent iskg/hl. Weight of 100 kernels of cereal is also usedas an indicator of bulk density. Under normalgrowing conditions, as bulk density declines, thereis usually a reduction in energy level, mainlyassociated with reduction in starch content of theendosperm. Concurrently protein content oftenincreases since protein is commonly found in theouter bran or pericarp layers. Bulk density is alsoa useful measure for calculation of needs forstorage space within the mill.Bulk density will vary with moisture content,and this should be taken into account duringmeasurement. Density is easily measured byweighing the cereal or feed into a container ofknown volume. The smaller the container, thegreater the care needed in standardizing thefilling and especially the packing of theingredient. Bulk density values are not always2.2 INGREDIENT TESTING
  • SECTION 2.2Ingredient testing78 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONadditive and so the density of a mash feedcannot always be predicted from knowledge ofbulk density of component ingredients. Thissituation arises, because of ‘mixing’ of particlesof different size within a feed, so affecting theempty space common with low bulk densityingredients such as wheat shorts or alfalfa meal.b. Proximate analysisProximate analysis is still the most widely usedsystem for monitoring the quality of ingredi-ents. At a time when we formulate diets basedon digestible or metabolizable nutrients, itsvalue is often questioned, since proximate com-ponents are very broad and encompass what canbe both digestible and indigestible components.However, proximate analysis is quite rapid andinexpensive, and does give an idea of continu-ity of composition. Proximate analyses canalso be used to predict the content of nutrientssuch as total and digestible amino acids. This typeof information is essentially regression analysesof simple proximate components versus analyticalvalues for amino acids.For proximate analysis an ingredient ispartitioned into six fractions, namely water,ether extract, crude fiber, nitrogen-free extract,crude protein and ash. Some of the informationfrom proximate analyses (usually the protein, etherextract, fiber and ash values) are shown ondescriptive feed labels, which accompany feed-stuffs and complete feeds. These valuesrepresent the guarantees of quality used by thefeed manufacturing industry.Water is usually determined by the loss in weightthat occurs in a sample upon drying to constantweight in an oven. Although water is considereda nutrient, it effectively is a diluent for othernutrients. Increase in moisture, therefore, reducesthe total nutritional value of a feedstuff. Becausewater content can vary, ingredients should be com-pared for their nutrient content on a dry matter basis.Moisture much in excess of 12 – 13% is cause forconcern regarding potential for mold growth.Fat is determined by extracting the drysample with ether. The weight of the extract isdetermined after distilling the ether and weigh-ing the residue. Although this is the usualmethod for determining fat in feeds, etherextraction does not remove all the fats, especiallyphospholipids or fats bound to protein. Often acidhydrolysis followed by extraction of the hydrolysatewith chloroform:methanol or ether is necessaryto obtain ‘total’ lipid values. Acid hydrolysis alsoliberates fat present as soap, and is more likelyto liberate fat from bacterial cell walls.Crude protein is determined by measuring thenitrogen content of the feed and multiplying thisby 6.25. This factor is based upon the fact that onaverage, a pure protein contains 16% nitrogen.Thus 100/16 = 6.25. For most ingredients, thisassumption is fairly accurate, and allows us to esti-mate protein (which is a very complex assay) basedsimply on assay for nitrogen, which is quitestraightforward and inexpensive. The nitrogen con-tent of a feedstuff is determined usually by theKjeldahl or heco methods. The Kjeldahl involvesconversion of the nitrogen in feedstuffs to anammonium salt by digestion with concentratedsulfuric acid in the presence of a suitable catalyst.The ammonia is distilled from the digestion mix-ture into a collecting vessel after the sample is madealkaline. The amount of ammonia is determinedby titration with standard acid, and then nitrogen,and hence crude protein are calculated.Ashing of an ingredient combusts all organicconstituents, leaving behind only the mineralelements. Some elements such as seleniumand arsenic form volatile oxides at this temper-ature. These losses can be avoided if the ash ismade alkaline by addition of known quantitiesof calcium oxide prior to ashing.
  • 79CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.2Ingredient testingCrude fiber refers to the organic residue ofa feed that is insoluble after successive boilingwith H2SO4 and NaOH solutions according tospecified procedures. The determination ofcrude fiber is an attempt to separate the morereadily digestible carbohydrates from those lessreadily digestible. Boiling with dilute acid andalkali is an attempt to imitate the process that occursin the digestive tract. This procedure is based onthe supposition that carbohydrates, which arereadily dissolved by this procedure, also will be read-ily digested by animals, and that those not solubleunder these conditions are not readily digested. Atbest,thisisanapproximationoftheindigestiblemate-rial in feedstuffs. Nevertheless, it is used as a gen-eral indicator in estimating the energy value of feeds.Feeds high in fiber will be low in ME.Nitrogen-free extract (NFE) is determined bysubtracting from 100 the sum of the percentagesof ash, crude protein, crude fiber, ether extractand water. The NFE is considered to be a measureof the digestible carbohydrates. A criticism of theproximate analysis system, is that its majorcontributor, namely NFE, is calculated by difference,and not actually determined directly.Proximate analysis gives some indicationof the nutritive value of an ingredient. Forexample, a material very high in crude fiber islikely to have a low energy value, while feedstuffslow in crude fiber and high in ether extract arelikely to be of high energy value. The crude pro-tein content of material is a good indicator of itspotential value as a protein source. Unless theamino acid composition is known, however, theactual quality of the protein cannot be determined.Certain ingredients such as meat meal normallycontain a high quantity of ash. In meat meal andfish meal, calcium and phosphorus may beestimated from the ash value since it consists main-ly of bone ash. Thus a determination of the ashof these materials may be very useful.Proximate analyses should perhaps be bettertermed ‘approximate analyses’, especially since itsmain component, NFE, is determined bydifference. However, it is a useful starting point fornecessity to conduct other more specific analyses.c. Amino acid analysesDetermination of total amino acids is timeconsuming and expensive and so tends not to bea routine procedure. The most common proceduretoday is gas-liquid chromatography, which canbe highly automated to give relatively speedyanalyses. However, the major time factor residesin preparation of the sample for analysis, since thecomponent amino acids have to be freed from with-in protein structures. This pre-analysis procedureis usually termed hydrolysis, and unfortunatelycare must be taken during this process, since twoimportant amino acids can be destroyed by inap-propriate processing. Tryptophan is almost com-pletely destroyed by acid hydrolysis and can onlybe determined following alkaline or enzymatichydrolysis. The acid buffers used in amino acidanalyses also cause loss of tryptophan. Special pre-cautions also must be taken against loss of methio-nine and cystine during hydrolysis. Perfomicacid oxidation is usually carried out prior tohydrolysis, such that methionine is converted tomethionine sulfone and cystine to cysteic acid.Amino acids are then liberated from the proteinsby hydrolysis with HCl. In the case of tryptophan,further precautions against destruction by acids andalkalis are essential. Such problems in prepara-tion of samples are often the reason that tryptophanis omitted from published data.For measurement of digestible (available)amino acids, it is necessary to feed birds and meas-ure total amino acids in the feed and excreta. Thedifference between amino acid input andoutput is assumed to be digestible or availableamino acids. The bioassay is most easily achieved
  • SECTION 2.2Ingredient testing80 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONby the TME precision force-feeding system,because the ingredient can be considered alone.In a classical bioassay, the bird voluntarily eatsfeed and only the test ingredient can supply aminoacids.This situation means that semi-purified diets(containing other basal ingredients such assugar, starch, sand and oils) are necessarilyused and the practicality of such diets are oftenquestioned. Today, virtually all estimates ofamino acid digestion are derived from the force-feeding method, and values are often termedTAAA(True Amino Acid Availability).d. Metabolizable Energy(AME or TME)Metabolizable energy is the most costlynutrient in an ingredient or diet, yet unfortunate-ly it is the most difficult to measure. As fordigestible amino acids, estimates of AME orTMErequire a bioassay involving live animals. Theonly lab assay for energy is gross energy and thisis merely a starting point used in AME or TMEdeterminations. Gross energy is the total heatevolved when an ingredient or diet is burned in anatmosphere of oxygen. Wood and corn haveapproximately the same gross energy.In an energy bioassay, birds are fed dietscontaining a given quantity of the ingredient, andfeed intake and excreta output measured over a3–5 d balance period. Gross energy is determinedon feed and dried excreta and calculations madeto determine the metabolizable energy derived fromthe ingredient under test. In theTME assay, the birdis force-fed only the ingredient under test, and sothe estimate of ME is simplified. With all thelaboratory and sample preparation necessary forthe test, it is challenging to generate resultswithin a 2–3 week period, at a cost approaching$1,000 USD per sample.Because of the complexity and cost involvedin measuring AME orTME, various chemical or invitro systems have been developed. Essentially thesemethods attempt to correlate more easily measurablecomponents, with available energy. One of the firstsuch calculations was applied by Carpenter andClegg (1956) and their equation is still as good asanything developed in the last 50 years.ME (kcal/kg) = 53 + 38(%CP + 2.25 x % fat+ 1.1 x % starch + % sugar)This type of prediction equation is accurate towithin ± 200 kcal/kg and so is useful for giving anestimate ofAME for a novel ingredient. There havealsobeenMEassaysbasedonenzymedigestion. Themostsuccessfulusesduodenalfluidtakenfromapig,and measuring the gross energy of solubilizedcomponents after 1 – 2 hr of incubation. AME hasalso been predicted by NIRA (see next section).e. Near Infra Red Analysis(NIRA)NIRA offers the possibility for very rapidanalyses of ingredients and feeds. The techniquehas the potential to assay many organic com-pounds. The system has the capability to measuremetabolizable energy as well as more simplecomponents such as fat, moisture, protein andfiber. Analysis relies on measuring how muchlight energy is absorbed when the sample isbombarded with light at very specific wavelengths.The basis of NIRA is chemometrics, whichis the application of mathematics to analyticalchemistry. The technique is an integration ofspectroscopy, statistics, and computer sciences.Mathematical models are constructed that relatechemical composition (active chemical groups)to energy changes in the near infra red region ofthe spectrum which ranges from 700 to 2500 nmin wavelength. In this region of the spectrum we
  • 81CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.2Ingredient testingmeasure mainly vibrations of chemical bonds inwhich hydrogen is attached to atoms such as nitro-gen, oxygen, or carbon. Because most feedstuffsare opaque, NIRA uses reflectance instead oftransmittance. The reflected light of a sample isused to indirectly quantify the amount of energyabsorbed in a sample. NIRA measures theabsorption of infra red radiation by variouscomponents, for example, peptide bonds atspecific wavelengths in the near infra red spectrum.Other components of the sample absorb energyas well, however, and have the effect of interfer-ing. This effect is eliminated by mathematical treat-ment of the spectral data and by multiple linearregression or other statistical procedures.Because each molecule usually exists in its low-est energy state, absorption of energy will raise itsenergy state to some degree. Such energy absorp-tion occurs at a wavelength that is characteristic forthat particular molecule. Energy absorption in thefundamental infra red region is very strong, but alsovery specific for certain molecular groups. For exam-ple, water has a characteristic absorption at the samewavelength as does starch. Strong, but specificfundamental wavelengths, would be difficult to dif-ferentiate for these two components. This does notmean to say that infra red analysis does not havea place in feed analysis. For example, with purenutrients (amino acids, vitamins) the use of lightreflectanceinthefundamentalrangemayofferpoten-tial for very specific analysis of purity. With sam-ples of mixed composition, whether it be ingredientsor complete feeds, then a more subtle analysis mustbeusedtodifferentiateallthevariouschemicalgroup-ings. In the weaker absorbing NIR range of wave-lengths, it is secondary absorption wavelengths thatare considered – these are most often referred toas ‘overtones’. By considering a spectrum ofwavelengths, a characteristic pattern of absorptionenergy is given for each major component of thesample. Chemometrics then involves calculationof correlation coefficients at each wavelength andsimultaneously selecting both the best fit with thenutrient under study, and also the best fit at all otherabsorptionfrequenciessoastoremoveallinterferenceproblems with application of a correction factor.The usefulness of NIRA, therefore dependsentirely on the careful and conscientious calibrationof the equipment. To some extent this exercisehas been simplified through introduction ofso-called scanning machines that cover a wideband of NIR. Prior to this technology, only fixedwavelength equipment was available, and soprior knowledge of likely absorption bands ortedious testing of numerous wavelengths wasessential in order to develop useful calibrations.Developing calibrations for componentssuch as moisture, fat, crude protein and fiber isa very straightforward procedure. These calibrationscan be combined within a single program suchthat from each ingredient scan, these variousanalyses are conducted concurrently. For mostcommercial machines, ensuring consistent fine-ness of grind and controlling moisture contentof samples eliminates much of the variationassociated with operating procedure.Determination of ME with NIRA provides aconsiderable challenge. Firstly, there is a needfor an extensive range of diets of determined analy-sis to be used for calibration. The conventionalbioassay for ME is both time consuming and veryexpensive, and these facts have undoubtedlylimited investigation to date. Secondly, ME perse provides a complex problem for NIRA,because energy contribution is not confined toone nutrient but rather is represented by a rangeof molecular bondings and configurations.Usefulness of NIRA to predict ME thereforedepends upon careful bioassay of a range of dietspreselected in terms of anticipated ME, nutrient
  • SECTION 2.2Ingredient testing82 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONcontribution and ingredient composition. Theselatter parameters are of importance if ‘universal’calibrations are to be developed. Similarly,great care must be taken in the mathematicalmanipulation of spectral coefficients. Over thelast few years Valdes and Leeson (1992, 1994)have developed a number of such calibrationsfor feeds and ingredients. Table 2.17 shows someof these results for ingredients.Table 2.17 Prediction of metaboliz-able energy by NIRA (kcal/kg)Ingredient Determined NIRApredictionCorn 3380 3370Barley 2720 2670Wheat 3275 3225Soybean meal 2340 2320Bakery meal 2990 3005Tallow 8690 8680Poultry fat 9020 8840Corn oil 9660 9530Palm oil 7300 7700Adapted from Valdes and Leeson (1992, 1994)There is also potential for NIRA to predictamino acids in ingredients (Table 2.18) as wellas antinutrients such as glucosinolates or trypsininhibitors. As with NIRA analyses, the accuracyTable 2.18 Prediction of aminoacids in fish meal%Amino AcidAssay NIRA predictionMethionine 1.5 1.6 ± 0.06Cystine 0.6 0.6 ± 0.07Lysine 3.7 4.0 ± 0.30Tryptophan 0.6 0.5 ± 0.03Threonine 2.2 2.3 ± 0.09Arginine 3.4 3.4 ± 0.09Valdes and Leeson (unpublished)f. Urease testing of soybeans andsoybean mealLevels of the enzyme urease are used as anindicator of trypsin inhibitor activity. Urease ismuch easier to measure than is trypsin inhibitorand both molecules show similar characteristicsof heat sensitivity. A rapid qualitative screeningtest for urease can be carried out usingconversion of urea to ammonia in the presenceof an indicator.A qualitative test for urease activity can becarried out using a simple colorimetric assay.Urea-phenol-red solution is brought to an ambercolor by using either 0.1 N HCl or 0.1 N NaOH.About 25 g of soybean meal is then added to 50ml of indicator in a petri dish. After 5 minutes,the sample is viewed for the presence of redparticles. If there are no red particles showing,the mixture should stand another 30 minutes, andagain if no red color is seen, it suggests overheatingof the meal. If up to 25% of the surface iscovered in red particles, it is an indication of accept-able urease activity, while 25 – 50% coveragesuggest need for more detailed analysis. Over50% incidence of red colored particles sug-gests an under-heated meal.g. Protein solubilityPlant proteins are normally soluble in weakalkali solution. However, if these proteins areheat-treated, as normally occurs during pro-cessing of many ingredients, the solubility ofprotein will decline. Dale and co-workers atGeorgia have developed a fairly rapid test whichseems to give a reasonable estimate of proteinsolubility and hence protein quality in soybeanmeal. The assay involves adding just 1.5 g of soy-bean meal to 75 ml of 0.2% potassium hydrox-of such predictions is greatly influenced bythe time and precision involved in calibration usingsamples of known composition.
  • 83CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.2Ingredient testingide solution, and stirring for 20 minutes. Solubleproteins will be in the liquid phase and so all ora portion of the centrifuged liquid is assayed forcrude protein, and protein content relative to theoriginal 1.5 g sample calculated accordingly. Byknowing the crude protein content of the orig-inal sample of soybean meal, percentage solu-bility can easily be calculated. Typical results,as shown by Dale and Araba are given in Table2.19. As heating time is increased, there is adecrease in protein solubility. Values of75–80%solubility seem to be ideal, with higher values sug-gesting under-heating, and lower values over-heat-ing of the protein. A variation of this test is to assessprotein solubility in water. Sometimes termedProtein Solubility Index, the results of water sol-ubility are said to be more highly correlated withfeeding value than are estimates of urease indexor protein solubility in KOH.h. Protein and amino aciddye-bindingProteins will bind with a number of dyes andso this provides the basis for colorimetric assays.These dye-binding techniques can be used totest protein per se or used to test for protein invarious extractions involved in assays of solubilityor digestibility. Dye-binding can thereforereplace the Kjeldahl analysis depending uponsensitivity needs. The most commonly usedmethods are as follows:Cresol Red J. Amer. Assoc. Anal.Chem. 43:440Orange G J. Nutr. 79:239Coomassie Blue Anal. Biochem. 72:248Lysine also reacts with certain dyes to givea colorimetric assay. Carpenter suggested thatif the e-amino group of lysine is free to reactwith dye, then the lysine can be considered as‘available’. The most commonly used dye is Fluoro-2,4 dinitrobenzene (FDNB), which gives ayellow/orange color when combined with lysine.Table 2.19 Protein solubility ofsamples of soybean meal heated forvarious timesUrease Protein WtHeating (ph solubility gain Feed:Gaintime change) (%) (g)0 (Raw) 2.40 99.2 343d 2.44c5 min 2.04 87.7 429c 2.29bc10 min 0.23 79.1 481ab 2.00a15 min 0 74.9 496a 2.09ab20 min 0 71.8 500a 2.03aDale and Araba (1987)i. Fish meal gizzard erosion factorIn some countries, fish meal is an econom-ical feed ingredient to use in poultry diets. Aspreviously described, some samples of fish mealwill cause severe gizzard erosion in young birds.Where fish meal is an integral part of a broiler diet,then it is common to carry out a chick growthtest with each shipment of fish meal. About 50chicks are fed a broiler starter diet, usuallywithout any fish meal, for 5 – 7 days. At this time,the diet is mixed with 40 – 50% of the test fishmeal, and this diet fed for another 7 – 10 days.Birds are then sacrificed and the gizzard exam-ined for erosion, often using a subjective scaleas follows:1. very mild erosion, with good gizzardcolor2. mild erosion, with evidence ofdestruction of the lining in some areas3. erosion in localized areas, with cracks inthe thinner lining4. severe erosion, cracking, thinning anddiscoloration5. sloughing of the gizzard lining withhemorrhage
  • SECTION 2.2Ingredient testing84 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONBecause 40 –50% fish meal is used, somegizzard erosion is expected with most samples.Scores of 4 – 5 are often used to reject samples,although this decision will to some extentdepend upon the level of fish meal to be usedin the commercial diet.j. Sorghum tanninsTannins are detrimental to protein utilization,and so levels should be minimized in poultry diets.Sorghum is a potential source of tannin, and thisis usually found in the outer seed coat.Unfortunately, there is not a clear relationshipbetween seed coat color and tannin content. Hightannin sorghums are usually darker in color,but some dark colored sorghums are also low intannin. The tannins are present in the testa, whichis the layer immediately beneath the outer peri-carp. One quick test is therefore to cut into theseed and observe for presence of a pigmented(tannin) testa. More recently, a bleach test hasbeen developed which again shows presence,or not, of a pigmented testa. About 20 g ofsorghum is mixed with 5 g potassium hydroxidecrystals and 75 ml of household bleach. Themixture is shaken until the KOH dissolves, andthen set aside for 20 minutes. Sorghum grainsare then strained, rinsed with water and placedon a paper towel. The KOH will remove the outerpericarp, and expose the testa. High tannin grainswill appear dark brown/black while low tanninsorghum will be bleached white/yellow.k. Gossypol in eggsFeeding gossypol to laying hens can result indiscoloration of both the yolk (green-brown)and albumen (pink). Gossypol is usually foundin cottonseed meal and, as described previ-ously for this ingredient, there are ways tominimize the effects of this compound by dietmodification. However, egg discoloration occursperiodically, and cottonseed meal or cotton-seed oil is often suspected. Placing egg yolks ina petri dish with ammonia quickly causes vary-ing degrees of brown discoloration dependingupon gossypol content.l. Fat assaysFat quality is best assessed by measurementof moisture, impurities and individual fattyacids. However, there are a number of lessextensive tests that can be used to give some ideaof fat composition and quality. Fat titre is ameasure of hardness, and simply relates tomelting point. The break-point between tal-lows and greases is about 40˚C. The higher themelting point, the more saturated the fat. Titreshould obviously be consistent for an individualclass of fat or fat blend from any one supplier.Iodine value can also be used as a measure ofhardness. Each double bond (unsaturated) willtake up a molecule of iodine, and so higher val-ues mean a greater degree of unsaturation,which in turn should relate to lower titre (Table2.20). Iodine value is greatly influenced bylevels of palmitic, oleic and linoleic acid inmost fats and oils. Generally, as titre increasesby 10 units over the range of 50 – 100, thenpalmitic acid content decreases by about 2%. Alsoas a rule of thumb iodine value = 0.9 x % oleicacid + 1.8% x linoleic acid.Table 2.20 Iodine value and titre ofcommon fatsIodine Value TitreºCTallow 45 45Lard 65 40Poultry fat 80 35Vegetable oil 120 15
  • 85CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.2Ingredient testingA major concern with the quality of fats andoils, is rancidity or the potential for rancidity.Rancidity is an irreversible oxidative process, thatis autocatalylic, meaning that breakdown productsfuel further degradation. Rancid fats will be lesspalatable, less digestible, and in extreme cases, theprocess of oxidative rancidity can continue inthe body of the bird following consumption of thesefats. The Initial PeroxideValue (IPV) is often usedto measure degree of rancidity upon delivery of afat. An IPV in excess of 18 – 20 meq is cause forconcern. If a fat is not stabilized with an antiox-idant, there is potential for subsequent rancidityduring storage. This potential can be measured bycreating extreme conditions for rancidity, name-ly bubbling pure oxygen through the heatedsample for 24 hr, and re-measuring peroxidevalue. As a word of caution, peroxide build-up istime dependent, since after reaching a peak, thereis a breakdown of peroxides to other indigestiblecompounds. Therefore fats that have finishedoxidizing can show a low peroxide value, but havevery poor nutritive value. Such samples are bestdetected by their ‘rancid smell’.m. Hulls in rice by-productsRice bran, sometimes called rice pollard, isused extensively in rice growing areas of the world.The major variable affecting nutritive value, is thecontent of hulls, which are essentially indi-gestible for poultry. A major component of hullsis lignin, and this reacts with the reagent phloroglu-cinol to produce a color reaction. The reagentis produced by combining 1 g of phloroglucinolwith 80 ml 2M HCl and 20 ml ethanol. The riceby-product is mixed 1:2 with reagent and heldat about 25ºC for 10 minutes. Development ofred color will be directly proportional to hullcontent. Actual hull content and a color score-card are necessary to ‘calibrate’ the assay.n. Mineral solubilityNeutralizing mineral salts with various acidscan be used to give some idea of mineral avail-ability, and when an assay is monitored over timethen information on rate of solubility is alsoobtained. Hopefully, all mineral sources will betotally available to the bird, although, at least withcalcium sources, there is concern about solubility.Slow solubilization is preferable to very rapidsolubilization, because the former more closelymatches the prolonged duration of need forcalcium supply to the shell gland in laying hens.Limestone solubility can easily be meas-ured by monitoring pH of the mineral in diluteacid. After recording the original pH of a 90 mlaliquot of 0.1 N HCl, 10 g of limestone is grad-ually added, and without stirring, pH measuredafter time intervals of say 10, 20, 30 and 60minutes. Limestone will result in an increase inpH, as H+ ions are liberated from solution. ApH change of +0.1 relates to a 20% solubility,while changes of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9 and 1.0 relate to about 37, 50, 60, 70, 75,80, 84, 87 and 90% solubility respectively. A pHchange of +2.0 means 99% solubility. A highsolubility after 60 minutes is expected from aquality limestone, whereas the rate of achieving95 – 99% solubility will give an indication of therate of calcium release in the proventriculus.Particle size and particle porosity are the factorsmost likely to affect rate of change of solubility.Optimum eggshell quality, and perhaps bone devel-opment in young birds, are dependent upon aconsistent pattern of calcium solubility.Neutralization of ammonium citrate hasbeen used to assess solubility of phosphatesources and also of manganese and zinc salts.
  • SECTION 2.3Feed additives86 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION2.3 FEED ADDITIVESAnumber of additives are often used in poul-try diets and most of these do not con-tribute any nutrients per se. Mostadditives are used to improve physical dietcharacteristics, feed acceptability or bird health.The following discussion is not intended toemphasize efficacy of the various products butrather to highlight various implications of theiruse in terms of diet formulation, ingredientcompatibility and/or general feeding management.a. Pellet bindersWhen pellet quality is of concern, a pelletdurability index is often ascribed to ingredientsand this is considered during formulation. Thisindex may range from 55 – 60 for corn soy dietsthat are notoriously difficult to pellet, to 90 – 95for wheat-based diets. With corn-based diets, itis often necessary to use synthetic pellet bindersin order to achieve desirable pellet quality. In mostinstances, the need for a good pellet is necessaryto placate the purchaser of the feed, because thebird per se is often tolerant of a range of qualityin terms of growth rate and feed efficiency. Theturkey poult is perhaps the most sensitive topellet or crumble quality, where growth ratecan be markedly influenced by both pellet sizeand the proportion of fines. The pelleting processis discussed in more detail in the followingsection on Feed Mixing and Pelleting.A number of pellet binders are available,although they are used at considerably differentinclusion levels, and such levels should beclearly specified for each product. When wheator wheat by-products are used at less than 10%of the diet, then a binder will often be necessaryif high pellet durability is desired. The twomajor types of binders have lignosulfonate orcolloidal clays as the base product, with inclu-sion levels of around 5 – 12 kg/tonne. There havebeen reports of colloidal-clay type productsbinding some B-vitamins and pigments in the gut,and so making them unavailable to the bird. Thecolloidal-clay products may also aid in reduc-ing apparent moisture content of the bird’s exc-reta and more recently, some forms of clay havebeen shown to have activity in binding aflatoxin.The lignosulfonate pellet binders often contain20 – 30% sugars, and so contribute to dietenergy level. Studies show lignosulfonatebinders to have ME values of 900 – 2200 kcal/kgdepending upon sugar content. Because thesebinders are often used at 1 – 1.2% of the diet,then energy contribution is meaningful at 10 –25kcal/kg of diet.b. AnticoccidialsAnticoccidials are used in diets for mostmeat birds and young breeding stock that are rearedon litter floors. Over the past 20 years, the so-called ionophore anticoccidials have predom-inated and they have proved most efficacious incontrolling clinical signs of coccidiosis. Froma nutritional viewpoint, some care must betaken in selection of these products as they caninfluence metabolism of the bird under certainsituations.Monensin has been a very successfulanticoccidial, and seems to work well withboth broiler chickens and turkeys. Monensin,like most ionophores, has an affinity to bind metalions, the most important in terms of bird metab-olism being sodium and potassium. Lasalocidalso binds metals, although its major affinity isfor potassium and secondly, sodium. Mostionophores also increase the permeability ofmembranes to H+ions, a factor that may beof significance in acid-base balance. For this
  • 87CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.3Feed additivesreason, there needs to be more work conductedon ionophores for heat-stressed birds. Ionophoreshave been shown to alter mineral availability,although this should not be of concern undercommercial conditions where most mineralsare present in excess of requirements. Studiesshow that the effect of ionophores on mineralmetabolism is not always consistent for variousminerals. For example, monensin may lead toincreased tissue level of certain minerals, whilelasalocid has the opposite effect, yet for anothermineral these effects could be reversed.Ionophores, and monensin in particular,seem to have an adverse effect when used in con-junction with low protein (methionine) diets. Whenlow protein diets or feed restriction are employedfor birds less than 21 d of age, alternatives toionophores should be considered in an attemptto alleviate potential growth depression, loss ofuniformity and poor feathering. However, withnormal diet protein levels, the ionophores do nothave a measurable effect onTSAA requirement.Ionophores and monensin in particular doimpart some growth depression in young birds,although this seems to be completely overcomewith compensatory growth during the with-drawal or finisher period. For monensin, a 5 – 7 dwithdrawal is optimum for compensatory gain,assuming that no major coccidiosis challenge willoccur during this time. With minimal challenge,a non-medicated withdrawal diet is recom-mended, while in situations of high challenge,an alternative anticoccidial may be necessary.There has also been some controversy on therelationship between wet litter and certainionophore products. Lasalocid in particularhas been associated with wet litter, and as such,recommendations are often given for reducingdiet sodium levels when this anticoccidial is used.Under such conditions adjustment of chloridelevels is often ignored, and as a consequenceperformance is sub-optimal. The relationshipbetween ionophores and water intake has not beenfully resolved other than the fact that birds fedmonensin do seem to produce drier manure.Non-ionophore anticoccidials are not usedextensively in chicken broiler production,although their use is often recommended inshuttle programs. Nicarbazin is an anticoccidialthat seems to work well in such shuttle programs,although again there are some potentialproblems with this product. Nicarbazin seemsto accentuate the undesirable effects of heatstress, and if inadvertently added to layer orbreeder diets at normal anticoccidial levels,can cause loss in reproductive performance.Nicarbazin fed to brown egg birds turns theireggshells white within 48 hr although this iscompletely reversible when the product is with-drawn from the feed. Even low levels ofnicarbazin can cause some loss in shell color,and mottling of egg yolks, and loss in fertility andhatchability of breeders.Amprolium is used extensively in diets forgrowing breeder pullets, because unlike theionophores, it allows some build-up ofimmunity.Amprolium induces a thiamin deficiencyin the developing oocysts, and as such, hasbeen queried with respect to thiamin status of thebird. In most instances thiamin deficiency willnot occur in birds, although cases have beenreported of combinations of amprolium andpoorly processed fish meal that is high inthiaminase enzyme, leading to thiamindeficiency in young birds.Coccidial vaccines are now commonly usedin breeders, and their use will likely increase forbroilers. There has been some discussion aboutdiet manipulation so as to improve the immune
  • SECTION 2.3Feed additives88 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONresponse. Oocysts start to cycle when birds are10 d of age, and if the litter is exceptionally drythis important cycling is less effective. Under suchextreme conditions, it may be advisable totemporarily increase diet or water sodiumlevels, so as to stimulate water intake.c. Antibiotics, GrowthPromotersThere has been a gradual reduction in the useof antibiotics per se, although growth promot-ing agents are still used extensively in mostregions. The mode of action of growth promotingagents is comparable to that of antibiotics in termsof beneficial modification of gut microflora. Inthis context, the type of dietary ingredients usedmay influence the efficacy of these productsbecause microbial activity is influenced bydigesta composition. There has been insuffi-cient work conducted in this area, e.g. thebeneficial effect seen when antibiotics are usedwith ingredients such as rye. It is unlikely thatgrowth promoters result in increased digestibil-ity of feed, rather improvements in feed efficiencyare a consequence of increased growth rateand hence reduced days to market. Over the pastfew years, there has been criticism about the useof antibiotics in poultry feeds, especially withrespect to the potential for build-up of microor-ganisms resistant to a specific antibiotic, andsubsequent transfer of this resistance to knownpathogens. In this context, the use of antibioticssuch as penicillin, that are also used in human-medicine, come under very close scrutiny.It is very difficult to grow broilers without theuse of growth promoters, since clostridial organ-isms often proliferate and clinical necroticenteritis develops. While some countries havea ban on sub-therapeutic growth promoters inthe feed, their use is escalating as water additives.Without the use of such ‘antibiotics’, there willundoubtedly be greater risk of bacterial overgrowthin the bird’s digestive tract and especially when‘poorly’ digested ingredients are used sincethese provide substrates for microbial fermentationin the lower gut. Such enhanced microbialgrowth can have various consequences for thebird. If the microbes are pathogens, then diseasecan occur. With proliferation of non-pathogensthere can still be effective loss of nutrients tothe bird and undoubtedly such conditionscontribute to ‘feed passage’ where feed particlescan be seen in the excreta. Using germ-free(gnotobiotic) birds, there is invariably a decreasein diet AMEn, since there is no ‘digestion’ bymicrobes.There will undoubtedly be future interest indeveloping nutritional strategies aimed atreducing our reliance on sub-therapeuticantimicrobials. In general, such strategies revolvearound limiting the nutrient supply to the intestinalmicrobes, altering the lumen environment so asto hinder microbial growth and/or priming orimproving the bird’s immune response (Table 2.21).If diets are made more digestible, thentheoretically, there should be fewer substratesavailable for microbial growth. The greatestsuccess in this area will likely occur fromdevelopments in feed processing and greaterapplication of exogenous feed enzymes. Thereseems great potential for modifying gut pH,either with use of feed or water source acids, orsimply by stimulating gizzard activity. Manyorganic acids are bactericidal, and while someare corrosive, there are few limitations in addingthem to diets in terms of stability of most othernutrients. While such acids may not have a dra-matic effect on pH of the small intestine,products such as lactic acid are bactericidalover quite a range of pH.
  • 89CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.3Feed additives89Laying hens and especially broiler chickenstoday have very rudimentary gizzards. Withincreased gizzard activity, there will be greater HClproduction from the proventriculus and this is obvi-ously bactericidal. Stimulating gizzard growth andactivity may, therefore become more important,and contribute to health management of thebirds There are often reports of higher digestibil-ity of broiler feeds when particle size of feed isreduced. However, in most of these trials, the‘young’ broilers likely have a rudimentary gizzard.For birds that have previously been fed larger sizeparticles and/or more fiber, such that gizzardactivity is increased, then there is greater digestibil-ity of feed with a larger particle size. Gizzard func-tion is generally a factor of fiber content of the feed,together with consideration of feed particle size.As detailed in Table 2.21 another potentialsubstitute for antibiotics is mannanoligosac-charides (MOS). Gram-negative bacteria havemannose specific fimbriae that are used forattachment to the gut wall. Mannan derivatesfrom the cell wall of yeast offer the bacterialfimbriae an alternate binding site, and consequentlyare excreted along with the undigested mann-anoligosaccarhride. Adding 1 – 3 kg of MOS pertonne feed, depending on bird age, will likely bepart of future strategies for growing birds on‘antibiotic-free’ diets.The other issue involving use of antibioticsand growth promoters in poultry feeds is thepotential for tissue or egg accumulation of thesecompounds. Adherence to regulated withdrawalperiods eliminates these problems, as doesscheduling of mixing non-medicated and med-icated feeds in the mill. Most countries arenow establishing GMP and HACCP programs atTable 2.21 Nutritional strategies to reduce reliance on sub-therapeuticgrowth promotersAreas of study Examples1. Limit microbial growth by 1. Use more digestible Corn vs small grainslimiting their nutrient ingredientssupply 2. Feed processing Pelleting, expansion etc.3. Use of feed enzymes NSP, lipase?4. Reduce diet nitrogen Increased use synthetic AA’s2. Limit microbial growth by 1. Feed/water acids Phosphoric, propionic, lactic acidsmanipulating digesta pH 2. Stimulate gizzard Feed whole grain or large feedactivity particles.3. Improve immunity to 1. Vaccines Coccidiosisinfection 2. Prime the immune Fatty acids, Vitamin Esystem4. Interfering with sites of 1. sugars Mannanoligosaccharidesbacterial attachment
  • SECTION 2.3Feed additives90 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONfeed mills to eliminate any potential forantibiotic residues in poultry products.A number of ingredients are still referred toas having ‘unidentified growth factors’. Onthis basis, ingredients such as alfalfa meal,distiller’s solubles, bakery yeasts and animalproteins are often added at 1 – 2% of the diet.Any ‘unexplained’ response to these ingredientsmost often relates to their containing tracelevels of vitamin or natural antibiotic residues.d. Antifungal agentsIn many regions of the world, molds andassociated mycotoxins are major problems,affecting both growth and reproductiveperformance. Mycotoxins produced by bothaerobic field molds and anaerobic storage moldscan accumulate, often undetected, in a range ofingredients. A number of antifungal agents areavailable, most of which are based on organic acids.By altering the pH of the feed, it is hoped to con-trol mold growth, although it must be rememberedthat any mycotoxin already present in feed willnot be destroyed by these antifungal agents.Apart from their cost, these organic acids can beproblematic in accelerating the corrosion ofmetal feeders and mill equipment.Gentian violet is also used in many countriesas an antifungal agent, and in this context, its effi-cacy is governed by factors that determine theefficacy of organic acids (i.e.: time, tempera-ture, moisture and feed particle size). Gentian vio-letalsohas some bacteriostatic activity and as such,is often used to maintain a beneficial gut microflo-ra, comparable to an antibiotic. In recent years,there has been some interest in use of alumi-nosiliacate (zeolites) as an ‘adsorbent’ of aflatoxin,and also products based on yeast cell walls.Unfortunately, relatively high levels of alumi-nosilicates must be used and these provide noother nutrients and may, in fact, act as chelatingagents for some essential minerals. However,where aflatoxin contamination is common, thenadding up to 15 kg aluminosilicates per tonneof feed may be necessary in order to minimizethe effect of this mycotoxin.In addition to, or as an alternative to using suchantifungal agents, there is a potential forminimizing mold growth through formulation,diet preparation and feeding management. Thereseems little doubt that the feed surface area is direct-ly related to potential fungal activity since the greaterthe surface area of feed exposed to the atmosphere,thegreaterthepossibilityoffungalsporecolonization.This fact is the most likely cause for the increasein mold growth often seen with feed as it travelsfrom the mill to the feed trough because particlesize is invariably reduced. Up to a 50% increasein fines can occur with high-fat pelleted broiler dietsbetween the time of pelleting and consumption bythe bird. At the same time, there is a 100%increase in the potential (and most often theoccurrence) of fungal activity. In areas of poten-tial mycotoxin contamination, there is obviouslyanadvantagetomaintainingaslargeapelletorcrum-ble size as possible. The heat generated during pel-letinghasbeenshowntosterilizefeedtosomeextent,because fresh pellets have low fungal counts.However,pelletingwillnotdestroymycotoxinsalreadyformed prior to pelleting, and warm moist pelletsare an ideal medium for fungal growth. Researchhas shown increased fungal activity in feed takenfrom trough vs tube feeders with the former hav-ing more feed exposed to the atmosphere.With toxins such as aflatoxin, there is abenefit to increasing the protein content of thediet, and in particular, sulfur amino acids. It ispossible that sulphates may also be beneficial in
  • 91CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.3Feed additives91helping to spare sulfur amino acids that arecatabolized during aflatoxicosis. Due to thespecific enzyme system involved with aflatox-icosis, selenium at up to 0.4 ppm may bebeneficial in overcoming major adverse effectsof this mycotoxin. There have also been reportsof niacin increasing the catabolism of aflatoxinB1, and so decreasing overall toxicity.It appears that diet modification and feedmanagement can be manipulated to minimizechances of mycotoxicosis. However, suchmeasures will not likely be 100% effective, andit should always be remembered that mostfungal growth can be reduced if moisturecontent of grains and feeds is kept below 14 – 15%.e. Probiotics and PrebioticsProbiotics, unlike antibiotics, imply the useof live microorganisms rather than specificproducts of their metabolism. Not being specificmolecules therefore, they are difficult toquantitate and even more difficult to describe interms of proposed modes of action. Probioticscan be classified into two major types – viablemicrobial cultures and microbial fermentationproducts. Most research has centered onLactobacilli species, Bacillus subtilis and someStreptococcus species. Similar to the situationwith antibiotics, the mode of action is stillunclear although the following have beensuggested: a) beneficial change in gut flora withreduction in population of E. Coli; b) lactateproduction with subsequent change in intestinalpH; c) production of antibiotic-like substances;d) reduction of toxin release (suppression ofE. coli). With these varied potential routes ofactivity, it is perhaps not too surprising thatresearch results are inconsistent. In mostinstances, the feeding of live cultures modifiesthe gut microflora of birds usually with increasesin number of Lactobacilli at the expense ofcoliforms. A healthy animal has a preponder-ance of lactic acid producing bacteria, and soit is only under situations of ‘stress’, whencoliforms often increase in numbers, that probioticswill be of measurable benefit. In this context thereis interest in the use of live cultures administered(orally) to day-old poultry as a means of preventingharmful bacteria such as salmonella fromcolonizing the gut.The term ‘competitive exclusion’ is oftenused synonymously with probiotics. It is assumedthat the probiotic will have a competitive advan-tage over any inherent pathogen, and eitherreplace it, or prevent its colonization. Bacterialantagonism may arise due to synthesis ofinhibitors by the probiotic organism. Lacticacid from Lactobacilli and other species is anexample of such a product. Probiotic organismsmay also stimulate mucosal immunity. Whileundefined mixtures of bacteria, usually derivedfrom cecal contents of healthy adult birds, seemto be effective probiotics, regulatory agencies areoften concerned about dosing animals withunknown organisms. Defined synthetic mixturesof bacteria seem less efficacious at this time,possibly because we have only scant knowledgeof the normal (beneficial) microbial populationwithin a healthy bird. However, this approachto developing a probiotic probably has the bestlong-term chance of success. With potentialinstability in most feeds for many Lactobacillusspecies, there has been recent interest in probioticsbased on Bacillus subtilis species, because theypossess a viable spore that has greater stabilitythan do most lactic acid producing cultures.Regardless of somewhat inconclusive results,it appears that probiotic use is increasing, andthat the animal industry looks to such productsas the substitutes for conventional antibiotics. These
  • SECTION 2.3Feed additives92 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONproducts seem ideal candidates for geneticmanipulation which has been inferred by anumber of researchers in this area. By usinggenetic engineering, some researchers suggestthat bacteria can be reformed to carry moredesirable gene characteristics, including theproduction of digestive enzymes and antimicrobialsubstances.Prebiotics are aimed at supplying probi-otics with an advantageous source of nutrients,implying that their needs are different to thoseof the host and/or different to those of potentialpathogens. Certain oligosaccharides, whichresist endogenous enzyme degradation, seem topromote a more favorable microflora in thelower small intestine and also the large intestine.However, certain pathogenic bacteria, such asClostridium perfringens are also able to fermentsome of the oligosaccharides. There is somepreliminary work with pigs suggesting synergismfor certain combinations of prebiotics andprobiotics, which is expected if both are efficacious.f. YeastsYeast, or single-celled fungi, have been used inanimal feed and the human food industry formany years. Brewer’s yeast was a common feedingredient in diets for monogastric animals prior tothe identification of all the B-vitamins. Today,some nutritionists still incorporate theseinactivated microbes as a source of so-called‘unidentified growth factor’. More recently therehas been an interest in the use of live yeastcultures. These cultures most often contain the yeastthemselves and the medium upon which theyhave been grown.Yeast cultures are usually derivedfrom Saccharomyces species, in particular,Saccharomycescerevisiae. Aswithprobiotics, theirmode of action in enhancing animal perform-ance is not fully understood. Yeasts may beneficiallyalter the inherent gut microflora, possibly throughcontrolling pH. The presence of living yeastcells may also act as a reservoir for free oxygen,which could enhance growth of other anaerobes.At the present time, there does not seem to be anymove to manipulate yeast for specific purposesrelated to animal nutrition. To some extent, thisrelates to scant knowledge on mode of action, andso should more facts be uncovered in this areaso-called ‘designer’ yeast may be considered.g. EnzymesEnzymes have been added to poultry diets eversince workers at Washington State Universityshowed improvement in digestibility of barley andrye-based diets when various enzymes wereused. In the 1950’s, corn-soybean diets pre-dominated, and these were assumed to behighly digestible and so there was little interestin feed enzyme application. Over the past fewyears, this area of nutrition has gained interest andactivity due to economics of small grain useand also because of a better understanding of modeof action and availability of various enzymes.Enzymes are now being manufactured specificallyfor feed use, and can be broadly categorized ascarbohydrases, proteinases and lipases. Increasingthe digestibility of various carbohydratefractions of cereals and plant proteins has receivedmost attention, although there is growinginterest in the potential for improving digesti-bility of both plant and animal proteins, and ofsaturated fatty acids for young birds. Currently,enzymes are used most commonly to aiddigestion of diets containing wheat, barley andrye where improvements are seen in dry matterdigestibility and also in consistency of theexcreta. There is also current interest in enzymesdesigned specifically to improve soybean mealdigestibility.
  • 93CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.3Feed additivesThe term non-starch polysaccharides (NSP)is now frequently used to describe what in thepast has been referred to as fiber. Birds have avery limited ability to digest fiber because theylack the enzymes necessary to cleave theselarge and complex molecules. In animals suchas the pig, and in ruminants, it is the resident micro-bial populations that synthesize cellulase typeenzymes that allow for varying degrees of fiberdigestion. If we can improve digestion of thecomplex carbohydrates, we not only increasepotential energy utilization, but also removeany negative impact that these products may haveon gut lumen activity and excreta consistency.The NSP content of cereals and other by-product feeds is usually inversely proportionalto their conventional energy level. These NSPcomponents are most often associated with thehull and underlying aleurone layers. In order fornormal endogenous enzymes to contact thestarch endosperm, these outer layers must bedisrupted or chemically degraded. Although manycompounds fit into the category of NSP’s, thereare three main types of importance in poultrynutrition. These are the ß-glucans in barley, thearabinoxylans or pentosans in wheat and the raf-finose group of oligosaccharides in soybeans. Barleyß-glucans are polymers of glucose while arabi-noxylans contain long chains, and cross chainsof fructose. The oligosaccharides in soybean arepolymers of sucrose. Most cell wall NSP’seither exist alone or as structural material oftencomplexed with protein and lignin. Solubility ofNSP’s usually relates to the degree of binding tolignin and other insoluble carbohydrates. In water,most NSP’s produce a very viscous solution, andthis has a predictably negative effect on diges-ta flow and interaction of all substrates withtheir endogenous enzyme systems. Some NSP’ssuch as pectins, have a three-dimensional struc-ture that can chelate certain metal ions. Anyincrease in digesta viscosity causes an increasein thickness of the unstirred water layer adjacentto the mucosal villi. Consequently, there isreduced solubilization and uptake of most nutri-ents. Digesta retention time increases, butbecause of the increased viscosity there is lessopportunity for substrates to contact enzymes.There are also more endogenous secretions andthese contain proportionally more bile acids. Inaddition to reduced digestibility, there are alsoreports of reduced net energy of diets due to NSP’s.The reduced NE may be a consequence ofincreased energy expended by the digestivesystem in simply moving digesta through the sys-tem. The increased digesta viscosity also influ-ences the gut microflora and there is an indicationthat their overgrowth may, in fact, add to the over-all deleterious effects. To the poultry producer,the most notable effect of NSP’s will be wetter,more sticky and viscous excreta. Table 2.22 detailsIngredient Cellulose Arabinoxylan Pectin ß-glucansCorn 2.5 5.0 0.1 -Wheat 2.5 6.0 0.1 1.0Barley 4.8 7.0 0.2 4.0 – 5.0Soybean meal 5.010.5 12.0 -1depending on hull fraction returnedTable 2.22 Non-starch polysaccharides in selected ingredients (%)
  • SECTION 2.3Feed additives94 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONlevels of NSP’s commonly found in cerealsand soybean meal. Oligosaccharides as foundin soybean meal are perhaps the most complexstructures within the NSP’s and to date have provendifficult to digest with exogenous enzymes.Depending upon variety, growing conditionsand oil extraction procedures, soybeans willcontain 4 – 7% of oligosaccharides mainly asraffinose and stachyose. Because of the absenceof -galactosidase in chickens, these oligosac-charides remain undigested, and again contributeto increased digesta viscosity, especially in youngbirds. Soybean oligosaccharides can beextracted using ethanol. Such treatment of soy-beans is not commercially viable at this time,although the residual meal has an AMEn valueapproaching 3,000 kcal/kg, and the meal seemsan interesting ingredient for very young birds. Sincethe oligosaccharides are removed by ethanol, thenthere is a corresponding loss of dry matter in theresidual soybean meal.Addition of feed enzymes could thereforeimprove NSP availability, and just as important,reduce the negative impact that these undi-gested residues have on digesta viscosity. Normaldigestion requires unimpeded movement ofenzyme, substrate and digestion productsthroughout the digesta and especially close tothe absorptive gut wall. As the viscosity of thedigesta increases, the rate of diffusion decreas-es, and this causes reduced digestibility of allsubstrates. The undigested viscous digestasubsequently translates to very sticky excreta whichcauses problems of litter management. Reductionin digesta viscosity is therefore highly correlatedwith efficacy of enzymes that can digest substratessuch as ß-glucans. In oats and barley the bulkof the NSP’s are ß-glucans, whereas in wheat andrye, arabinoxylans predominate. Enzymestailored for barley therefore contain ß-glucanaseenzymes, while those designed to improvewheat digestibility should contain cellulaseand arabinoxylanase enzymes.There is potential for adding lipase enzymesto feeds or fats, to improve digestibility.Improvement in digestion of saturated fats for youngbirds seems to have the greatest potential.Although there are no lipase enzymes currentlydesigned for use in animal feeds, preliminarystudies with enzymes obtained from otherindustries suggest that a 7 – 10% improvementis possible, with a corresponding increase in dietAME. Since the young chick does not efficientlyre-cycle its bile salts, there have also beenindications that fat digestion can be improvedby adding synthetic bile salts to the feed. Again,these are not commercially available, but itdoes suggest some potential for the developmentof emulsifying agents or detergents.The most widely used feed enzyme is phy-tase. Phytase cleaves the phytic acid in soybeanmeal and cereals, to release phosphorus andcalcium. Phytic acid is a complex structurethat tightly binds phosphorus, and is the mainstorage source of phosphorus in plant material(Fig. 2.1). Few animals possess the phytaseenzyme necessary to cleave the molecule andso phytic acid is largely undigested. Interest inthe phytase enzyme arose because phosphorushas become an expensive nutrient, as well as thefact that undigested phytic acid adds greatly tomanure loading of phosphorus. Phytate also bindsother trace minerals and may conjugate withproteins and carbohydrates. Digestion of themolecule therefore can potentially release traceminerals, amino acids and energy, as well ascalcium and phosphorus.Phytase enzymes are commonly found in plantmaterials, and especially for wheat and wheat
  • 95CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.3Feed additivesby-products the values are quite high. Corn, forexample, contains just 15 FTU/kg while wheatshorts can contain as much as 10,000 FTU/kg.However, such endogenous phytase may haveonly limited usefulness in the digestive tract, sincemost plant phytases are effective only at aroundpH 5, whereas exogenous phytases, usually ofmicrobial origin, seem efficacious from pH 3 to7. There are variable results reported for efficacyof phytase in commercial diets. It has beensuggested that diet calcium level is perhaps themajor factor in such variance, since high levelsof calcium seem to reduce the effectiveness ofphytase enzyme. However, if this concept is true,then one wonders why phytase enzymes seemso efficacious in layer diets that contain from 4– 4.5% calcium. If phytase is used in formulation,there are a number of different approaches toaccount for increased phytate availability. Wherefew ingredients are used, the available phosphoruslevel of these ingredients can be increasedaccordingly. Alternatively, the specification foravailable phosphorus in the diet can be reducedor phytase enzyme can be included as aningredient with specifications for availablephosphorus and calcium. Each 500 units ofphytase activity are equivalent to about 1 g ofphosphorus as provided by sources such asdi-calcium phosphate. Using 500 FTU ofphytase/kg feed therefore provides the equiva-lent of 0.1% P.Phytase also liberates some trace minerals andso theoretically, supplemental levels can bereduced. As described previously for calcium,there is an indication that phytase is more effec-tive when moderate, rather than high, levels ofsupplemental zinc are used. The release ofenergy and amino acids by phytase is a morecontentious issue. Some research suggests up to2% improvement in AMEn and digestible aminoacids, although more conservative estimatesare for 15 kcal ME/kg release of energy, with noincrease in amino acid availability. Somecommercial sources of phytase are sensitive toheat, and pelleting at 85 – 90ºC can causesignificant loss in phytase. In pelleted feeds, thesesources of phytase are most appropriately usedas post-pelleting additives. Other sources ofphytase seem more heat stable, and can beadded to the mix prior to pelleting.Figure 2.1 Phytic acid
  • SECTION 2.3Feed additives96 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONh. PigmentsThe yellow to orange color in avian fattytissue is caused by various carotenoid pigments.These pigments control the color of the eggyolk, as well as the shanks and beaks of layers,and also the skin color that may be important inmeat birds. The xanthophylls are the mostimportant carotenoids in poultry nutrition, andnatural ingredients rich in these compoundsare alfalfa meal, corn gluten meal and marigoldpetal (Table 2.23).Table 2.23 Xanthophyll content ofselected ingredients (mg/kg)Ingredient XanthophyllCorn 20Wheat 4Milo 1Alfalfa meal 175Corn gluten meal 275Marigold petal 7,000Corn contains much more xanthophylls thando other cereals, although high levels of pig-mentation can only be achieved from naturalingredients by including other products such asalfalfa and corn gluten meal.The various xanthophylls differ in their effecton skin and yolk pigmentation. ß-carotene haslittle pigmenting value, although pigments suchas zeaxanthin as found in corn, is more easilydeposited, while there is a very high incorporationrate of synthetic products such as ß-apo-8-carotenoic ethyl ester. The zeaxanthin in corntends to impart the darker orange-red colors, where-as the luteins, as found in alfalfa, cause a moreyellow color. Pigments are destroyed by oxidation,and so addition of antioxidants to feed, andgeneral feed management applied to fat protectionalso apply to preservation of pigments. Coccidiosis,malabsorption and certain mycotoxins will allreduce pigment absorption. Pigmentation in theyoung meat bird is directly proportional topigments fed throughout growth. For the layinghen however, yolk color is a consequence ofpigments consumed in the layer feed, and alsothe transfer of pigments accumulated in theskin and shanks when the bird was immature.This transfer of pigments to the ovary occursregardless of diet pigments, and is responsiblefor the ‘bleaching’ effect of the shanks and beakof yellow-skinned birds over time.Because many of the naturally carotenoid-rich ingredients are low in energy, it is difficultto achieve high levels of pigmentation of meatbirds without using various synthetic sources.Canthaxanthin, astaxanthin and ß-apo-8-carotenoic acid (where allowable in poultrydiets) can be used to impart the spectrum fromyellow to orange/red coloration in either skin oregg yolk. As described more fully in Chapter 4,there is now interest in enriching eggs withlutein, since this carotenoid is known to beimportant in maintenance of eye health inhumans. Future designer eggs may well containconcentrated levels of lutein.i. Flavoring agentsThe chicken is not usually considered tohave the ability to select feed based on flavor, ororganoleptics per se. The chicken has onlyabout 24 taste buds in comparison to 9,000 inhumans and 25,000 in cattle. Relatively fewstudies have been conducted with flavoringagents for poultry, and for this reason, caremust be taken in extrapolating data from otherspecies. For example, sucrose octa-acetatesolution is reported to be readily accepted by birds,but universally rejected by humans. Thereseems little scope for use of flavoring agents withbroiler chickens and turkeys that already seem
  • 97CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.3Feed additivesto be eating at near physical capacity. However,there may be some potential with breeders foridentification of agents that are distasteful to birds,as an aid in limiting their feed intake.We have studied the effect of feedingcinnamamide to young broilers, as a means ofregulating feed intake. Cinnamamide is relatedto the spice known as cinnamon and is anaturally occurring product in some weed seedsthat is thought to impart bird resistancecharacteristics as do tannins. Table 2.24 showsthe effect of feeding cinnamamide on growth andfeed intake of young broilers. At the highestinclusion level, cinnamamide reduced voluntaryfeed intake by around 50%.Table 2.24 Effect of cinnamamideon feed intake and body weight ofyoung broilersBody Weight Feed Intake(gms) 4-12 day(gms/bird)Day 4 Day 12Control 82.2 266.4 257.3Cinnamamide 81.4 170.8 159.2(0.2%)Cinnamamide 82.8 122.7 104.4(0.42%)Flavor agents may be beneficial in maskingany unpalatable ingredients, and for maintaininga constant feed flavor during formulation changes.Flavors may also be useful tools in maskingany undesirable changes in drinking water dur-ing medication. It is conceivable that use of a sin-gle flavor agent in both feed and medicatedwater may prevent some of the refusals seenwith medicated water, especially for turkey poults.j. Worming compoundsMost floor grown birds are exposed to infec-tion from various species of worms. In manyinstances such challenge can be prevented orminimized with the use of antihelmintic agents.Products based on piperazine and hygromycinhave been used most commonly over the last 15– 20 years. Piperazine used in diets for layingbirds has been shown to result in discolorationof the yolk. When administered at 28 d intervals,one report indicated about 4% incidence ofdiscolored yolks which appeared as irregular areasof olive to brownish discoloration. Such yolkdiscoloration is most pronounced in summermonths especially after prolonged storage atregular egg cooler temperatures. The mottlingof yolks seen with another commercial producthas been compared to the mottling seen withcalcium-deficient birds, suggesting a similar modeof action. However, we are unaware of any pub-lished reports relating worming compounds tocalcium deficiency and problems with shellquality.k. Ammonia controlVarious extracts of the yucca plant areclaimed to reduce ammonia levels in poultryhouses. A soluble component of the yuccaplant seems able to bind ammonia, preventingits release from manure, which is especiallyimportant in confinement housing systems.Most poultry will react adversely to 50 ppmammonia, and this is in contrast to the level of20 – 30 ppm which is the usual detection rangefor humans. Products such as Deodorase® addedto feed at 100 – 150 g/tonne have been shownto reduce environmental ammonia levels by20 – 30%, and this has been associated withimproved growth rate and reduced mortality.
  • SECTION 2.4Feed toxins and contaminants98 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONProducing poultry feed that is free oftoxins and contaminants is obviouslythe goal of all feed mills. However, thisis difficult to achieve because many natural feedingredients will contain toxins that are inherentin the feedstuff or have ‘naturally’ contaminatedthe feedstuff prior to feed preparation. Mycotoxinsare perhaps the best example of such ‘natural’toxins, and together with many plant lectins cancause poor bird growth and reduced egg production.In addition to these biological contaminants,there is also concern about accidental inclusionof such products as polychlorinated biphenyls,pesticides, fungicides etc.a. MycotoxinsMycotoxins are now virtually ubiquitous inpoultry diets, and with ever increasing sophis-tication of testing sensitivity, they are routinelyisolated as contaminants of most grains andsome vegetable protein ingredients. We still donot know the cause of high levels of moldgrowth occurring in pre-harvest grains. Certainlysuch aerobic molds are more prevalent in hothumid conditions, and insect damage to thestanding crop seems to provide a route of entryfor the mold. Unfortunately, visual inspectionof harvested grains can be misleading in regardto mycotoxin content. Likewise, merely becausegrains appear moldy, does not mean to say thatthey are contaminated with harmful toxins. Instorage, the major factors affecting mold growthare again temperature and humidity. The higherthe temperature, the greater the chance of moldgrowth. However such mold growth rarelyoccurs in grains containing less than 14 – 15%moisture. Unfortunately, many grain silos are notwaterproof, or grains are not aerated, and sopockets of moisture can cause microclimatesideal for mold growth. The following is a reviewof the major mycotoxins affecting meat birds andegg layers.Aflatoxin - Produced by the Aspergillus flavus mold,aflatoxin is one of the most potent carcinogensknown. Usually present in cereals in ppb lev-els, acute toxicity will occur at 1.2 ppm. AflatoxinB1 is the most common form of the toxin, the Bdesignation relating to the fact that the toxin flu-oresces a blue color when exposed to ultravio-let light, and so this can be used in the screen-ing of ingredients. Blue fluorescence occurs withother components, and so this simple test screensout negative samples, but needs subsequentchemical analysis for confirmation. Aflatoxin isfound in most cereals, although corn and miloare the most common hosts. As with any mold,Aspergillus growth is greatly reduced whencorn or milo moisture levels are less than 15%.Aflatoxin is a potent hepatotoxin, and sovarying degrees of liver breakdown occur. Astoxicity develops, normal liver function declines,and reduced growth rate is quickly followed bydeath. Toxicity is enhanced by the presence ofother toxins such as ochratoxin andT2 toxin. Theeffects of aflatoxin are also much worse if birdsare infected with aspergillosis. There also seemsto be a nutrient interaction, because toxicity ismore severe when diets are low in either crudeprotein or methionine or when the diet containsmarginal levels of riboflavin, folic acid orvitamin D3. There is no treatment for acuteaflatoxicosis, although because of the liverdisruption, giving higher levels of antioxidantsand/or selenium seems to slow the onset ofsymptoms and speed up recovery if aflatoxin isremoved from the diet.2.4 FEED TOXINS and CONTAMINANTS
  • 99CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.4Feed toxins and contaminantsThere are a number of effective preventativemeasures, although not all of these areeconomical. Treating infected grains withammonia, hexane or hydrogen peroxide have allbeen shown to reduce aflatoxin levels. Undercommercial conditions adding binding agents tothe feed seems to reduce the adverse effects ofaflatoxin. To date, aluminosilicates, bentoniteclays and yeast cell walls have proven effective.For example adding 10 – 15 kg/tonne of hydrat-ed sodium-calcium aluminosilicate has beenshown to drastically reduce mortality in broilersand turkeys fed diets containing 0.5 – 1.0 ppmaflatoxin. Such aluminosilicates have limited effectson other mycotoxins.Tricothecenes -Three mycotoxins, namelyT2, DAS(diacetoxyscirpenol) and DON (Deoxynivalenolor vomitoxin) are included in this group. All ofthese mycotoxins are produced by Fusariumspecies molds such as Fusarium graminearum andFusarium roseum. The tricothecenes affectprotein metabolism and have the characteristicfeature of causing mouth lesions in most animals.However DON does not seem to be particularlyharmful to poultry. Unlike the situation in pigsand other mammals, birds can tolerate up to 20ppm of this mycotoxin. T2 and DAS however aremore toxic, causing problems at 2 – 4 ppm.The adverse effect of tricothecenes is made evenworse by the presence of aflatoxin or ochratoxin,and seems to be worse in young broilers fedionophore vs non-ionophore anticoccidials.There are no really effective treatments, andwhile the addition of relatively high levels ofantioxidants may slow the disruption of proteinsynthesis, they are not effective long-term.Adsorbents and binding agents are being devel-oped that specifically bind these toxins.Ochratoxin - As with other mycotoxins, there area number of forms of ochratoxin, although ochra-toxin A (OA) is by far the most significant for poul-try. OA is produced by a number of molds,with Aspergillus and Penicillium species being mostcommonly involved. OA is toxic at 2 ppm andas with tricothecenes, it has an adverse effect onprotein synthesis. However, OA also affectskidney function and so the classical signs areswollen kidneys and associated increased waterintake with wet excreta. Secondary visceralgout, which appears as urate deposits over the vis-cera, is common with OA toxicity, dueessentially to failure of uric acid clearance by thekidney tubules. OA toxicity is compounded bythe presence of aflatoxin, DON andT2 toxicosis,and also made worse by feeding diets high invanadium (usually as a contaminant of phosphatesor limestone). There are no effective preventa-tive measures, although birds sometimes respondto diet manipulation in the form of increasing crudeprotein levels. There are also reports of benefi-cial response to increasing diet vitamin C levels,especially in egg layers.Other mycotoxins - There are a diverse group ofother mycotoxins that periodically cause problemsfor poultry. Their occurrence is lessfrequent than the major mycotoxins already dis-cussed, and in some instances exact toxicity lev-els have not been clearly established.Table 2.25summarizes these mycotoxins in terms of effect onpoultry and their probable threshold for toxicity.b. Plant toxinsA number of cereals and vegetable proteincrops contain natural toxins that can affect birdperformance.Cyanides - While there are a number of poten-tial feed ingredients that contain natural cyanides,cassava (manioc), is probably the most commonand contains relatively high levels of this toxin.
  • SECTION 2.4Feed toxins and contaminants100 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONCassava meal is derived from the tuberous rootof the cassava plant. Ingestion of this materialby animals can result in enlarged thyroids, dueto the presence in the meal of cyanogenic glu-cosides, the main one being linamarin. Theseglucosides are concentrated in the peel of the root.On hydrolysis by the enzyme linamarase, the glu-cosides produce hydrocyanic acid (HCN), whichis highly toxic. In addition to the enzyme in theroot, glucosidic intestinal enzymes and HClcan also hydrolyze the glucosides.Hydrocyanic acid inhibits animal tissue res-piration by blocking the enzyme cytochrome-oxi-dase. HCN is detoxified to produce thiocyanatein the liver which is then excreted via the urine.This detoxification system utilizes sulfur frommethionine in the conversion of cyanate tothiocyanate, thus increasing the bird’s require-ment for this amino acid. Thiocyanate is respon-sible for the goitrogenic effect of cassava, due toits effect on iodine uptake and metabolism in thethyroid, resulting in reduced output of thyroxine,which regulates tissue oxidative functions.Cyanate is known to alleviate the toxicity of anexcess of dietary selenium by complexing withselenium, thus making it less available to the bird.Linseed meal, which has been known for sometime to alleviate selenium toxicity in animals, hasbeen shown to contain two cyanogenic gluco-sides, namely linustatin and neolinustatin. Thesecompounds are closely related in structure tolinamarin and thus on hydrolysis yield HCN.The cyanide content of cassava varies withvariety and can range from 75 to 1000 mg/kg ofroot. Crushing the root releases the enzymelinamarase which acts on the glucosides toMycotoxin Effect Toxicity CommentsFumonisin Degeneration of nerve > 80 ppm Diet thiamin levelscell lipids importantCyclopiazonic acid Mucosal inflammation 50 – 100 ppm Often present alongwith aflatoxinOosporin Kidney damage, gout > 200 ppm Most commonly foundin cornCitrinin Kidney damage > 150 ppm Commonly associatedwith ochratoxinErgot Tissue necrosis > 0.5% Wheat and ryeFusarochromanone Tibial > 50 ppm Fusarium speciesdyschondroplasiaMoniliformin Acute death > 20 ppm Mechanism unknownZearalenone Reproduction, vitamin > 200 ppm Can affect shell qualityD3 metabolismTable 2.25 Effect of minor mycotoxins on poultry
  • 101CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.4Feed toxins and contaminantsproduce volatile HCN which is then eliminatedduring drying. Rate of drying in commercial forcedair driers is important as it has been reported thatat 80 to 100ºC, only 10 to 15% of cyanide isremoved compared to 80 to 100% detoxifica-tion occurring at 47 to 60ºC but with a longertime. Steam pelleting can also assist in thevolatization of free HCN.While there are differing reports as to how muchcassava meal can be incorporated into poultry dietswithout reducing performance, this will obviouslydepend on the concentration of cyanide in themeal. Cassava meals containing up to 50 mg totalcyanide/kg have been fed successfully up to50% inclusion in broiler diets.Glucosinolates –These belong to a group of anti-nutritive compounds of which over 100 differ-ent types are known to occur in members of theCruciferae family. The genus Brassica is a mem-ber of this family which includes many impor-tant feeds and foods such as, rapeseed,mustard, kale, radish, cabbage, cauliflower,etc. In individual species, usually around 12 to20 glucosinolates are found, although most ofthese are present in small amounts. Hydrolysisof these glucosinolates is brought about by theenzyme myrosinase, which is usually present inmost glucogenic plants. In the intact plant, theenzyme and its substrate are separated, butwith cellular rupture (grinding, insect damage,etc.) these components are combined andhydrolysis can occur.For many plants including rapeseed,glucosinolates can be readily divided into threemain groups, based on physiological effectsand hydrolysis products. By far the largest of thesegroups are glucosinolates that yield isothio-cyanates on hydrolysis. These compounds arevolatile and possess a range of antimicrobial,antifungal and antibacterial properties, andhave a very pungent taste (mustard, horseradish,etc.). A second, but much smaller group, formpotent anti-thyroid compounds on hydrolysis with5-vinyloxazolidine-2-thione being the mostcommon. If present in large amounts thesecompounds can impart an intense bitterness.Glucosinolates in the third group all contain anindole side chain, and on hydrolysis yieldthiocyanate ions which are anti-thyroid orgoitrogenic. The glucosinolate contents of thevarious rapeseed cultivars ranges from a high of100 to 200 µM/g to less than 30 µM/g, while newvarieties are claimed to be glucosinolate-free.A significant research program was initiatedin Canada in the early 60’s to develop rapeseedvarieties low in glucosinolates and erucic acid,a fatty acid known to result in detrimental meta-bolic problems with certain animals. In 1968,the first low erucic acid variety was licensed andshortly thereafter a low glucosinolate varietyappeared. In 1974, the first double low variety,very low in erucic acid and glucosinolates waslicensed. A number of improved varieties weredeveloped and in 1979 the name canola wasadopted in Canada to apply to all double lowrapeseed cultivars. For reasons not yet completelyunderstood, reduction of total glucosinolatehad little effect on the content of the indole group.Thus, when expressed as a percent of totalglucosinolates, this group increases from around5 to 40% in the low glucosinolate varieties.While the feeding value of canola meal hasbeen markedly increased for poultry, as comparedto the older rapeseed varieties, there are still someproblems encountered. The occurrence of liverhemorrhages with the feeding of rapeseed mealis well documented. Unlike the fatty liver hem-orrhagic syndrome, these hemorrhages are notassociated with increased liver or abdominal fat
  • SECTION 2.4Feed toxins and contaminants102 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONcontents. Certain strains of laying hens were moresusceptible than others, however, with moststrains it was not uncommon to see signs of thecondition. While liver hemorrhages have beensignificantly reduced in laying hens with intro-duction of canola meal, isolated cases are seenwhen feeding 10% or more of this product.Research to date suggests that this is the resultof intact glucosinolates, rather than any of theirproducts of hydrolysis. However, it is stillunclear how glucosinolates function in theetiology of hemorrhagic liver.An increase in weight of the thyroid stilloccurs following feeding of canola meal, althoughseverity is much reduced from that seen with theolder rapeseed varieties. Thiocyanate is respon-sible for the goitrogenic effect noted with theseproducts due to their effect on iodine uptake andmetabolism, and so increase in thyroid size is seen.Because thiocyanate is the end product of indoleglucosinolate hydrolysis and levels of thiscompound are still high in canola, then thisproduct probably accounts for the enlargedthyroids still seen with low glucosinolate meals.Another major problem with the feeding ofrapeseed or canola meal is egg taint which isexperienced in certain flocks of layers, andespecially brown egg layers containing RhodeIsland Red ancestory. This is the result of a singlemajor autosomal semi-dominant gene beingpresent which is responsible for the bird lackingthe ability to oxidize trimethylamine (TMA) toTMAoxide which is the odorless excretory product ofTMA. While the double low varieties of canolacontain very low levels of glucosinolates, thereis still sufficient present, along with the soluble tan-nins, to impair TMA oxidation and thus taintedeggs can result. Because brown-egg layers are quitecommon in many parts of the world, canola meal,in such regions is used sparingly for layers.Nitrates – The nitrate content of cereals and plantproteins can vary from 1-20 ppm. While havinglittle affect on the bird per se, reduction tonitrite, usually by intestinal microbes, can leadto toxicity. Nitrite is readily absorbed from thegut and diffuses into red blood cells where it oxi-dizes the ferrous iron of oxyhemoglobin to theferric state, forming methemoglobin, which isunable to transport oxygen. Because there hasbeen an interest in the role of dietary nitrite inthe incidence of pulmonary hypertension and spon-taneous turkey cardiomyopathy. Feeding broil-ers nitrite up to 1600 ppm had no effect on pul-monary hypertension. However, turkey poults fed1200 ppm nitrite had a numerically higher inci-dence of STC than did controls (20 vs. 5%).Interestingly, both chicks and poults developedanemia; poults appeared to be more sensitive tothe adverse effects of nitrite on hemoglobincontent since the minimum dietary level-caus-ing anemia was 800 ppm in poults and 1200 ppmin chicks. Decreased perormance was observedwith the highest dietary concentration. Theresults of this study indicate that the dietarylevels causing methemoglobinemia, anemia,and decreased body weight are not likely to beencountered in cereal grains and legume seeds.However, nitrate and nitrite may also be presentat significant levels in water sources.Tannins –These are water soluble polyphenolicplant metabolites that are known to reduce theperformance of poultry when fed at moderate lev-els in a diet. Grain sorghum is probably the mostcommon feedstuff which contains relativelyhigh levels of tannin. However, faba beans, rape-seed and canola meal all contain sufficient tan-nins to affect poultry performance.The growth depressing effect of tannins isundoubtedly due to their ability to bind proteins.Tannic acid is hydrolyzed by the chick to gallic
  • 103CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.4Feed toxins and contaminantsacid, its major hydrolytic product, and to alesser extent to the somewhat toxic compounds,pyroacetol and pyrogallol. A large portion of thegallic acid is methylated and excreted in the urineas methyl gallic acid. This pathway offers apossible explanation as to why additions ofmethionine, choline and other methyl donors havebeen reported to be beneficial when includedin diets containing tannic acid.Much of the work on toxicity of tannins hasinvolved purified tannic acid. Legume andcereal tannins are of a condensed type whiletannic acid is of a hydrolyzable type. Since thereare conflicting reports on the degree of growthdepression and the role of methionine in alleviatingtannin toxicity, it follows that the predominantdetoxification process may differ between thesetwo compounds. More recent work suggests thatwhile gallic acid is the breakdown product of bothcondensed tannins and tannic acid, and can bedetoxified by methyl groups, the stability ofcondensed tannins is such that this route ofdetoxification may be of little importance.i) Sorghum tannins - The nutritive value ofsorghum is usually considered to be 90 to 95%that of corn, due in large part, to its tannin content.There are a number of varieties of sorghum on themarket which are usually classified as bird resist-ant or non-bird resistant varieties. These have eithera low (less than 0.5%) or high (1.5% or higher)level of tannins. A number of toxic effects havebeen reported with the feeding of high tanninsorghum. These include depressed growth andfeed utilization, reduced protein digestibility,lower egg production and leg abnormalitieswith broilers.A number of procedures have been tried inan attempt to reduce the toxicity of the tanninsin sorghum. These include soaking in water oralkali solution, which are reported to deactivatetannins and thus improve the nutritive value ofthe cereal. Besides the addition of the methyldonors which have been reported to improve thefeeding value of high tannin sorghum, productssuch as polyvinylpyrrolidone, and calciumhydroxide, or a slurry of sodium carbonate havealso been reported to give positive responses.However, several crude enzyme preparations thathave been tried were not effective in enhancingthe feeding value of high tannin sorghum.Tannins have also been implicated in egg yolkmottling. Yolk mottling is a condition whichperiodically appears in a flock and without a directinvolvement of nicarbazin, gossypol or certainworming compounds, there is usually no readyexplanation for its appearance. While severalreports have suggested tannic acid and itsderivatives as possible causes, other than theaddition of commercial tannic acid at levelsabove 1%, there appears to be no mottling seenwith diets containing up to 2.5% tannins.There are reports suggesting that tanninsare bound tightly to a fraction of the nitrogen insorghum and that this reduces protein digestibil-ity. However, because the tannins are relativelyinsoluble they appear to have little influence incomplexing with protein. In a recent studywith turkeys, a high tannin sorghum varietywhen used at 40% in the diet, resulted indepressed performance to 8 weeks of age.However, the feeding of a similar level to turkeysbeyond 8 weeks of age had no detrimentaleffects. The authors suggest that a more fullydeveloped digestive system of the older birds maybe able to overcome the anti-nutritional effectsof the tannins.While dark colored varieties of sorghumseed usually contain higher levels of tanninthan do lighter colored varieties, seed color, ingeneral, is a poor indicator of the tannin contentof sorghum.
  • SECTION 2.4Feed toxins and contaminants104 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONii) Faba Bean Tannins - Raw faba beans areknown to result in depressed performance ofpoultry while autoclaving results in a significantimprovement in bird performance. Dehulling alsoresults in improved energy value with this effectbeing greater than can be accounted for byreduction in fiber content. The growth depressingproperties of faba beans are due to two water-acetone soluble fractions, one containing low weightpolyphenolic compounds, the other containingcondensed tannins, the latter being the major growthinhibiting substance. These condensed tanninsare similar to those found in sorghum and areconcentrated in the hull fraction.While proper heat treatment of faba beanscan markedly increase their nutritive value,there appears to be some detrimental effect onintestinal villi structure regardless of the degreeof heat treatment or the fraction of seed consumed.This has led to reports that factors other than thoseusually considered, such as protease inhibitors,phytates and lectins, may be contributing tothe low nutritional value of faba beans. Tannin-free varieties of faba beans are available thatcontain less than 0.1% condensed tannins in theirhulls compared to over 4% in the high tanninvarieties. These lighter colored seeds are ofimproved nutritive value. Regardless of tannincontent, appropriate heat treatment improves thenutritive value of faba beans.iii) Rapeseed and Canola Tannins - Rapeseed andcanola meal have been reported to contain 2 to3% tannin, which is concentrated in the hull. Thesetannins have been shown to contribute to the eggtaint problem of these meals, when fed tobrown-egg layers, due to their inhibitory effecton trimethylamine oxidase. The original methodfor assaying tannin also includedsinapine. Because the sinapine content ofcanola is around 1.5%, a value of 1.5% fortotal tannins is more realistic than earlierreported values of around 3%. With tanninsconcentrated in the hull of both rapeseed andcanola, the amount of extractable tannins has beeninvestigated and appears to range from 0.02 to2%. The ability of these tannins to inhibitamylase in-vitro was not detected. Hence, it hasbeen assumed that the tannins in rapeseed andcanola are bound in such a manner that theirinfluence on digestibility of other ingredients isnegligible.Lathyrism -As with many species of animals, poul-try are susceptible to lathyrism, a metaboliccondition caused by the consumption of legumeseeds of the genus Lathyrus, of which sweetpeas are a member. The seeds are rich inprotein (25 to 27%) and their availability andrelatively low cost in many Asian and mid-Eastern countries often results in their use inpoultry feeds. The causative agents for lathyrismare the lathyrogens, of which lathyrogenbeta-aminopropionitrile (BAPN) is the principletoxin found. However, there are some syntheticlathyrogens available that have been used instudying the condition.Lathyrism manifests itself in two distinctiveforms. Firstly, there is a disorder of the nervoussystem leading to a crippling condition andreferred to as neurolathyrism, and secondly adisorder of the collagen and elastin componentof connective tissue resulting in a skeletal and/orvascular disease and referred to as osteolathyrism.Typical symptoms seen with poultry consumingsignificant quantities of toxins are depressedperformance, ruffled feathers, enlarged hocks,curled toes, ataxia, leg paralysis and eventuallymortality.Most of the poultry research involves specificsynthesized lathyrogens rather than natural seeds.BAPN has been shown to inhibit cross-linking
  • 105CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.4Feed toxins and contaminantscompounds in elastin and collagen by inhibitingthe enzyme lysyl oxidase, an important componentin the synthesis of these compounds. It has alsobeen reported to reduce growth rate of chicks, poultsand ducklings and to reduce egg production ofadults of these species. BAPN can result indefective shell membranes, so ultimately affectingshell calcification, leading to malformed andsoft-shelled eggs. This effect is similar to that seenwith copper deficiency since the enzyme lysyloxidase is a metalloenzyme that requires copper.Consequently, there are reports of copperalleviating the symptoms of BAPN toxicity.While recommended maximum levels ofinclusion of the various lathyrus seeds, to avoidmetabolic problems, varies with the type ofseed and the lathyrogen content of the seed, ageneral recommendation would be to keep thedietary level of BAPN below 50 mg/kg of diet.While the addition of lathyrogens to a laying dietresults in a decrease in production after 4 to 5days, hens seem to return to normal productionin 10 to 14 days after receiving a normal diet.Interestingly there has been some researchinterest on the ability of BAPN to tenderizemeat from spent hens. This is obviously relatedto its effect in altering collagen cross-linking byinhibiting the enzyme lysyl oxidase.Gossypol -The use of cottonseed products in dietsfor laying hens has long been a problem for nutri-tionists as well as producers. As early as 1891there were reports of mottled egg yolks result-ing from the feeding of cottonseed meal to lay-ers. In the early 1930’s gossypol was identified asthe compound involved in discoloration of eggyolks when hens were fed cotton seed meal. Itsoon became evident that there were twoproblems that could occur with the feeding ofcottonseed meal to layers: the albumen ofstored eggs developed a pink color and thus thedisorder became known as pink egg white; andsecondly there was brown or olive pigment inthe yolks. This later defect was the result of gossy-pol from the cottonseed pigment glands interactingwith iron in the egg yolk.Although pink albumen discoloration isknown to occur spontaneously, it is usually seenwith ingestion of products from plants of thebotanical order, Malvales. Two naturally occurringcyclic fatty acids have been isolated from plantsknown to cause the unusual color. These com-pounds were called malvalic and sterculic acids.A color test developed many years ago byHalpen, can be used to identify cottonseed oil invegetable oil mixtures. The test has been shownto be very specific to cyclopropenoid compounds,especially malvalic and sterculic fatty acids.The pink-white albumen condition noted instored eggs, which is common with the ingestionof either malvalic or sterculic fatty acids, resultsfrom a combination of conalbumen and eggwhite protein mixing with iron that diffuses fromthe yolk. This is due, in part, to changes inmembrane permeability and an increase in yolkpH. The amount of these compounds fed,storage conditions and breed of hen, have all beenshown to influence the degree and incidence ofthe condition.Yolk discoloration is also caused by theingestion of gossypol and/or malvalic or sterculicacid. However, there is a difference in incidenceand degree of discoloration and mottling depend-ing on whether intact gossypol or the fatty acidsare involved. Changes in membrane permeabilityand a shift in yolk and albumen pH result in waterand albumen protein migrating to the yolks.The severity of the condition will depend on theamount of gossypol ingested and can lead to pastycustard-like or viscous yolks being observed. Thesecan be seen at ovulation but the condition can
  • SECTION 2.4Feed toxins and contaminants106 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONbe accentuated with storage. There are reportsof increased embryo mortality during the first weekof incubation when breeders are fed high levelsof malvalic or sterculic acid, however, thelevels fed must be much higher than thosenormally present in laying hen diets.Although varieties of cottonseed have beendeveloped that are gossypol free, their low yieldhas meant that they are not widely used incommercial production. Consequently, muchof the cottonseed grown world-wide still containsappreciable quantities of gossypol. Processingmethod can markedly reduce the gossypolcontent of the meal to levels less than 0.04% freegossypol. In addition, soluble iron salts can beadded to diets containing cottonseed meal. Theiron will complex with gossypol reducing its toxiceffects. In a recent report, broilers fed a diet withup to 30% cottonseed meal, with soluble ironadded (to provide a 2:1 ratio of iron to freegossypol) resulted in no detrimental effect on weightgain or liveability.Alkaloids - Alkaloids are found in a number offeedstuffs but by far the most important are thelupine legumes. Seeds of the plant Crotalaria retusaL., contain up to 4.5% of the pyrolizidine alkaloidmonocrotaline and these can be a problem incereal contamination in some areas of Asia andAustralia. The older varieties of lupines were oftenreferred to as bitter lupines, due to the presenceof significant quantities of quinolizidine alkaloids,mainly lupanine. These alkaloids affect thecentral nervous system causing depressedlaboured breathing, convulsions and death fromrespiratory failure. Newer varieties of lupines nowbeing grown are very low in alkaloids (less than0.02%) and have been shown to be well toler-ated by poultry.One of the most common sources of alkaloidsfinding its way into animal feeds is grain con-taminated with ergot. Samples of ergot canrun as high as 0.4% total alkaloids. Chickensreceiving 1 to 2% of ergot in their diet canshow symptoms ranging from depressed growthto necrosis of the extremities, staggers, ataxia,tremors and convulsions.c. AutointoxicationAutointoxication could be defined as self-poisoning as it is endogenous in origin andresults from the absorption of waste products ofmetabolism or from products of decompositionin the intestine. High fiber diets fed to young chickscan cause obstruction of the digestive tract withsubsequent absorption of products of decompositionor metabolic wastes. Litter consumed by chicksor over-consumption of green grass or plantscan also lead to gut impaction problems.The chilling or overheating of chicks can leadto vent pasting and occlusion resulting in stasisof the intestine contents with autointoxicationbeing the end result. Birds suffering from autoin-toxication are anorexic, and show increasedwater consumption, followed by weakness andprostration. A generalized toxaemia may resultleading to nervous symptoms prior to death.d. Bacterial toxinsAlthough losses in birds due to bacterialtoxins are not of great economic importance, theydo occasionally result in heavy losses in a par-ticular flock. The main organism affecting poul-try is Clostridium botulinum. No significantlesions are found in botulism poisoning and apositive diagnosis is usually based on identificationof the organism and its toxin.
  • 107CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.4Feed toxins and contaminantsBotulism is caused by the toxin produced fromthe C. botulinum organism under anaerobicconditions. C. botulinum is a saprophyte foundin soil and dirt and can also be found in intestinalcontents and feces. The mere presence of theorganism is sufficient to cause disease or to beof diagnostic significance. Growth of the organ-ism, in anaerobic conditions, results in theproduction of toxins. Botulism can result frombirds eating carcasses of birds which have diedfrom the disease and also fly larvae from suchcarcasses. The toxins present in the meat areingested by larva rendering them extremelypoisonous. Symptoms may appear within afew hours to a day or two after contaminated feedis eaten. The common symptom noted is paral-ysis, with the leg and wing muscles first affected.If the neck muscles are affected the head hangslimp, hence the name ‘limberneck’ which hasbeen used to refer to the disease. In mild cases,leg weakness, ruffled feathers and soft pastyfeces may be noted. The severity of the diseasedepends on the amount of toxin consumed.However, death usually occurs as this toxin is verypotent. Losses in birds are most commonly dueto type A and C toxins. Type A, is common in themountainous regions of North and SouthAmerican,while type C is world-wide in distribution.For many years, a disease of wild ducks andother aquatic birds was common in the westernpart of North America. It is now known that thisis due to botulism poisoning. Insect larvae in anaquatic environment may die as the result ofanaerobic conditions caused by decaying vegetation.Whentheselarvaeareeatenbybirds,botulismorgan-isms invade tissues and produce toxins. Preventionrelates to proper management procedures that elim-inate dead and decomposed carcasses around apoultry house. A good rodent and fly control pro-gram is also essential as is screening of the build-ing to eliminate entry of wild birds.e. Chemotherapeutic drugsWhile the use of various pharmaceuticalcompounds has contributed significantly to thedevelopment of the modern poultry industry, theirmisuse can result in toxicity. Some of the morecommon drugs that can result in problems if usedat toxic levels are:i. Sulfonamides – Toxicity is manifested by signsof ruffled feathers, paleness, poor growth andincreased blood clotting time. Hemorrhages inskin and muscle may be noted and necrosis of theliver, spleen, lungs and kidney are often seen.ii. Nitrofurans – Toxicity results in depressedgrowth and hyperexcitability, where chickscheep and dash about. Enteritis and congestionof the kidneys and lungs, along with bodyedema and cardiac degeneration may be noted.iii. Nicarbazin – Toxicity in chicks results inbirds being listless and showing signs of ataxia,with incoordination and a stilted gait especial-ly in hot weather. Fatty degeneration of the livermay be noted. The most common problemwith nicarbazin is its effect on laying hens.Brown eggs will be depigmented and yolk mot-tling may be noted with white and brown eggs.f. Toxic seedsPhytotoxins can be considered as any toxicsubstance derived from plants including roots,stems, leaves, flower and seeds. Some plants aretoxic throughout the whole growing seasonwhile others are only toxic during certain stagesof development. The majority of toxic plants arerelatively unpalatable and are usually avoidedby birds. However, with the absence of succulentfeed, range birds will consume sufficient foliageor seeds to result in poisoning. Some of the morecommon poisonous plants are as follows:
  • SECTION 2.4Feed toxins and contaminants108 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONi) Black locust (Robinia pseudoacacia) –The toxinis the glycoside robitin-alectin (hemagglutinin).It has been reported that the leaves of black locustare toxic during early July and August in the N.Hemisphere and cause mortality with chick-ens if consumed at this period. Symptomsnoted are listlessness, diarrhea, anorexia and paral-ysis with death occurring within several days.Hemorrhagic enteritis may also be seen.ii) Castor bean (Ricinus communis) – Manylegume seeds contain a protein fraction whichis capable of agglutinating red blood cells.These compounds are referred to as lectins andthey vary widely in their degree of specificity totypes of red blood cells and also their degree oftoxicity. Such legumes must be degraded by heattreatment in order to detoxify them and soenhance their nutritive value. Castor bean wasone of the first such legumes to be investigatedand a lectin called ricin was isolated which isextremely poisonous. However, the steaming ofcastor meal for 1 hour will reduce the toxicityof the meal to 1/2000 of its original level.Toxicity is seen as progressive paralysis startingwith the legs and progressing to completeprostration. With the exception of blood-stainedmucus in the droppings, clinical signs are indis-tinguishable from those of botulism. A paleswollen mottled liver is often seen with petechialhemorrhages present on the heart and visceral fat.iii) Coffee bean seed (Cassia occidentalis;C.obtusi-folia) – Mechanical harvesting methods haveincreased the danger of contamination of cornand soybeans with coffee bean plants which arefrequently found in relatively large numbers inthe southern USA. At all levels of incorporationof the anthraquinone lectins from coffee seeds,egg production and weight gain are reduced.Platinum colored yolks and profuse diarrhea arealso noted with layers. Birds fed 2 to 4% of thecoffee seeds become ataxic or partially paralysedbefore death. Muscle lesions are similar tothose seen with vitamin E deficiency. Death oftenoccurs due to a hyperkalemic heart failure.Production will return to normal with the removalof the contaminated feed.iv) Corn cockle (Argostemma githago) – Corncockle is often harvested with wheat and socan become incorporated into poultry feeds. Thediet must contain 5% or more of corn cockle toshow toxic symptoms, which are caused bygithagenin, a plant saponin. General weakness,with decreased respiration and heart rate may benoted often associated with diarrhea.Hydropericardium and edema of the intestine canbe seen along with petechial hemorrhages in themyocardium and congestion and degenerationof the liver.v) Coyotillo (Karwinskia humboldtiana) – Thisplant is indigenous to southwest Texas andMexico. The fruit and seed are toxic to poultryand 3 to 4 days after ingestion generalized tox-aemia signs can be noted, followed by paraly-sis and death.vi)Cacao(Theobromacacao) –Highlevelsofcacaobean wastes (in excess of 7% of the diet) arerequiredtoshowtoxicsymptomscausedbythetoxintheobromine. Such symptoms include nervous andexcitable birds. Birds die in convulsions andusually are on their back with legs drawn tightlyagainst their body. The comb is often cyanotic.vii) Crotalaria seed – A few species are toxic topoultry the most problematic being C. spectabilisand C. giant (striata). The toxin is a pyrolizidinealkaloid, designated, monocrotaline. Crotalariais a small black or brownish seed and is a con-taminant in corn and soybeans in the southeastUSA. One percent in a chick diet can result indeath by 4 weeks of age. Birds become huddled
  • 109CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.4Feed toxins and contaminantshaving a pale comb and diarrhea and mayexhibit a duck-like walk. With young birdsabdominal fluid and edema, similar to that seenwith ascites may be noted. With mature birds, thereis a reduced egg production and massive liver hem-orrhages may be noted. The lesions are similarto those reported for toxic fat and salt poisoning.viii) Daubentonia seed (Daubentonia longifolia) –This seed can be a problem in the southernUSA. As little as 9 seeds can cause death in 24– 72 hours. The comb can be cyanotic, with thehead hanging to one side. Emaciation anddiarrhea may also be noted. Severe gastroenteritis,ulceration of the proventriculus and degenera-tion of the liver are not uncommon.ix) Glottidium seed (Glottidium vesicarium) –Thisseed is often found in the southeastern USA.Clinical symptoms are a cyanotic comb andwattles, ruffled feathers, emaciation andyellow diarrhea. Necrotic enteritis as well as liverand kidney degeneration are also commonobservations.x) Death camas (Zygadenus) –This is a green rangeplant with an alkaloid toxin called nuttallii.Consumption of 5 to 10 g by a chicken can resultin clinical symptoms in 12 hours that includeincoordination, diarrhea and prostration fol-lowed by death.xi) Vetch (Vicia sativa) - Vetch belongs to theLeguminosae family which is related to thelegumes Lathyrus, Pisum and Ervum. It is com-mon in the northwest USA and produces acyanogenic glucoside called viciana, which isconverted by the enzyme vicianase into hydro-cyanic acid. Problems comparable to lathyrismare observed, including excitability, incoordination,respiratory problems and convulsions.xii) Milkweed – Two common species areAsclepias tuberosa and A. incarnata. They con-tain the bitter glucoside, asclepdin, which is toxicto birds. Symptoms vary widely depending onthe quantity of material consumed. The first signis usually lameness, developing quickly intocomplete loss of muscle control. The neckbecomes twisted with the head drawn back. Insome cases symptoms gradually subside. Infatal cases, symptoms become more progressiveand prostration, coma and death result. No char-acteristic lesions are seen on necropsy.xiii) Algae – Certain types of algae, includingMicrocystis aeruginosa, which readily grows inmany lakes, can become concentrated by windand deposited on shore or in shallow water.Degradation of this material produces toxins whichhave been responsible for losses in wild anddomestic birds. The condition is usually notedin summer months. Toxicity is proportional tothe amount of toxin consumed. Death canresult in 10 to 45 minutes for mature ducksand chickens. Clinical symptoms include rest-lessness, twitching, muscle spasms, convul-sions and death. These symptoms aresimilar to those seen with strychnine poisoning.
  • SECTION 2.5Feed manufacture110 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION2.5 FEED MANUFACTUREIn the early days of poultry nutrition feeds con-tained relatively few synthetic ingredients andthe smallest amount of any addition amount-ed to 0.5% or more. Some natural ingredients, how-ever,havebeengraduallyreplacedandsupplementedby extremely small quantities of synthetic and puri-fied ingredients, especially the vitamins, traceminerals, pigments and various pharmacologicalcompounds. Consequently, the proper mixing offeed requires ever increasing technical knowledge.Improper mixing can result in variation in thequality of feed and vitamin or mineral deficienciesresultinginlackofprotectionagainstdiseaseorchem-ical or drug toxicity.a. Vitamin-Mineral PremixesMicro-ingredients should be properly premixedbefore being added to a feed. It is desirable tohave similar physical characteristics amongingredients to be premixed. The diluent suggestedfor use in the vitamin-mineral premixes is groundyellow corn or wheat middlings, both being ofmedium grind for best results. If thecarrier is too coarse, it is not possible to obtaingood distribution of the supplements, while toofine a carrier leads to dustiness and caking.For mineral mixes, limestone or kaolin (china clay)make satisfactory carriers. Where premixes arebeing stored for relatively short periods of time,the vitamin and mineral premix can be combined.However, where mixes are to be stored formore than 6 weeks in a warm moist environment,it may be advisable to make separate vitamin andmineral mixes. Also, if premixes are to beshipped long distances and thus subjected to agreat deal of handling, and perhaps high tem-perature, it is advisable to make separate vitaminand mineral mixes. This helps to reduce thephysical separation of nutrients and leads toless vitamin deterioration.When vitamin-mineral premixes are pre-pared in quantity ahead of time, they should beclearly labeled and stored in a cool dry place forfuture use. With the addition of an antioxidant andthe margins of safety provided in mostpremixes, they can be held for two to threemonths under ideal conditions. Rather than sug-gesting the use of products with specific poten-cies to supply the vitamins and other nutrients (Table2.26) the units or weights of the compoundshave been indicated and the decision as to prod-uct use is left to the individual. Some feed man-ufacturers are capable of making premixes frommore concentrated vitamin and mineral preparations,since this usually results in a cost saving com-pared with the use of more dilute preparations.The choice of potency of products for use in thepremixes should be governed, to a large extent,by personnel and the facilities available. Becausevitamin and mineral supplements represent a rel-atively small part of the total cost of a diet,margins of safety are being added in most cases.Lower levels can be used with satisfactory resultsunder ideal conditions.The direct addition of vitamin premixes or othersupplements to the feed, at a usage rate less than1 kg/tonne, is not usually recommended. Thesemicro-ingredients should be suitably premixedfirst, so that at least 1 kg/tonne is added. It is gen-erally recommended that vitamin-mineral pre-mixes be added to the mixer after about one-halfof the other ingredients have been included. Thetime required for a satisfactory mix is very importantand varies considerably depending upon theequipment used. Usually 2 – 3 minutes is the opti-mum for horizontal mixers and up to 5 minutes forvertical machines although mixing times are beingcontinuallyreducedwithnewerequipment. Thiscanvary with the type of mixer and manufacturer’sspecifications should always be followed.
  • 111CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.5Feed manufactureTable2.26Vitamin-mineralpremixes(withoutcholine)–allpremixesshouldbemadeupto1–5kgbytheadditionofacarriersuchaswheatmiddlings.Theamountsshownbelowarethelevelsofnutrientstobeaddedpertonneoffinishedfeed.CHICKENTURKEYWATERFOWLVITAMINSStarterGrowerLayingBreederStarterGrowerBreederStarterGrowerBreederVitaminA(M.IU)10.08.07.511.010.08.011.010.08.010.0VitaminD3(M.IU)3.53.33.33.33.53.33.32.52.53.0VitaminE(T.IU)30.020.050.070.040.030.0100.020.015.040.0Riboflavin(g)6.05.05.08.06.05.08.05.04.05.5Thiamin(g)4.04.04.04.04.04.04.04.04.04.0Pyridoxine(g)3.33.33.35.03.33.35.03.33.33.3Pantothenicacid(g)15.010.010.015.015.012.015.012.010.010.0VitaminB12(g).015.012.015.015.015.012.015.015.010.015Niacin(g)50.030.040.050.050.040.050.050.040.050.0VitaminK(g)2.02.02.03.02.02.03.01.51.51.5Folicacid(g)1.01.01.01.01.00.51.01.00.50.5Biotin1(g)0.150.100.100.150.20.150.20.10.10.1MINERALSManganese(g)70.070.070.070.070.070.070.070.070.070.0Zinc(g)60.060.060.060.060.060.060.060.060.060.0Copper(g)8.08.08.08.08.08.08.08.08.08.0Selenium(g)0.30.30.30.30.30.30.30.30.30.3Iron(g)50403040504040403030AllvitaminpremixesshouldcontainEthoxyquintoprovide125g/tonnefeed.1Increaseifdietcontains>10%wheat.
  • SECTION 2.5Feed manufacture112 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONThe segregation of ingredients in a mixed feedcan occur due to improper handling after mixing.This can be a problem when mash feeds containingno added fat are blown into bulk bins. However,care in unloading and a cyclone on top of thebulk tank will help overcome the problem. Thisis usually not a great problem when the feed ispelleted or crumbled.b. Vitamin StabilityNaturally occurring vitamin E is quite unstable,particularly in the presence of fat and traceminerals, however, vitamin E added as a sup-plement usually is in a highly stable form (e.g.gelatin coated beadlet containing an antioxidant).Vitamin A in fish oil and pro-vitamin Acompounds in yellow corn are easily destroyedin the typical mixed ration. Most dehydrated greenfeeds are now treated with an antioxidant thathelps prevent the destruction of the pro-vitaminA compounds during storage. Today, mostpoultry feeds contain supplementary gelatin-or starch-coated synthetic vitamin A which is quitestable. The inclusion of antioxidants in the feedhelps to retain the potency of vitamins A and Ein mixed feed.Vitamin D3 is the only form of the productto be used in poultry diets, since birds cannotmetabolize vitamin D2. Vitamin D3 supple-ments are available in a dry, stabilized form. Theseproducts are reported to be stable when mixed withminerals. Hy-D®, a commercial form of 24(OH)D3is also very stable within premixes and mixed feed.Calcium pantothenate may be destroyed inthe presence of supplements containing acidingredients such as niacin, arsenilic acid and 3-nitro.The calcium chloride complex of calciumpantothenate is more stable than is conventionalcalcium pantothenate under acid conditions.Recent work has shown that thiamin, folic acid,pyridoxine and some vitamin K supplements canbe relatively unstable in the presence of tracemineral supplements. This is especially truewhere the minerals are supplied as sulphatesalts, hence special consideration must be givento the above mentioned vitamins whenpremixes contain both vitamins and minerals, andstorage is for 4 – 6 weeks.Most of the other vitamins are fairly stable.However, care should be taken in storing vita-mins to ensure their potency. Always store in acool, dry, lightproof space or container. Whilevitamin supplements are an extremely importantpart of a well balanced diet, animals usually havesufficient body stores to meet their require-ments for several days. Modern poultry farmsreceive feed deliveries on a weekly or evenmore frequent basis. Failure to incorporate thevitamin premix in a delivery of feed will likelyhave little or no effect on the performance of mostclasses of poultry, assuming the ‘next delivery’contains the vitamin supplement. For breedingbirds, this may not be true, especially forriboflavin, which could well affect hatchabilityif hens are fed a deficient diet for 5 to 7 days.c. PelletingThe pelleting process usually involves treat-ing ground feed with steam and then passing thehot, moist mash through a die under pressure. Thepellets are then cooled quickly and dried bymeans of forced air. Sufficient water should beapplied so that all feed is moistened. Pelleting attoo low a temperature, or with too little steam, resultsin a ‘shiny pellet’, due to increased friction on thepellet going through the die. Often such pelletsare only the original mash enclosed in a hard cap-sule and have not benefited from the ‘cooking’process brought about by moisture and heat.
  • 113CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.5Feed manufactureOptimum moisture content of a feed requiredfor good pelleting will vary with the composi-tion of the feed, however, a range of 15 to 18%moisture is usually desirable. Feeds containingliberal quantities of high fiber ingredients willrequire a higher level of moisture while feeds lowin fiber will require less moisture. A good pellet,when hot, can be reduced to two-thirds of its lengthwithout crumbling. Such feed has been ‘steam-cooked’ and holds together well. Rations canbe pelleted at any temperature up to 88ºC thatwill allow for maximum production per hourwithout any major fear of vitamin destruction.Feed mills sometimes experience difficulty inobtaining good pellets when manufacturingcorn-soybean diets containing added fat. Productssuch as lignosol or bentonite are reasonablyeffective as binding agents, however, they ahave little nutritive value, and so one should con-sider whether the advantage of introducing suchmaterial into pelleted or crumbled diets warrantsthe cost. The inclusion of 10 to 15% of wheat,wheat middlings or to a lesser extent barley willoften give a pellet of satisfactory hardness. Whenthese ingredients are too expensive, the additionof about 2% of extra water to the mash will aidin producing a better pellet. If this procedure isfollowed, however, extra drying of the pellets isrequired so that mold growth does not occur dur-ing storage. Work in our laboratory has indicatedthat molasses may be used as a pellet binder. Inaddition to aiding in pelleting, molasses unlikeother binders, also contributes energy to thediet and so inclusion levels of 1 to 2% in certaindiets may be beneficial.In addition to the advantages of less feedwastage and ease of handling, pelleted diets aremore efficiently utilized by poultry. While someof this improvement is due to chemical changesbrought about by heat, moisture and pressure,a significant part of the enhanced efficiency isdue to birds spending less time when eatingpellets resulting in a reduction in maintenanceenergy requirements by the bird. This situationwas demonstrated in the classical study byJensen et al. (Table 2.27).Table 2.27 Time spent eating mashand pelleted dietsAv. time spent Av. feedAGE eating consumed(min/12 hr day) (g/bird/12 hr)Mash Pellets Mash PelletsTurkeys(38-45 d) 136 16 62 57Chickens(21-28 d) 103 34 38 37Jensen et al. (1962)The need for good quality pellets is oftenquestioned by feed manufacturers sinceregrinding of pellets or crumbles and feeding theseto birds has little apparent effect on performance.There seems little doubt that good qualitycrumbles and pellets can be advantageous forimproving the growth rate of turkeys. However,pellet quality seems of less importance withbroiler chickens, especially where high-energydiets are considered. More important in thepelleting process is the treatment of feed with steamand pressure, although it is realized that in certainmarkets it is difficult to sell feed that is not of ‘ideal’pellet quality.d. Expanding, extrusion andthermal cookingExtrusion has been used for a number of yearsto produce dry cereal snack foods and more recent-ly, various pet foods. Extrusion usually involveshigher temperatures and pressure than doesconventional steam pelleting, and so there is greater
  • SECTION 2.5Feed manufacture114 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONpotential for starch gelatinization and theoreti-cally higher digestibility. Extrusion is howevermuch slower than conventional pelleting, andinitial capital cost is very high.Thermal cooking offers the most extremeprocessing conditions, where high temperaturescan be maintained for very long periods oftime, relative to pelleting, extrusion or expansion.Thermal cooking will result in the best possiblestarch gelatinization etc. and will also give thebest control over microbial content.While all heat processing conditions aregoing to reduce microbial counts in feed therewill be a concomitant loss of heat-sensitivenutrients such as some vitamins and aminoacids. In this context synthetic amino acidsmay be more susceptible to heat processingthan those naturally present in other ingredi-ents. One recent study suggested some 6% lossof total methionine in an extruded broiler starterthat contained 0.18% supplemental methionine.For most vitamins, other than vitamin C andMSBC, normal pelleting conditions are expect-ed to result in 8 – 10% loss of potency. Extrusionhowever, which usually employs much highertemperatures, can lead to 10 – 15% loss of mostvitamins. Under any heat treatment conditionsthere will always be significant loss ( 50%) ofregular forms of vitamin C, and up to 30 – 50%loss of MSBC (Table 2.28).Table 2.28 Effect of steam pelleting, extrusion and expansion on loss ofvitamin potencyLoss of Vitamin Potency (%)Pelleting Expander ExtrusionVITAMIN (82ºC, 30 sec) (117ºC, 20 sec) (120ºC, 60 sec)Vitamin A (beadlet) 7 4 12Vitamin D3 (beadlet) 5 2 8Vitamin E 5 3 9MSBC 18 30 50Thiamin 11 9 21Folic acid 7 6 14Vitamin C 45 40 63Choline chloride 2 1 3Adapted for Coehlo, (1994)
  • 115CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.6WaterFig. 2.2 Water consumption of laying hensin relation to time of oviposition.(from Mongin and Sauveur, 1974)2.6 WATERWater, is the most critical nutrient thatwe consciously supply to birds, yetin most instances, it is taken completelyfor granted and often receives attention only whenmechanical problems occur. Water is by far thelargest single constituent of the body, and rep-resents about 70% of total body weight. Of thisbody water, about 70% is inside the cells of thebody and 30% is in the fluid surrounding the cellsand in the blood. The water content of the bodyis associated with muscle and other proteins.This means that as a bird ages, and its body fat con-tent increases, then its body water contentexpressed as a percent of body weight willdecrease. The bird obtains its water by drinking,from the feed and by catabolism of body tissueswhich is a normal part of growth and development.a. Water intakeWater intake of a bird increases with age,although it decreases per unit of body weight.Drinking behaviour is closely associated with feedintake, and so most factors affecting feed intakewill indirectly influence water intake. Atmoderate temperatures, birds will consumealmost twice as much water by weight as theyeat as feed. Any nutrients that increase mineralexcretion by the kidney will influence water intake.For example, salt, or an ingredient high insodium, will increase water intake.Similarly, feeding an ingredient high inpotassium such as molasses or soybean meal, orcalcium/phosphorus sources contaminated withmagnesium, will result in increased water intake.Such increases in water intake are of no majorconcern to the bird itself, but obviously result inincreased water excretion and so wetter manure.Table 2.29 indicates average water consumptionof various poultry species maintained at 20 or32ºC. These figures indicate approximate waterusage values and will vary with the stage ofproduction, health and feed composition. Asa generalization, for any bird up to 8 weeks ofage, an approximation of water needs can becalculated by multiplying age in days x 6 (e.g.42 d = 252 ml/d).In calculating the water needs of egg producingstock, it should be realized that water intake isnot constant throughout the day, rather it variesdepending upon the stage of egg formation (Fig2.2). These data clearly show a peak in water con-sumption immediately following egg laying,and again, at the time just prior to the end of anormal light cycle. This means that water needsmust be accommodated during these peak times(around 10 – 11 a.m. and 6 – 8 p.m.) within a6 a.m. – 8 p.m. light cycle, because most birdswill be in the same stage of egg formation as direct-ed by the light program.
  • SECTION 2.6Water116 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONTable 2.29 Daily ad-lib water consumption ofpoultry (litres per 1,000 birds)20ºC 32ºCLeghorn pullet 4 wk 50 7512 wk 115 18018 wk 140 200Laying hen 50% prod. 150 25090% prod. 180 300Non-laying hen 120 200Broiler breeder pullet 4 wk 75 12012 wk 140 22018 wk 180 300Broiler breeder hen 50% prod 180 30080% prod 210 360Broiler chicken 1 wk 24 403 wk 100 1906 wk 240 5009 wk 300 600Turkey 1 wk 24 504 wk 110 20012 wk 320 60018 wk 450 850Turkey breeder hen 500 900Turkey breeder tom 500 1100Duck 1 wk 28 504 wk 120 2308 wk 300 600Duck breeder 240 500Goose 1 wk 28 504 wk 250 45012 wk 350 600Goose breeder 350 600These figures indicate approximate water usage values and will vary with the stage ofproduction, health and feed consumption.
  • 117CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.6WaterThe contribution of feed is not usuallyconsidered in calculating water balance, yetmost feeds will contain around 10% of freewater. Other bound water may becomeavailable during digestion and metabolism,such that 7 – 8% of total requirements canoriginate from the feed.Water is created in the body as a by-productof general metabolism. If fats are broken down,then about 1.2 g of water are produced from eachgram of fat. Likewise protein and carbohydratewill yield about 0.6 and 0.5 g per gram respec-tively. Total metabolic water can be moreeasily estimated from the bird’s energy intakebecause on average 0.14 g of water is producedfor each kcal of energy metabolized. This meansthat for a laying hen, consuming 280 kcalME/day, about 39 g of metabolic water will beproduced. Feed and metabolic water togethertherefore account for about 20% of total waterneeds, and so are very important in the calcu-lation of water balance.b. Water outputThe quantities of water excreted in the fecesand urine are dependent on water intake. Broilerchickens produce excreta containing about 60– 70% moisture, while that produced by thelaying hen contains about 80% moisture. For thelaying hen at least, the quantity of waterexcreted in the feces is about four times thatexcreted as urine. Undoubtedly, this loss issubject to considerable variation with the amountand nature of undigested feed.Evaporation is one of four physical routes bywhich poultry can control their body tempera-ture. Due to its molecular structure and bonding,water has an unusually high latent heat ofvaporization. Some 0.5 kcals of heat are requiredto vaporize one gram of water. Evaporativeheat loss takes place mainly through therespiratory tract. The fowl has no sweat glands,consequently evaporation via the skin isminimal. Evaporation overwhelmingly occursvia the moist surface layer of the respiratorytract to the inspired air which is ‘saturated’ withwater vapor at body temperature. Evaporationrate is therefore proportional to respiratory rate.Heat loss through evaporation represents onlyabout 12% of total heat loss in the broiler chickenhoused at 10ºC, but this increases dramaticallythrough 26 – 35ºC where it may contribute asmuch as 50% of total heat loss from the body.At high temperatures, evaporative water loss willapproximate water intake and so this obviouslyimposes major demands on the ventilation systems.c. Water balance anddehydrationUnder normal physiological conditions foradult birds, water intake and output are controlledto maintain a constant level of water in thebody. A positive water balance is found in thegrowing bird to accommodate growth. Withdrinking water being supplied ad libitum undermost commercial conditions, dehydration dueto lack of drinking water should not occur. Theadverse effects of short term reduced waterintake are often a result of a concomitantreduction in feed intake.The turkey poult is most susceptible to dehy-dration resulting from drinking water deprivation,and mortality occurs when drinking water isre-introduced to the poults. Poults 11 days of age,subjected to a 48-hour period of water deprivation,showed 83% mortality following reintroductionof ad libitum cold water, and in most casesdeath occurred within 30 minutes. Poults 18 daysof age showed less mortality which was some-what delayed (2 –34 hours) while older turkeyssubjected to the same conditions showed no
  • SECTION 2.6Water118 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONmortality. The exact reason for this mortality isnot fully understood. Poults deprived of watershow reduced body temperature, and whenwater is introduced, body temperature continuesto decrease for 30 minutes or so. Poults oftendrink large amounts of water following dehydration,and it has been suggested that the problemrelates to simple water intoxication and associateddilution of electrolytes in the body. If young poultsare dehydrated for whatever reason, thenadministration of electrolytes in the water maybe beneficial. This problem does not seem to occurwith chickens.d. Drinking water temperatureWater offered to birds is usually at ambienttemperature. This means that for laying birdshoused under controlled environmental condi-tions, the temperature of drinking water is heldfairly constant, while for broiler chickens, watertemperature decreases with age correspondingto a reduction in brooding temperature. It is onlyfor the first few days of a chick’s life that drinkingwater temperature is specified, where traditionalmanagement recommendations suggest the useof ‘warm’ water. However, there is little documentedevidence supporting this recommendation.Birds drink more water at higher environmentaltemperatures, yet the cooling of water mayresult in even higher intakes. Table 2.30 outlinesthe results of a small scale study conductedwith layers housed at 33ºC.Table 2.30 Layer performance at 33ºCwith hot vs cold drinking waterWater temperature33ºC 2ºCFeed/bird/day (g) 63.8 75.8Egg production (%) 81.0 93.0Egg weight (g) 49.0 48.5When birds received cool water for a 4-weekperiod, they were able to maintain peak egg pro-duction, possibly due to higher feed intake.Under commercial conditions, with long runs ofwater pipe, it is obviously very difficult to dupli-cate these conditions. However, it does show theimportance of trying to keep the water as cool aspossible, and in this regard, the usual practice ofplacing water tanks on high towers in direct sun-light should be seriously questioned.e. Water restrictionMost birds should have continuous access towater. Some breeders recommend water restric-tion of laying hens as a means of preventing wetmanure, especially in hot climates, althoughserious consideration should be given to other pre-ventative measures prior to this last resort.Production may drop as much as 30% whenhens are deprived of water for 24 hours, and it maytake as long as 25 to 30 days before productionreturns to normal. Similar results have beenreported for broilers where decreases in water sup-ply have resulted in marked depressions in weightgain. Table 2.31 shows the results of a con-trolled test where water restriction was imposedon broilers. There was a marked drop in feed intake-with the greatest reduction occurring with the first10% reduction in water intake, causing a 10%decline in feed intake.Table 2.31 Effect of water restric-tion on relative weekly feed con-sumption of broilersAge (weeks) Degree of water restriction (%)0 10 20 30 40 502 100 84 84 75 84 714 100 99 102 90 85 806 100 88 81 78 73 718 100 86 83 79 74 67Total 100 90 87 81 77 73* All birds receive water ad libitum for first week.(Data from Kellerup et al. 1971)
  • 119CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.6WaterThe effect of an accidental 48-hour cut inwater supply to layers is shown in Fig. 2.3.Production dropped off very quickly to virtu-ally 0%, although interestingly a few birdsmaintained normal production. Most birdsthat resumed production within 28 d achievednormal output for their age, and there was anindication of improved shell quality.For certain classes of stock, intentional waterrestriction is used as a management tool. To date,this is most common with broiler breeders fedon a skip-a-day program. Water restriction mayoccur on both feed-days and off-feed days.Restriction on off-feed days is done because itis assumed that birds will over-consume wateron these days due to hunger or boredom.However, it seems as though breeders do not drinkthat much water on an off-feed day (Table 2.32).All birds drank the same average amount ofwater over a 2 day feeding schedule regardlessof water treatment. When birds are givenfree-choice water, they obviously over-consumeon a feed-day, but drink little on an off-feed day.These data suggest the need for water restrictionof skip-a-day fed birds, although specialattention on feed-days rather than off-feed dayswill be most advantageous in preventing wet litter.Table 2.32 Water intake of 13week-old broiler breeders(ml/bird/day)Water restrictedAd-libeach only on waterday feed daysFeeding day 175 182 270Non-feed day 108 109 36Average 141 145 153Fig. 2.3 Effect of a 48-hour period of waterdeprivation on egg numbers.f. Water qualityWater quality should be monitored withassays conducted at least each 6 months.Chemical contaminants are the most seriousproblem affecting water quality. However,poultry usually adjust to high levels of certainminerals after a period of time, and so only in arelatively small number of cases does themineral content of water significantly affect theperformance of a flock. There are certain areaswhere water salinity is high enough to adverselyaffect flock performance. In such cases, it maybe necessary to remove some of the supplementalsalt from the diet. However, this should bedone only after careful consideration to ensurethat there will be a sufficient salt intake becauseperformance can be severely reduced if saltintake is too low.Any bacterial contamination of water is anindication that surface water is entering thewater supply and steps should be taken to cor-rect the situation. Alternatively, the water maybe chlorinated to eliminate contamination.Another problem that can exist with water is a
  • SECTION 2.6Water120 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONbuild-up of nitrates or nitrites. Such contaminationis usually an indication of run-off from animalwastes or fertilizers leaching into the watersystem. Although the standard for human watersupply is 10 to 20 ppm of nitrate nitrogen, higherlevels can usually be tolerated by animals.Levels beyond 50 ppm need to be present beforewater is suspected as a factor in the poor per-formance of poultry. As nitrites are 10 times moretoxic than nitrates, and because bacteria in theintestinal tract and in the water supply canconvert nitrates to nitrites, levels of these twocontaminants in the water supply must be keptto a minimum. Superchlorination of the waterwill quickly oxidize nitrites to nitrates therebyreducing their toxicity. Before initiating a super-chlorination program, check with a localpathologist to ensure a proper level of chlorinationin order not to interfere with the performance orefficiency of vaccines or other drugs.Table 2.33 Concentration of waterminerals above which problemsmay occur with poultry (ppm)Total soluble salts (hardness) 1500Chloride 500Sulphate 1000Iron 50Magnesium 200Potassium 500Sodium 500Nitrate 50Arsenic 0.01pH 6.0 – 8.5Table 2.33 outlines standards for drinking waterin terms of mineral levels. Toxicity and loss ofperformance will vary dependent upon birdage and class of stock, but in general thesevalues can be used as guidelines to indicate thepossibility of toxicity with birds consumingsuch water over prolonged periods.In the last few years, there has been aninterest in the treatment of water for poultry. Inlarge part, this is carried out in an attempt toprevent problems of mineral deposits occurringin pipelines, boilers and automatic waterers,rather than preventing toxicity problems perse. Such treatments involves orthophosphates,which sequester calcium and magnesium, there-by preventing precipitation in the water supply.In most situations, these systems will notunduly alter the water composition in terms ofthe bird’s nutritional requirements. As a last resort,some producers use water softeners, and inthese situations, there is some cause for concern,regarding the bird’s health. These softenerscontain an active column of resin, that hasthe ability to exchange one ion (mineral) foranother. Over time, the resin column becomessaturated with the absorbed minerals (usuallycalcium and magnesium salts) that are extractedfrom the water, and so it must be flushed andre-charged with the donor mineral. In mostsofteners, this recharging process involvessodium from NaCl. This means that sodium isreplacing other minerals in the water, becausesodium salts readily dissolve, and will not leavemineral scale in the equipment. The amount ofsodium that is pumped into the water supply istherefore in direct proportion to the hardminerals extracted from the water. In areas of veryhard water, one can expect higher levels ofsodium in water reaching the birds, and vice-versain areas of lower water hardness. Problems inwater sodium will likely occur if softener salt useexceeds 40 kg/40,000 litres of water.
  • 121CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSECTION 2.6Waterg. General managementconsiderations with waterWhere continuous flow water troughs are usedfor caged birds, one must be sure that birds atthe end of the trough obtain sufficient water.A rise in house temperature will result inincreased water consumption, and unless the watersupply can be adjusted accordingly, shortagesof water may result for the birds at the far end ofthe line. It has also been demonstrated that poor-ly beak-trimmed birds may not be able to drinksufficient water to sustain maximum production.When the lower beak of the bird is too long, upto 20% loss in egg production can occur, com-pared with properly beak-trimmed birds. Whendisease or stress occur, a decrease in water con-sumption is usually noted a day or two before adecrease in feed consumption. For this reason,managers should consider installing water meterson all water lines to each pen or cage row andhave the attendant keep a daily record of waterconsumption. Such records can give early warn-ing of potential problems with the flock.
  • 122 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATIONSuggested ReadingAngel, R. et al. (2002). Phytic acid chemistry:Influence on phytin phosphorus availability andphytase efficacy. J. Appl. Poult. Res. 11:471-480.Bedford, M.R., (2002). The foundation of conductingfeed enzyme research and the challenges of explain-ing the results. J. Appl. Poultry Res. 11:464-470.Coelho, M.B., (1994). Vitamin stability in premixesand feeds: A practical approach. BASF TechnicalSymposium. Indianapolis. May 25. pp 99-126.Dale, N., (1997). Metabolizable energy of meat andbone meal. J. Appl. Poultry Res. 6:169-173.Kersey, J.H. et al., (1997). Nutrient composition ofspent hen meals produced by rendering. J. Appl.Poultry Res. 6:319-324.Lane, R.J. and T.L. Cross, (1985). Spread sheetapplications for animal nutrition and feeding.Reston Publ., Reston, Virginia.Leeson, S., G. Diaz and J.D. Summers, (1995). In:Poultry Metabolic Disorders and Mycotoxins. Publ.University Books, Guelph, Ontario, CanadaMateos, G.G., R. Lazaro and M.I. Garcia, (2002).The feasibility of using nutritional modification toreplace drugs in poultry feeds. J. Appl. Poult. Res.11:437-452.McDowell, L.R., (1989). In: Vitamins in AnimalNutrition. Academic Press, N.Y.Moritz, J.S. and L.D. Latshaw, (2001). Indicators ofnutritional value of hydrolysed feather meal.Poultry Sci. 80:79-86.National Academy of Sciences, (1973). In: Effect ofProcessing on the Nutritional Value of Feeds. NASWashington, D.C.National Academy of Sciences, (1974). In: Nutrientsand Toxic Substances in Water for Livestock andPoultry. NAS Washington, D.C.National Academy of Sciences, (1980). In: MineralTolerances of DomesticAnimals. NAS Washington, D.C.National Academy of Sciences, (1987). In: VitaminTolerance of Animals. NAS Washington, D.C.National Academy of Sciences, (1994). In: NutrientRequirements of Poultry. 9th Rev. Ed. NAS Washing-ton, D.C.Novus, (1994). In: Raw Material Compendium. 2ndEdition. Publ. Novus Int., Brussels.Pesti, G.M. and B.R. Mitter, (1993). In: Animal FeedFormulation. Publ. Van Nostrand Reinhold, N.Y.Shirley, R.B. and C.M. Parsons, (2000). Effect of pres-sure processing on amino acid digestibility of meatand bone meal for poultry. Poult. Sci. 79:1775-1781.Sibbald, I.R., (1983). The TME system of feed eval-uation. Agriculture Canada 1983-20E. AnimalResearch Centre, Ottawa, Canada.Sibbald, I.R., (1987). Examination of bioavailableamino acids in feedstuffs for poultry and pigs. Areview with emphasis on balance experiments. Can.J. Anim. Sci. 67:221-301.Valdes, E.V. and S. Leeson, (1992). Near infraredreflectance analysis as a method to measure metabo-lizable energy in complete poultry feeds. Poult. Sci.71:1179-1187.Wiseman, J., F. Salvador and J. Craigon, (1991).Prediction of the apparent metabolizable energy con-tent of fats fed to broiler chickens. Poult. Sci.70:1527-153.CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION
  • FEEDING PROGRAMSFOR GROWINGEGG-STRAIN PULLETS12333.1 Diet specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1233.2 Strain specific nutrient requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1293.3 Feeding management of growing pullets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137a. General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137b. Manipulating nutrient intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141c. Suggested feeding program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143d. Manipulation of body weight at sexual maturity . . . . . . . . . . . . . . . . . . . .146e. Nutrient management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148f. Prelay nutrition and management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149i. considerations for calcium metabolismii. prelay body weight and compositioniii. early eggsizeiv. pre-pausev. urolithiasisg. Lighting programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157h. Feed restriction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160PageCHAPTER3.1 Diet specificationsTable 3.1 shows diet specificationsfor Leghorn pullets, while Table 3.2provides comparable data for brownegg birds. These nutrient specifications areintended for guidelines in diet formulationwhen general growth and development (asoutlined by the primary breeders) is the goalof the rearing program. Pullets are grown undera range of environmental conditions andhousing systems and these can influencenutrient needs. In most situations, variablemanagement conditions influence energyneeds, and so it is important to relate all othernutrients to energy level. In hot climates forexample, the pullet will eat less and sonutrients, such as amino acids, will have tobe increased accordingly. Pullets grownon the floor, rather than in cages, will eat morefeed, and so amino acid levels can bereduced. The diet specifications are basedon using conventional ingredients wherenutrient digestibility is fairly predictable.When non-standard ingredients are used, itis essential to formulate to more stringent stan-dards of digestibility, such as for digestibleamino acids. Tables 3.3 – 3.6 show exam-ples of diet formulations using corn, wheator sorghum with and without meat meal.SECTION 3.1Diet specifications
  • 124 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.1Diet specificationsStarter Grower Developer Pre-layAge (weeks) (0 to 6) (6 to 10) (10 to 16) (16 to 18)Crude Protein (%) 20.0 18.5 16.0 16.0Metabolizable Energy (kcal/kg) 2900. 2900. 2850. 2850.Calcium (%) 1.00 0.95 0.92 2.25Available Phosphorus (%) 0.45 0.42 0.40 0.42Sodium (%) 0.17 0.17 0.17 0.17Methionine (%) 0.45 0.42 0.39 0.37Methionine+cystine (%) 0.78 0.72 0.65 0.64Lysine (%) 1.10 0.90 0.80 0.77Threonine (%) 0.72 0.70 0.60 0.58Tryptophan (%) 0.20 0.18 0.16 0.15Arginine (%) 1.15 0.95 0.86 0.80Valine (%) 0.75 0.70 0.65 0.60Leucine (%) 1.30 1.10 0.92 0.88Isoleucine (%) 0.70 0.60 0.51 0.48Histidine (%) 0.35 0.32 0.29 0.26Phenylalanine (%) 0.65 0.60 0.53 0.49Vitamins (per kg of diet):Vitamin A (I.U) 8000Vitamin D3 (I.U) 2500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 2Riboflavin (mg) 5Pyridoxine (mg) 4Pantothenic acid (mg) 12Folic acid (mg) 0.75Biotin (µg) 100Niacin (mg) 40Choline (mg) 500Vitamin B12 (µg) 12Trace minerals (per kg of diet):Manganese (mg) 60Iron (mg) 30Copper (mg) 6Zinc (mg) 60Iodine (mg) 0.5Selenium (mg) 0.3Table 3.1 Diet specifications for leghorn pullets
  • 125CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.1Diet specificationsStarter Grower Developer PrelayAge (wks) (0 to 5) (5 to 10) (10 to 15/16) (15/16 to 17)Crude Protein (%) 20.0 18.0 15.5 16.0Metabolizable Energy (kcal/kg) 2900 2850 2800 2850Calcium (%) 1.00 0.95 0.90 2.25Av. Phosphorus (%) 0.45 0.42 0.38 0.42Sodium (%) 0.17 0.17 0.17 0.17Methionine (%) 0.45 0.41 0.35 0.34Methionine+cystine(%) 0.78 0.71 0.63 0.61Lysine (%) 1.10 0.90 0.75 0.73Threonine (%) 0.72 0.68 0.60 0.57Tryptophan (%) 0.20 0.18 0.15 0.15Arginine (%) 1.15 0.95 0.86 0.80Valine (%) 0.75 0.70 0.65 0.60Leucine (%) 1.30 1.10 0.92 0.88Isoleucine (%) 0.70 0.60 0.51 0.45Histidine (%) 0.35 0.32 0.27 0.24Phenylalanine (%) 0.65 0.60 0.50 0.45Vitamins (per kg of diet):Vitamin A (I.U) 8000Vitamin D3 (I.U) 2500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 2Riboflavin (mg) 5Pyridoxine (mg) 4Pantothenic acid (mg) 12Folic acid (mg) 0.75Biotin (µg) 100Niacin (mg) 40Choline (mg) 500Vitamin B12 (µg) 12Trace minerals (per kg of diet):Manganese (mg) 60Iron (mg) 30Copper (mg) 6Zinc (mg) 60Iodine (mg) 0.5Selenium (mg) 0.3Table 3.2 Diet specifications for brown egg pullets
  • 126 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.1Diet specifications1 2 3 4 5 6Corn 544 555Wheat 628 643Sorghum 578 568Wheat shorts 100 105 100 100 100 100Meat meal 50 30 50Soybean meal 310 258 227 191 27 250Fat 10 10 10 10 10 10DL-Methionine* 1.1 1.3 1.5 1.6 1.7 1.6Salt 3.1 2.8 2.7 2.3 3.4 2.9Limestone 18 13.2 19.3 16.1 18.5 13.3Dical Phosphate 12.8 3.7 10.5 5 11.4 3.2Vit-Min Premix** 1 1 1 1 1 1Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 21.0 21.0 20.6 20.6 20.0 21.0ME (kcal/kg) 2930 2930 2900 2930 2930 2930Calcium (%) 1.05 1.05 1.00 1.05 1.05 1.05Av. Phos. (%) 0.47 0.47 0.45 0.45 0.45 0.47Sodium (%) 0.18 0.18 0.18 0.18 0.18 0.18Methionine (%) 0.46 0.47 0.45 0.46 0.45 0.45Meth + Cys. (%) 0.78 0.78 0.78 0.78 0.81 0.81Lysine (%) 1.16 1.17 1.10 1.10 1.10 1.20Threonine (%) 0.89 0.87 0.76 0.74 0.78 0.80Tryptophan (%) 0.29 0.28 0.31 0.30 0.27 0.27* or eqivalent MHA** with cholineTable 3.3 Examples of chick starter diets (kg)
  • 127CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.1Diet specifications1 2 3 4 5 6Corn 550 555Wheat 620 590Sorghum 568 558Wheat shorts 150 165 150 160 150 150Meat meal 50 20 20Soybean meal 256 200 188 180 238 234Fat 10 10.5 10 23.5 10 10DL-Methionine* 1.2 1.3 1.3 1.3 1.7 1.6Salt 3.3 2.7 2.7 2.5 3.4 3.2Limestone 17.3 12.5 18 15.6 17.9 15.4Dical Phosphate 11.2 2 9 6.1 10 6.8Vit-Min Premix** 1 1 1 1 1 1Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 19.0 19.0 19.4 19.5 18.9 19.5ME (kcal/kg) 2930 2930 2900 2930 2930 2930Calcium (%) 0.97 0.97 0.97 0.97 0.97 0.97Av. Phos. (%) 0.43 0.43 0.42 0.43 0.42 0.43Sodium (%) 0.18 0.18 0.18 0.18 0.18 0.18Methionine (%) 0.43 0.45 0.42 0.42 0.42 0.42Meth + Cys. (%) 0.72 0.72 0.73 0.72 0.75 0.76Lysine (%) 1.0 1.0 1.0 1.0 1.0 1.1Threonine (%) 0.8 0.78 0.7 0.7 0.72 0.74Tryptophan (%) 0.26 0.25 0.29 0.28 0.25 0.26* or eqivalent MHA** with cholineTable 3.4 Examples of pullet grower diets
  • 128 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.1Diet specifications1 2 3 4 5 6Corn 534 535Wheat 648 649Sorghum 572 580Wheat shorts 239 240 197 200 205 203Meat meal 20 20 20Soybean meal 186 167 114 96 181 161Fat 10 10 10 10 10 10DL-Methionine* 1.1 1.2 1.4 1.4 1.3 1.3Salt 3.3 3.1 2.7 2.4 3.5 3.2Limestone 16 16.4 17.5 15.4 17 15Dical Phosphate 9.6 6.3 8.4 4.8 9.2 5.5Vit-Min Premix** 1 1 1 1 1 1Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 16.5 16.5 16.5 16.5 16.5 16.5ME (kcal/kg) 2855 2855 2850 2850 2850 2850Calcium (%) 0.92 0.92 0.92 0.92 0.92 0.92Av. Phos. (%) 0.39 0.39 0.39 0.39 0.39 0.39Sodium (%) 0.18 0.18 0.18 0.18 0.18 0.18Methionine (%) 0.39 0.39 0.38 0.38 0.35 0.35Meth + Cys. (%) 0.63 0.63 0.63 0.63 0.64 0.64Lysine (%) 0.82 0.83 0.79 0.79 0.86 0.86Threonine (%) 0.69 0.68 0.57 0.56 0.62 0.61Tryptophan (%) 0.22 0.22 0.24 0.24 0.22 0.21* or eqivalent MHA** with cholineTable 3.5 Examples of pullet developer diets
  • 129CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.2Strain specific nutrient requirementsThere are often questions about the needfor strain-specific diets in growing whiteor brown egg pullets. Such differenceswould most likely be induced by differential growthrate and/or different mature body weight. As showninTable 3.12 there are differences in growth rateof commercial pullets throughout the 18 weekgrow-out period. At 4 weeks of age, there is a14% difference in body weight between thelightest and heaviest strain, while at 18 weeks thisdifference is 10%. This differential growth rateis reflected in nutrient needs, where for exam-ple, amino acid levels in the starter diet are10-15% higher for this smaller strain.Starter diets are shown inTable 3.7 where thereis a fairly consistent energy base for all strains,although the diet for the smallest body weightstrain, namely Lohmann, is much higher inlysine and threonine. This same trend continuesfor the grower diets (Table 3.8). Interestingly, forthe developer diets (Table 3.9), the highestamino acid needs are for the heaviest pulletTable 3.6 Examples of prelay diets1 2 3 4 5 6Corn 527 481Wheat 615 629Sorghum 574 593Wheat shorts 227 306 180 180 180 180Meat meal 50 34 60Soybean meal 168 100 122 90 167 105Fat 10 10 16.7 11 11 10DL-Methionine* 1.4 1.6 1.4 1.4 1.6 1.5Salt 3 2.4 2.5 2 3.2 2.7Limestone 51.6 46.6 51.5 48.2 51.3 46.8Dical Phosphate 11 1.4 9.9 3.4 10.9Vit-Min Premix** 1 1 1 1 1 1Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 16.0 16.0 16.6 17.0 16.0 16.2ME (kcal/kg) 2850 2850 2850 2850 2850 2900Calcium (%) 2.25 2.25 2.25 2.25 2.25 2.30Av Phosphorus (%) 0.42 0.42 0.42 0.42 0.42 0.42Sodium (%) 0.17 0.17 0.17 0.17 0.17 0.18Methionine (%) 0.41 0.42 0.38 0.39 0.37 0.37Meth + Cystine (%) 0.64 0.64 0.64 0.64 0.66 0.65Lysine (%) 0.78 0.78 0.81 0.84 0.82 0.84Threonine (%) 0.66 0.63 0.58 0.58 0.60 0.58Tryptophan (%) 0.22 0.20 0.25 0.24 0.21 0.20* or eqivalent MHA** with choline3.2 Strain specific nutrient requirements
  • 130 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.2Strain specific nutrient requirementsShaver Hyline 36 Hyline 98 Lohmann BovanAge fed (wks) (0 to 6*) (0 to 6) (0 to 6) (0 to 3) (0 to 6)Protein (%) 19.5 20 20 21 20ME (kcal/kg) 2900 2960 2960 2900 2980Calcium (%) 1.0 1.0 1.0 1.05 1.0Av. Phosphorus (%) 0.47 0.50 0.5 0.48 0.5Sodium (%) 0.16 0.19 0.19 0.16 0.18Linoleic acid (%) 1.2 1.0 1.0 1.4 1.3Methionine (%) 0.42 0.48 0.48 0.48 0.45Methionine+cystine (%) 0.73 0.8 0.8 0.83 0.8Lysine (%) 0.95 1.1 1.1 1.2 1.1Tryptophan (%) 0.20 0.20 0.20 0.23 0.21Threonine (%) 0.68 0.75 0.75 0.8 0.75* Extrapolated from Management Guide InformationTable 3.7 Starter diets for white egg pulletsTable 3.8 Grower diets for white egg pulletsShaver Hyline 36 Hyline 98 Lohmann BovanAge fed (weeks) (6 to 12*) (6 to 8) (6 to 8) (3 to 8) (6 to 10)Protein (%) 17.5 18 18 19 18ME (kcal/kg) 2800 3025 2960 2800 2970Calcium (%) 0.95 1.0 1.0 1.03 1.0Av Phosphorus (%) 0.47 0.47 0.48 0.46 0.48Sodium (%) 0.16 0.18 0.18 0.16 0.17Linoleic acid (%) 1.0 1.0 1.0 1.44 1.3Methionine (%) 0.38 0.44 0.44 0.39 0.4Methionine+cystine (%) 0.66 0.73 0.73 0.69 0.72Lysine (%) 0.86 0.9 0.9 1.03 1.0Tryptophan (%) 0.18 0.18 0.18 0.22 0.19Threonine (%) 0.62 0.7 0.7 0.72 0.7* Extrapolated from Management Guide Information
  • 131CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.2Strain specific nutrient requirementsShaver Hyline 36 Hyline 98 Lohmann BovanAge fed (weeks) (12 to 17) (8 to 15) (8 to 16) (8 to 16) (10 to 15)Protein (%) 16.5 16.0 16.0 14.9 16.0ME (kcal/kg) 2750 3075 2940 2800 2960Calcium (%) 1.15 1.0 1.0 0.92 1.0Av Phosphorus (%) 0.45 0.45 0.46 0.38 0.45Sodium (%) 0.16 0.17 0.17 0.16 0.17Linoleic acid (%) 1.0 1.0 1.0 1.03 1.3Methionine (%) 0.36 0.39 0.39 0.34 0.36Methionine+cystine (%) 0.63 0.65 0.65 0.58 0.65Lysine (%) 0.81 0.75 0.75 0.67 0.88Tryptophan (%) 0.16 0.16 0.16 0.16 0.17Threonine (%) 0.58 0.60 0.60 0.51 0.60Table 3.9 Developer diets for white egg pulletsTable 3.10 Prelay diets for white egg pulletsHyline 36 Hyline 98 Lohmann BovanAge fed (weeks) (15 to 19*) (16 to 18) (16 to 18*) (15 to 17)Protein (%) 15.5 15.5 18 15ME (kcal/kg) 3040 2940 2800 2930Calcium (%) 2.75 2.75 2.05 2.25Av Phosphorus (%) 0.4 0.45 0.46 0.45Sodium (%) 0.18 0.18 0.16 0.18Linoleic acid (%) 1.0 1.0 1.03 1.2Methionine (%) 0.36 0.36 0.37 0.36Methionine+cystine (%) 0.60 0.60 0.70 0.63Lysine (%) 0.75 0.75 0.87 0.8Tryptophan (%) 0.15 0.15 0.21 0.16Threonine (%) 0.55 0.55 0.62 0.55* Extrapolated from Management Guide Information
  • 132 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.2Strain specific nutrient requirementsWeek Shaver Hyline 36 Hyline 98 Lohmann Bovan1 70 65 65 70 702 135 110 110 115 1053 205 180 180 170 1754 280 250 260 240 2505 365 320 350 320 3206 450 400 450 400 3957 535 500 550 470 4758 620 590 650 540 5609 700 680 750 614 65010 775 770 850 682 73511 845 870 930 749 82012 915 950 1000 816 90013 975 1030 1070 878 97514 1035 1100 1130 941 104515 1095 1160 1180 998 111016 1165 1210 1230 1056 117017 1235 1250 1270 1118 122518 1300 1280 1320 1181 1270Shaver1 Hyline 36 Hyline 98 Lohmann BovanStarter 1099 1085 1141 350 931Grower 2072 621 665 1258 1239Developer 2702 2645 3241 3327 2023Pre-lay 860 980 1048 924Layer 448 476Total (to 18wks) 5873 5659 6027 5983 55931No prelay diet.(Shaver) while the smaller Lohmann apparent-ly need much lower amino acid intake. Thereis considerable variation in the specifications forstrain-specific prelay diets (Table 3.10).To some extent, variable diet specifications forprelay diets relate to age of bird. Prelay diets aremost beneficial in terms of optimizing calcium accre-tion, and so it is somewhat surprising that there isa considerable range of calcium (2.05 to 2.75%)and available phosphorus (0.4 to 0.5%) given forthe various strains. At this time, the Lohmann seemsto have higher amino acid needs. The various strainsof pullets consume anywhere from 5.6 to 6.0 kgof feed to 18 weeks, and this is somewhat influ-enced by diet energy level (Table 3.11).Table 3.11 Feed intake for white egg pullets (grams)Table 3.12 Body weight of white egg pullets (grams)
  • 133CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.2Strain specific nutrient requirementsBody weight of pullets are shown inTable 3.12.There are significant differences in vitamin-mineral premixes suggested for the variousstrains of commercial pullets (Table 3.13). In someinstances, the breeding companies do not givea specification for a certain nutrient, and pre-sumably this means that the natural ingredi-ents provide adequate levels for this strain of bird.For critical nutrients such as vitamin E there aresix-fold differences in suggested specifications.Comparable diet specifications for brown eggpullets are shown in Tables 3.14 to 3.20. Thereseems to be more consistency in strain specif-ic specifications for brown egg pullets, althoughit should be emphasized that the feedingschedule in terms of bird age is more variable.units/kg Shaver Hyline 36,98 Lohmann BovanfeedVitamin A IU 12000 8000 12000 8000Vitamin D3 IU 2500 3300 2000 2500Vitamin E IU 30 66 20* 10Vitamin K IU 3 5.5 3 3Thiamin mg 2.5 0 1 1Riboflavin mg 7 4.4 4 5Pantothenic acid mg 12 5.5 8 7.5Niacin mg 40 28 30 30Pyridoxine mg 5 0 3 2Biotin µg 200 55 50 100Folic acid mg 1 0.22 1 0.5Vitamin B12 µg 30 8.8 15 12Choline mg 1000 275 200* 300Iron mg 80 33 25 35Copper mg 10 4.4 5 7Manganese mg 66 66 100 70Zinc mg 70 66 60 70Iodine mg 0.4 0.9 0 1Selenium mg 0.3 0.3 0.2 0.25* Extrapolated from Management Guide InformationTable 3.13 Vitamin-mineral premix for white egg pullets
  • 134 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.2Strain specific nutrient requirementsShaver ISA Hyline Lohmann BovanAge fed (wks) (4 to 10) (5 to 10) (6 to 9) (0 to 8) (6 to 10)Protein (%) 19.0 20.0 16.0 18.5 18.0ME (kcal/kg) 2850 2850 2890 2775 2940Calcium (%) 1.0 1.0 1.0 1.0 1.0Av Phosphorus (%) 0.42 0.44 0.46 0.45 0.5Sodium (%) 0.16 0.17 0.18 0.16 0.17Linoleic acid (%) 1 1.4 1.3Methionine (%) 0.45 0.47 0.44 0.38 0.4Methionine+cystine (%) 0.76 0.80 0.70 0.67 0.72Lysine (%) 0.98 1.03 0.9 1.0 1.0Tryptophan (%) 0.19 0.2 0.18 0.21 0.19Threonine (%) 0.66 0.69 0.7 0.7 0.7Shaver ISA Hyline BovanAge fed (weeks) (0 to 4) (0 to 5) (0 to 6) (0 to 6)Protein (%) 20.5 20.5 19.0 20.0ME (kcal/kg) 2950 2950 2870 2980Calcium (%) 1.07 1.07 1.0 1.0Av Phosphorus (%) 0.48 0.48 0.48 0.5Sodium (%) 0.16 0.16 0.18 0.18Linoleic acid (%) 1.0 1.3Methionine (%) 0.52 0.52 0.48 0.45Methionine+cystine (%) 0.86 0.86 0.8 0.8Lysine (%) 1.16 1.16 1.1 1.1Tryptophan (%) 0.21 0.21 0.2 0.21Threonine (%) 0.78 0.78 0.75 0.75Table 3.14 Starter diets for brown egg pulletsTable 3.15 Grower diets for brown egg pullets
  • 135CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.2Strain specific nutrient requirementsShaver ISA Hyline Lohmann BovanAge fed (wks) (16 to 17) (16 to 17*) (16 to 18*) (16 to 18*) (15 to 17)Protein (%) 17.0 17.0 16.5 17.5 14.8ME (kcal/kg) 2750 2750 2850 2775 2820Calcium (%) 2.05 2.05 2.75 2.0 2.25Av Phosphorus (%) 0.45 0.45 0.44 0.45 0.45Sodium (%) 0.16 0.16 0.18 0.16 0.18Linoleic acid (%) 1.0 1.0 1.2Methionine (%) 0.36 0.36 0.35 0.36 0.35Methionine+cystine (%) 0.65 0.65 0.60 0.68 0.63Lysine (%) 0.80 0.80 0.75 0.85 0.80Tryptophan (%) 0.17 0.17 0.17 0.20 0.16Threonine (%) 0.54 0.54 0.55 0.60 0.55* Extrapolated from Management Guide InformationShaver ISA Hyline Lohmann BovanAge fed (wks) (10 to 16) (10 to 16) (9 to 16) (8 to 16) (10 to 15)Protein (%) 16.0 16.8 15.0 14.5 15.5ME (kcal/kg) 2750 2750 2830 2775 2840Calcium (%) 0.95 1.0 1.0 0.9 1.0Av Phosphorus (%) 0.36 0.38 0.44 0.37 0.45Sodium (%) 0.16 0.17 0.16 0.16 0.17Linoleic acid (%) 1.0 1.0 1.2Methionine (%) 0.33 0.35 0.39 0.33 0.35Methionine+cystine (%) 0.60 0.63 0.60 0.57 0.63Lysine (%) 0.74 0.78 0.70 0.65 0.85Tryptophan (%) 0.16 0.17 0.15 0.16 0.16Threonine (%) 0.50 0.53 0.60 0.50 0.60Table 3.16 Developer diets for brown egg pulletsTable 3.17 Prelay diets for brown egg pullets
  • 136 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.2Strain specific nutrient requirementsAll poultry breeding companies recommendprelay diets for their brown egg pullets, andwhile most nutrient specifications are similar, thereare again major differences in recommendationsfor calcium. These brown egg pullets weigh from1475g to 1580g at 18 weeks, and consume any-where from 6.3 to 6.8 kg feed (Tables 3.18 and3.19). As for the white egg pullets, the strain spec-ifications for vitamin-mineral premixes for the brownpullets show tremendous variation, and again forsome strains, certain nutrients are not deemed essen-tial within these premixes (Table 3.20).Table 3.18 Feed intake1for brown egg pullets (grams)Shaver ISA Hyline Lohmann BovanStarter 600 840 1099 1148Grower 2100 1694 966 1764 1351Developer 3000 2758 3346 3577 2170Pre-lay 588 525 1163 1029 1015Layer 600 480 539Total (to 18 wks) 6888 6297 6574 6370 62231Dependent on diet energy levelTable 3.19 Body weight of brown egg pullets (grams)Week Shaver ISA Hyline Lohmann Bovan1 60 50 70 75 70*2 100 100 115 130 110*3 200 190 190 195 180*4 300 280 280 275 2905 380 380 380 367 3706 480 480 480 475 4507 570 580 580 580 5308 650 675 680 680 6109 760 770 770 780 69010 850 850 870 875 77011 940 950 960 960 85012 1030 1040 1050 1040 93513 1120 1130 1130 1120 102014 1220 1220 1210 1200 111015 1320 1300 1290 1265 120016 1400 1390 1360 1330 130017 1490 1475 1430 1400 140018 1580 1560 1500 1475 1500* Extrapolated from Management Guide Information
  • 137CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsunits/kg Shaver ISA Hyline Lohmann BovanfeedVitamin A IU 13000 13000 8800 12000 8000Vitamin D3 IU 3000 3000 3300 2000 2500Vitamin E IU 25 25 66 10-30 10Vitamin K IU 2 2 5.5 3 3Thiamin mg 2 2 0 1 1Riboflavin mg 5 5 4.4 6 5Pantothenic acid mg 15 15 5.5 8 7.5Niacin mg 60 60 28 30 30Pyridoxine mg 5 5 0 3 2Biotin µg 200 200 55 50 100Folic acid mg 0.75 0.75 0.22 1.0 0.5Vitamin B12 µg 20 20 8.8 15.0 12Choline mg 600 600 275 300 300Iron mg 60 60 33 25 35Copper mg 5 5 4.4 5 7Manganese mg 60 60 66 100 70Zinc mg 60 60 66 60 70Iodine mg 1 1 0.9 0.5 1Selenium mg 0.2 0.2 0.3 0.2 0.25a) General considerationsDiet formulation and feeding managementare now critical aspects of growingpullets to the onset of sexual maturity.Age at maturity is getting earlier although it is ques-tionable that this has changed suddenly in justa few years. In fact, what has been happeningis that age at maturity has slowly been decreas-ing by almost 1 d per year, and this is especial-ly true for many strains of brown egg pullets.Moving birds to laying cages at 19-20 weeks isno longer feasible and often results in manage-ment problems. Similarly, first egg appearing at15-17 weeks means that we must criticallyreview our rearing programs. The key to successfulnutritional management today is through opti-mizing (maximizing) body weight of the pullet.Pullets that are on-target or slightly above targetweight at maturity will inevitably be the best pro-ducing birds for the shell egg market.The traditional concern with early maturityhas been too small an egg size. Results from ourearly studies indicate the somewhat classicalTable 3.20 Vitamin-mineral premix for brown egg pullets3.3 Feeding management of growing pullets
  • 138 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletseffect of early maturity in Leghorns withoutregard to body weight (Table 3.21).There seems little doubt that body weight andperhaps body composition at this time are themajor factors influencing egg size both at matu-rity and throughout the remainder of the layingperiod. Summers and Leeson (1983) conclud-ed that body weight is the main factor control-ling early egg size (Table 3.22).Table 3.22 Effect of body weight onegg size18 wk wt (g) Early egg wt (g)1100 46.91200 48.41280 48.81380 49.7Although there is some evidence to indicatethat nutrients such as protein, methionine and linole-ic acid can influence egg size throughout the lay-ing cycle, these nutrients have only moderate effectson early egg size. This is probably related to thepullet producing at maximum capacity at least upto the time of peak egg mass.Although it is fairly well-established thatbody weight is an important criterion for adequateearly production, there is still insufficient evidenceregarding optimum body structure and com-position. Frame size is still discussed, althoughstandards are now rarely given in the breeder man-agement guides. It is known that most (90%) ofthe frame size is developed early, and so by 12-16 weeks of age, the so-called ‘size’ of the pul-let is fixed. While this parameter is useful as anoth-er monitoring tool, we have had little success inaffecting frame size without also affecting bodyweight. It therefore seems very difficult to pro-duce, by nutritional modification, pullets that arebelow target weight, yet above average frame sizeand vice versa. Since shank length and ‘framesize’ are so highly correlated with body weight,their measurement or monitoring is no longer con-sidered necessary. However, an exception to thisrule occurs in hot weather conditions where hightemperatures seem to stimulate leg bone growthindependent of body weight. It is not clearwhy birds held at higher temperatures havelonger shank bones, although there is a possibilityof altered hormone balance. For example, thy-roid hormones are known to influence bone devel-opment through mediation of somatomedinsand it has been shown that even though birds heldat 30 vs. 22ºC have reduced thyroid size, theircirculating T4 levels are increased by 100%.Another factor that may be of importance isblood flow to the feet and legs during heatstress. It is well known that birds divert more bloodto the legs during heat stress as a means ofcountercurrent cooling between the arterialand venous supply. In some types of birds,heat loss from the legs can be the largest con-tributor to overall heat loss, and it is interestingthat this has been recorded to occur at 30ºC sinceTable 3.21 Pullet maturity and egg characteristicsAge at Lighting Egg production (%) Egg size (% large)(wk) 18-20 wk Mean 30 wk 63 wk(to 35 wk)15 32 92 17 4418 12 92 21 6521 0 91 37 69
  • 139CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsat higher tempertures evaporative losses becomemore important. Since the hind limbs are appar-ently more heavily supplied with blood at 30 vs.18ºC, and even though nutrient intake is reducedat higher temperatures, it is conceivable that theactive growth plate receives a greater supply ofnutrients related simply to increased blood flow.It would be interesting to see if environmentaltemperature influences development of other partsof the skeleton and especially the keel.While pullets are maturing earlier, there hasbeen little change in body weight at time of firstegg. As will be discussed in section 3.3g), light-ing program is the most important stimulus to matu-rity. Pullets as young as 8 weeks of age will beinfluenced by light stimulation, and regardlessof body weight or composition, will produce eggsearlier than normal. Without any light stimulation,then a minimum threshold body weight and/orbody composition is most likely the stimulus tomaturity. There may, in fact, be a need forattainment of a minimum lean body mass priorto sexual maturation. With most mammals,attainment of minimum fat reserves are essen-tial for puberty, and so it seems likely that bodycomposition is as important as total body massin influencing the onset of egg production. Instudies involving a relatively small number of birds,we have seen no correlation between age at firstegg and either percentage or absolute levels ofbody fat. While no clear picture has yet emergedwith respect to body composition and maturi-ty, it seems likely that birds having some ener-gy reserve, as they approach peak egg produc-tion, are less prone to subsequent productionproblems. A production curve as shown inFigure 3.1 is often observed in flocks, related toinadequate body size or energy reserves at thetime of maturity.Fig. 3.1 Reduction in egg production after peak, associated with smallappetite and body weight.
  • 140 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsWhen this type of production loss is not dueto an identifiable disease and/or management prob-lem, then it most likely relates to birds beingdeficient in energy. It is perhaps not too surpris-ing that birds are in such a precarious situation withrespect to energy balance. Dairy cows and sowsinvariably lose body weight during peak lactationin order to meet energy requirements. Perhaps themost classical case of energy deficiency at this timeis seen with the turkey breeder. Due to a declinein feed intake from time of first lighting throughto peak egg production, the turkey breeder nec-essarily loses considerable body mass in anattempt to maintain energy balance. It is likelythat the same situation applies to Leghorn pulletsand in some cases, to brown egg birds. Obviously,the effect is most pronounced for underweight flockswith small appetites where energy intake is min-imal. In fact, with many flocks exhibiting productioncharacteristics as shown in Figure 3.1, it is bodyweight at housing that deserves immediate inves-tigation rather than factors occurring at the actu-al time of the production loss.The key to optimizing layer performancewould seem to be attainment of body weight goalsat time of maturity. It is likely that body condi-tion will be a factor of the flock in question, beinginfluenced by stocking density, environmentaltemperature, feather cover, etc. Unfortunatelyattainment of desired weight for age is notalways easy to achieve especially where earli-er maturity is desired or when adverseenvironmental conditions prevail. Leeson andSummers (1981) suggested that energy intake ofthe pullet is the limiting factor to growth rate, sinceregardless of diet specifications, pullets seem toconsume similar quantities of energy (Table3.23). In this study, all pullets had a similar bodyweight at 15 weeks even though diet specificationswere dramatically variable. As seen inTable 3.23,birds consumed similar quantitities of energy eventhough protein intake varied by 85%. These datasuggest that if protein and amino acid intake areadequate, additional diet protein does little tostimulate growth rate.In other studies, we have reared Leghorn pul-lets on diets varying in protein or energy, and again,energy intake seems to be the major factorinfluencing body weight (Tables 3.24 and 3.25).These studies indicate that growth rate is morehighly correlated with energy intake than withprotein intake. This does not mean to say thatprotein (amino acid) intake is not important tothe growing pullet. Protein intake is very impor-tant, but there does not seem to be any measurablereturn from feeding more than 800 g of proteinto the pullet through 18 weeks of age. On theother hand, it seems as though the more ener-gy consumed by the pullet, the larger the bodyweight at maturity. Obviously, there must be afine line between maximizing energy intakeand creating an obese pullet.Table 3.23 Nutrient intake of pullets (8-15 weeks)Diet energy-protein 15 wk Body wt. Energy intake Protein(g) (Mcal) intake (g)2950 kcal – 15% CP 1272 9.77 464c3100 kcal – 24% CP 1267 9.17 718a3200 kcal – 20% CP 1291 9.51 597b
  • 141CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsb) Manipulating nutrient intakeIf one calculates expected energy output in termsof egg mass and increase in body weight, and relatesthis to feed intake, then it becomes readily appar-ent that the Leghorn must consume at least 90g/bird/day and the brown egg bird close to 100g/bird/day at peak production. Because feedingis ad-libitum, management programs must begeared at stimulating early appetite. The practi-cal long-term solution is to rear birds with opti-mum body weight and body reserves at maturity.This situation has been aggravated in recentyears, with the industry trend of attempting to rearpullets on minimal quantitites of feed. Unfortunately,this move has coincided with geneticallysmaller body weights and hence smaller appetites,together with earlier sexual maturity.In order to maximize nutrient intake, one mustconsider relatively high nutrient dense diets,although these alone do not always ensure opti-mum growth. Relatively high protein (16-18%CP) with adequate methionine (2% CP) andlysine (5% CP) levels together with high energylevels (2800-3000 kcal/kg) are usually given toLeghorn pullets, especially in hot weathersituations. However, there is some evidence tosuggest that high energy diets are not always help-ful under such warm conditions. (Table 3.26)Leghorn pullets were heavier at 126 d whenfed the high energy diet in the cool environment,but diet had no effect at 30ºC. As expected, pul-lets ate less of the high energy diet, and becauseTable 3.24 Effect of diet protein level (0-20 wks) on pullet growth andnutrient intakeDiet Protein Body wt. Energy intake Protein intake(%) (g) (Mcal) (kg)15 1445 24.3 1.28d16 1459 22.9 1.28d17 1423 22.9 1.37cd18 1427 22.0 1.39c19 1444 22.9 1.53b20 1480 23.0 1.62aAll diets 2850 kcal ME/kgTable 3.25 Effect of diet energy level (0-20 wks) on pullet growth andnutrient intakeDiet energy Body wt. Energy intake Protein intake(kcal ME/kg) (g) (Mcal) (kg)2650 1320c20.6c1.40a2750 1378bc21.0bc1.37a2850 1422ab21.8ab1.37a2950 1489a22.1ab1.35ab3050 1468a21.4abc1.26c3150 1468a22.5a1.29bcAll diets:18% CP, 0.36% methionine aand 0.9% lysine
  • 142 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsall other nutrient levels were fixed, this result-ed in reduced intake of all nutrients exceptenergy. Pullets therefore ate less protein and aminoacids when fed 3000 vs. 2500 kcal ME/kg, andthis can be critical where intake per se is less at30ºC. The pullets fed 3000 kcal/kg are border-line in intake of balanced protein at 870 g vs. ourrequirement for 800 g to this age. High energydiets may therefore not always be beneficialunder heat stress conditions, and intake of othernutrients such as protein and amino acids mustbe given priority during formulation.The Leghornpullet eats for energy requirement, albeit with someimprecision, and so energy:protein balance is crit-ical. All too often there is inadequate amino acidintake when high energy corn-based diets are used,the result of which is pullets that are both smalland fat at maturity.One of the most important concepts todayin pullet feeding, is to schedule diets accordingto body weight and condition of the flock, ratherthan according to age. For example, tradition-al systems involve feeding starter diets for about6 weeks followed by grower and then developerdiets. This approach does not take into accountindividual flock variation, and this will be inap-propriate for underweight flocks. It is becom-ing more difficult to attain early weight for age.This means that flocks are often underweight rel-ative to management guide values (Table 3.12)at 4-6 weeks of age. This situation can arise fora variety of reasons such as sub-optimal nutri-tion, heat stress, disease, etc. For such flocks itis inappropriate to change from starter to grow-er diet, merely because the flock has reached somearbitrary age. It is more appropriate to feed thehigher nutrient dense starter until the targetweight is reached. For example, Figure 3.2shows an underweight flock at 6 weeks. For thisflock to receive a grower at 6 weeks of age willcause problems because the flock will likely staysmall until maturity, be late maturing, and thenproduce a sub-optimal number of eggs that willalso be small. This type of flock can most effec-tively be ‘corrected’ in growth by prolongedfeeding of the starter diet. In this situation, thebirds reach the low end of the guide weight atalmost 10 weeks of age (Figure 3.2). At this time,a grower diet could be introduced. Since the flockis showing a growth spurt, then feeding toalmost 12 weeks could be economical. The flockis now slightly over-weight and so ideally suit-ed to realizing maximum genetic potential dur-ing peak production. Some producers, andespecially contract pullet growers, are sometimesreluctant to accept this type of program, since theycorrectly argue that feeding a high protein starterdiet for 10-12 weeks will be more expensive.Depending upon local economic conditions,Table 3.26 Influence of diet energy on growth and nutrient intake ofleghorn pullets maintained at 30 or 18ºC to 18 weeks of ageBody wt 126 d Total feed intake ME intake Protein intake(g) (kg) (Mcal) (g)Temperature 18ºC2500 kcal ME/kg 1398 7.99 20.04 13303000 kcal ME/kg 1434 6.98 21.07 1160Temperature 30ºC2500 kcal ME/kg 1266 6.05 15.17 10103000 kcal ME/kg 1218 5.19 15.69 870
  • 143CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsfeeding an 18% protein starter diet for 12 vs. 6weeks of age, will cost the equivalent of 2 eggs.A bird in ideal condition at maturity will producefar in excess of these 2 eggs relative to a bird thatis underweight at maturity.c) Suggested feeding programDiet specification, together with approximateages for feeding, are given inTables 3.1 and 3.2for Leghorns and brown egg birds respectively.In practice, flocks may not grow according toexpected standards, and for Leghorns at least, theyare more likely to be underweight than on tar-get. Brown egg strains on the other hand,because of their inherently higher feed intake,sometimes achieve weights that are greater thanstandard goals. For these reasons, there needsto be flexibility in time of change from, forexample, starter to grower etc. Table 3.27shows various scenarios for the feeding sched-uling of a Leghorn strain to 17 weeks of age.According to the standard schedule, the starterand grower are each fed for 6 weeks, followedby developer. In Scenario #1, the body weightis below standard at 3 weeks, and pullets are only400 g at 6 weeks relative to the standard of450 g at this time. If this flock is changed to thelower nutrient dense grower diet at 6 weeks, thebirds will not likely achieve target weight atmaturity. For this reason in Scenario #1, the starterdiet is continued until weight-for-age is achievedat 9 weeks of age. In Scenario #2 there is evengreater cause for concern since the flock suddenlyslows down in growth at 9 weeks of age. Thistype of growth depression is seen in situationsof disease challenge, with severe beak trim-ming or when there is sudden increase in envi-ronmental temperature. For this flock, it isessential to re-introduce the higher nutrientdense starter diet in order to stimulate growth.In this extreme situation, the grower diet isintroduced at 12 weeks since the pullets seemto be making acceptable weekly gains in growth.Fig. 3.2 Pullet growth in relation to feeding program.
  • 144 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsHowever, grower is fed for two weeks longer thannormal, during weeks 13 and 14, to ensure idealweight at 17 weeks.Table 3.28 shows examples for feed sched-uling of brown egg birds where increased growthis the problem. In Scenarios 1 and 2, the pul-lets are overweight at various ages according tothe standard. In Scenario #1, pullets are over-weight at 5 weeks and so the lower nutrient densegrower diet is introduced a week early. Likewisedeveloper diet type is used from 10 rather than11 weeks. In Scenario #2, pullet growth ismuch higher than standard. This growth is tem-pered somewhat by earlier introduction of grow-er and developer diets, yet pullets are still over-weight at 16 weeks. Because such rapid growthwill result in earlier maturity it may be advisableto light stimulate this flock a week earlier thanscheduled, with appropriate early introductionof the layer diet.The examples shown inTable 3.27 andTable3.28 emphasize the need for flexibility in feedscheduling. For most flocks, the end goal willlikely be the breeder’s recommended targetweight at 16-18 weeks or whenever light stim-ulation occurs. In certain situations it may be nec-essary to manipulate mature body weight accord-ing to economics of manipulating egg size andegg grade (see Section d). As a generalization,the smaller the body weight of the pullet, the small-er the size of the egg throughout the entire lay-ing cycle. Conversely, a larger pullet will alwaysproduce a bigger egg and this is little influ-enced by layer nutrition.Table 3.27 Feeding scenarios for White pullets according to growth (g)Standard Scenario #1 Scenario #2Week(s) Body Feed type Body Feed type Body Feed typewt. wt. wt.1 70 Starter 70 Starter 70 Starter2 135 Starter 130 Starter 135 Starter3 205 Starter 190 Starter 205 Starter4 280 Starter 255 Starter 280 Starter5 365 Starter 320 Starter 365 Starter6 450 Starter 400 Starter 450 Starter7 535 Grower 500 Starter* 535 Grower8 620 Grower 600 Starter* 620 Grower9 700 Grower 700 Starter* 650 Starter*10 775 Grower 775 Grower 720 Starter*11 845 Grower 845 Grower 800 Starter*12 915 Grower 915 Grower 870 Grower13 975 Developer 975 Developer 950 Grower*14 1035 Developer 1035 Developer 1000 Grower*15 1095 Developer 1095 Developer 1095 Developer16 1165 Developer 1165 Developer 1165 Developer17 1235 Developer 1235 Developer 1235 Developer* different from standard
  • 145CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsAn argument that is often heard about the roleof body weight at maturity, is that it is not in fact,too important because the pullet will showcatch-up growth prior to first egg. In otherwords, if the pullet is small, it will take a few dayslonger to mature, and start production at the ‘sameweight’. However, this does not seem to hap-pen, as small birds at 18 weeks are smaller at timeof laying their first egg (Table 3.29).For the smaller pullet there is a degree of com-pensatory growth up to the time of the first egg,although this is insufficient to allow for total ‘catch-up’ growth. It is also interesting to note the rela-tionship between body weight and age at first eggand also between body weight and size of firstegg. In other studies, we have monitored thegrowth of pullets through a production cycle inrelation to 18 week body weight which is the ageof light stimulation. Again, there is a remarkablyBody weight (g) Age at first Weight of18 wks 1st egg Change egg (d) first egg (g)1100 1360 +260 153 40.71200 1440 +240 150 42.01280 1500 +220 149 43.71380 1590 +210 148 42.5Standard Scenario #1 Scenario #2Week(s) Body Feed type Body Feed type Body Feed typewt. wt. wt.1 50 Starter 50 Starter 50 Starter2 100 Starter 110 Starter 110 Starter3 190 Starter 200 Starter 210 Starter4 280 Starter 290 Starter 320 Grower*5 380 Starter 420 Grower* 460 Grower*6 480 Grower 510 Grower 550 Grower7 580 Grower 600 Grower 650 Grower8 675 Grower 700 Grower 780 Developer*9 770 Grower 790 Grower 900 Developer*10 850 Grower 870 Developer* 980 Developer*11 950 Developer 960 Developer 1050 Developer12 1040 Developer 1040 Developer 1200 Developer13 1130 Developer 1130 Developer 1260 Developer14 1220 Developer 1220 Developer 1320 Developer15 1300 Developer 1300 Developer 1350 Developer16 1390 Developer 1390 Developer 1430 Layer** different from standardTable 3.29 Effect of immature body weight on development to sexual maturityTable 3.28 Feeding scenarios for ISA Brown pullets according to growth (g)
  • 146 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletssimilar pattern of growth for all weight groupsindicating that immature weight seems to ‘set’the weight of the bird throughout lay (Figure 3.3).More importantly from a production viewpoint,is the performance of birds shown in Figure 3.3.When the lightest weight birds were fed diets ofvery high nutrient density (20% CP, 3000 kcalME/kg) they failed to match egg production andegg size of the largest weight pullets that were fedvery low nutrient dense diets (14% CP, 2600 kcalME/kg). These results emphasize the impor-tance of mature body weight in attaining maxi-mum egg mass output.The actual body weight achieved will obvi-ously vary with strain and bird type (Tables3.12, 3.19). For Leghorns, weight should be around400-450 g at 6 weeks, 850-1000 g at 12 weeksand 1200-1300 g at 18 weeks. The brown eggstrains will be 450-480 g at 6 weeks, 1000 g at12 weeks and 1500-1600 g at 18 weeks. Thebrown egg strains will likely mature 7-10 d ear-lier than the Leghorn strains.d) Manipulation of body weightat sexual maturityIn the previous section, the main emphasiswas on attaining the breeder’s recommendedweight at time of sexual maturity. Under certainconditions, some tempering of mature bodysize may be economically advantageous. Becausebody size has a dramatic effect on egg size, largebirds at maturity can be expected to produce largeeggs throughout their laying cycle. Dependingupon the pricing of various egg grades, a very largeegg may be uneconomical to produce, and in mostinstances tempering of egg size of birds from 40-65 weeks of age is often difficult to do withoutassociated loss in egg numbers. Because bodyweight controls feed intake and egg size, an eas-ier way of manipulating life-cycle egg size isthrough the manipulation of mature body size.Fig. 3.3 Effect of immature body weight on subsequent body weightduring lay.
  • 147CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsIf the maximum possible egg size is desired, thenefforts must be made to realize the largest pos-sible mature weight. However, where a small-er overall egg size is economical then a small-er pullet is desirable. Such lightweight pulletscan be obtained by growing pullets more slow-ly or most easily by light-stimulating pullets atan earlier age. Figure 3.4 gives a schematic rep-resentation of the above concept. In this scenario,birds are on the heavy side of the breeder’sweight guide, and so if moved at 18 weeks, wouldbe heavier than the ideal weight and be expect-ed to produce very large eggs. If this situationis not economical in the laying house, thenthese birds should be moved at the ‘ideal weight’which in this scenario means moving at 17 ratherthan 18 weeks of age. Moving the bird, andlight stimulating at 17 vs. 18 weeks will have noadverse effect on performance, as light stimulationis still at the desired body weight standard (that hasbeen achieved one week earlier than anticipated).Early maturity is not a problem for flocks thathave ideal body weight and condition. Early matu-rity and light stimulation will only result in sub-sequent small egg size and increased incidenceof prolapse if the bird is small at this age. Thisconcept is preferred over attempts at trying to slowthe bird down during growth in an attempt to delaymaturity (Figure 3.5).Fig. 3.4 Light stimulation at target weight rather than age.
  • 148 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsSuch adjustments are invariably brought aboutby use of very low nutrient dense diets and/or useof restricted feeding. Both of these practices havethe desired ‘effect’ of slowing down mean growth,but at the great cost of loss of pullet uniformity.e) Nutrient managementAlthough growing pullets do not produce largequantities of manure in relation to adult layers,nutrient loading of manure will likely be a man-agement consideration. Under average condi-tions of feeding and management, pullets will retainabout 25% of nitrogen and 20% of phosphorusconsumed. Most of the remaining phosphoruswill be retained in the manure while around 30%of the excreted nitrogen will be lost as ammo-nia, either in the pullet house or during storageprior to land disposal. Based on these values fornutrient balance, Table 3.30 provides informa-tion on nutrient flow for pullets through to 18weeks. On a per pullet basis therefore, each birdproduces about 0.1 kg N and 0.03 kg P in themanure to 18 weeks of age.Manure nutrient loading is in direct pro-portion to corresponding diet nutrient levels. Usinglower protein or lower phosphorus diets will invari-ably result in less of these elements appearingin the manure. Attempts at reducing crudeprotein levels in pullet diets, as a means ofreducing feed cost and/or manure N loading, oftenresults in poor growth rate (Table 3.31). Regardlessof constant levels of the most important aminoacids in these diets, pullets responded adverse-ly to any reduction in crude protein. This datasuggests that pullets have minimal needs fornon-essential amino acids and/or that require-ments for amino acids such as threonine andarginine are of more importance than normallyFig. 3.5 Potentially harmful adjustment to pullet weight.
  • 149CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsestimated. Regardless of mode of action, itseems that there is only limited potential toreduce the crude protein levels in pullet diets asa means of reducing manure nitrogen loading.There does seem to be potential for reducing dietphosphorus levels in pullet diets, to limit manureloading. Keshavarz (2000) shows acceptable pul-let growth with diet levels as low as 0.2% in thestarter diet (Table 3.32). There was an indicationof slightly lower egg production to 30 weeks ofage in pullets fed the lowest level of diet P,although growth characteristics were little affect-ed. The P loading of manure of 28 kg/1000 agreeswell with the prediction shown inTable 3.30. Itseems as though there is potential for at least 30%reduction in manure P output of pullets throughdiet formulation.f) Prelay nutrition andmanagementi) Considerations for calcium metabolism –Prelay diets and prelay management are designedto allow the bird the opportunity to establish ade-quate medullary bone reserves that are neces-Table 3.30 Nitrogen and phosphorus balance for 50,000 pullets to 18 weeksof ageIntake (kg)1Body retention Excretion Gas Loss Manure(kg) (kg) (kg) (kg)Nitrogen 7680 1920 5760 1760 5000Phosphorus 1950 390 1560 - 15601Assumes 6 kg feed per pullet, averaging 16% CP (2.56% N) and 0.65% total phosphorusTable 3.31 Body weight of Leghorn and brown egg pullets fed low proteindiets with constant levels of TSAA, lysine and tryptophanDiet CP (%) Brown bird weight (g) Leghorn weight (g)Starter1Grower256d 98d 126d 56d 98d 126d20 16 746a1327a1524a592a1086a1291a18 14 720b1272b1471b576b1046b1235b16 12 706b1144c1301c546c921c1085c14 10 540c989d1175d434d781d932d10.66% TSAA: 0.90% lysine; 0.24% tryptophan20.55% TSAA; 0.72% lysine; 0.19% tryptophanTable 3.32 Effect of dietary phosphorus on pullet development andphophorus excretionDiet available P (%) Body weight (g) Feed intake Tibia Manure PStarter Grower Developer 6 wk 18 wk (kg) ash (kg/1000)(%)0.40 0.35 0.30 345 1210 5.94 50.7 280.30 0.25 0.20 340 1260 5.98 49.3 240.20 0.15 0.10 330 1200 5.85 48.8 18Adapted form Keshavarz (2000)
  • 150 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletssary for calcifying the first egg produced. In prac-tice, there is considerable variation in formula-tion and time of using prelay diets, and to someextent this confusion relates to defining sexualmaturity per se. Historically, prelay diets werefed from about 2 weeks prior to expected matu-rity, up to the time of 5% egg production. Withearly, rapid and hopefully synchronized matu-ration with today’s strains, we rarely have the oppor-tunity to feed for 2 weeks prior to maturity.Likewise, it is unwise to feed inadequate levelsof calcium when flocks are at 5% production.One of the major management decisions todayis the actual need for prelay diets, or whether pul-lets can sustain long-term shell quality when movedfrom grower diet directly to a high calciumlayer diet.The bird’s skeleton contains around 1 g ofmedullary calcium that is available for shell cal-cification on any one day. This calcium is con-tinually replenished between successive ovula-tions, and in times of inadequate calcium repletion,the medullary reserve may be maintained at theexpense of structural cortical bone. Around 60-70% of the medullary calcium reserves are locat-ed in the long bones, and so long-term problemsof calcium deficiency can lead to lameness andcage layer fatigue.Prelay diets normally contain 2-2.5% calcium,and when fed over a 10-14 d period provide thebird with the opportunity to deposit medullarybone. This bone deposition coincides with fol-licular maturation and is under the control of bothestrogens and androgens. The latter hormoneseems essential for medullary bone growth,and its presence is manifested in growth of thecomb and wattles. Consequently, there willbe little medullary deposition, regardless of dietcalcium level, if the birds are not showing comband wattle development and this stage of matu-rity should be the cue for increasing the bird’scalcium intake.Because egg production is an ‘all or none’event, the production of the first egg obviouslyplaces a major strain on the bird’s metabolismwhen it has to contend with a sudden 2 g lossof calcium from the body. Some of this calciumwill come from the medullary bone, and sothe need to establish this bone reserve prior tofirst egg. The heaviest pullets in a flock will like-ly be the first to mature, and so it is these birdsthat are most disadvantaged if calcium metab-olism is inadequate. If these early maturingpullets receive a 1% calcium grower diet atthe time they are producing their first few eggs,they will only have a sufficient calcium reserveto produce 2-3 eggs. At this time, they will like-ly stop laying, or less frequently continue tolay and exhibit cage layer fatigue. If these ear-lier maturing birds stop laying, they do so for 4-5 days, and then try to start the process again.The bird goes through very short clutches, whenat this time she is capable of a very prolonged30 – 40 egg first clutch. Advocates of pro-longed feeding of grower diets suggest that it makesthe bird more efficient in the utilization orabsorption of calcium, such that when she is even-tually changed to a layer diet, improved efficiencycontinues for some time, with the bird having morecalcium available for shell synthesis. Figure3.6 indicates that percentage calcium absorptionfrom the diet does decline with an increased levelof calcium in the diet.
  • 151CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsHowever, with 40% retention of 5 g of cal-cium consumed daily, there will be greaterabsolute calcium retention (2 g/d) than the birdconsuming 2.5 g Ca/d and exhibiting 60% effi-ciency of retention (1.5 g retained/d). There isalso no evidence to support the suggestion of carryover of this higher efficiency during early egg pro-duction. If 1% calcium grower diets are usedaround the time of maturity, then these diets shouldnot be used after the appearance of first egg, andto 0.5% production at the very latest. It must beremembered that under commercial conditions,it is very difficult to precisely schedule dietchanges, and so decisions for diet change needto precede actual time of diet change, suchthat production does not reach 5 – 10% beforebirds physically receive the calcium enriched diets.Prelay diets provide more calcium than domost grower diets, but still not enough Ca for sus-tained production. Prelay diets should allow thebuild up of medullary reserves without adverse-ly influencing general mineral metabolism.However, as previously discussed for grower diets,2 – 2.5% calcium prelay diets are inadequate forsustained egg production, and should not be fedbeyond 1% egg production. The main disad-vantage of prelay diets is that they are used fora short period of time, and many producers donot want the bother of handling an extra diet atthe layer farm. There is also a reluctance by someproducers with multi-age flocks, at one site, touse prelay diets where delivery of diets with 2%calcium to the wrong flock on site can have dis-astrous effects on production.Simply in terms of calcium metabolism, themost effective management program is earlyintroduction of the layer diet. Such high calci-um diets allow sustained production of even theearliest maturing birds. As previously men-tioned, higher calcium diets fed to immature birds,Fig. 3.6 Relationship between calcium intake and calcium retention.
  • 152 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletslead to reduced percentage retention, althoughabsolute retention is increased (Table 3.33).Feeding layer diets containing 3.5% calcium,prior to first egg, therefore results in a slightincrease in calcium retention of about 0.16 g/drelative to birds fed 0.9% calcium grower dietsat this time. Over a 10 d period, however, thisincreased accumulation is equivalent to theoutput in 1 egg. Since there is only about 1 g ofmobile medullary calcium reserve in the maturebird, then the calcium retention values shownin Table 3.33 suggest accumulation of somecortical bone at this time.Early introduction of layer diets is thereforean option for optimizing the calcium retentionof the bird. However, there has been somecriticism leveled at this practice. There is the argu-ment that feeding excess calcium prior to layimposes undue stress on the bird’s kidneys,since this calcium is in excess of her immediaterequirement and must be excreted. In the studydetailed inTable 3.33, there is increased excretacalcium. However, kidney histology from thesebirds throughout early lay revealed no changedue to prelay calcium feeding. Recent evi-dence suggests that pullets must be fed a layerdiet from as early as 6 – 8 weeks of age beforeany adverse effect on kidney structure is seen (seefollowing section on urolithiasis). It seems like-ly that the high levels of excreta calcium showninTable 3.33 reflect fecal calcium, suggesting thatexcess calcium may not even be absorbed intothe body, merely passing through the bird withthe undigested feed. This is perhaps too simplistica view, since there is other evidence to suggestthat excess calcium may be absorbed by the imma-ture bird at this time. Such evidence is seen inthe increased water intake of birds fed layerdiets prior to maturity (Figure 3.7).Early introduction of a high calcium layer dietseems to result in increased water intake, and aresultant increase in excreta moisture.Unfortunately this increased water intake and wet-ter manure seems to persist throughout the lay-ing cycle of the bird, (Table 3.34). These data sug-gest that birds fed high calcium layer dietsduring the prelay period will produce manure thatcontains 4 – 5% more moisture than birds fed 1%calcium grower or 2% calcium prelay diets.There are reports of this problem being most pro-nounced under heat stress conditions. A 4-5%increase in manure moisture may not be prob-lematic under some conditions, although for thosefarms with a chronic history of wet layer manure,this effect may be enough to tip the balance andDiet Ca (%) Daily Ca Excreta Caretention (g) (% dry matter)0.9 0.35 1.41.5 0.41 3.02.0 0.32 5.72.5 0.43 5.93.0 0.41 7.53.5 0.51 7.7Table 3.33 Effect of % diet calcium fed to birds immediately prior to lay oncalcium retention
  • 153CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsproduce a problem. The current trend of feedingeven higher calcium levels to laying hens may accen-tuate this problem, and so dictate the need for prelaydiets with more moderate levels of calcium.In summary, the calcium metabolism of theearliest maturing birds in a flock should be thecriterion for selection of calcium levels duringthe prelay period. Prolonged feeding of low-cal-cium diets is not recommended. Early introductionof layer diets is ideal, although where wetmanure may be a problem, a 2% calcium prelaydiet is recommended. There seems to be no prob-lem with the use of 2% calcium prelay diets, aslong as birds are consuming a high calciumlayer diet no later than at 1% egg production.ii) Prelay body weight and composition –Prelay diets are often formulated and used on theassumption that they will improve body weightand/or body composition, and so correct problemsarising with the prior growing program. Body weightFig. 3.7 Effect of introducing a 4% calcium layer diet at 112 days ( _____ ) andat 138 ( _ _ _ _ ) on daily water intake.Prelay diet Ca (%) Bird age (d)(16 – 19 weeks)1147 175 196 2451.0 71.4 78.7 75.3 65.52.0 71.6 77.2 73.9 63.93.0 72.1 77.7 74.1 63.94.0 77.0 80.0 76.0 69.41All birds fed 4.0% Ca after 20 weeks of ageTable 3.34 Effect of prelay calcium level on excreta moisture (%)
  • 154 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsand body condition should not really be consideredin isolation, although at this time, we do not havea good method of readily assessing body con-dition in the live pullet. For this reason our mainemphasis at this time is directed towardsbody weight.Pullet body weight is the universal criterionused to assess growing program. Each strain ofbird has a characteristic mature body weight thatmust be reached or surpassed for adequate eggproduction and egg mass output. In general, prelaydiets should not be used in an attempt to manip-ulate mature body size. The reason for this is thatfor most flocks, it is too late at this stage ofrearing to meaningfully influence body weight.However, if underweight birds are necessarilymoved to a layer house, then there is perhapsa need to manipulate body weight prior tomaturity. With black-out housing, this cansome-times be achieved by delaying photo-stimulation – this option is becoming less use-ful in that both Leghorns and brown egg strainsare maturing early without any light stimulation.If prelay diets are used in an attempt to correctrearing mismanagement, then it seems as thoughthe bird is most responsive to energy. This factfits in with the effect of estrogen on fat metab-olism, and the significance of fat used for liverand ovary development at this time. While usinghigh nutrient density prelay diets may have a minoreffect in manipulating body weight, it must beremembered that this late growth spurt (if it occurs)will not be accompanied by any meaningfulchange in skeletal growth. This means that inextreme cases, where birds are very light weightand of small stature at say, 16 weeks of age, thenthe end result of using high nutrient denseprelay diets may well be pullets of correct bodyweight, but of small stature. Pullets with ashort shank length seem more prone to pro-lapse/pick-out, and so this is another exampleof the limitations in the use of high nutrient denseprelay diets.While body composition at maturity maywell be as important as body weight at this age,it is obviously a parameter that is difficult toquantitate. There is no doubt that energy is like-ly the limiting nutrient for egg production of allstrains of bird, and at peak egg numbers, feed maynot be the sole source of energy. Labile fatreserves seem essential to augment feed sourcesthat are inherently limited by low feed intake. Theselabile fat reserves become critical during situationsof heat stress or general hot weather conditions.Once the bird starts to produce eggs, then its abil-ity to build fat reserves is greatly limited. Obviously,if labile fat reserves are to be of significance,then they must be deposited prior to maturity. Aswith most classes of bird, the fat content of the pul-let can best be manipulated through changing theenergy:protein balance of the diet. If labile fatreserves are thought necessary, then high energy,high fat prelay diets should be considered. As pre-viously stated, this scenario could well be ben-eficial if peak production is to coincide withperiods of high environmental temperature.The requirement for a specific body com-position at the onset of maturity has not been ade-quately established. With mammals, onset andfunction of normal estrus activity is dependenton attainment of a certain body fat content. Inhumans, for example, onset of puberty will notoccur if body fat content is much less than14%. No such clear cut relationship has emergedwith egg layers. Work conducted with broilerbreeders, in fact, indicates a more definite rela-tionship between lean body mass and maturity,rather than fat content and maturity.iii) Early egg size – Egg size is greatly influ-enced by the size of the yolk that enters the oviduct.In large part this is influenced by body weight
  • 155CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsof the bird and so factors described previouslyfor mature body weight can also be applied toconcerns with early egg size. There is a gener-al need for as large an early egg size as is pos-sible. Most attempts at manipulating early eggsize have met with limited success. Increasedlevels of linoleic acid in prelay diets may be ofsome use, although levels in excess of the usual1% found in most diets produce only marginaleffects on early egg size. From a nutritional stand-point, egg size can best be manipulated with dietprotein, and especially methionine concentra-tion. It is logical, therefore to consider increas-ing the methionine levels in prelay diets.iv) Pre-pause – In some countries, and most notablyJapan, pre-pause feeding programs are used tomaximize early egg size. The idea behind theseprograms is to withdraw feed, or feed a very lownutrient dense diet at the time of sexual matu-rity. This somewhat unorthodox program isdesigned to ‘pause’ the normal maturation pro-cedure, and at the same time to stimulate greateregg size when production resumes after about10-14 days. This type of prelay program istherefore most beneficial where early small eggsize is economically undesirable.Pre-pause can be induced by simply with-drawing feed, usually at around 1% egg pro-duction. Under these conditions, pullets imme-diately lose weight, and fail to realize normalweight-for-age when refed. Egg productionand feed intake normalize after about 4 weeks,although there is 1-1.5 g increase in egg size.Figure 3.8 shows the production response ofLeghorn pullets fed only wheat bran from 18 weeks(or 1% egg production) through to 20 weeks of age.Fig. 3.8 Early egg production of pullets fed wheat bran at 1% egg productionor at 18 weeks of age.
  • 156 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsThe most noticeable effects resulting from useof a pre-pause diet such as wheat bran, are a veryrapid attainment of peak egg production and anincrease in egg size once refeeding commences.This management system could therefore beused to better synchronize onset of production(due to variance in body weight), to improve earlyegg size or to delay production for various man-agement related decisions. The use of suchpre-pause management will undoubtedly beaffected by local economic considerations, andin particular the price of small vs. medium vs.large grade eggs.v) Urolithiasis – Kidney dysfunction often leadsto problems such as urolithiasis that some-timesoccurs during the late growing phase of thepullet or during early egg production. While infec-tious bronchitis can be a confounding factor,urolithiasis is most often induced by diet min-eral imbalance in the late growing period. At post-mortem, one kidney is often found to be enlargedand contain mineral deposits known as uroliths.Some outbreaks are correlated with a largeincrease in diet calcium and protein in layer vs.grower diets, coupled with the stress of physicallymoving pullets at this time, and being subject-ed to a change in the watering system (usuallyonto nipples in the laying cages). The urolithsare most often composed of calcium-sodium-urate.The occurrence is always more severe whenimmature pullets are fed high calcium diets foran extended period prior to maturity. For exam-ple, urolithiasis causing 0.5% weekly mortali-ty often occurs under experimental conditionswhen pullets are fed layer diets from 10-12weeks of age (relative to maturity at 18-19weeks). However, there is no indication that earlyintroduction of a layer diet for just 2-3 weeks priorto maturity is a causative factor.Because diet electrolytes can influence waterbalance and renal function, it is often assumedthat electrolyte excess or deficiency may bepredisposing factors in urolithiasis or gout.Because salts of uric acid are very insoluble, thenthe excretion of precipitated urate salts could serveas a water conservation mechanism, especial-ly when cations are excreted during salt loadingor when water is in short supply. When roost-ers are given saline water (1% NaCl) and fed highprotein diets, uric acid excretion rates are dou-bled compared to birds offered the high proteindiet along with non-saline drinking water.Because uric acid colloids are negatively charged,they attract cations such as Na, and so when theseare in excess, there is an increased excretion viaurates, presumably at the expense of conventionalNH4 compounds. There is some evidence of animbalance of Na+K:Cl levels influencing kidneyfunction. When excess Na+K relative to Cl is fed,a small percentage of the birds develop urolithi-asis. It is likely that such birds are excreting amore alkaline urine, a condition which encour-ages mineral precipitation and urate formation.As previously described, Urolithiasis occursmore frequently in laying hens fed high levels ofcalcium well in advance of sexual maturity.Feeding prelay (2-2.5% Ca) or layer diets con-taining 4-5% calcium for 2-3 weeks prior to firstegg is usually not problematic, and surprising-ly, uroliths rarely form in adult male breeders fedhigh calcium diets. High levels of crude proteinwill increase plasma uric acid levels, and poten-tially provide conditions conducive to urateformation.In humans, urolith formation (gout) can becontrolled by adding urine acidifiers to the diet.Studies with pullets show similar advantages.Adding 1% NH4Cl to the diet results in a more
  • 157CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsacidified urine, and uroliths rarely form underthese conditions. Unfortunately, this treatmentresults in increased water intake, and associat-ed wet manure. One of the potential prob-lems in using NH4Cl once the birds start layingis that the metabolic acidosis is detrimental toeggshell quality especially under conditions ofheat stress. Such treatment also assumes the kid-ney can clear the increased load of H+, and fora damaged kidney, this may not always be pos-sible. As a potential urine acidifier withoutsuch undesirable side effects, several researchershave studied the role of Alimet® a methionineanalogue. In one study, pullets were fed diets con-taining 1 or 3% calcium with or without Alimet®from 5-17 weeks. Birds fed the 3% calcium dietexcreted alkaline urine containing elevated cal-cium concentrations together with urolith formationand some kidney damage. Feeding Alimet® acid-ified the urine, but did not cause a generalmetabolic acidosis. Alimet® therefore reducedkidney damage and urolith formation without caus-ing acidosis or increased water consumption.Urine acidification can therefore be used as a pre-vention or treatment of urolithiasis, and thiscan be accommodated without necessarilyinducing a generalized metabolic acidosis.From a nutritional viewpoint, kidney dysfunctioncan be minimized by not oversupplying nutri-ents such as calcium, crude protein and electrolytesfor too long a period prior to maturity.g) Lighting programsPhotoperiod has a dramatic influence on thegrowth and body composition of the growing pul-let and so light programs must be taken intoaccount when developing feeding programs. Interms of pullet management, day length has twomajor effects, namely the development of repro-ductive organs and secondly a change in feed intake.It is well known that birds reared on a step-up ornaturally increasing day length will mature ear-lier than those reared on a constant day length.Similarly, if birds are subjected to a step-down daylength much after 12 weeks of age, they willlikely exhibit delayed sexual maturity. The longerthe photoperiod, the longer the time that birds haveto eat feed, and so usually this results in heavierbirds. Table 3.35 shows the growth rate andfeed intake of pullets reared on constant daylengths of 6, 8, 10 or 12 hours to 18 weeks of age.For Leghorn pullets, each extra hour of day lengthduring rearing increased body weight by about 20g and feed intake by 100 g. For brown egg pul-lets there was a 13 g increase in weight and 70g increase in feed intake for each hour of extra light.Table 3.35 Effect of day length during rearing on growth and feed intake ofpulletsHours ofLeghorn Brown egglight/d 18 wk Feed 17 wk egg 18 wk Feed 17 wk egg7d-18 wkswt (g) intake production wt (g) intake production(kg) (%) (kg) (%)6 1328c 6.14 0 1856b 7.53 128 1376b 6.00 1.2 1930ab 7.83 1210 1425a 6.30 2.0 1889ab 7.60 1012 1455a 6.71 3.4 1953a 8.06 12
  • 158 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsLonger photoperiods may be beneficial in hotweather situations where feed intake of pulletsis often depressed. As the day length for the grow-ing pullet is increased, there is a reduction in ageat maturity. Research data suggests earlier matu-rity with constant rearing day lengths up to 16-18 hours per day, although longer daylengths suchas 20-22 hours per day seem to delay maturity.Another potential problem with longer daylength during rearing is that it allows less poten-tial for light stimulation when birds are moved tolaying facilities. However, in equatorial regionswhere maximum day length fluctuates between11-13 hours, many birds are managed withoutany light stimulation. In fact, under such hot weath-er, high light intensity conditions, excessivestimulation often results in prolapse and blowouts.In these situations if light stimulation is given, itshould follow rather than lead, the onset of eggproduction. It seems that for modern strains ofbirds, light stimulation at ‘maturity’ is not alwaysnecessary for adequate layer performance. In arecent trial, we have shown some advantages toconstant 14 h photoperiods for the entire life ofthe bird vs. an 8 h rearing photoperiod followedby a 14 h layer photoperiod (Table 3.36). Pulletsthat were grown on constant 14 h light and notgiven any extra day length at maturity producedfewer eggs mainly due to reduced peak pro-duction. However, this flatter peak was associ-ated with a significant increase in egg size anda significant improvement in shell quality (lowereggshell deformation). The reason for improvedshell quality is not clear, although we have seenthis with other flocks that fail to show adequatesustained peaks – maybe giving up a few eggs atpeak is a means of improving shell quality. Theincreased egg size for birds on the constant 14h photoperiod is undoubtedly due to birds beingheavier at maturity, and then eating more feedthroughout the laying period.When birds are light stimulated prior to firstegg, their age at light stimulation will have an effecton age at first egg. Our data suggest that after98d of age, for each 1 d delay in age at light stim-ulation, first egg will occur about 0.5 d later (Figure3.9). This means that light stimulating a pulletat 105 d rather than 125 d, will likely result inearlier maturity by about 10 days. At this time,it is important to re-emphasize the previousdiscussion concerning adequacy of body weightand body condition before considering earlierlight stimulation. Another program that can beused to stimulate growth is ‘step-down’ lighting(Figure 3.10).In Figure 3.10, birds are given 23 hr light/d forthe first week and then day length is reduced byabout 1 h each week until 10 h per day isachieved, at which time it is held constant. Whenbirds are in open-sided houses, the minimum daylength achieved is dictated by the maximumnatural day length during this time. Birds can thenPhotoperiod 336d egg Egg weight Shell deformationRearing Laying production (g) (µg)8h 14h 271a 58.4b26.5a14h 14h 256b 60.3a25.4bTable 3.36 Effect of rearing daylength on subsequent layer performance
  • 159CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsFig. 3.9 Age at light stimulation (8-14 hr) and sexual maturity.Fig. 3.10 Step-down lighting.
  • 160 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsbe photostimulated at the normal time. The step-down program has the advantage of allowing thepullets to eat feed for considerably more time eachday during their early development. In hotweather conditions, this long day length meansthat birds are able to eat more feed during cool-er parts of the day. The system should not be con-fused with historical step-down lighting pro-grams that continued step-down until 18-20weeks; these older programs were designed to delaymaturity. For the program in Figure 3.10, matu-rity will not be affected as long as the step-downregime is stopped by 10 – 12 weeks of age, i.e.before the pullet becomes most sensitive tochanges in day length. The step-down lighting pro-gram is one of the simplest ways of increasing growthrate in pullets and is practical with both blackoutand open-sided buildings.Keshavarz (1998) shows increased body weightof 15 week old pullets grown on a step-downlightingprogramof23to8hby16weeks(Table3.37).In this study the step-down photoperiod was con-tinued through to 16 weeks, and this delayed sex-ual maturity resulting in a 1 g increase in egg size.h) Feed restrictionFeed restriction may be necessary for controllingthe weight of brown egg pullets during cooler win-ter months. The goal of any restriction programis to ensure optimum weight-for-age at sexual matu-rity. Because many strains of brown egg birds arenow maturing very early and since their maturebody size has been decreased, the need forrestriction occurs less frequently. A major con-cern with restriction programs is maintenance offlock uniformity. With a mild restriction program,birds can be allowed to ‘run-out’ of feed one dayper week and usually this will do little harm touniformity. If it is necessary to impose a greaterdegree of feed restriction on a daily basis, thenit is important to ensure rapid and even feed dis-tribution, as subsequently discussed for broilerbreeders (Chapter 5). Feed restriction should berelaxed if birds are subjected to any stressessuch as beak trimming, vaccination, generaldisease challenges or substantial reduction in envi-ronmental temperature. An alternative man-agement procedure for overweight birds is to sched-ule an earlier light stimulation and move tolayer cages (see Figure 3.4).Brown egg pullets do seem to consume lessenergy and so are smaller when given lower ener-gy diets. For example providing pullets grow-er-developer diets at 2750 vs. 3030 kcal ME/kgresulted in an 8% reduction in energy intake and4% reduction in body weight. These same dietsfed to Leghorn pullets resulted in just 4% reduc-tion in energy intake of the lower energy diet withvirtually no change in body weight. Reduced nutri-ent density should therefore be considered in con-junction with physical feed restriction, for con-trolled growth of brown egg pullets.Table 3.37 Effect of continuous weekly step-down lighting on pulletdevelopmentRearing Body wt 18 wk Feed intake Age first eggphotoperiod (15 wk) (g) uniformity (%) (0-18 wk) (kg) (d)8 h 1070a69 5.98 13023 to 8 h @ 16 wk11120b78 6.20 14011 hour decrease/wk Adapted from Keshavarz (1998)
  • 161CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETSSECTION 3.3Feeding management of growing pulletsSuggested ReadingsKeshavarz, K. (1998). The effect of light regimen,floor space and energy and protein levels during thegrowing period on body weight and early egg size.Poult. Sci. 77:1266-1279.Keshavarz, K. (2000). Re-evaluation of non-phytatephosphorus requirement of growing pullets withand without phytase. Poult. Sci. 79:1143-1153.Leeson, S. and J.D. Summers, (1985). Response ofgrowing Leghorn pullets to long or increasing pho-toperiods. Poult. Sci. 64:1617-1622.Leeson, S. and J.D. Summers, (1989). Performanceof Leghorn pullets and laying hens in relation tohatching egg size. Can. J. Anim. Sci. 69:449-458.Leeson, S. and J.D. Summers, (1989). Response ofLeghorn pullets to protein and energy in the dietwhen reared in regular or hot-cyclic environments.Poult Sci. 68:546-557.Leeson, S., (1986). Nutritional considerations ofpoultry during heat stress. World’s Poult. Sci.42:619-681.Leeson, S., (1991). Growth and development ofLeghorn pullets subjected to abrupt changes in envi-ronmental temperature and dietary energy level.Poult. Sci. 70:1732-1738.Leeson, S. and L.J. Caston, (1993). Does environmen-tal temperature influence body weight; shank lengthin Leghorn pullets? J. Appl. Poult. Res. 2:253-258.Leeson, S., J.D. Summers and L.J. Caston, (1993).Growth response of immature brown egg strain pul-lets to varying nutrient density and lysine. Poult.Sci. 72:1349-1358.Leeson, S., J.D. Summers and L.J. Caston, (1998).Performance of white and brown egg pullets fedvarying levels of diet protein with constant sulfuramino acids, lysine and tryptophan. J. Appl. Poult.Res. 7:287-301.Leeson, S., J.D. Summers and L.J. Caston, (2000).Net energy to improve pullet growth with low pro-tein amino acid fortified diets. J. Appl. Poult. Res.9:384-392.Lewis, P.D. and G.C. Perry, (1995). Effect of age atsexual maturity on body weight gain. Br. Poult. Sci.36:854-856.Martin, P.A., G.D. Bradford and R.M. Gous, (1994).A formula method of determining the dietary aminoacid requirements of laying type pullets during theirgrowing period. Br. Poult. Sci. 35:709-724.Patterson, P.H. and E.S. Lorenz, (1997). Nutrients inmanure from commercial White Leghorn pullets. J.Appl. Poult. Res. 6:247-252.Summers, J.D. and S. Leeson, (1994). Laying henperformance as influenced by protein intake to six-teen weeks of age and body weight at point of lay.Poult. Sci. 73:495-501.
  • 163FEEDING PROGRAMSFOR LAYING HENS44.1 Diet specifications and formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1644.2 Feed and energy intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1704.3 Problems with heat distress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177a. Bird’s response to heat stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179b. Maintaining energy balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182c. Protein and amino acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184d. Minerals and vitamins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184e. Electrolyte balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185f. Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188g. Effect of physical diet change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188h. Summary of nutritional management during heat . . . . . . . . . . . . . . . . . .1894.4 Phase Feeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1904.5 Formulation changes and feed texture . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1924.6 Nutrition and shell quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1934.7 Controlling egg size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1984.8 Diet and egg composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2034.9 Diet involvement with some general management problems . . . . . . . . . . . . .2144.10 Nutrient management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .222PageCHAPTER
  • 164 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.1Diet specifications and formulationsDiet specifications for laying hens areshown in Table 4.1, and are catego-rized according to age and feed intake.There is no evidence to suggest that the energy levelof diets needs to be changed as the birds progressthrough a laying cycle. The layer’s peak energyneeds are most likely met at around 35 weeks ofage, when production and daily egg mass outputare maximized. However, the layer quite preciselyadjusts its intake according to needs for energy andso variable energy needs are accommodated bychange in feed intake.Most Leghorn strains will now commence eggproduction with feed intakes as low as 80 – 85g/day, and it is difficult to formulate diets for sucha small appetite. For brown egg strains, initialfeed intake will be around 92 - 95 g/day and soformulation is more easily accommodated. Forall diets, maintaining the balance of all nutrientsto energy is the most important consideration dur-ing formulation.In general terms, diet nutrient concentrationsdecrease over time, with the notable excep-tion of the need for calcium. Thus, diet proteinand amino acids expressed as a percent of thediet or as a ratio to energy, decline as the birdprogresses through the laying cycle. In order tosustain shell quality, it is important to increasediet calcium level, and to concomitantly decreasediet phosphorus level, as the bird gets older. Theneed for less methionine is partially related to theneed for tempering late-cycle increase in egg size,since this is usually uneconomical regarding eggpricing and larger eggs have thinner shells.There is little evidence for change in needs forvitamins and trace minerals as birds get older, andso a single premix specification is shown inTable 4.1. For most of the B-vitamins, it is pos-sible to phase feed with up to 30% reduction bythe end of the laying cycle.Examples of layer diets using corn, wheat, orsorghum as the main energy source and with orwithout meat meal, are shown inTables 4.2 – 4.5.The diets are categorized according to age of bird.It is difficult to achieve desired energy level inPhase I diets (Table 4.2) without resorting to inclu-sion of significant quantities of fat. If fat supplyand quality is questionable, it may be advisableto reduce the energy level of the diet (and alsoall other nutrients in the same ratio), by up to 50– 70 kcal ME/kg.4.1 Diet specifications and formulations
  • 165CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.1Diet specifications and formulationsApproximate age 18-32 wks 32-45 wks 45-60 wks 60-70 wksFeed intake (g/bird/day) 90 95 95 100 100 105 100 110Crude Protein (%) 20.0 19.0 19.0 18.0 17.5 16.5 16.0 15.0Metabolizable Energy (kcal/kg) 2900 2900 2875 2875 2850 2850 2800 2800Calcium (%) 4.2 4.0 4.4 4.2 4.5 4.3 4.6 4.4Available Phosphorus (%) 0.50 0.48 0.43 0.4 0.38 0.36 0.33 0.31Sodium (%) 0.18 0.17 0.17 0.16 0.16 0.15 0.16 0.15Linoleic acid (%) 1.8 1.7 1.5 1.4 1.3 1.2 1.2 1.1Methionine (%) 0.45 0.43 0.41 0.39 0.39 0.37 0.34 0.32Methionine + Cystine (%) 0.75 0.71 0.70 0.67 0.67 0.64 0.6 0.57Lysine (%) 0.86 0.82 0.80 0.76 0.78 0.74 0.73 0.69Threonine (%) 0.69 0.66 0.64 0.61 0.60 0.57 0.55 0.52Tryptophan (%) 0.18 0.17 0.17 0.16 0.16 0.15 0.15 0.14Arginine (%) 0.88 0.84 0.82 0.78 0.77 0.73 0.74 0.70Valine (%) 0.77 0.73 0.72 0.68 0.67 0.64 0.63 0.60Leucine (%) 0.53 0.50 0.48 0.46 0.43 0.41 0.40 0.38Isoleucine (%) 0.68 0.65 0.63 0.60 0.58 0.55 0.53 0.50Histidine (%) 0.17 0.16 0.15 0.14 0.13 0.12 0.12 0.11Phenylalanine (%) 0.52 0.49 0.48 0.46 0.44 0.42 0.41 0.39Vitamins (per kg of diet):Vitamin A (I.U) 8000Vitamin D3 (I.U) 3500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 2Riboflavin (mg) 5Pyridoxine (mg) 3Pantothenic acid (mg) 10Folic acid (mg) 1Biotin (µg) 100Niacin (mg) 40Choline (mg) 400Vitamin B12 (µg) 10Trace minerals (per kg of diet):Manganese (mg) 60Iron (mg) 30Copper (mg) 5Zinc (mg) 50Iodine (mg) 1Selenium (mg) 0.3Table 4.1 Diet specifications for layers
  • 1 2 3 4 5 6Corn 507 554Wheat 517 619Sorghum 440 373Wheat shorts 42 68 184Meat meal 70 70 70Soybean meal 327 245 261 171 311 214Fat 45 31 60 40 60 59DL-Methionine* 1.2 1.2 1.6 1.5 1.8 1.8Salt 3.6 2.6 3.0 2.0 3.6 2.6Limestone 99.5 92.3 100 94 100 93Dical Phosphate 15.7 2.9 14.4 1.5 14.6 1.6Vit-Min Premix** 1 1 1 1 1 1Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 20 20 20 20 20 20ME (kcal/kg) 2900 2900 2900 2900 2900 2900Calcium (%) 4.2 4.2 4.2 4.2 4.2 4.2Av Phosphorus (%) 0.5 0.5 0.5 0.5 0.5 0.5Sodium (%) 0.18 0.18 0.18 0.18 0.18 0.18Methionine (%) 0.45 0.46 0.45 0.45 0.45 0.45Meth + Cystine (%) 0.76 0.75 0.77 0.76 0.8 0.78Lysine (%) 1.14 1.15 1.12 1.05 1.17 1.16Threonine (%) 0.86 0.83 0.75 0.7 0.78 0.75Tryptophan (%) 0.28 0.26 0.30 0.28 0.28 0.26* or eqivalent MHA** with choline166 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.1Diet specifications and formulationsTable 4.2 Examples of Phase 1 layer diets (18-32 wks)
  • 167CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.1Diet specifications and formulations1 2 3 4 5 6Corn 536 581Wheat 586 508Sorghum 419 382Wheat shorts 8 123 118 200Meat meal 70 60 65Soybean meal 301 220 233 156 279 192Fat 39 24.6 50 50 60 56DL-Methionine* 0.9 1.1 1.3 1.2 1.5 1.5Salt 3.3 2.3 2.7 1.8 3.4 2.5Limestone 106 100 107 99 107 100Dical Phosphate 12.8 11.0 11.1Vit-Min Premix** 1 1 1 1 1 1Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 19 19 19 19 19 19ME (kcal/kg) 2875 2875 2875 2875 2875 2875Calcium (%) 4.4 4.4 4.4 4.4 4.4 4.4Av Phosphorus (%) 0.43 0.44 0.43 0.44 0.43 0.44Sodium (%) 0.17 0.17 0.17 0.17 0.17 0.17Methionine (%) 0.41 0.42 0.41 0.41 0.41 0.41Meth + Cystine (%) 0.70 0.70 0.72 0.70 0.74 0.72Lysine (%) 1.07 1.07 1.04 1.04 1.08 1.09Threonine (%) 0.82 0.79 0.71 0.67 0.74 0.71Tryptophan (%) 0.26 0.25 0.28 0.26 0.26 0.25* or eqivalent MHA** with cholineTable 4.3 Examples of Phase 2 layer diets (32-45 wks)
  • 1 2 3 4 5 6Corn 584 626Wheat 648 571Sorghum 550 483Wheat shorts 113 35 143Meat meal 60 50 55Soybean meal 261 190 187 115 248 169Fat 29 14.8 40 40 40.5 40DL-Methionine* 1 1.2 1.3 1.5 1.5 1.5Salt 3 2 2.5 1.5 3.2 2.5Limestone 111 105 111 107 111 105Dical Phosphate 10 9.2 9.8Vit-Min Premix** 1 1 1 1 1 1Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 17.5 17.5 17.5 17.5 17.5 17.5ME (kcal/kg) 2850 2850 2850 2850 2850 2850Calcium (%) 4.5 4.5 4.5 4.5 4.5 4.5Av Phosphorus (%) 0.38 0.39 0.38 0.38 0.38 0.38Sodium (%) 0.16 0.16 0.16 0.16 0.16 0.16Methionine (%) 0.40 0.42 0.39 0.41 0.39 0.39Meth + Cystine (%) 0.67 0.67 0.67 0.67 0.70 0.68Lysine (%) 0.95 0.95 0.92 0.93 0.98 0.98Threonine (%) 0.76 0.73 0.63 0.60 0.68 0.64Tryptophan (%) 0.24 0.22 0.26 0.24 0.24 0.22* or eqivalent MHA** with choline168 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.1Diet specifications and formulationsTable 4.4 Examples of Phase 3 layer diets (45-60 wks)
  • 169CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.1Diet specifications and formulations1 2 3 4 5 6Corn 638 619Wheat 570 527Sorghum 485 467Wheat shorts 51 126 190 156 200Meat meal 49 38 42Soybean meal 221 157 138 90 192 138Fat 13 9.7 40 40 40 37DL-Methionine* 0.8 1 1.1 1.2 1.2 1.4Salt 3 2.3 2.4 1.8 3 2.6Limestone 115 110 115 111 115 111Dical Phosphate 8.2 6.5 6.8Vit-Min Premix** 1 1 1 1 1 1Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 16 16 16 16 16 16ME (kcal/kg) 2800 2800 2800 2800 2800 2800Calcium (%) 4.6 4.6 4.6 4.6 4.6 4.6Av Phosphorus (%) 0.33 0.35 0.35 0.35 0.35 0.35Sodium (%) 0.16 0.16 0.16 0.16 0.16 0.16Methionine (%) 0.36 0.37 0.35 0.36 0.34 0.34Meth + Cystine (%) 0.60 0.60 0.60 0.60 0.62 0.61Lysine (%) 0.83 0.83 0.80 0.80 0.85 0.85Threonine (%) 0.70 0.67 0.57 0.55 0.60 0.59Tryptophan (%) 0.22 0.20 0.24 0.23 0.21 0.20* or eqivalent MHA** with cholineTable 4.5 Examples of Phase 4 layer diets (60-70 wks)
  • 170 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.2Feed and energy intake4.2 Feed and energy intakeFeeding programs for layers cannot bedeveloped without consideration for the rear-ing program as discussed in Chapter 3.Unfortunately, many egg producers purchase point-of-lay pullets from independent pullet grow-ers, and here the goals of the two producers arenot always identical. Too often the egg produceris interested in purchasing mature pullets at thelowest possible cost per bird regardless of theircondition. For pullet growers to make a profitthey must produce birds at the lowest possiblecost. With feed representing some 60 to 70% ofthe cost to produce a pullet, the obvious way forthe pullet grower to reduce costs is to save onfeed cost. While they may be able to save a smallamount of feed by eliminating feed waste or byensuring that house temperatures are optimum,the only way to save a substantial amount of feedis to place the pullets on a growing program suchthat feed consumption is reduced and/or cheap-er diets are used. Because it is not possible toenhance the efficiency with which pullets con-vert feed into body weight gain, the net result isa smaller bird at time of transfer. If the birds havebeen on an increasing light pattern, they mightwell be mature, as judged from appearance, atthe onset of production. However, such pulletsmust still grow before they reach their opti-mum weight and condition as a laying hen.Consequently, the egg producer will have to feedthis pullet in an attempt to bring the body weightup to normal if a profitable laying flock is to beobtained. If egg producers attempt to save on feed,the result will be underweight birds at peak eggproduction. This situation leads to smaller eggs,and often lower than normal peak or birds drop-ping relatively quickly in production shortlypast peak as discussed in the previous chapter.It takes a certain amount of feed to producea laying hen with optimum body size. If this feedis not consumed in the growing period, it mustbe fed in the laying house. Of course, onewould have to be sure that the pullets are healthyand are not carrying an excess of body fat.However, the problem of excess body fat withtoday’s modern type, early maturing pullet, doesnot usually occur. Egg producers should also findout as much as possible about the pullets they arepurchasing, such as the type of feeding programthey have been on, the health status of the flock,and the type of waterers used in rearing. Withthis type of information, they should be in abetter position to ensure a profitable laying flock.It is now common practice to describe feed-ing programs for layers according to the level offeed intake. It is well known that under normalenvironmental and management conditions,feed intake will vary with egg production and/orage of bird, and this must be taken into accountwhen formulating diets. While layers do adjustfeed intake according to diet energy level, thereis no evidence to suggest that such precision occurswith other nutrients.The following daily intakes of nutrients are sug-gested under ideal management and environmentalconditions (Table 4.6).
  • 171CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.2Feed and energy intakeTable 4.6 Daily nutrient needs for Leghorn birds.Table 4.7 Feed intake of Leghorns as influenced by body weight, eggproduction, egg weight and environmental temperature1Body weight Egg production Egg weight TemperatureBody wt Intake Egg production Intake Egg wt Intake ºC Intake(g) (g/d) (%) (g/d) (g) (g/d) (g/d)1200 92.7 98 100.5 50 90.8 10 102.21250 94.9 94 98.8 55 94.0 15 102.11300 97.1 90 97.1 60 97.1 20 97.11350 99.3 86 95.4 65 100.3 25 92.11400 101.5 82 93.8 70 103.4 30 87.123g 1 g 2.4% 1 g 1.6 g 1 g 1ºC 1 g1 Assumes 1300 g body weight, 90% egg production, 60 g egg weight and 20 C as the standard, with diet at 2850 kcal/kgAt any given time, it is necessary to adjust dietspecifications according to the actual feed intakeof the flock. Within a single strain it is possibleto see a ± 15 g variance in feed intake at any agerelated to stage of maturity, egg mass, bodysize and most importantly, environmental tem-perature.It is possible to predict energy needs, and hencefeed intake, based on knowledge of the majorvariables. The equation most commonly usedis described below. Using this equation, Table4.7 was developed with variable inputs of bodyweight, egg production, egg weight and envi-ronmental temperature. Feed intake was calculatedassuming a diet energy level of 2850 kcal ME/kg.Energy (kcal ME/bird/day) = [Body weight (kg)] [170 – 2.2 x ºC]+ [2 x Egg mass/d (g)]+ [5 x Daily weight gain (g)]Age (wks)18 – 32 32 – 45 45 – 60 60 – 70Protein (g) 20 18.5 17.5 16Metabolizable energy (kcal) 260 290 285 280Calcium (g) 4.0 4.2 4.4 4.6Av. Phosphorus (mg) 550 450 380 330Methionine (mg) 500 430 390 340TSAA (mg) 830 740 670 600Lysine (mg) 950 840 780 730
  • 172 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.2Feed and energy intakeFor these calculations, one factor at a time waschanged, and the standards for other parametersare highlighted across the middle ofTable 4.7. Forexample, in the case of body weight, the effecton feed intake was calculated with 50 g incre-ments of weight from 1200 to 1400 g. For eachof these calculations for body weight, egg pro-duction was fixed at 90%, egg weight at 60 g andenvironmental temperature at 20˚C. Likewise,when egg production was the variable consideredall other factors remained constant. The summarydata appearing as the last row inTable 4.7 showthe relative change in each input parameter nec-essary to change feed intake by one gram/bird/day.Consequently, ± 23 g body weight, ± 2.4% eggproduction, ±1.6 g egg weight, and ± 1ºC all changefeed intake by ± 1 g/bird/day. Of these factors envi-ronmental temperature is usually the most vari-able on a day-to-day basis, and so, is likelyresponsible for most of the variation in feedintake seen in commercial flocks.With variable feed intake, it is necessary toadjust the ratios of nutrients to energy to main-tain constant intakes of these nutrients. Whileit is impractical to consider reformulation basedon day-to-day fluctuation in environmental tem-perature, trends in feed intake associated withhigh vs. low body weight etc. should be accom-modated in diet formulation.A knowledge of feed intake, and the factorsthat influence it, are therefore essential for anyfeed management program. To a degree, the ener-gy level of the diet will influence feed intake,although one should not assume the precisionof this mechanism to be perfect. In general, birdsover consume energy with higher energy diets,and they will have difficulty maintaining normalenergy intake when diets of less than 2500 kcalME/kg are offered. In most instances, under- con-sumption rather than over-consumption is the prob-lem, and so use of higher energy diets during sit-uations such as heat stress will help to minimizeenergy insufficiency. Table 4.8 shows theLeghorn bird’s response to variable diet energy.These Leghorn strain birds performed sur-prisingly well with the diluted diets, and showedan amazing ability to adjust feed intake as dietnutrient density changed, and down to 2600kcal ME/kg were able to maintain almost constantenergy intake. Only at 2450 kcal/kg, whichrepresents a 15% dilution of the original diet, werethere indications of failure to consume ade-quate amounts of energy (or other nutrients?).Diet Feed intake (g/b/d) Feed (kg) Egg Energyenergy _____________________ ____________ ___________________ intake(kcal/kg)143 51 65 (19 – 67 wk) Number Mass (Mcal/365d)wks wks wks (kg)2900 100b 103bc 103b 33.9b 290 17.9a 98.32750 100b 103bc 103b 34.3b 294 16.9b 94.72600 116a 113a 109ab 37.1a 304 17.9a 96.82450 112a 111a 115a 37.1a 302 17.3ab 91.21 All other nutrients in same ratio to energy across all diets Adapted from Leeson et al. (2001)Table 4.8 Layer response to diet dilution (19 - 67 wks age)
  • 173CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.2Feed and energy intakeThese birds were maintained at 20 - 22˚C, andit is suspected that the layers may have had dif-ficulty maintaining nutrient intake with the dilut-ed diets if any heat distress conditions occurred.The diet specifications listed inTable 4.1 showvalues for crude protein. If soybean meal andcorn, wheat or sorghum make up 60 – 70% ofthe diet, then protein per se gives an indicationof the likely adequacy of amino acid needs.Obviously formulation to total and digestible aminoacids is critical in more precisely meeting the bird’snutrient needs, yet there is still a need for othernitrogen containing nutrients that are variablydescribed as crude protein or non-essentialamino acids. Theoretically, a layer diet has to pro-vide only the ten essential amino acids andunder ideal conditions, these will be at require-ment levels. However, when diets are formulatedon this basis, production, and economic returnsare reduced, suggesting the need for a ‘minimal’level of crude protein. Under commercial con-ditions, production goals are rarely achieved whencrude protein levels much less than 15% are usedthrough the layer cycle regardless of the supplyof essential amino acids. Such effects imply arequirement for nitrogen or non-essential aminoacids and/or that our assessment of essential aminoacid needs are incorrect. As crude protein levelof the diet is reduced, regardless of amino acidsupply, there is also increase in mortality andreduced feather score (Table 4.9). The feather-ing of white and especially brown egg birds isadversely affected by low protein diets (lower score).There is little doubt that body weight atmaturity is a major factor influencing feed intakeof laying hens. Body weight differences seen atmaturity are maintained throughout lay almostregardless of nutrient profile of layer diets. It istherefore difficult to attain satisfactory nutrientintakes with small birds. Conversely, largerbirds will tend to eat more, and this may becomeproblematic in terms of the potential for obesi-ty and/or too large an egg towards end of lay. Phasefeeding of nutrients can overcome some ofthese problems, although a more simplisticlong-term solution is control over body weightat maturity. Under most economic conditions,‘heavier’ birds at maturity are ultimately most eco-nomical for table egg production in terms of eggrevenue relative to feed costs.Table 4.9 Effect of crude protein on mortality and feather scoreFeather score(Scale 0-20)%CP %Cannibalism White Brown11.1 17.6 12.4 10.712.5 8.3 13.7 11.313.8 5.1 13.9 12.815.2 2.7 15.0 13.116.5 4.2 14.8 14.117.9 0.4 14.9 14.619.3 2.5 15.9 15.0Adapted from Ambrosen and Petersen (1997)
  • 174 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.2Feed and energy intakeFeed management becomes even more crit-ical with earlier and higher sustained peak eggproduction from today’s strains of bird. Energyinsufficiency during pre-peak production can causeproblems during post-peak production. Eggproduction curves that show a 5 – 8% reductionafter peak are characteristic of birds with insuf-ficient appetite caused by too small a pullet atmaturity (Figure 3.1). The reduction in appetiteis of concern relative to the adequacy of ener-gy intake. Calculations of energy balance indi-cate a somewhat precarious balance aroundthe time of peak egg numbers, emphasizingthe need for stimulating feed intake and thepossibility of providing some labile energyreserves in the form of carcass energy (fat) stores.Tables 4.10 and 4.11 show such calculated val-ues for Leghorn and brown egg strains respec -tively, and relate these to the required intake ofa standard diet.The significance of energy intake as the lim-iting nutrient for egg production with modern strainsof layer is shown in Figure 4.1. There is a dra-matic response to energy intake from 184 – 312kcal/bird/day, in the form of egg output. Atvery high energy intakes, there is little apparentresponse to protein intake over the range of13 – 21 g/bird/day. Only when energy intake islimiting is there any measurable increase inegg numbers in response to increased proteinintake. However, as will be detailed later(Figure 4.13), the converse applies in terms ofegg size, when the bird shows a dramaticresponse to protein intake, and little response toenergy intake.Table 4.10 Energy balance of leghorn pullets during early egg productionTheoretical Daily Energy Requirement Required intake ofAge (kcal ME per bird) 17% CP, 2850 ME(wks) Maintenance Growth Eggs Total diet (g/d)16 133 40 177 6217 137 40 181 6418 142 40 186 6519 150 35 5 190 6720 154 35 10 199 7021 154 30 24 208 7322 154 30 44 228 8023 154 25 57 242 8524 154 25 78 257 9025 155 20 85 260 9126 155 18 87 262 9227 158 15 92 265 9328 158 15 95 268 9429 160 13 97 270 9530 161 12 100 273 96
  • 175CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.2Feed and energy intakeTable 4.11 Energy balance of brown egg pullets during early egg productionTheoretical Daily Energy Requirement Required intake ofAge (kcal ME per bird) 17% CP, 2850 ME(wks) Maintenance Growth Eggs Total diet (g/d)16 148 50 2 200 7017 148 50 8 205 7218 134 50 30 214 7519 138 40 50 228 8020 142 40 60 242 8521 148 30 70 248 8722 152 30 80 262 9223 155 25 95 271 9524 160 25 96 274 9625 164 15 97 276 9726 166 15 98 279 9827 168 15 99 282 9928 173 12 100 285 10029 175 12 101 288 10130 176 12 102 290 102Fig. 4.1 Egg production (18-66 weeks) in response to daily intakes of energyand protein.
  • An argument against being overly concernedabout uniformity, is that birds will adjust theirintake according to nutrient (energy) needs, andso early maturing birds will eat more, and late matur-ing birds less, during the early phases of produc-tion. However, if birds are given diets formulat-ed based on feed intake, this can lead to problems,the most serious of which is overfeeding of the larg-er early maturing bird. Another confoundingfactor is that as birds mature within a flock, the per-cent production realized on a daily basis does notreflect the number of birds laying at that time. Asshown in Figure 4.2, the proportion of layingbirds always exceeds the percent production cal-culated and this difference is most pronounced inearly production. For example, at about 40% pro-duction, there are, in fact, around 70% of the birdsmature and requiring proportionally more nutri-ents than suggested by egg production alone.176 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.2Feed and energy intakeMany problems associated with marginal nutri-ent intake of young layers can most often be over-come by ensuring optimum body weight andappetite of young laying pullets. Unfortunately,mean weight of the flock at this age, is toooften considered independently of flock uniformity.Pullets may be of ‘mean’ body weight, yet be quitevariable in weight, and often outside the accept-ed range of 85% of the flock being within ± 10%of mean weight. The major problem with anon-uniform flock is variability in age at first egg,and so variability in feed intake. If diets are tai-lored to feed intake, then late maturing smallerbirds (with small appetites) will likely be under-fed. Conversely heavier, early maturing pulletswith increased appetites may be overfed at thistime. The consequence is often a delayed peak,and reduced overall egg production.Fig. 4.2 Comparison of number of birds producing eggs and actual egg production
  • 177CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distress4.3 Problems with heat distressThe majority of the world’s laying hens arekept in areas where heat stress is likely tobe a major management factor at somestage during the production cycle. The major prob-lem relates to birds not consuming enough feedat this time, although there are also some sub-tle changes in the bird’s metabolism that affectboth production and shell quality. While all typesof poultry thrive in warm environments duringthe first few weeks of life, normal growth anddevelopment of older birds is often adversely affect-ed. Obviously, the bird’s requirements for sup-plemental heat declines with age, because insu-lating feathers quickly develop and surfacearea, in relation to body size, is reduced. Heatstress is often used to describe bird status in hotenvironments, although it is obvious that morethan just environmental temperature per se isinvolved. Because birds must use evaporativecooling (as panting) in order to lose heat athigh temperatures, humidity of inhaled airbecomes critical. High temperature and humid-ity combined are much more stressful to birds thanis high temperature alone. Other environmen-tal factors such as air speed and air movement arealso important. It is also becoming clear that adap-tation to heat stress can markedly influenced birdresponse. For example, laying birds can tolerateconstant environmental temperatures of 35˚C andperform reasonably well. On the other hand, mostbirds are stressed at 35˚C when fluctuatingday/night temperatures are involved. In the fol-lowing discussion, it is assumed that fluctuatingconditions exist, since these are more commonand certainly more stressful to the bird.Figure 4.3 shows the bird’s generalized responseto variable temperature and humidity. Regardlessof housing system, environmental conditions of >32˚C and > 50% RH are likely to cause some degreeof heat distress. Table 4.12 shows typical layerresponse to high environmental temperatures.Table 4.12 Performance of brown egg layers at 18˚C vs. 30˚CFeed intake Egg production Egg weight Shell (% of egg)(g/b/d) (%) (g) 40 wk 60 wk18˚C 131 91.2 60.9 9.5 9.130˚C 108 83.6 57.2 9.0 8.6Adapted from Chen and Balnave (2001)
  • 178 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distressThe main concern under hot weather con-ditions is the layer’s ability to consume feed. Aspoultry house temperature increases, then lessheat is required to maintain body temperatureand the birds consume less feed. In this situation,‘environmental’energy is replacing feed energyand is economical. However, the relationshipbetween body heat production and house tem-perature is not linear, since at a certain criticaltemperature, the bird’s energy demands areincreased in order to initiate body coolingmechanisms. The following factors should be con-Fig. 4.3 Generalized bird response to temperature and humidity.Fig. 4.4 Environmental temperature and body heat production.
  • 179CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distresssidered in attempting to accommodate the bird’sreaction to heat stress:a) Bird’s response to heat stress –Figure 4.4 is a schematic representation ofa heat stress effect. Minimal body heat production(and hence the most efficient situation) is seenat around 23˚C. Below this temperature, (lowercritical temperature) birds generally have togenerate more body heat in order to keep warm.However, there is only a narrow range of tem-perature (19-27˚C) over which heat productionis minimal. Above 27˚C birds start to use moreenergy in an attempt to stay cool. For example,at 27˚C, birds will start to dilate certain blood ves-sels in order to get more blood to the comb, wat-tles, feet etc. in an attempt to increase coolingcapacity. More easily observed is the characteristicpanting and wing drooping that occurs at slight-ly higher temperatures. These activities at highenvironmental temperatures mean that the birdhas an increased, rather than decreased, demandfor energy. Unfortunately, the situation is not asclear cut as depicted in Figure 4.4 and this is like-ly the reason behind the variability seen inflock response to various environmental conditions.Rather than lower and upper critical temperaturebeing rigidly fixed under all conditions, heat pro-duction is likely to fluctuate in response to a num-ber of very practical on-farm conditions.Variation in response can be caused by suchfactors as (a) increased feed intake; (b) degree offeathering or; (c) increased bird activity. Suchpotential variability in bird response should betaken into account when interpreting the quan-titative data discussed in Figures 4.5 and 4.6. Thewhole picture is further confused by the normalenergy intake pattern of the bird (Figure 4.5). Theupper line of Figure 4.5 represents energy intakefor a 1.5 kg white egg layer. As environmentaltem-peratureincreases,energyintakedeclines. However,above 27 – 28˚C the decline becomes quitedramatic since the bird is changing its metabolicFig. 4.5 Environmental temperature and energy balance.
  • 180 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distressprocesses in response to the heat load, andactions such as panting, etc. adversely influencethe feeding mechanisms in the brain and also reducethe time available for feeding. The shaded areabetween the lines in Figure 4.5 represents the ener-gy available for production. At around 28˚C theenergy available for production is dramaticallyreduced and around 33˚C actually becomes neg-ative. If energy available for production is plot-ted against temperature, the energy potential foregg production is clearly evident (Figure 4.6).A 60 g egg contains around 80 kcal gross ener-gy, and this requires around 100 kcal ME of dietaryinput, assuming 80% efficiency of utilization ofthis ingested energy. If the bird is at 95% pro-duction, then there is a need for 95 kcal ME/dto sustain peak egg output. There will also beneed for 15 – 25 kcal ME for daily growth of thisyoung pullet, for a total need of around 115 kcalME/d for productive purposes. At moderateenvironmental temperatures, such energy yieldis readily obtained from the feed, since with aver-age intakes of 270 – 275 kcal ME/bird/day,there is adequate energy for production andmaintenance. However, as feed intake declines,available energy will decline. Although main-tenance energy needs are less at higher tem-peratures, the non-linear relationship (Figure4.5) causes problems of energy sufficiency ataround 28˚C (Figure 4.6). Above this tempera-ture, if production and growth are to be sustained,the birds will have to use body energy reservesin order to balance energy demands. Thereare obvious limits to such fat reserves, especiallywith young pullets, and so it is unlikely that thepullet can sustain 95% egg production for toolong a period under these conditions.Fig. 4.6 Environmental temperature and energy balance.
  • 181CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distressThe bird has no option but to reduce egg out-put in order to sustain energy needs for main-tenance. Under actual farm conditions, thetemperatures at which critical changes occur (28˚Cand 33˚C in Figure 4.6) will vary, especiallywith acclimatization to temperature, but eventswill likely be initiated within ± 2˚C of the val-ues shown in Figure 4.6.A major factor affecting the bird’s energy intakein response to environmental temperature isfeather cover, which represents insulating capac-ity for the bird. Coon and co-workers havedeveloped equations that take into accountdegree of feathering, although this assumes a lin-ear trend across all temperatures. Figure 4.7 usesthese equations to predict energy intake up toaround 25˚C, at which time it is assumed that adegree of heat distress will occur and this willbe most prevalent for the well-feathered bird. Theresponse after 26˚C assumes increased energyneed, as shown in Figure 4.5. The actual situ-ation may be more complex than this in tropi-cal regions where birds are held in open-sidedhouses and where there is the expectation of coolnightime temperatures.Fig. 4.7 ME intake of layers with 60, 75 or 90% feather cover at 10-34˚CAdapted from (Peguri and Coon, 1995)
  • 182 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distressb) Maintaining energy balance –The key to sustaining production in hotclimates is to maintain a positive energy balance.i) Changing diet energy level - It is well knownthat birds consume less feed as the energy levelof the feed increases. This is because the birdattempts to maintain a given energy intake eachday. However, the mechanism is by no meansperfect and as energy level is increased, theactual decline in feed intake is often imper-fectly regulated, leading to ‘overconsumption’of energy. As environmental temperature increas-es, the mechanism seems even less perfect andso increasing diet energy level is often consid-ered in an attempt to stimulate energy intake. Payne(1967) showed this classical effect with brownegg layers fed 2860 to 3450 kcal ME/kg at 18˚Cor 30˚C (Table 4.13). At 18˚C there is fairlygood adjustment by the bird in that feed intakeis sequentially reduced as energy level increas-es and energy intake is maintained constant. Athigh temperatures, birds adjust feed intake lessperfectly and ‘overconsumption’ of energyoccurs. It is not suggested that these extremesof diet energy be used commercially, ratherthat energy intake will be maximized with as higha diet energy level as is possible. In order toincrease diet energy level, the use of supplementalfat should be considered. Dietary fat has the advan-tage of increasing palatability and also reducingthe amount of heat increment that is producedduring its utilization for production.ii) Physical stimulation of feeding activity –Various methods can be used to stimulate feedintake. Feeding more times each day usuallyencourages feeding activity. Feeding at cooler timesof the day, if possible, is also a useful method ofincreasing the bird’s nutrient intake. If artificiallights are used, it may be useful, under extremeenvironmental conditions, to consider a so-calledmidnight feeding when temperature will hopefullybe lower and birds are more inclined to eat.When heat stress is extreme, making the dietmore palatable may be advantageous. Suchpractices as pouring vegetable oil, molasses, oreven water directly onto the feed in the troughswill encourage intake. Whenever high levels offat are used in a diet, or used as a top dressing asdescribed here, care must be taken to ensure thatrancidity does not occur. This can best be achiev-ed by insisting on the incorporation of qualityTable 4.13 Effect of diet energy level on metabolizable energy intake18˚C 30˚CDiet energy Feed/day Energy/day Feed/day Energy/day(kcal ME/kg) (g) (kcal) (g) (kcal)2860 127 363 107 3063060 118 360 104 3203250 112 364 102 3303450 106 365 101 350Adapted from Payne (1967)
  • 183CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distressantioxidants in the feed and that feed not beallowed to ‘cake’ in tanks, augers or troughs.Freshness of feed becomes critical under theseconditions.Diet texture can also be used to advantage.Crumbles or large particle size mash feed tend tostimulate intake while a sudden change fromlarge to small feed particles also has a transitoryeffect on stimulating intake. It is interesting to observethat a sudden change from small to large crumblesseems to have a negative effect on intake (Table 4.14).Midnight feeding is often used when birds aresubjected to heat stress conditions. Light for 1– 2 hrs has at least a transitory effect on increas-ing feed intake (1 – 3 %) and often has a long-term effect. With moderately high tempera-tures it may only be necessary to provide lighting,while with extreme hot weather it is advisableto also run the feeder lines during this 1 hour timeperiod. An interesting observation with midnightfeeding is the bird’s dramatic increase in waterintake (see Figure 4.8). Layers will eat more feedin hot weather conditions, if the ‘effective tem-perature’ is reduced. This is sometimes achievedwith evaporative cooling depending upon inher-ent levels of humidity. A less costly, but very effec-tive system of stimulating intake, is to increaseair movement. Body temperature of the bird isclose to 41˚C, and the air within the 1-2 mmboundary layer around the bird will be close tothis temperature. By increasing air speed, theboundary layer is disrupted, so aiding in cool-ing the bird. Table 4.15 shows the effect of airmovement on the cooling effect on the birdand the expected increase in feed intake.iii) Body fat reserves – Adequacy of pulletrearing programs become most critical whenbirds are to be subjected to hot weather in thetime up to peak egg mass production. Asdetailed in Figure 4.6, the layer may well haveto rely on its body energy reserves as a supple-ment to its diminished energy intake from thefeed. Rearing programs designed to maximizegrowth have been discussed previously. Theheavier the bird at maturity, the larger the bodyweight throughout lay, and hence the largerthe potential energy reserve and also thegreater the inherent feed intake (Table 4.16)It is not suggested that extremely fat pullets aredesirable, but it is obvious that birds of opti-mum weight with a reasonable fat reserve arebest suited to heat stress situations. Pulletsthat are subjected to heat stress and have less‘available’ energy than that required to sustainproduction, have no recourse but to reduceegg mass output in terms of egg weight and/oregg numbers, since maintenance energyneeds are always a priority.Table 4.14 Effect of sudden change in feed particle size on feed intake5-7d following this changeCrumb sizeRegular to small Regular to largeRegular (<2.4 mm) (> 2.4 mm)Feed (g/bird/day) 112b 124a 81c
  • 184 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distressc) Protein and amino acids –It is tempting to increase the crude proteinlevel of diets during heat stress conditions. Thishas been done on the basis of reduced feed intake,and hence protein levels have been adjustedupwards in an attempt to maintain intakes ofaround 19 g crude protein/bird/day. It is now real-ized that such adjustments may be harmful.When any nutrient is metabolized in the body,the processes are not 100% efficient and sosome heat is produced. Unfortunately, proteinis the most inefficiently utilized nutrient in thisregard and so, proportionately more heat isevolved during its metabolism compared tothat of fat and carbohydrates. The last thing thata heat stressed bird needs is additional waste heatbeing generated in the body. This extra heat pro-duction may well overload heat dissipationmechanisms (panting, blood circulation). We aretherefore faced with a difficult problem of attempt-ing to maintain ‘protein’ intake in situations ofreduced feed intake, when crude protein per semay be detrimental. The answer to the problemis not to increase crude protein, but rather to increasethe levels of essential amino acids. By feeding syn-thetic amino acids, we can therefore maintain theintake of these essential nutrients without theneed to catabolize excess crude protein (nitrogen).General recommendations are, therefore, toincrease the use of synthetic methionine andlysine and perhaps threonine to maintain dailyintakes of approximately 420, 820 and 660 mgrespectively for birds around peak egg production.d) Minerals and vitamins –Calcium level should be adjusted accordingto the anticipated reduction in feed intake, so thatbirds consume at least 4.2 g per day. Underextreme conditions, this may be difficult since,Table 4.15 Cooling effect of air movement (wind chill) and expectedincrease in feed intake of layers maintained at 30ºCAir movement Cooling effect Expected increase in(meters/second) (˚C) feed intake (g/b/d)0.5 1 Up to 1 g0.75 2 1 – 2 g1.0 3 2 - 3 g1.25 4 3 - 4 g1.50 5 4 – 5 g1.75 6 5 – 6 gTable 4.16 Leghorn pullet size and energy intakeBody Weight (g) Daily energy consumption18 wk 24 wk 18-25 wks (kcal)1100 1400 2471200 1500 2541300 1600 2631400 1700 273
  • 185CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distressas previously indicated, high energy diets are alsodesirable and these are difficult to achieve withthe increased use of limestone or oyster shell. Table4.17 shows the diet specifications needed to main-tain intakes of Ca, P, and vitamin D3, all ofwhich are critical for eggshell quality.Table 4.17 Diet nutrient levelsneeded to maintain constant intakeof these nutrients at varying levelsof feed intakeFeed intake Av P Ca Vit. D3(g/d) (%) (%) (IU/kg)80 0.52 5.3 412590 0.47 4.7 3660100 0.42 4.2 3300110 0.38 3.8 3000Because it is also necessary to increase theenergy level of the diet when feed intake islow, then it is counterproductive to add high lev-els of limestone and phosphates, which effectivelydilute the feed of all nutrients other than Ca andphosphorus. The problem of potential calciumdeficiency is most often met by top dressing feedwith oystershell or large particle limestone. Thedeficit of vitamin D3 is best met with use of D3supplements in the drinking water rather than for-mulation of a new premix.There seems to be some benefit to adding sodi-um bicarbonate to the diet or drinking water.However, this must be done with care so as notto impose too high a load of sodium on the bird,and so salt levels may have to be altered. Thisshould be done with great caution, taking intoaccount sodium intake from the drinking water,which can be quite high during heat stress con-ditions. In most situations, there will be nonegative effects from replacing 30% of supple-mental salt with sodium bicarbonate on a kg forkg basis. There is also an indication of benefi-cial effects of increasing the potassium levels inthe diet, although again, this must be accomplishedonly after careful calculation, since higher lev-els can be detrimental to electrolyte balance. Whilefew reports indicate any improvement in addingsupplemental B vitamins during heat stress,there are variable reports of the beneficial effectswith the fat soluble vitamins. Although notalways conclusive, increasing the levels of vita-minsA, D3 and E have all been shown to be advan-tageous under certain conditions. While vitaminC (ascorbic acid) is not usually considered in poul-try diets, there is evidence to support its useduring hot weather conditions. Under most cir-cumstances, birds are able to synthesize their needsof vitamin C but under heat stress, such productionmay be inadequate and/or impaired. Adding upto 250 mg vitamin C/kg diet has proven benefi-cial for layers in terms of maintaining productionwhen temperatures exceed 28ºC.e) Electrolyte balance –As environmental temperature increases,birds increase their respiration rate in an attemptto increase evaporative cooling. As birds pant,they tend to lose proportionally more CO2 andso changes in acid-base balance can quickly devel-op. With mild to severe alkalosis, blood pH maychange from 7.2 through 7.5 to 7.7 in extremesituations. This change in blood pH, together withloss of bicarbonate ions can influence eggshellquality and general bird health and metabolism.Under such heat stress conditions, it is the avail-ability of bicarbonate per se which seems to bethe major factor influencing eggshell synthesisand in turn, this is governed by acid-base bal-ance, kidney function and respiration rate.Shell formation normally induces a renalacidosis related to the resorption of filteredbicarbonate. At the same time, shell secretioninduces a metabolic acidosis because the formation
  • 186 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distressof insoluble CaCO3 from HCO3 and Ca2+ involvesthe liberation of H- ions. Such H- release wouldinduce very acidic and physiologically destructiveconditions, and be necessarily balanced by the bicar-bonate buffer system in the fluid of the uterus. Whilea mild metabolic acidosis is therefore normalduring shell synthesis, a more severe situationleads to reduced shell production because ofintense competition for HCO3 as a buffer ratherthan for shell formation. A severe metabolic aci-dosis can be induced by feeding products such asNH4Cl, and this results in reduced shell strength.In this scenario, it is likely that NH4 rather than Cl-is problematic because formation of urea in the liver(from NH4) needs to be buffered with HCO3ions, creating added competition for shell formation.Conversely, feeding sodium bicarbonate, especiallywhen Cl- levels are minimized, may well improveshell thickness. Under commercial conditions, theneed to produce base excess in order to buffer anydiet electrolytes must be avoided. Likewise it isimportant that birds not be subjected to severe res-piratory excess, as occurs at high temperatures,because this lowers blood bicarbonate levels andinextremecases,causesametabolicacidosis. Underpractical conditions, replacement of part (30-35%) of the supplemental dietary NaCl withNaHCO3 may be beneficial for shell production.Acclimatization to heat stress is a con-founding factor because short-term (1-2 d) acuteconditions are more problematic to the bird. Forexample, pullets grown to 31 weeks under con-stant 35 vs 21ºC conditions exhibit little differ-ence in pattern of electrolytes. If birds areallowed to acclimatize to high environmental tem-peratures there is little correlation between plas-ma electrolytes and shell quality. Temporary acuteheat stress and cyclic temperature conditions areundoubtedly the most stressful to the bird.Severe electrolyte imbalance can be preventedby considering the ratio of cation:anion in dietformulations. However, it must be accepted thatthe diet is only one factor influencing potentialimbalance, and so, general bird management andwelfare also become of prime importance.Electrolyte balance is usually a consideration ofNa+K-Cl in the diet, and under most dietary sit-uations, this seems a reasonable simplification.Electrolyte balance is usually expressed in termsof mEq of the various electrolytes, and for an indi-vidual electrolyte this is calculated as Mwt ÷ 1,000.This unit is used on the basis that most miner-als are present at a relatively low level in feeds.As an example calculation, the mEq for a diet con-taining 0.17% Na, 0.80% K and 0.22% Cl canbe calculated as follows:Sodium Mwt = 23.0, Eq = 23g/kg, mEq = 23mg/kgDiet contains 0.17% Na = 1,700 mg/kg = 1700/23 mEq = 73.9 mEqPotassium Mwt = 39.1, Eq = 39.1g/kg, mEq = 39.1mg/kgDiet contains 0.80% K = 8,000 mg/kg = 8,000 /39.1 mEq = 204.6 mEqChloride Mwt = 35.5, Eq = 35.5g/kg, mEq = 35.5mg/kgDiet contains 0.22% Cl = 2,200 mg/kg, = 2,200/35.5 mEq = 62.0 mEqoverall diet balance becomes Na + K – Cl = 73.9 + 204.6 – 62.0 = 216.5 mEq.
  • 187CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distressA balance of around 250 mEq/kg is usual, andso for this diet, there needs to be either anincrease in Na or K level of the diet, or adecrease in Cl level.Under practical conditions, electrolyte bal-ance seems to be more problematic when chlo-ride levels are high. On the other hand, use ofNaHCO3 to replace NaCl, as is sometimes rec-ommended during heat stress, can lead to adeficiency of chloride. Changes in diet electrolytebalance most commonly occur when there is amajor change in ingredient usage and espe-cially when animal protein sources replace soy-bean meal and vice versa. Table 4.18 outlineselectrolyte balance of some major feed ingredients.Within the cereals, Na+K-Cl for milo is low,while wheat is high relative to corn. Major dif-ferences occur in the protein-rich ingredients, andrelative to soy, all sources are low in electrolytebalance. As shown in Table 4.18, this situationdevelops due to the very high potassium contentof soybean meal. Careful consideration to elec-trolyte balance must therefore be given whenchanges are made in protein sources used in for-mulation. For example, the overall balance fora diet containing 60% milo and 25% soy is210 mEq/kg, while for a diet containing 75% miloand 10% fish meal, the balance is only 75mEq/kg. The milo-fish diet would need to be sup-plemented with NaHCO3.Assuming that heat stress cannot be temperedby normal management techniques, then elec-trolyte manipulation of the diet may be benefi-cial. However, the technique should be differ-ent for immature birds compared to egg layers.With layers, there is a need to maintain thebicarbonate buffer system as it influences eggshellquality. As such, diet or water treatment with sodi-um bicarbonate may be beneficial, again empha-sizing the necessity to meet minimum chloriderequirements. On the other hand, treatment ofrespiratory alkalosis in layers with acidifierssuch as NH4Cl, while relieving respiratory dis-tress, may well result in reduced shell quality. Forimmature pullets, treatment with electrolytesis often beneficial and there is less need forcaution related to bicarbonate buffering. Up to0.3% dietary NH4Cl may improve the growth rateof heat stressed birds, although it is not clear ifany effect is via electrolyte balance/blood pH orsimply via the indirect effect of stimulatingwater intake. Under commercial conditions,adding salt to the drinking water of young birdshas been reported to alleviate bird distress andto stimulate growth.Table 4.18 Electrolyte content of feed ingredientsINGREDIENT Na K Cl Na+K-Cl (mEq)Corn 0.05 0.38 0.04 108Wheat 0.09 0.52 0.08 150Milo 0.04 0.34 0.08 82Soybean meal 0.05 2.61 0.05 675Canola meal 0.09 1.47 0.05 400Meat meal 0.55 1.23 0.90 300Fish meal 0.47 0.72 0.55 230Cottonseed meal 0.05 1.20 0.03 320
  • 188 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distressf) Water –A nutritional factor often overlooked duringheat stress is the metabolism of water. It is wellknown that birds in hot environments drinkmore water, yet this has not been capitalized uponto any degree. Table 4.19 shows the water bal-ance of layers held at 22˚C or 35˚C.Table 4.19 Water balance of layersat 22ºC or 35ºC (ml/bird/day)22˚C 35˚CWater intake 210 350Manure water 85 150Egg water 50 50Respiration water 75 150Layers will drink at least 50% more water at35 vs. 22˚C. If such adaptation is not seen, thenit likely relates to birds not being able to consumesufficient quantities of water at times of peak need.Figure 4.8 shows the daily pattern of waterintake of layers when lights are on from 6:30 a.m.to 6:30 p.m. There is a doubling of water intakein the last 3 hours of the day, compared to all pre-vious times, and so the water system must be ableto accommodate this demand, especially inhot weather conditions.Since water intake is often increased attimes when feed intake is decreased, it would belogical to try and provide limiting nutrients in thewater. However, this concept has met withonly limited success, possibly related to changein ‘taste’ of the water and/or the nutrients stim-ulating bacterial growth in the water lines.However there are always positive results seenwhen the drinking water is cooled. Feed intakecan be stimulated as much as 10% by coolingthe water 5 to 8˚C when environmental tem-perature is around 30 – 32˚C. Although this man-agement practice is relatively easy to achieve underexperimental conditions, it is a much morecomplex engineering problem with large com-mercial flocks.g) Effect of physical diet change –Discussion to date has centered on thepotential of diet manipulation to alleviate heatstress. However, diet change per se may be detri-mental under certain conditions. It seems thatwhen the bird is confronted with an acute heatstress situation, diet change may impose anoth-er stress, which merely accentuates any meta-bolic imbalance. For example, it was recentlyreported that a diet change brought about byadding fat caused an immediate rise in body tem-perature for up to 4 d which can be disastrousto the bird and cause death. At the same time,the diet change had the desirable effect of stim-ulating energy intake. For this reason, it is sug-gested that under extreme heat stress condi-tions of 36 – 40˚C, that no diet change beimplemented, since it could lead to death fromheat prostration.Fig. 4.8 Daily pattern of relative water intake. Lights on @ 6:30am for 12 hrs/d
  • 189CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.3Problems with heat distress@ 21 wks of age @ 33 wks of ageEgg Feed Shell Egg Feed ShellDiet type prod. intake deformation prod. intake deformation(%) (g) (µm) (%) (g) (µm)Pre-test7 d (18ºC) Control 82 86 21 92 101 24Stress Control 92 64a22b71 50a35b3 d (35ºC) High CP 90 36c24a56 20b41abHigh Energy 94 40c23ab60 27b46aHigh Density 96 53b24a67 28b37bPost- Control 84a76a26c77a84a30bstress 4 d High CP 39c24b35ab45b61bc41a(18ºC) High Energy 56b33b41a64a57c42aHigh Density 69ab76a31bc67a73ab29ba-cmeans followed by different letters are significantly differentTable 4.20 Effect of diet change on layer performance during heat stressUnder these conditions, it would be usefulto be able to prejudge the rise in environmen-tal temperature and make the diet change ear-lier, when the bird is under ‘moderately’ stress-ful conditions (28 – 35˚C). However, even withshort-term heat stress situations, it may be inad-visable to change the diet (Table 4.20).In these studies, birds were fed a control rationfor 7 d at an environmental temperature of18˚C. A heat stress of 35˚C was suddenlyimposed, and birds offered the same control diet,or diets high in energy, protein or all nutrients(termed high density). Feed intake was depressedalmost immediately in response to heat stress,although changes in egg production and shell qual-ity were not seen until after the 3 d stress peri-od. However, during this post-stress period, birdsshowed a dramatic loss in egg numbers and shellquality. There was no instance of diet change alle-viating the effects of heat stress, and in most sit-uations, production deteriorated. Under such con-ditions of short-term heat stress, it is suggestedthat sudden diet change merely imposed anadditional stress and was not beneficial to the bird.h) Summary of nutritionalmanagement during heat1. Never place underweight pullets in the laying house.They will always remain small with low feedintake and have little body fat reserve to sustainenergy balance through the period of peak eggmass production.2. Increase the energy level of the diet with a min-imum of 2850 kcal ME/kg, ideally by incorporationof fats or oils. Limit the level of crude fiber.3. Reduce crude protein (17% CP maximum) whilemaintaining daily intakes of methionine (420mg), lysine (820 mg) and threonine (660 mg).4. Increase mineral-vitamin premix in accordance withanticipated change in feed intake. Maintaindaily intakes of calcium (4.2 g) and available phos-phorus (400 mg).
  • 190 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.4Phase Feeding5. Where shell quality is a problem, considerthe incorporation of sodium bicarbonate. Atthis time, monitor total sodium intake, andensure adequate chloride levels in the diet.6. Use supplemental vitamin C at 250 mg /kg.7. Increase the number of feedings per dayand try to feed at cooler times of the day.4.4 Phase FeedingPhase feeding refers essentially to reduc-tions in the protein and amino acid levelof the diet as the bird progresses througha laying cycle. The concept of phase feeding isbased on the fact that as birds get older, their feedintake increases, while egg mass output decreas-Fig. 4.9 Bird age: egg production, egg weight and egg mass.8. Keep drinking water as cool as possible.9. Use crumbled feed or large particle mash feedif available.10. Do not make any diet change when suddenshort-term (3 – 5 d) heat stress occurs.es. For this reason, it should be economical toreduce the nutrient concentration of the diet. Atthis time, it is pertinent to consider a conventionalegg production curve of a layer, and superimposeboth egg weight and daily egg mass output(Figure 4.9).
  • 191CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.4Phase FeedingIf nutrient density is to be reduced, this shouldnot occur immediately after peak egg numbers,but rather after peak egg mass has been achieved.The two reasons for reducing the level of dietaryprotein and amino acids during the latter stagesof egg production are first, to reduce feed costsand second, to reduce egg size. The advantagesof the first point are readily apparent if protein costsare high, but the advantages of the second pointare not so easily defined and will vary depend-ing upon the egg pricing. When a producer is beingpaid a premium for extra large and jumbo eggs,there is no advantage to using a phase feeding pro-gram unless eggshell quality is a problem.It is difficult to give specific recommendationsregarding any decrease in dietary protein oramino acid level that can be made to temper eggsize without also decreasing the level of production.The appropriate reduction in protein level willdepend on the season of the year (effect of tem-perature on feed consumption, age and productionof the bird, and energy level of the diet). Hence,it is necessary that every flock be considered onan individual basis before a decision is made toreduce the level of dietary protein. As a guide,it is recommended that protein intake be reducedfrom 19 to 18 g/day after the birds have droppedto 90% production, and to 15-16 g/day after theyhave dropped to 80% production. With anaverage feed intake of 95 g/day, this would beequivalent to diets containing 20, 19 and 16%protein. It must be stressed that these values shouldbe used only as a guide, and after all other fac-tors have been properly considered. If a reduc-tion in the level of protein is made and eggproduction drops, then the decrease in nutrientintake has been too severe and it should beimmediately increased. If, on the other hand, pro-duction is held constant and egg size is notreduced, then the decrease in protein or aminoacid intake has not been severe enough and itcan be reduced still further. The amino acid tobe considered in this exercise is methionine, sincethis is the amino acid that has the greatest effecton egg size. As for the situation with protein, toolarge a single step reduction in methionine willlikely lead to loss in egg production and possi-bly an increase in feed intake. A one-timereduction in diet methionine of 20% has beenreported to reduce egg size by 3% with con-commitant loss in egg production of 8%.Phase feeding of phosphorus has also been rec-ommended as a method of halting the decline inshell quality invariably seen with older birds.Using this technique, available phosphorus lev-els may be reduced from approximately 0.42 –0.46% at peak production to slightly less than 0.3%at end of lay. Table 4.21 shows an example ofTable 4.21 Phase feeding of major nutrients after peak egg mass, assumingconstant daily feed intake at 100 gBird characteristics Diet levels (%)Age (wks) Egg production Crude Methionine Calcium Av.(%) protein phosphorus<35 93 19.0 0.41 4.2 0.4445 90 18.0 0.38 4.3 0.4155 85 17.0 0.36 4.4 0.3670 80 16.0 0.34 4.5 0.32
  • 192 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.5Formulation changes and feed texturesphase feeding of protein, methionine and phos-phorus, related to controlling egg size, opti-mizing shell quality and minimizing feed costs.A major criticism of phase feeding is that birdsdo not actually lay ‘percentages’ of an egg. Forexample, if a flock of birds is producing at 85%production does this mean that 100% of the flockis laying at 85% or is 85% of the flock laying at100% production. If a bird lays an egg on a spe-cific day, it can be argued that its production is100% for that day, and so its nutrient requirementsare the same regardless of the age of bird.Alternatively, it can be argued that many of thenutrients in an egg, and especially the yolk,accumulate over a number of days, and so thisconcept of 100% production, regardless of age,is misleading.Advocates of phase feeding indicate thatbirds can be successfully managed by reducingprotein/amino acid contents of the diet – otherssuggest that nutrient specifications are too highto start with initially, and that phase feedingmerely accomplishes normalization of diet in rela-tion to requirement. The bottom line is that envi-ronmental and management conditions varyfrom flock to flock, and certainly from season toseason within a flock. For this reason, the basisof phase feeding must be an accurate assessmentof the nutrient intake relative to requirement forproduction, growth and maintenance.With diets formulated to least costingredient input, it is often necessaryto change ingredient concentrations,and depending upon economic circumstances,the computer invariably ‘asks’ for major changesat certain times. In these situations, nutritionistsare often reluctant to make major ingredient sub-stitutions in consecutive diets, on the basis thatsuch change may adversely affect feed intake andhence product. In a recent study, birds were feda range of diets over a 12-month cycle, with thesituation of least cost where major changes in ingre-dient use occurred in most months. Control birdswere fed least cost formulated diets, although inthis situation major ingredient changes frommonth to month were not allowed, rather thesechanges occurred more gradually as occurscommercially. Birds responded reasonably to thesechanges and no major adverse effects wereseen. However, a slight improvement in egg pro-duction and egg size with a conventional leastcost system, where diet changes were temperedto prevent drastic swings in diet composition, some-what negated the savings in feed costs seenwith absolute least cost. The economic situationin terms of egg return minus feed cost was in favorof conventional least cost, mainly due to a dou-bling of the mortality rate with the major swingsin diet composition. It seems that while theabsolute least cost diets are initially attractive inreducing feed cost, they offer little overall eco-nomic advantage and generally pose an additionaleconomic risk.The texture of diets for laying hens is perhapssubject to more variability than for any other classof poultry. In some countries, very fine mash-es are used, whereas crumbles are used in otherareas. There is little doubt that any type of feedtexture can be made to work physically, althoughbird response is not always the same. Ourresearch data suggests that regardless of nutrientprofile, layers prefer large particles of feed.When layers were offered a crumbled diet, theyshow a marked preference for the largest size par-ticles available. Smaller particles of feed only4.5 Formulation changes and feed texture
  • 193CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.6Nutrition and shell qualitystart to disappear later within a 24 h period, whenall the large particles have been eaten. In thisstudy, there was no disappearance of very fineparticles <0.6 mm, although this result may beconfounded with the break down of large parti-cles. Feed intake increased when birds were sud-denly presented with feed of small particle size,and intake temporarily declined when birdswere offered only large size particles. A criticismof mash diets is that they tend to separate out whenused in long runs of feed trough, and especial-ly where continous chain feeders are used. Froma survey of commercial flocks in Ontario, we foundcomparable physical separation of feed withboth mash and crumbles (Table 4.22).In this study, feed samples were taken direct-ly from the feed tank and then at points pro-gressively further from the initial point of distributionwithin the feed trough. Particle and nutrient sep-aration were seen at all farms (Table 4.22).With crumbled feed, particle size was dramat-ically reduced as feed traveled along the trough,although this was not associated with any majorchange in nutrient profile. Higher calcium lev-els per se in the trough, rather than the tank, relatesto feed samples in the trough including all feedin front of the bird that included fine particlesbeneath the feeder chain. Particle separation wasalso seen with the mash feeds, although this wasonly during the first 18 m run of the feed trough.Table 4.22 Particle segregation and calcium analysis of feed collected fromfarms using either mash or crumbles (%)Type of feed Particle At feed Distance along feed trough (m)size (mm) tank+18 +36 +72 +108Crumbles >2.36 46.0 29.8 25.3 20.6 16.0>1.18 28.8 26.5 25.5 24.7 23.7>0.85 6.9 9.4 10.1 10.9 11.1>0.71 3.4 5.5 6.1 6.7 7.1>0.60 3.2 5.6 6.2 6.7 7.1<0.60 11.7 23.2 26.8 30.3 33.8%Calcium 3.5 4.3 4.5 4.7 4.5Mash >2.36 17.3 10.0 8.3 8.5 10.5>1.18 22.7 21.1 20.0 19.6 21.0>0.85 11.9 13.4 13.2 14.5 15.1>0.71 7.2 8.9 9.0 9.2 9.0>0.60 7.4 8.6 9.0 9.3 8.2<0.60 33.5 38.0 40.5 38.9 36.2%Calcium 4.0 4.9 5.3 5.6 5.04.6 Nutrition and shell qualityNutrition can have a major impact oneggshell quality, and is often the firstparameter considered when problemsarise. After peak egg production, the layer pro-duces a fairly consistent quantity of shell mate-rial for each egg, regardless of its size. As the egggets larger, therefore, the shell necessarily getsthinner, and this becomes more prone to breakage.
  • 194 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.6Nutrition and shell qualityEven with ideal conditions,4–5% of eggs leavingthe farm will be graded as ‘cracks’, and togetherwith cracked and broken eggs on-farm, means that7–8% of eggshells break for various reasons.The composition of the shell is very consistent sincethe major constituent is calcium carbonate.When considering eggshell quality, the nutri-tional factors most often investigated are dietlevels of calcium, phosphorus, and vitamin D3.Since larger eggs have thinner shells, then levelsof protein, methionine, andTSAA may also comeunder scrutiny.A shell contains around 2 g of calcium theorigin of which is the feed, with a portion of thiscycling through the medullary bone. The mostactive period for shell formation usually coincideswith the dark phase of the photoperiod, and sobirds are not eating at this time (Figure 4.10). Inthe first 6 hours of the 24 h ovulatory cycle, thereis virtually no shell deposition. This is the timeof albumen and shell membrane secretion, andthe time of redeposition of medullary bone.From 6 – 12 hr about 400 mg calcium aredeposited, while the most active period is the 12– 18 hr period when around 800 mg shell cal-cium accumulates. This is followed by a slow-er deposition of about 500 mg in the last 6 hr,for a total of around 1.7 g shell calcium, depend-ing upon egg size.During the evening, when shell calcificationis greatest, a portion of the required calcium willcome from the medullary bone reserves. The totalmedullary calcium reserves are probably less than1 g.This reserve normally contributes no more than0.1 g to a shell containing 2g calcium, yet areessential for the almost daily shell formation processof the modern layer. The medullary bone is com-posed of calcium phosphate, and so the quantityof calcium liberated for shell synthesis, is asso-ciated with a similar release of phosphorus.Fig. 4.10 Shell mineral deposition over a 24h ovulation cycle
  • 195CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.6Nutrition and shell qualitySince there is little immediate need for thisphosphorus, it is excreted and there is need forboth calcium and phosphorus to replenish thismedullary reserve during periods between suc-cessive ovulations. Figure 4.11 shows the cal-cium and phosphorus balance of a bird ataround 35 weeks of age.Figure 4.11 shows zero net accretion of cal-cium and phosphorus in medullary bone. It islikely that the quantity of medullary calcium andphosphorus reserves are maximum when the birdis around 30 weeks of age, and a slight negativebalance over time contributes to reduced shellquality in older birds.There is often discussion about the physicalform and source of calcium supplied to layers.Calcium is usually supplied as limestone, oras oystershell which is much more expensive.Oystershell and large particle limestone areexpected to be less soluble than is fine particlelimestone, and so remain in the gizzard forlonger and will hopefully be there in the periodof darkness when the bird is not eating. Table 4.23Table 4.23 Limestone types and solubilityDescription Particle Relative1size (mm) solubilityFine < 0.2 100Medium 0.2 – 0.5 85Coarse 0.6 – 1.2 70Extra coarse 1.3 – 2.0 55Large (hen size) 2.0 – 5.0 30Oystershell 2.0 – 8.0 301Reduced solubility results in longer retention within the digestive tractgives an example of descriptions used for lime-stone and associated relative solubility.Twelve hours after feeding, there will likelybe twice as much calcium in the gizzard fromlarge vs. fine particle limestone. Oystershell isexpected to have solubility characteristics sim-ilar to those of large particle limestone. The largeparticles are more important for older birds andseem to help maintain the quantity and activi-ty of medullary bone. The only problem with largeparticle limestone is its abrasive characteristic withmechanical equipment.Fig. 4.11 Schematic of daily calcium balance in a laying hen.
  • 196 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.6Nutrition and shell qualityUsing particulate limestone or oystershell doesallow the bird a degree of nutrient selection. Thepeak in calcium requirements coincides with shellcalcification, and this starts each day in thelate afternoon. If given a choice situation, lay-ers will voluntarily consume more calcium at thistime of day. In fact, a specific appetite for cal-cium is the likely reason for the late afternoonpeak in feed intake seen when layers do not havethe opportunity at nutrient/ingredient selection.If birds do not receive adequate quantities ofcalcium there will be almost immediate loss inshell integrity. If the deficit is large, ovulation oftenceases and so there is no excessive bone resorp-tion. With marginal deficiencies of calcium, ovu-lation often continues, and so the birds relymore heavily on bone resorption. Total medullarybone calcium reserves are limited and so afterproduction of 3 – 4 eggs on a marginally calci-um deficient diet, cortical bone may be erodedwith associated loss in locomotion. As calciumcontent of the diet decreases, there is a transient(1 – 2 d) increase in feed intake, followed by adecline associated with reduced protein and ener-gy needs for egg synthesis. Calcium deficiencyis exacerbated by high levels of dietary chloride(0.4 – 0.5%). In such dietary situations, there isgreater benefit to feeding sodium bicarbonate.If birds are fed a calcium deficient diet, eggproduction and eggshell calcium return to nor-mal in 6 to 8 days after the hens receive a dietadequate in calcium. After three weeks, the legbones will be completely recalcified. The find-ing that the adrenal gland is enlarged in calci-um deficiency indicates that this is a stress in theclassical sense.Calcium is the nutrient most often consideredwhen shell quality problems occur,althoughFig. 4.12 Decline in shell weight for hens fed a diet devoid of Vitamin D3 supplementation.
  • 197CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.6Nutrition and shell qualitydeficiencies of vitamin D3 and phosphorus canalso result in weaker shells. Vitamin D3 isrequired for normal calcium absorption, and ifinadequate levels are fed, induced calciumdeficiency quickly occurs. Results from ourlaboratory suggest that diets devoid of synthet-ic vitamin D3 are quickly diagnosed, because thereis a dramatic loss in shell weight (Figure 4.12).A more serious situation occurs when amarginal, rather than absolute deficiency ofvitamin D3 occurs. For example, birds fed a dietwith 500 IU D3/kg showed only an 8% declinein shell quality, yet this persisted for the entirelaying cycle and would be difficult to detect interms of cracked and reject eggs etc. A major prob-lem with such a marginal deficiency of vitaminD3 is that this nutrient is very difficult to assayin complete feeds. It is only at concentrationsnormally found in vitamin premixes, that mean-ingful assays can be carried out, and so if vita-min D3 problems are suspected, access to thevitamin premix is usually essential. In additionto uncomplicated deficiencies of vitamin D3, prob-lems can arise due to the effect of certain myco-toxins. Compounds such as zearalenone, thatare produced by Fusarium molds, have beenshown to effectively tie up vitamin D3, resultingin poor egg shell quality. Under these circum-stances dosing birds with 300 IU D3 per day, forthree consecutive days, with water soluble D3may be advantageous.Vitamin D3 is effectively ‘activated’ byprocesses occurring first in the liver and then inthe kidney. This first activation in the liveryields 25(OH)D3 while the second product is theresult of further hydroxylation to yield1,25(OH)2D3. This latter compound is a verypotent activator of calcium metabolism, althoughis not likely to be available as a feed ingredient.The first hydroxylation product, 25(OH)D3, is how-ever, now available to the feed industry, and seemsto promote increased calcium retention in lay-ers (Table 4.24).Table 4.24 Effect of Hy-D®25(OH)D3on daily calcium rententionHy-D®Calcium(µg/kg) retained (mg)0 41010 45020 50040 53060 540Adapted from Coelho (2001)Minimizing phosphorus levels is also advan-tageous in maintaining shell quality, especially underheat stress conditions. Because phosphorus is avery expensive nutrient, high inclusion levelsare not usually encountered, yet limiting these with-in the range of 0.3% to 0.4%, depending upon flockconditions, seems ideal in terms of shell quality.Periodically, unaccountable reductions in shell qual-ity occur and it is possible that some of these maybe related to nutrition. As an example, vanadi-um contamination of phosphates causes anunusual shell structure, and certain weed seedssuch as those of the lathyrus species, cause majordisruptions of the shell gland.Up to 10% reduction in eggshell thicknesshas been reported for layers fed saline drinkingwater, and a doubling in incidence of total shelldefects seen with water containing 250 mgsalt/liter. If a laying hen consumes 100 g of feedand 200 ml of water per day, then water at 250mg salt/liter provides only 50 mg salt comparedto intake from the feed of around 400 mg salt.The salt intake from saline water therefore,seems minimal in relation to total intake, but nev-ertheless, shell quality problems are reported tooccur under these conditions. It appears that saline
  • 198 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.7Controlling egg sizewater results in limiting the supply of bicar-bonate ions to the shell gland, and that this is medi-ated via reduced activity of carbonic anhydraseenzyme in the mucosa of the shell gland.However, it is still unclear why saline waterhas this effect, in the presence of overwhelminglymore salt as provided by the feed. There seemsto be no effective method of correcting this lossof shell quality in established flocks, although fornew flocks the adverse effect can be minimizedby adding 1 g vitamin C/liter drinking water.The main factor dictating the size of an eggis the size of yolk released from theovary and this in turn is greatly influencedby body weight of the laying hen. The weight ofthe hen at maturity is therefore the major factorinfluencing egg size, and so it is expected thata large bird will produce more large grade eggsand vice-versa for a small bird. Assuming a givenweight of bird, then nutrition can have some influ-ence on egg size. Within a flock, birds that eatthe most feed tend to produce the largest egg. Forcommercial flocks, where eggs are priced accord-ing to specific weight classes (grade) there is theneed to maximize egg size as soon as possible.However, once 80% of eggs are falling into thelargest, most economic weight category there isoften need to temper further increases in eggweight, so as to sustain good eggshell quality. Thisearly increase in egg size and late tempering ofegg size can be influenced by nutrition to someextent. For the rapidly developing egg breakoutmarket, weight of individual eggs assumes lessimportance than overall egg mass output. Apartfrom manipulating feed intake, egg size cansometimes be manipulated by adjusting dietarylevels of energy and/or fat and/or linoleic acid,or by adjustment to levels of protein and/ormethionine and/orTSSA. Assuming that diet nutri-ents are tied to energy level, and that the bird canmaintain its energy intake, then energy per se haslittle effect on egg size. The effects of protein andenergy on egg size are shown in Figure 4.13 whichdepicts the bird’s response to a range of nutrientintakes. Unlike the situation with egg produc-tion (Figure 4.1) there is an obvious relationshipbetween increased egg size and increased pro-tein intake. At low protein intakes (less than 14– 15 g/d) there is an indication of reduced eggsize when energy intake is increased.The response in egg weight to diet protein ismost likely related to intakes of methionine orTSAA (Table 4.25). Roland et al. (1988) showeda consistent linear trend for increase in eggweight of young birds as the level of TSAA wasincreased from 0.65 to 0.81%. Analysis of thisdata indicates that egg size of young layersincreases by 0.7 g for each 0.05% increase in dietTSAA. Table 4.26 shows a summary of 6 exper-iments reported by Waldroup et al. where arange of methionine levels were tested, at 0.2%cystine, for various ages of bird. As methioninelevel of the diet is increased, there is an almostlinear increase in egg size.As the bird progresses through a productioncycle, the egg weight response to methioninechanges slightly. In the first period, between 25– 32 weeks, using 0.38 vs. 0.23% methionineresults in a 5.6% increase in egg size (Table 4.26).4.7 Controlling egg size
  • 199CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.7Controlling egg sizeComparable calculations for the other age peri-ods show 7.3% improvement from 38 – 44weeks, and 6.7% and 6.0% at 51 – 58 and 64– 71 weeks respectively. The egg weight responseto methionine therefore, closely follows the nor-mal daily egg mass output of the laying hen.Dietary levels of methionine orTSAA’s are mosteasily adjusted by use of synthetic methionine.There has recently been a resurgence in discussionregarding the efficacy of DL-methionine vs.methionine hydroxy analogue, and in particu-lar Alimet®, as they influence layer perform-ance and in particular egg weight. When unbi-ased studies are conducted, and the levels ofmethionine are comparable to industry standards,then DL-methionine is comparable to Alimet®on an equimolar basis. In terms of egg weight,Harms and Russell (1994) show similar respons-es to the two products (Table 4.27).There has been a suggestion that L-methio-nine may, in fact, be superior to any othersource. This product is not usually produced com-mercially, because routine manufacture ofmethionine produces a mixture of D- and L-methio-nine. This is the only amino acid where there isapparently 100% efficacy of the D-isomer.However, most research data indiates no differencein potency of L- vs DL-methionine sources.Methionine acts as a methyl donor, and so theefficacy of methionine vs. choline is often discussed.While choline can spare some methionine in adiet, it is obvious that there are severe limitationsto this process, and this becomes most obviouswhen egg size, rather than simply egg production,is a major consideration. Data from Parsonsand Leeper (Table 4.28) clearly shows the advan-tage of using methionine over choline in termsof egg size, and that this effect becomes most crit-ical as diet crude protein level is reduced.Fig. 4.13 Egg weight (18-66 weeks) in response to daily intakes of energy and protein.
  • 200 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.7Controlling egg sizeTable 4.25 Effect of TSAA on egg weight from young laying hens (g)Table 4.26 Effect of methionine on egg weight – mean of 6 experimentsTable 4.27 Effect of methionine source on layer performance 1Bird age Total sulphur amino acids (%)(wks) 0.65 0.69 0.72 0.76 0.8125 49.3 49.1 50.2 50.2 51.629 53.8 53.5 53.9 54.4 54.733 55.3 55.1 56.0 56.0 56.3Adapted from Roland et al. (1998)Bird age (wks) % Diet methionine with 0.2% cystine0.23 0.26 0.29 0.32 0.35 0.3825 - 32 49.8 51.0 51.9 52.1 52.0 52.638 – 44 53.2 55.0 56.4 56.3 56.3 57.151 - 58 56.2 57.9 59.6 59.2 59.2 60.064 - 71 56.8 59.4 59.5 59.5 59.5 60.2Adapted from Waldroup et al. (1995)Diet methionine (%) Egg weight (g)Exp #1 Exp #2DL Alimet® DL Alimet®0.228 (basal) 54.5 54.5 51.5 51.50.256 56.2 55.3 53.2 52.70.254 56.8 56.8 55.1 56.20.311 57.6 57.2 55.9 55.70.366 - 378 58.0 57.5 57.0 56.81Mean 80% egg production Harms and Russell (1994)Table 4.28 Egg size with methionine vs. choline (23 – 35 wks)Diet Supplement Egg production Egg weightprotein (%) (g)None 82.8 53.216% 0.1% methionine 84.0 56.60.1% choline 82.4 54.0None 72.8 52.514% 0.1% methionine 84.5 54.90.1% choline 78.9 51.9Adapted from Parsons and Leeper (1984)
  • 201CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.7Controlling egg sizeBird age Linoleic acid (% of diet)(wks) 0.79 1.03 2.23 2.7320 – 24 60.5 61.3 61.4 61.425 – 28 60.8 61.7 62.0 62.029 – 32 62.8 63.7 63.1 63.4Adapted from Grobas et al. (1999)Table 4.29 Effect of linoleic acid on egg weight (g)Table 4.30 Effect of reducing dietary protein level on egg size of 60wk-oldlayers (Av. for 2, 28-day periods)Dietary Egg Av. feed Egg wt. (g) Daily egg Av. proteinprotein level production intake per mass (g) intake per(%) (%) day (g) day (g)17 78.8 114 64.8 51.0 19.415 77.5 109 64.3 49.7 16.413 78.3 107 62.2 49.1 13.911 72.7 108 61.7 45.1 11.99 54.3 99 58.2 36.1 8.9All diets 2800 kcal ME/kgThe other nutrient most often consideredwhen attempting to maximize early egg size islinoleic acid. In most situations, 1% dietary linole-ic acid meets the bird’s needs, although formaximizing egg size, levels as high as 2% are oftenused. It is difficult to separate the effect oflinoleic acid versus that of energy, since sup-plemental fat is usually used in such studies.Assuming that the bird is consuming adequateamounts of energy, then the response to extradietary linoleic acid is minimal (Table 4.29). Inthis study there was no increase in egg sizewith levels of linoleic acid greater than 1%,which is the quantity normally found in a cornbased diet.As layers get older, then depending on strainof bird, it is often economical to try and tempersubsequent increases in egg size, in order to helpmaintain shell quality. It seems more difficult totemper egg size than to increase egg size. Forolder birds, body weight is still the major factorinfluencing egg size, and so it is difficult tocontrol egg size if birds are overweight. Reducingthe level of linoleic acid has no effect on egg size,and so the only options are for reducing crudeprotein and/or methionine levels in the diet.Our studies indicate that protein levels around13% and less are necessary to bring about a mean-ingful reduction in egg size (Table 4.30). However,with protein levels much less than this, loss inegg numbers often occurs.Methionine levels can also be adjusted in anattempt to control late cycle egg size. Results ofPeterson show some control of egg size withreduced methionine levels (Table 4.31). However,these results are often difficult to achieve undercommercial conditions because reduction indiet methionine levels often leads to loss inegg numbers and body weight. Phase feedingof amino acids must therefore be monitored
  • 202 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.7Controlling egg sizevery closely, since the bird is very sensitive to ‘defi-ciencies’ of methionine. Uzu et al., (1993)using brown egg birds show the sensitivity ofchanges in feed intake (Figure 4.14) when birdswere alternated monthly between adequate(0.33% methionine; 0.6% TSAA) and deficientdiets (0.23% methionine; 0.5% TSAA). Layerswere very sensitive to levels of methionineand increased their feed intake apparently in anattempt to maintain methionine intake. Interestinglythis same precise pattern of feed intake wasseen when diets were changed weekly. Thesedata confirm that it is important not to reducemethionine levels too much or too quickly,since any economic saving can be offset byincrease in feed intake. Waldroup et al. (1995)suggest that for older birds the methionine andTSAA requirements of layers are greater for eggnumbers than for optimizing egg weight (Table4.32). These data reinforce the concept that phasefeeding of methionine to control egg size mayhave a detrimental effect on egg numbers.During peak egg mass output (38 – 45 weeks) themethionine requirement for egg size is greaterthan for egg numbers, while the latter require-ment peaks at 51- 58 weeks of age.Table 4.31 Methionine and late cycle egg size (g)Daily methionine Exp. 1 Exp. 2 Exp. 3intake (mg/d) (38-62 wk) (38 – 70 wk) (78 – 102 wk)300 60.1a 63.7a 66.3a285 60.3a 63.1b 65.5b270 59.1ab 62.0c 64.0c255 58.5b 62.0c 63.9cAverage egg prod (%) 86 80 75Adapted from Peterson et al. (1983)Fig. 4.14 Feed intake of brown- egg layers hens fed adequate on deficient levels ofmethionine. (g/b/d)Adapted from Uzu et al. (1993)
  • 203CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.8Diet and egg compositionThis data suggests that we should be very care-ful in reducing methionine levels much before60 weeks of age.As stated at the outset of this section, maturebody weight is the main determinant of egg size,and this applies particularly to late-cycle per-4.8 Diet and egg compositionformance. The best way to control late cycle eggsize is through manipulation of body weight at timeof initial light stimulation. Larger birds at matu-rity will produce much larger late cycle eggs andvice versa. There is an obvious balance necessarybetween trying to reduce late cycle egg size with-out unduly reducing egg size in young birds.Table 4.32 Estimated methionine and methionine + cystine requirements(mg/day) for egg number, weight and mass.Table 4.33 Egg components and major nutrients (60 g egg)Bird age (wks) Egg # Egg weight Egg massMethionine 25 – 32 364b356b369b38 – 45 362b380a373b51- 58 384a364a402a64 - 71 374ab357b378bMethionine + 25 – 32 608b610ab617bCystine 38 – 45 619b636a627b51 – 58 680a621ab691a64 - 71 690a601b676aAdapted from Waldroup et al. (1995)Yolk Albumen ShellWet weight (g) 19.0 35.0 6.0Dry weight (g) 10.0 4.2 5.9Protein1(%) 17.0 11.0 3.0(g) 3.2 3.9 0.2Fat (%) 32.0 - -(g) 6.0 - -Carbohydrate (%) 1.0 1.0 -(g) 0.2 0.4 -Minerals (%) 1.0 0.6 95.0(g) 0.2 0.2 5.71As is basisTables 4.33 – 4.35 show egg compositionand nutrient content together with anindication of the contribution of these nutri-ents to human nutrition.
  • 204 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.8Diet and egg compositionTable 4.34 Vitamin and mineral composition of contents from a 60 g eggVitaminsA (I.U.) 300D3 (I.U.) 30E (I.U.) 2K (mg) .02B1 (mg) .06B2 (mg) .18B6 (mg) .20B12 (mg) .001Pantothenic acid (mg) 1.2Folacin (mg) .008Niacin (mg) .06Choline (mg) 350Biotin (mg) .01Minerals (mg)Calcium 30Phosphorus 130Sodium 75Chloride 100Potassium 80Magnesium 7Manganese 2Iron 1Copper 2Zinc 1Iodine .02Selenium .01
  • 205CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.8Diet and egg compositionTable 4.35 Contribution of eggs toHuman DRI for selected nutrientsNutrientTwo eggs supply thefollowing of an adult’sdaily requirement (%)Protein 20Energy 8Calcium 10Phosphorus 20Iron 20Vitamin A 25Vitamin D3 20Thiamin 10Riboflavin 30Niacin 15i) Yolk color - In most markets it is important tocontrol and maintain the color of the yolk. Theyellow/orange color of the yolk is controlled bythe bird’s intake of xanthophyll pigments and inparticular lutein, zeaxanthin and various syntheticpigments such as canthaxanthin and apoc-arotenoic esters. As the level of dietary xanthophyllsincreases, there is increase in yolk color asassessed on the Roche Scale of 1 to 15. Figure4.15 shows the general relationship between xan-thophyll content of the feed and egg yolk on theRoche Color Score.The desired yolk color will vary in differentmarkets, although a color score of 8 – 9 is com-mon in many areas. A high degree of pigmen-tation is a score of 11 – 12 while for some spe-cialty pasta markets, there may be need toachieve 14 – 15. The common feed ingredientshigh in xanthophylls, are corn and corn glutenmeal as well as dehydrated alfalfa. Table 4.36shows the expected color score contributed bythe various levels of each of these ingredients.Fig. 4.15 Roche color scale and dietary xanthophylls
  • 206 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.8Diet and egg compositionTable 4.36 Ingredients and yolkcolorIngredient Inclusion Yolk colorlevel (%) (Roche scale)0 220 6Corn 40 860 9Corn 2 6gluten 6 9meal 8 142 4Alfalfa 6 7meal 8 9Carotenes themselves have little pigment-ing value for poultry, although the various hydrox-ylated carotenes are excellent pigments and thebird preferentially stores these in yolk, body fat,and its shanks. The red/orange colors can be pro-duced by adding synthetics such as canthaxan-thin, although usually this degree of coloring isunacceptable to most consumers. These pigmentscan be used in limited quantities as long as thediet has a base level of xanthophylls – otherwisethe yolk color tends towards an objectionable red,rather than acceptable orange color. These redpigments also produce undesirable color in noo-dles made from egg yolk, and so care must be takenin selection of pigmenting agents in eggs destinedfor industrial uses. In most markets, it is commonto add 7 – 8 g of supplemental xanthophylls pertonne of feed. Levels below 5 g/tonne usually resultin too pale a yolk.There are a number of dietary and man-agement factors which can reduce the effectivedeposition of xanthophylls in the yolk. Ingredientswhich are potential oxidizing agents, such as min-erals and certain fatty acids, have been shownto reduce pigmentation. High levels of vitaminA, as sometimes used during water medicationfor various stress situations, have been shown tocause temporary loss in yolk pigmentation.High environmental temperature, coccidiosis andaflatoxin contamination of feed are also impli-cated in production of pale colored yolks.Natural pigments in cereals tend to declinewith prolonged storage, with up to 50% loss report-ed at elevated temperatures. Without blendingof corn therefore, a slight natural loss in pigmentsis expected to cause subtle loss in yolk colorthroughout the year. Yolk color seems to beenhanced when high levels of vitamin E areused, and when the diet contains antioxidants.In addition to pigmenting the yolk for mar-keting needs, there is growing evidence thatlutein and zeaxanthin may be important nutri-ents for humans. These pigments concentrate inthe macular region of the eye, and are thoughtto help prevent macular degeneration, whichtogether with cataracts, are the leading causesof blindness in developed countries. The mac-ula is found on the back wall of the eye and isresponsible for sharp central vision. The irreversibleand untreatable degeneration of the maculaleads to loss of central vision and eventually totalblindness. Some 20% of North Americans overthe age of 65 have some degree of maculardegeneration. It seems that diets rich in luteinand zeaxanthin increase the level of these pig-ments in the macula and acting as antioxidantsand/or filters to damaging blue light, protectthis sensitive area of the inner eye surface.Current intakes of lutein and xeaxanthin in mostcountries are less than 1 mg/d which is much lessthan the 5 – 6 mg/d now suggested for preventionof macular degeneration and also occurrence ofcataracts. It seems possible to further increasethe xanthophyll content of the layers diet, toproduce eggs enriched in this important nutrient.
  • 207CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.8Diet and egg compositionii. Egg yolk fatty acids – The fatty acid contentof the yolk is greatly influenced by the fattyacid profile of the bird’s diet. Since there is nowconcern about our consumption of saturated fattyacids, it seems beneficial to manipulate theratio of unsaturates:saturates in the yolk. This isachieved by including proportionally moreunsaturated fatty acids in the bird’s diet.Additionally there is the opportunity for feedingthe bird specific polyunsaturates that are now rec-ommended for improved human health. Thesefatty acids are termed omega-3 fatty acids, asopposed to omega-6 fatty acids which are the mostcommon unsaturates in ingredients such ascorn oil and soybean oil. The omega-3 fatty acidsof greatest interest are linolenic acid, (18:3n3)eicosapentaenoic acid (20:5n3) and docosa-hexaenoic acid (22:6n3), and these are knownto reduce the risk of chronic heart disease.Individuals suffering from CHD seem tohave lower levels of linolenic acid in their adi-pose tissue. Linolenic acid is a precursor ofprostaglandin E, which is reported to be a coro-nary vasodilator, an inhibitor of free fatty acidrelease (as occurs during acute CHD) and is oneof the most potent inhibitors of platelet aggregation.Unfortunately, the diet of most humans is not wellfortified with linolenic acid, which is most com-monly found in plant tissues. However, thechicken has the somewhat unique ability todivert large quantities of linolenic acid into theegg when its diet contains high levels of this nutri-ent. This situation is most easily achieved by includ-ing 8 – 10% flaxseed in the bird’s diet. There seemsto be a linear relationship between flax inclusionlevel and egg linolenic acid content. Figure 4.16was compiled from 6 different research studiesinvolving linolenic acid enrichment of eggs.Fig. 4.16 Relationship between dietary flaxseed and egg omega-3 content.
  • 208 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.8Diet and egg compositionTable 4.37 Effect of 2% dietary menhaden oil on egg organoleptics(Subjective score 0-10)Category Control Menhaden oil2% 2%DeodorizedAftertaste 6.3a 7.5ab 8.2bOff-Flavor 3.9a 6.5b 6.9bAdapted from Gonzalez and Leeson (2000)In most markets such designer eggs need tohave a guarantee of 300 mg omega-3 fattyacids, and so this necessitates around 10% flaxin the birds diet (Figure 4.16). Perhaps themost important fatty acid for prevention of CHDin humans is docosahexaenoic acid (DHA).Flax does not contain very much DHA and eggDHA level seems to quickly plateau at 70 – 80mg with 5% flaxseed (Figure 4.17).A more useful and concentrated source of DHAis fish oils. With menhaden oil, it is possible toincrease egg DHA up to 200 mg with inclusionof 2% in the bird’s diet (Figure 4.18). Unlike thesituation with using flaxseed, the inclusion of fishoil in the bird’s diet will result in a change in tasteof the egg. In a recent study, we fed layers 2%menhaden oil or 2% deodorized menhadenoil to study the effect on DHA enrichment.When these eggs were assessed in taste panels,there was a distinct negative effect regarding ‘aftertaste’ and off-flavors. Deodorizing the oil priorto use in the layer diet had no beneficial effecton egg taste (Table 4.37).Fig. 4.17 Effect of dietary flaxseed on egg DHA
  • 209CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.8Diet and egg compositionFig. 4.18 Effect of dietary menhaden on egg DHA content.Fig. 4.19 Effect of dietary menhaden oil on egg weight of layers at 2,6 and 9 monthsof production.(Gonzalez and Leeson, 2000)
  • 210 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.8Diet and egg compositionRegardless of bird age, the inclusion of men-haden oil also reduced egg size by up to 0.35 gper 1% fish oil inclusion in the diet (Figure4.19). The reduction in egg weight may berelated to the decrease in circulating triglycerides,which is common in birds fed fish oils, so lim-iting lipids for yolk synthesis.Table 4.38 summaries the enrichment ofeggs with omega-3 fatty acids and DHA inresponse to using flaxseed and fish oil.Table 4.38 Egg enrichment of fattyacidsFatty acid Ingredient EnrichmentTotal omega-3 1% Flaxseed 40 mgDHA 1% Fish oil 50 mgDHA 1% Flaxseed 8 mgCLA 1% CLA 50 mgFor total omega-3’s in response to flax andDHA with fish oil, there is a linear response with-in the range of ingredient levels likely to beused in a diet. There is a distinct plateau withDHA in response to flaxseed, where regardlessof flaxseed levels, egg enrichment does not getmuch beyond 70 mg /egg.Conjugated linoleic acid (CLA) is a posi-tional isomer of linoleic acid that is claimed tohave potent anticarcinogenic properties. Thereare a few natural ingredients rich in CLA, and sostudies to date have used CLA itself as a feed ingre-dient. Each 1% inclusion of dietary CLA seemsto result in 50 mg deposition of CLA in the egg.iii) Egg cholesterol – Eggs naturally contain a highlevel of cholesterol because of its role in sustainingthe developing embryo. Cholesterol has manyand varied functions in the embryo including itsrole as a structural component of cell membranes,and as a precursor for sex and adrenal hor-mones, vitamin D, and the bile acids. Young chicksdo not have the enzymes necessary for choles-terol synthesis, which emphasizes the importanceof cholesterol being deposited in the egg. An eggcontains about 180 mg cholesterol and it seemsvery difficult to reduce this without adversely affect-ing other production parameters.Factors that influence egg cholesterol con-tent include the hen’s body weight and herintake of energy and fat. Diet fat per se does notseem to be a factor, although in most instanceshigh fat diets imply that high-energy diets are used.Restricting the energy intake of laying hensresults in less cholesterol being deposited inthe egg, although this is usually associated witha reduction in egg production. The influence ofdietary energy and body weight of the hen on eggcholesterol is mediated through their effects onyolk size and egg size. Reducing energy intakein order to achieve a measurable reduction in eggcholesterol concentration has the disadvantageof adversely affecting both egg production andegg weight.Dietary fiber influences cholesterol metab-olism by a possible combination of differentprocesses. These include lowered cholesterolabsorption and resorption, binding with bilesalts in the intestinal tract, shortening the intes-tinal transit time, and increasing fecal sterolexcretion. Alfalfa is one of the most effectivesources of fiber with minimal detrimental effectson egg size, egg production, and feed efficien-cy. Alfalfa seems to efficiently bind bile acids.Reduction in egg cholesterol achieved by suchdietary manipulations is, however only mar-ginal, with little evidence to suggest a com-mercially important change.
  • 211CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.8Diet and egg compositionThere is an indication that very high levelsof dietary copper can reduce egg cholesterol con-tent. High levels of copper decrease the productionof liver glutathione, which in turn regulatescholesterol synthesis through stimulation ofmethyl glutaryl Co-A. Using up to 250 ppm dietarycopper has been reported to reduce egg cholesterolby up to 25% (Table 4.39). In this particular study,egg production was unaffected, although inmore long-term trials, reduced egg output has beenrecorded. Of concern today is the bioaccumulationof copper in the manure, since the vast major-ity of the dietary copper is not retained (Table 4.39).One reason for the insensitivity of egg cho-lesterol to diet manipulation is the basic bio-chemistry of the lipoproteins within eggs. Eggcholesterol is determined by the cholesterolcontent of individual yolk lipoprotein moieties,rather than by the bird’s plasma cholesterolconcentration. Given that most cholesterol inlipoproteins is associated with the surface lay-ers, reduction in egg cholesterol content can there-fore occur only when the lipoprotein particle sizeis increased. Such a scenario will reduce the con-tribution of surface cholesterol molecules rela-tive to total fat. Unfortunately, an increase inlipoprotein particle size will tend to reduce theefficiency of the critical transport of bigger sized‘molecules’ through the follicle wall.iv) Egg vitamins - Many food items are nowenriched with vitamins and consumers considerthese as healthy products. The egg contains bothfat and water soluble vitamins and there is poten-tial for enrichment. Currently, most omega-3enriched eggs also contain additional vitamin E,ostensibly as a natural antioxidant. It is likely thatthe fat soluble vitamins will be the easiest groupto manipulate. The influence of dietary vitaminintake on vitamin enrichment of the egg is quitevariable among vitamins. Riboflavin level in theyolk and albumen responds rapidly to manipu-lating the dietary level of this vitamin. Similarly,the egg content of vitamin B12 is almost exact-ly proportional to diet content over one to fourtimes normal inclusion levels. There does notseem to be a ceiling on vitamin B12 transfer tothe eggs although a plateau is quickly reachedwith riboflavin enrichment. There are somenatural changes in egg vitamin levels related toage of bird. Riboflavin, pyridoxine and vitaminB12 levels of eggs decline while biotin levelincreases with increasing age of hens. Thedecline in egg content of some vitamins withincreasing age is related to a higher rate of pro-duction, since egg output is not completelycompensated for by increasing dietary intake ofthese vitamins. Thiamin content of eggs fromWhiteLeghorn hens was reported to be about 50% greaterthan that of eggs laid by Rhode Island Reds orBarred Plymouth Rocks fed the same diet.Table 4.39 Effect of dietary copper on egg cholesterol and copperaccumulation in yolk and manureDiet Cu Egg cholesterol (mg) Yolk Manure copperppm 4 wk 8 wk copper (µg) (ppm DM)6 163a 176a 9.4 36130 121b 123b 11.9 540255 114b 116b 13.9 937Adapted from Pesti and Bakalli (1998)
  • 212 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.8Diet and egg compositionNaber (1993) in a review of factors influ-encing egg vitamin content concluded that feedvitamin content has the greatest and most wide-spread influence on egg vitamin content. Usingdata from studies that reported diet vitamin leveland feed intake on the one hand, and egg output,i.e. egg weight and production on the other,Naber calculated the efficiency of vitamin trans-fer into eggs as a function of intake (Table 4.40).The transfer efficiency of vitamin A was veryhigh (up to 80%), but this dropped markedlywhen the dietary level was raised to four timesrequirement. This is an indication of the possi-bility of egg enrichment with vitamin A, eventhough this trend declines at high levels of dietvitamin enrichment. The transfer of dietaryvitamin B12 into eggs was as efficient as forriboflavin, pantothenic acid and biotin, e.g.about 50% with dietary levels at one to two timesrequirement. Unlike riboflavin, however, this levelof transfer efficiency continued in the case of vita-min B12 even at very high dietary levels of up to40 times requirement. Clearly, substantialenrichment of eggs with vitamin B12 is possible.All of the research work conducted to datehas studied the potential of enriching singlevitamins in isolation. In a recent study, weattempted to enrich all vitamins. Considering theexpected transfer efficiency (Table 4.40) avitamin premix was formulated that contained2 – 10 times the regular level of inclusion. Afterfeeding layers for 60 d, eggs were assayed for allvitamins (Table 4.41).The results were somewhat discouraging inthat only for vitamin B12 and vitamin K were weable to achieve adequate enrichment to supply100% of DRI. The enrichment for other vitaminswas quite variable, where, for example, with pan-tothenate there was little response, while for vita-mins D3 and E there was some 3-fold increasein egg concentration. It is possible that at the high-er levels of vitamins used, there is some antag-onism and/or preferential loading of absorp-tion mechanisms.Table 4.40 Classification of vita-mins by relative transfer efficiencyfrom diet to eggTransfer efficiency VitaminVery High (60 – 80%) Vitamin AHigh (40 – 50%) RiboflavinPantothenic acidBiotinVitamin B12Medium (15 – 25%) Vitamin D3Vitamin ELow (5 – 10%) Vitamin KThiaminFolacinAdapted from Naber (1993)v. Yolk mottling - Egg yolk mottling continuesto be a problem that appears sporadically in anumber of flocks. Although the condition hasbeen known for some time, there appears to beno definite evidence as to its cause or of waysto alleviate it. Diet has been implicated, but thereis no real evidence that nutrition is a factorwith the majority of mottling problems thatappear. However, it is known that certain feedadditives such as nicarbazin can cause a mot-tling condition if they are inadvertently added toa laying diet. Most cases of yolk mottling are report-ed in the spring of the year and most often ‘dis-appear’ during the summer or fall. However,
  • 213CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.8Diet and egg compositionTable 4.41 Vitamin content of eggs from hens fed regular or enriched levelsof vitaminsTable 4.42 Yolk mottling as influenced by temperatureVitamin Units Regular egg Enriched egg DRI1% DRIBiotin µg/kg 16 18 30 60Folic acid µg/kg 8.7 10 400 3Niacin mg/kg 0.04 0.08 16 1Pantothenate mg/kg 0.76 0.77 5 15Vit A IU/kg 17.7 22.5 270 8Vit B1 mg/kg 0.048 0.06 1.2 5Vit B2 mg/kg 0.21 0.25 1.3 19Vit B6 mg/kg 0.027 0.03 1.3 2Vit B12 µg/kg 0.872 3.37 2.4 140Vit D3 µg/kg 0.39 1.1 5 22Vit E mg/kg 1.3 3.78 15 25Vit K mg/kg 0.12 0.13 0.12 1081 Daily recommended intake for adultHaugh Yolk color Severity ofunits index mottling (%)Fresh eggs 85.4 11.3 7.1Eggs held 1 week at 12.5˚C 70.8 10.9 45.6Eggs held 2 weeks at 12.5˚C 66.7 10.9 44.0Eggs held 1 week at room temperature - - 47.6Eggs held 2 days at 31.7˚C - - 60.0whether the season of the year or the type of lay-ing house management is a factor has not beenproven. Table 4.42 shows the result of a studyin which eggs held for various lengths of time andunder different environmental conditions, werechecked for severity of yolk mottling. It is evi-dent that the majority of mottling appears dur-ing storage. Storing, even at ideal temperaturefor one week, can result in a marked increase inthe condition. It has been suggested that the mod-ern strains of birds are more prone to yolk mot-tling than are traditional strains although researchdata does not confirm this assertion.The vitelline membrane surrounding theyolk is much weaker when yolks are mottled. Withsevere mottling it is very difficult to manually sep-arate the yolk without breaking the membrane.It is not known if the change in vitelline mem-brane integrity is a cause or effect of mottled yolks.In terms of nutrition, nicarbazin or high gossy-pol cottonseed are most usually implicated.vi Albumen quality – The main factor influencingalbumen quality is storage time. Over time, espe-cially at temperatures > 10˚C, there will be a break-down of thick albumen, and so loss in egg quality.
  • 214 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.9Diet implications with some general management problemsOver the last few years there has been increas-ing concern about the quality of the thin rather thanthick albumen in fresh eggs. Most measures ofalbumen quality, such as Haugh unit, only meas-ure characteristics of the thick albumen, and soapparently ‘GradeA’ eggs can have problems withthe thin albumen. In certain birds, we see the areaof thin albumen to be as much as 120 sq. cm., com-pared to 60 – 70 sq. cm. for a ‘normal’ egg.These spreading albumens are especially problematicin the fast-food industry where eggs are pre-pared on flat-surface grills. We have tested var-ious levels of protein and amino acids, and fed birdsdiets of vastly different acid-base balance, and seenno effect on this phenomenon. We have select-ed birds producing normal vs. spreading albumenand their offspring show similar characteristics. Thecurrent thin albumen problem therefore seems tobe an inherited characteristic.Magnesium plays a role in stabilization of thickalbumen, and so there have been studies aimedat improving albumen quality by feeding layershigh levels of this mineral. In one study, feed-ing 4 – 8,000 ppm Mg on top of a basal level of1500 ppm did help maintain thick albumenafter egg storage for 20 d at 20˚C. In control eggs,there was almost 70% liquification of thickalbumen, while in magnesium enriched birds therewas only 25% conversion of thick to thin albu-men. Unfortunately, high levels of dietary mag-nesium cause loss in shell quality and so this hasto be considered if magnesium salts are used inlayer diets.There have been inconsistent reports ofimprovement in albumen quality in response to10 ppm dietary chromium. On the other hand10 ppm vanadium results in dramatic loss in albu-men quality. Such levels of vanadium can be con-tributed by contaminated sources of phosphates.Interestingly, the negative effect of vanadium isreported to be corrected by use of 10 ppmchromium in the diet.4.9 Diet involvement with some general management problemsi) Hysteria -Although not widespread in commer-cial flocks, hysteria can be a very seri-ous nuisance and economic cost factorif encountered in a flock. Hysteria is easy to dis-tinguish from an ordinary flighty flock, as the birdsseem to lose all normal social behaviour and senseof direction and will mill and fly in every direc-tion making unusual crying and squawkingsounds. Birds often go into a molt, and then eggproduction declines. The condition of hysteriais more difficult to distinguish from flightiness inbirds that are cage-reared rather than floor-reared. However, if one studies the flock for aperiod of time, differences can be seen.The exact cause of hysteria is unknown,and attempts to artificially induce it in flocks havefailed. Many people believe it is related tonutritional or environmental factors, or to acombination of both. Hysteria is more oftenencountered in birds 12 to 18 weeks of age;although it is sometimes also seen in olderbirds. Overcrowding is thought to be a factor intriggering the condition. Many drugs, feed sup-plements and management practices have beentried in an attempt to cure the condition with lit-tle or no success. Some people believe that itis a behavioral problem with the hens reactingto any noise or stimulus to which they are notaccustomed. Why some flocks react different-ly to others is not known; however, it is well known
  • 215CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.9Diet implications with some general management problemsthat small differences in various stressors resultin markedly different responses in flocks. Anumber of diet modifications have been tried inan attempt to alleviate hysteria. These includehigh levels of methionine (2 kg/tonne), niacin (200g/tonne supplement) or tryptophan (up to 5kg/tonne supplement). The latter is thought tohave a sedative-like effect by influencing brainneuro- transmitters. However, the responsehas been variable, and hysteria seems to returnonce tryptophan is withdrawn from the diet. Inaddition, until the price of tryptophan is reducedthe treatment is prohibitively expensive. Thereis anecdotal evidence that adding meat meal orfish meal to a diet resolves the situation in birdsfed all-vegetable diets.ii) Prolapse - In the past, prolapse mortality of2 to 3% per month over several months after hous-ing pullets was not uncommon. Such losses wereusually the result of a number of factors work-ing together rather than any single problem.In most cases, the prolapse was due to pickingrather than any physical stress resulting in ‘clas-sical prolapse’. Some of the problems that canlead to pickouts or blowouts are as follows:- lights too bright (or sunlight streaming intoopen-sided buildings)- temperature too high (poor ventilation)- improper beak trimming- pullets carrying excess of body fat- poor feathering at time of housing- too early a light stimulation- too high protein/amino acid level in the dietcausing early large egg size in relation tobody and frame sizeThe condition is usually more severe with larg-er cage size groups and is a factor of floor spaceper bird rather than bird density. Frequently theincidence of picking has been shown to behigher in multiple bird cages where there is inexcess of 460 sq. cm. of space per bird. Whenbirds are more confined, they do not seem to beas aggressive. One of the most effective ways ofavoiding a problem is to reduce light intensity.Where rheostats are available, these should beadjusted to a sufficiently low level that pickingor cannibalism is kept to a minimum. With bet-ter control and understanding of light programstoday, prolapse and associated problems aremore likely to occur later in the productioncycle. Mortality of 0.1% per month due toprolapse is now considered problematic.While this type of problem is aggravatedby high light intensity as well as high stockingdensity and poor beak trimming, it is felt that oneof the main factors triggering the condition is lowbody weight. Even if pullets mature at bodyweights recommended by the breeder, many ofthem are up to 100 g lighter than standard at peakproduction. This, we suspect, is because the pul-let is maturing with a minimum of body reserves.The bird also has a low feed consumption as ithas been conditioned on a feed intake near tomaintenance just prior to commencement of layand so hasn’t been encouraged to develop a largeappetite. The pullet is laying at 92-96% and thusutilizes her body reserves (fat) in order to main-tain egg mass production. This smaller body weightbird is often more nervous and so more proneto picking. Under these conditions, the nutritionalmanagement program of pullets outlined earli-er in this chapter should be followed.Prolapse can sometimes be made worse byfeeding high protein/amino acid diets to smallweight pullets in an attempt to increase early eggsize. Coupled with an aggressive step-up light-ing program this often leads to more double yolkeggs and so greater incidence of prolapse andblowouts. Such pullets are often below standardweight at 12 – 14 weeks, and so any catch up
  • 216 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.9Diet implications with some general management problemsgrowth is largely as fat, which also accentuatesthe problem. Being underweight at 12 – 14 weeksusually means that they have reduced shank length,and because the long bones stop growing at thistime, short shanks are often used as a diagnos-tic tool with prolapse problems in 22 – 34 weekold pullets.iii) Fatty Liver Syndrome - The liver is themain site of fat synthesis in the bird, and so a ‘fatty’liver is quite normal. In fact, a liver devoid offat is an indication of a non-laying bird. However,in some birds, excess fat accumulates in the liverand this fat can oxidize causing lethal hemorrhages.Excess fat accumulation can only be causedby a surfeit of energy relative to needs for pro-duction and maintenance. Low protein, high-energy diets, and those in which there is an aminoacid imbalance or deficiency can be majorcontributors to a fatty liver condition in layers.It is known that diets low in lipotrophic factorssuch as choline, methionine, and vitamin B12 canresult in fatty infiltration of the liver. However,these nutrients are seldom directly involved inmost of the fatty liver problems reported from thefield. Excessive feed intake and more specificallyhigh energy intake is the ultimate cause of thecondition. It is well known that laying hens willover-consume energy, especially with higherenergy diets and this is particularly true of highproducing hens. Pullets reared on a feeding pro-gram that tends to develop a large appetite orencourages ‘over-eating’ (high fiber diets orskip-a-day feeding), are often more suscepti-ble to the condition when subsequently offereda high energy diet on a free-choice basis duringlay. There is some information to suggest that dailyfluctuations in temperature, perhaps affectedby the season of the year, will stimulate hens toover-consume feed. Hence, it is important toattempt some type of feed or energy restrictionprogram if feed intake appears to be excessive.When fatty liver is a problem, adding a mix-ture of so-called ‘lipotrophic factors’ to the dietis often recommended. A typical addition mayinvolve 60 mg CuSO4; 500 mg choline; 3 µg vita-min B12 and 500 mg methionine per kg of diet.It should be emphasized that in many cases, theaddition of these nutrients will not cure theproblem. Increasing the level of dietary proteinby 1 to 2% seems to be one of the most effec-tive ways of alleviating the condition. However,such treatments do not work in all cases. Anothertreatment that may prove effective is to increasethe supplemental fat content of the diet. This appar-ently contradictory move is designed to offer thebirds a greater proportion of energy as fat ratherthan carbohydrate. The idea behind this dietmanipulation is that by reducing carbohydrateload there is less stress on the liver to synthesizenew fat required for egg yolk production. By sup-plying more fat in the diet, the liver merely hasto rearrange the fatty acid profile within fats, ratherthan synthesize new fat directly. For this treat-ment to be effective, the energy level of thediet should not be increased, the recommendationmerely being substitution of carbohydrate withfat. This concept may be the reasoning forapparent effectiveness of some other treatmentsfor fatty liver syndrome. For example, substitutionof barley or wheat for corn has been suggestedand this usually entails greater use of supplementalfat with these lower energy ingredients. Similarly,substitution of soybean meal with canola orsunflower meals usually means using more sup-plemental fat if energy level of the diet is to bemaintained.More recent evidence suggests that mortal-ity is caused by eventual hemorrhaging of the liverand that this is accentuated or caused by oxida-tive rancidity of the accumulated fat. On this basis,we have seen a response to adding variousantioxidants, such as ethoxyquin and vitamin E.
  • 217CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.9Diet implications with some general management problemsAdding ethoxyquin at 150 mg/kg diet and extravitamin E at 50 – 60 IU/kg has been shown toreduce the incidence of hemorrhage mortality.Experience has shown that it is difficult toincrease production in a flock once the conditionis established. Thus, it is important that a prop-er program be followed to prevent the develop-ment of fatty livers. In some cases, the cause ofthe trouble can be traced back to pullets cominginto the laying house carrying an excess of bodyfat. If these birds are then fed a diet in which thebalance of protein and energy is slightly subop-timal for a particular strain of bird, a buildup offat in the liver may occur. In addition, the feed-ing of crumbles or pellets in the laying house mayaggravate this condition since the hen may over-consume energy. The results of an experiment study-ing effects of the level of dietary protein on per-cent liver fat are shown in Table 4.43.These older birds were all laying at a reasonablelevel and no Fatty Liver Syndrome problemswere reported. As can be noted, all birds hadlivers high in fat. This is perfectly normal for agood laying bird and thus should not be confusedwith the Fatty Liver Syndrome where liver hem-orrhage is the condition that usually kills the hen.Recent information suggests that a conditionsimilar to the so-called Fatty Liver Syndrome maybe caused by certain types of molds or mold tox-ins. Although no definite relationship has beenestablished to date between molds and fattylivers, care should be taken to ensure that moldsare not a factor contributing to poor flock per-formance. Periodically canola meal has beenimplicated with the Fatty Liver Syndrome. Whilethere were earlier reports with some of the highglucosinolate rapeseed meals triggering such acondition, there is no evidence to suggest thatcanola varieties are a factor in the fatty liver con-dition. Hemorrhage due to feeding rapeseed isusually not associated with excess fat infiltrationof the liver.iv) Cage Layer Fatigue - As its name implies, CageLayer Fatigue (CLF) is a syndrome most commonlyassociated with laying hens held in cages, andso its first description in the mid 1950’s coincideswith the introduction of commercial cage sys-tems. Apart from the cage environment, CLF alsoseems to need a high egg output to trigger thecondition, and for this reason it has traditionallybeen most obvious in White Leghorns. Ataround the time of peak egg output, birdsbecome lame, and are reluctant to stand in thecage. Because of the competitive nature of thecage environment, affected birds usually moveto the back area of the cage, and death can occurdue to dehydration/starvation because of their reluc-tance to drink or eat.Table 4.43 Influence of dietary protein on liver fatDietary protein level Egg production Feed Liver fat(%) (HDB) (%) (g/d) (dry weight basis) (%)13 76.4 108 49.315 77.0 107 40.217 78.0 107 38.2
  • 218 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.9Diet implications with some general management problemsThe condition is rarely seen in litter floor man-aged birds and this leads to the assumptionthat exercise may be a factor. In fact, removingCLF birds from the cage during the early stageof lameness and placing them on the floor usu-ally results in complete recovery. However,this practice is usually not possible in largecommercial operations. In the 1960 – 70’s, upto 10% mortality was common, although nowthe incidence is considered problematic if 0.5%of the flock is affected. There is no good evidenceto suggest an association of CLF to general bonebreakage in older layers, although the two con-ditions are often described as part of the samegeneral syndrome.If birds are identified early, they appear alertand are still producing eggs. The bones seem frag-ile and there may be broken bones. Dead birdsmay be dehydrated or emaciated, simply due tothe failure of these birds to eat or drink. The ribsmay show some beading although the mostobvious abnormality is a reduction in the den-sity of the medullary bone trabeculae. Paralysisis often due to fractures of the fourth and fifth tho-racic vertebrae causing compression and degen-eration of the spinal cord. If birds are examinedimmediately after the paralysis is first observed,there is often a partly shelled egg in the oviduct,and the ovary contains a rich hierarchy of yolks.If birds are examined some time after the onsetof paralysis, then the ovary is often regressed, dueto reduced nutrient intake.CLF is obviously due to an inadequate sup-ply of calcium available for shell calcification,and the bird’s plundering of unconventionalareas of its skeleton for such calcium. Becausecalcium metabolism is affected by the avail-ability of other nutrients, the status of phos-phorus and vitamin D3 in the diet and theiravailability are also important. Birds fed diets defi-cient in calcium, phosphorus or vitamin D3will show Cage Layer Fatigue assuming there isa high egg output.Calcium level in the prelay period is often con-sidered in preventative measures for CLF. Feedinglow calcium (1%) grower diets for too long a peri-od or even 2% calcium prelay diets up to 5% eggproduction often leads to greater incidence of abnor-mal bone development. It has been suggested thatthe resurgence in cases of CLF in some commercialflocks may be a result of too early a sexual matu-rity due to the genetic selection for this trait cou-pled with early light stimulation. Feeding a layerdiet containing 3.5% Ca vs a grower diet at 1%Ca as early as 14 weeks of age has proven ben-eficial in terms of an increase in the ash andcalcium content of the tibiotarsus (Table 4.44).Table 4.44 Diet calcium and bone characteristics of young layers in responseto prelay diet calciumTime of change to Tibiotarsus3.5% Ca (wk) Ash (%) Ca (mg/g)20 53.5c 182b18 55.7b 187b17 59.3a 202a16 58.9a 199a15 58.9a 197aAdapted from Keshavarz (1989)
  • 219CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.9Diet implications with some general management problemsFeeding a high calcium diet far in advanceof maturity seems unnecessary, and in fact, maybe detrimental in terms of kidney urolithiasis.Change from a low to a high calcium dietshould coincide with the observation of secondarysexual characteristics, and especially combdevelopment, which usually precedes first ovipo-sition by 14 – 16 d.We recently observed CLF in a group ofindividually caged Leghorns. The birds were 45weeks of age and all fed the same diet. Withina 10 d period, 5% of the birds had CLF, and feedanalyses showed adequate levels of calciumand phosphorus. The only common factor wasan exceptionally high egg output for these affect-ed birds. All these birds averaged 96% productionfrom 25 – 45 weeks of age, and all had individualclutch lengths of 100 eggs. One bird had a clutchlength of 140 eggs (i.e. 100% production). Theirsisters in adjacent cages fed the same diet andwithout CLF, had maximum clutch lengths of 42eggs in this period, and average productioncloser to 90%. These data suggest that in cer-tain situations CLF is correlated with excep-tionally high egg output.There have been surprisingly few reportson the effect of vitamin D3 on CLF in young birds.It is assumed that D3 deficiency will impaircalcium utilization, although there are no reportsof testing graded levels of this nutrient as a pos-sible preventative treatment. The other major nutri-ent concerned with skeletal integrity is phosphorus,and as expected, phosphorus deficiency can accen-tuate effects of CLF. While P is not directlyrequired for shell formation, it is essential for thereplenishment of Ca, as CaPO4, in medullary boneduring periods of active bone calcification.Without adequate phosphorus in the diet, thereis a failure to replenish the medullary Ca reserves,and this situation can accelerate or precipitatethe onset of CLF and other skeletal problems. Lowphosphorus intake is sometimes caused by thetrend towards lower levels of diet phosphorus cou-pled with very low feed intake of pullets throughearly egg production. For strains susceptible toCLF, then at least 0.5% available phosphorus isrecommended in the first layer diet to be fed upto 28 – 30 weeks of age.v) Bone breakage in older hens - CLF mayrelate to bone breakage in older hens, althougha definitive relationship has never been verified.It is suspected that like the situation of CLFwith young birds, bone breakage in older birdsresults as a consequence of inadequate calcifi-cation of the skeleton over time, again relatedto a high egg output coupled with the restrict-ed activity within the cage environment. Few livebirds have broken bones in the cage, the majorproblem occurring when these birds are removedfrom their cages and transported for processing.Apart from the obvious welfare implications, bro-ken bones prove problematic during the mechan-ical deboning of the muscles.Adding more calcium to the diet of older lay-ers does not seem to improve bone strength,although this can lead to excessive eggshellpimpling. Adding both calcium and phospho-rus to the diet has given beneficial results in someinstances, although results are quite variable. Inyoung birds at least, adding 300 ppm fluorine tothe water has improved bone strength, althoughthere are no reports of such treatment with endof lay birds. Moving birds from a cage to litterfloor environment seems to be the only treatmentthat consistently improves bone strength. Thisfactor indicates that exercise per se is an impor-tant factor in bone strength of caged birds, butdoes not really provide a practical solution to theproblem at this time.It is not currently known how to improve thebone integrity of older high producing hens
  • 220 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.9Diet implications with some general management problemswithout adversely affecting other traits of economicsignificance. For example, it has been shown thatbone breaking strength in older birds can beincreased by feeding high levels of vitamin D3.Unfortunately, this treatment also results in anexcessive pimpling of the eggshells (as occurs withextra calcium) and these extra calcium depositson the shell surface readily break off causing leak-age of the egg contents. It may be possible toimprove the skeletal integrity of older birds bycausing cessation of ovulation for some time priorto slaughter. Presumably, the associated reduc-tion in the drain of body calcium reserves wouldallow re-establishment of skeletal integrity.Currently such a feeding strategy is uneco-nomical, although consideration for bird welfaremay provide the impetus for research in this area.vi) Molting programs - Molting has come underscrutiny over the last few years, and in some coun-tries, it is not allowed based on welfare issues.Undoubtedly, the most efficient way to moltbirds, in terms of time and optimum second cycleproduction, is with light, water and feed with-drawal. It is the extensive period of feed with-drawal that raises welfare concerns even thoughmortality during this period is exceptionallylow. With one molting, it is possible to prolongthe production cycle to 90 weeks (52 + 40weeks), while with two moltings the cycle canbe 45 + 40 + 35 weeks. The productive life ofthe bird can therefore be doubled. When birdsresume their second or third laying cycle,eggshell quality is almost comparable to that of20-week-old birds, while even the first eggsproduced will be large grade. Shell quality dete-riorates more quickly in second and third cyclesand this situation dictates the shorter cycles. Theaim of a molting program is not necessarily to inducefeather loss, but rather to shut down the reproductivesystem for a period of time. Generally the longerthe pause in lay, the better the post-molt production.Egg pricing usually dictates the length of themolting period. If egg prices are high then a shortmolt period may be advantageous, whereas a longermolt period may ultimately be more economicalwhen egg prices are low.Examples of molt induced by feed with-drawal are shown in Table 4.45. With the typeof programs shown in Table 4.45, one canexpect birds to molt and to decline to near zeropercent egg production. The lowest egg productionwill likely occur about 5 – 7 d after initiation ofthe program, and maximum feather loss will occura week later than this. Programs should beadjusted depending upon individual flock cir-cumstances. For example, under very hotweather conditions it would be inadvisable to with-draw water for extended periods of time. Witha feed withdrawal program, body weight of thebird is one of the most important factors. Ideally,the body weight at the end of the first moltshould be the same as the initial mature weightwhen the bird was 18 – 19 weeks of age. Thiseffectively means that the molting programhas to induce a weight loss equivalent to theweight gain achieved in the first cycle of lay.
  • 221CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.9Diet implications with some general management problemsIn reality this is difficult to achieve and a +100g weight for second vs first cycle ‘mature’ weightis more realistic. Mortality is usually exceptionallylow during the period of feed withdrawal, andin fact less than in the 4 – 8 week period priorto the molt. If mortality exceeds 0.1% perweek, then it is cause for concern and perhapsa need for reintroducing feed. The actual peri-od of feed withdrawal should be no more than7 d, and ideally less than this if the desiredweight loss is achieved.The reduction in day length is a major stim-ulus to shutting down the ovary. While this is eas-ily achieved in blackout houses, special condi-tions must be used with open-sided buildings. Inorder for the bird to be subjected to a significantstep-down in daylength, then 5 – 7 d prior to thestart of the molt, birds should be given 23 – 24hr light each day. This means that with 16 hr nat-ural light per day, removing the artificial light inducesa significant reduction in day length which willhelp to reduce estrogen production.Alternatives to feed withdrawal for moltingare now being considered due to welfare issues.These alternative systems involve either high lev-els of minerals in conjunction with ad-lib feed-ing or the use of low nutrient dense diets/ingre-dients that are naturally less palatable.Considerable work has been conducted using highlevels of dietary zinc, where up to 20,000 ppmcauses a pause in lay, often without a classicalmolt, followed by resumption of productionand fairly good second cycle production. Virtuallyall of this dietary zinc will appear in the manure,and so today there are environmental concernsregarding its disposal. Birds can also be molt-Table 4.45 Molting with feed withdrawalWhite egg Brown egg1. Light0 – 1 d None None1 – 40 d 8 hr or natural18 hr or natural141d+ Step-up Step-up2. Water0 – 1 d None None1 d+ Ad-lib Ad-lib3. Feed0 – 7 d None None7 – 10 d 20 g cereal/d 25 g cereal/d10 – 20 d 45 g cereal/d 50 g cereal/d20 – 35 d Pullet developer Pullet developer35 d+ Layer II Layer II4. Body weight (kg)1st cycle maturity 1.25 1.40End 1st cycle 1.60 1.75End 1st molt 1.35 1.50End of 2nd cycle 1.70 1.851 provide 23 – 24 hr light/d for 5 d prior to start of molt
  • 222 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.10Nutrient managemented by feeding diets deficient in sodium or chlo-ride, although results tend to be quite variable withthis system.Using low nutrient density diets and ingredientsseems to hold some promise for inducing apause in lay. Dale and co-workers at Georgia haveused diets with 50% cottonseed meal fed ad-lib,and recorded weight loss comparable to a feedwithdrawal program. Birds fed this special dietlost 20% body weight within 10 d and egg pro-duction ceased after 5 d. Offering a diet containing90% grape pomace also seems to work well incausing a dramatic decline in egg production.Adding thyroxine to the diet is also a potentstimulus to shutting down the ovary, although eggsproduced by such birds contain elevated levelsof thyroxine and so could not be marketed.4.10 Nutrient managementPoultry manure is a valuble source ofnitrogen, phosphorus and potassium forcrop production. However, with thescale of layer farms today, the issue is the quan-tity of these nutrients produced within a smallgeographic location. The composition of manureis directly influenced by layer feed composition,and so higher levels of nitrogen in feed forexample are expected to result in more nitrogenin the manure. One approach to reducing theproblem of manure nutrient loading on farmland,is to reduce the concentration of these nutrientsby altering feed formulation. Since this essentiallyentails reduction in feed nitrogen and phospho-rus there are obviously lower limits for feed for-mulation such that production is not adversely affect-ed. As a generalization, about 25% of feednitrogen and 75% of feed phosphorus ends up inthe manure. Also, layers will produce about asmuch manure (on a wet basis) as the feed eatenover a given period of time. The actual weight ofmanure is obviously greatly influenced by mois-ture loss both in the layer house and during stor-age. Table 4.46 shows average compositon of freshcage layer manure.The major issue today is loading of manurewith nitrogen and phosphorus. Of these two nutri-ents, the level of nitrogen assayed in manure isthe most variable since housing system andtype of manure storage can have a dramatic effecton nitrogen loss as ammonia (Table 4.47).Table 4.46 Composition of freshcage layer manureMoisture (%) 70.0Gross energy (kcal/kg) 250Crude Protein (%) 8.0True Protein (%) 3.0Nitrogen (%) 1.2Uric acid (%) 1.7Ash (%) 8.0Calcium (%) 2.2Phosphorus (%) 0.6P205 (%) 1.3K20 (%) 0.6Sodium (%) 0.1Fat (%) 0.5NSP (%) 10.0Crude Fiber (%) 4.2Arginine (%) 0.12Leucine (%) 0.18Lysine (%) 0.11TSAA (%) 0.10Threonine (%) 0.12Tryptophan (%) 0.10
  • 223CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.10Nutrient managementTable 4.47 Nitrogen loss as ammo-nia for 10,000 layers per year (kg)Total nitrogen excretion into manure 7200Average house NH3 loss -660Average storage NH3 loss -120Average land NH3 loss -1140Total nitrogen loss as ammonia -1920Total nitrogen available for crops 5280Variable losses:a) Housing system:Liquid deep pit 680High-rise solid 290Belt, force drying 290Deep litter 1470b) Storage system:Belt drying 410Lagoon 3870c) Application system:Dry 710Slurry 1740Adapted from Van Horne et al. (1998)of essential amino acids. At some point in thereduction of crude protein, we seem to losegrowth rate or egg production/egg size which sug-gests that either we have reached the point at whichnon-essential amino acids become important, orthat we have inadequately described the bird’samino acid needs or that the synthetic amino acidsare not being used with expected efficiency.Of these factors, the need to more adequatelydescribe amino acid needs under these specif-ic formulation procedures is probably mostimportant. However, we can readily reduce crudeprotein supply by 15 – 20% if the use of syntheticamino acids is economical or if there is a costassociated with the disposal of manure nutrients.The expected reduction in nitrogen output relativeto diet crude protein in shown in Figure 4.20. Aspreviously described, we cannot use extremely lowprotein levels without reduction in performance.For example, in the study in Figure 4.20, reduc-ing CP from 17 to 13% resulted in a 2 g loss in eggsize. Currently we can probably reduce proteinlevels to 14 – 15% for older layers. However, a5% reduction in crude protein from 19% to 14%means a reduction in nitrogen output of about 2tonnes per year for 10,000 layers.Manure phosphorus levels are more easilypredicted, since there is no subsequent lossonce the manure is produced. As expected,manure phosphorus level is largely a factor of dietphosphorus level. Because phosphorus is anexpensive nutrient, it tends not to be overfor-mulated, however, there is usually some poten-tial to reduce levels. Most of the manure phos-phorus is undigested phytate phosphorus fromthe major feed ingredients such as corn and soy-bean meal. The phytate level in corn and soy-bean is variable and so this results in somevariance in phosphorus in the manure. Table 4.48shows the range of phosphorus in corn andsoybean samples from Ontario, Canada.Most of the nitrogen excreted by the bird relatesto undigested material and those amino acids thatare imbalanced with respect to immediate needsfor tissue or egg synthesis. Nitrogen excretioncan, therefore, be dramatically reduced by sup-plying a balance of amino acids that moreexactly meets the bird’s needs with minimum ofexcess, and also by providing these amino acidsin a readily digested form. With methionine, lysine,and threonine now available at competitiveprices, it is possible to formulate practical dietsthat provide a minimum excess of amino acidsand non-protein nitrogen. Unfortunately, we seemunable to take this approach to its logical con-clusion and formulate diets with very low lev-els of crude protein that contain regular levels
  • 224 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.10Nutrient managementTable 4.48 Phosphorus content of corn and soybean meal1Average Lowest 15% Highest 15%Corn:Samples tested 198 30 30Average P (%) 0.31 0.26 0.36Minimum P (%) 0.24 0.34Maximum P (%) 0.28 0.40Soybean meal:Samples tested 106 16 16Average P (%) 0.70 0.53 0.88Minimum P (%) 0.43 0.80Maximum P (%) 0.59 1.001 adjusted from analysis of soybeans assuming 20% fat content Adapted from Leach (2002)Fig. 4.20 Nitrogen intake and excretion of layers in relation to diet protein level.
  • 225CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSECTION 4.10Nutrient managementTable 4.49 Hectares of corn land required for manure disposal from10,000 layers/yrDiet CP (%) Hectares Diet P (%) Hectares20 47 0.55 4519 45 0.50 4018 44 0.45 3617 41 0.40 3216 40 0.35 2815 37 0.30 2314 35 0.25 19A corn-soy diet containing ingredients fromthe highest 15% vs lowest 15% grouping ofphosphorus content is expected to increasemanure phosphorus content by 20 – 25%.Phytase enzyme now allows for significantreduction in diet phosphorus levels (25 – 30%)and this relates to a corresponding reduction inmanure phosphorus levels. For more details onphytase, see Section 2.3 g.Although there are lower limits to protein andphosphorus levels in layer diets, phase feedingprograms involving the sequential reductions inN and P content of layer feed over time will havea meaningful effect on manure nutrient loading.Table 4.49 shows the land base required for 10,000layers per year assuming that the land is used togrow corn and fertilizer rate is 140 kg N/hectareand 40 kg P/hectare. As CP level of the dietdecreases from 20 to 14%, the land base requiredto adequately use the manure is reduced by 25%.With phosphorus there is potential reduction of50% in land based relative to diet P levels usedin formulation.In the future, we may have to re-evaluate thelevels of trace minerals fed to layers, sincemanure concentration of zinc and copper maycome under closer scrutiny regarding soil accu-mulation.
  • 226 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSSuggested ReadingsAtteh, J.O. and S. Leeson (1985). Response of layinghens to dietary saturated and unsaturated fatty acidsin the presence of varying dietary calcium levels.Poult. Sci. 64:520-528.Bean, L.D. and S. Leeson, (2002). Metabolizableenergy of layer diets containing regular or heat-treat-ed flaxseed. J. Appl. Poult. Res. 11:424-429.Bean, L.D. and S. Leeson, (2003). Long-term effectsof feeding flaxseed on the performance and egg fattyacid composition of brown and white hens. Poult.Sci. 82:388-394.Calderon, V.M. and L.S. Jensen, (1990). The require-ment for sulfur amino acid by laying hens as influ-enced by protein concentration. Poult. Sci. 69:934-944.Caston, L.J., E.J. Squires and S. Leeson, (1994). Henperformance, egg quality and the sensory evaluationof eggs from SCWL hens fed dietary flax. Can. J.Anim. Sci. 74:347-353.Chah, C.C., (1972). A study of the hen’s nutrientintake as it relates to egg formation. M.Sc. Thesis,University of Guelph.Chen, J. and D. Balnave, (2001). The influence ofdrinking water containing sodium chloride on per-formance and eggshell quality of a modern, coloredlayer strain. Poult. Sci. 80:91-94.Clunies, M. and S. Leeson, (1995). Effect of dietarycalcium level on plasma proteins and calcium fluxoccurring during a 24h ovulatory cycle. Can. J.Anim. Sci. 75:539-544.Faria, D.E., R.H. Harms, and G.B. Russell, (2002).Threonine requirement of commercial laying hensfed a corn-soybean meal diet. Poult Sci. 81:809-814.Gonzalez, R. and S. Leeson, (2001). Alternatives forenrichment of eggs and chicken meat with omega-3fatty acids. Can. J. Anim. Sci. 81:295-305.Gonzalez R. and S. Leeson, (2000). Effect of feedinghens regular or deodorized menhaden oil on pro-duction parameters, yolk fatty acid profile and sen-sory quality of eggs. Poult. Sci. 79:1597-1602.Harms, R.H. and G.B. Russell, (1994). A compari-son of the bioavailability of DL-methionine andMHA for the commercial laying hen. J. Appl. Poult.Res. 3:1-6.Harms, R.H. and G.B. Russell, (2000). Evaluation ofthe isoleucine requirement of the commercial layerin a corn-soybean meal diet. Poult. Sci. 79:1154-1157.Hoffman-La Roche, (1998). Egg yolk pigmentationwith carophyll. 3rd Ed. Publ. F. Hoffmann-La Rocheand Co. Ltd. Publ. 1218. Basle, Switzerland.Ishibashi, T., Y. Ogawa, T. Itoh, S. Fujimura, K.Koide, and R. Watanabe, (1998). Threonine require-ments of laying hens. Poult. Sci. 77:998-1002.Keshavarz, K., (1989). A balance between osteo-porosis and nephritis. Egg industry. July p 22-25.Keshavarz, K., (2003). The effect of different levelsof nonphytate phosphorus with and without phy-tase on the performance of four strains of layinghens. Poult. Sci. 82:71-91.Leach S.D., (2002). Evaluation of and alternativemethods for determination of phytate in Ontariocorn and soybean samples. MSc Thesis, Universityof Guelph.Leeson, S. and J.D. Summers, (1983). Performanceof laying hens allowed self-selection of variousnutrients. Nutr. Rep. Int. 27:837-844.Leeson, S. and L.J. Caston, (1997). A problem withcharacteristics of the thin albumen in laying hens.Poult. Sci. 76:1332-1336.Leeson, S., (1993). Potential of modifying poultryproducts. J. Appl. Poult. Res. 2:380-385.Leeson, S., R.J. Julian and J.D. Summers, (1986).Influence of prelay and early-lay dietary calciumconcentration on performance and bone integrity ofLeghorn pullets. Can. J. Anim. Sci. 66:1087-1096.Naber, E.C., (1993). Modifying vitamin compositionof eggs: A review. J. Appl. Poult. Res. 2:385-393.Newman, S. and S. Leeson, (1997). Skeletal integri-ty in layers at the completion of egg production.World’s Poult. Sci. J. 53:265-277.
  • 227CHAPTER 4FEEDING PROGRAMS FOR LAYING HENSPeganova, S. and K. Eder, (2003). Interactions of var-ious supplies of isoleucine, valine, leucine and tryp-tophan on the performance of laying hens. Poult.Sci. 82:100-105.Rennie, J.S., R.H. Fleming, H.A. McCormack, C.C.McCorquodale and C.C. Whitehead, (1997). Studieson effects of nutritional factors on bone structure andosteoporosis in laying hens. Br. Poult. Sci. 38 (4):417-424.Roland, D.A., (1995). The egg producers guide tooptimum calcium and phosphorus nutrition. Publ.Mallinckrodt Feed Ing.Sell, J.L., S.E. Scheideler and B.E. Rahn, (1987).Influence of different phosphorus phase-feedingprograms and dietary calcium level on performanceand body phosphorus of laying hens. Poult. Sci.66:1524-1530.Waldroup, P.W. and H.M. Hellwig, (1995).Methionine and total sulfur amino acid require-ments influenced by stage of production. J. Appl.Poult. Res. 3:1-6.Zhang, B. and C.N. Coon, (1994). Nutrient model-ing for laying hens. J. Appl. Poult. Res. 3:416-431.
  • FEEDINGPROGRAMS FORBROILER CHICKENS22955.1 Diet specifications and feed formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2305.2 Feeding programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238a. General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238b. Prestarters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244c. Low nutrient dense diets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246d. Growth restriction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248e. Heavy broilers/roasters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252f. Feed withdrawal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2555.3 Assessing growth and efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257a. Broiler growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257b. Feed efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2595.4 Nutrition and environmental temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261a. Bird response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261b. Potential nutritional intervention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2655.5 Nutrition and lighting programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2675.6 Nutrition and gut health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2705.7 Metabolic disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273a. Ascites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273b. Sudden death syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277c. Skeletal disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277d. Spiking mortality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2815.8 Carcass composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2815.9 Skin integrity and feather abnormalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285a. Feather development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285b. Skin tearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287c. Oily bird syndrome (OBS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2885.10 Environmental nutrient management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289PageCHAPTER
  • 230 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.1Diet specifications and feed formulationsGenetic selection for growth rate con-tinues to result in some 30-50 g yearlyincrease in 42-49 d body weight. Therehas also been an obvious improvement in feedefficiency and reduction in the incidence ofmetabolic disorders over the last 5 years, and sothese changes have dictated some changes in feedformulation and feed scheduling. The modernbroiler chicken is however, able to respondadequately to diets formulated over a vast rangeof nutrient densities. If there is no concern regard-ing classical measures of feed efficiency, then thehighest nutrient dense diets are not always themost economical.To a large extent, the ability of the broiler togrow well with a range of diet densities relatesto its voracious appetite, and the fact that feedintake seems to be governed by both physical sati-ety as well as by cues related to specific nutri-ents. For example, varying the energy level ofa broiler diet today has much less of an effect onfeed intake, as expected on the basis of appetitebeing governed by energy requirement. This appar-ently subtle change in bird appetite has led toincreased variability in diet type and diet allo-cation used by commercial broiler growers.However, as will be discussed later, attemptingto ‘cheapen’ broiler diets through the use of lowerprotein/amino acid levels, while not havingmajor effects on gross performance, leads to sub-tle changes in carcass composition. Feed pro-grams may, therefore, vary depending upon thegoals of the producer versus the processor.Another major change in broiler nutrition thathas occurred over the last 5 years is the realizationthat maximizing nutrient intake is not always themost economical situation, at least for certain timesin the grow-out period. A time of so-called‘undernutrition’, which slows down early growthrate appears to result in reduction in the incidenceof metabolic disorders such as Sudden DeathSyndrome and the various skeletal abnormali-ties. A period of slower initial growth, followedby ‘compensatory’ growth is almost alwaysassociated with improved feed efficiency, becauseless feed is directed towards maintenance. Asincreasing numbers of broilers are grown inhot climates, an understanding of the bird’sresponse to temperature, humidity and pho-toperiod is becoming more important.Diet specifications are shown in Tables 5.1,5.2 and 5.3. Table 5.1 shows relatively high nutri-ent dense diets, whileTable 5.2 indicates an alter-nate program for low nutrient dense diets. Thechoice of such feeding programs is often dictatedby strain of broiler, environmental temperatureand the relative cost of major nutrients such asenergy and protein. Within these feeding pro-grams a common vitamin-mineral premix isused, albeit at different levels, according tobird age. Because birds will eat more of the lowvs. high nutrient dense diets, there is potentialto reduce the premix nutrient levels by up to 10%forTable 5.2 vs.Table 5.1. When broilers are grownto very heavy weights (63 d+) then there is anadvantage to using lower nutrient dense diets (Table5.3). Tables 5.4 – 5.7 show examples of high nutri-ent dense diets appropriate for the specificationsshown in Table 5.1. There are six variations ofdiets for the starter, grower, finisher and withdrawalperiods. The diets differ in the major cereal usednamely corn, sorghum or wheat, and with or with-out meat meal as another option.5.1 Diet specifications and feed formulation
  • 231CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.1Diet specifications and feed formulationsApproximate age 0-18d 19-30d 31-41d 42d+Starter Grower Finisher WithdrawalCrude Protein (%) 22 20 18 16Metabolizable Energy (kcal/kg) 3050 3100 3150 3200Calcium (%) 0.95 0.92 0.89 0.85Available Phosphorus (%) 0.45 0.41 0.38 0.36Sodium (%) 0.22 0.21 0.2 0.2Methionine (%) 0.5 0.44 0.38 0.36Methionine + Cystine (%) 0.95 0.88 0.75 0.72Lysine (%) 1.3 1.15 1.0 0.95Threonine (%) 0.72 0.62 0.55 0.5Tryptophan (%) 0.22 0.2 0.18 0.16Arginine (%) 1.4 1.25 1.1 1.0Valine (%) 0.85 0.66 0.56 0.5Leucine (%) 1.4 1.1 0.9 0.8Isoleucine (%) 0.75 0.65 0.55 0.45Histidine (%) 0.4 0.32 0.28 0.24Phenylalanine (%) 0.75 0.68 0.6 0.5Vitamins (per kg of diet) 100% 80% 70% 50%Vitamin A (I.U) 8000Vitamin D3 (I.U) 3500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 4Riboflavin (mg) 5Pyridoxine (mg) 4Pantothenic acid (mg) 14Folic acid (mg) 1Biotin (µg) 100Niacin (mg) 40Choline (mg) 400Vitamin B12 (µg) 12Trace minerals (per kg of diet) 100% 80% 70% 50%Manganese (mg) 70Iron (mg) 20Copper (mg) 8Zinc (mg) 70Iodine (mg) 0.5Selenium (mg) 0.3Table 5.1 High nutrient density diet specifications for broilers
  • 232 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.1Diet specifications and feed formulationsApproximate age 0-18d 19-30d 31-41d 42d+Starter Grower Finisher WithdrawalCrude Protein (%) 21 19 17 15Metabolizable Energy (kcal/kg) 2850 2900 2950 3000Calcium (%) 0.95 0.9 0.85 0.8Available Phosphorus (%) 0.45 0.41 0.36 0.34Sodium (%) 0.22 0.21 0.19 0.18Methionine (%) 0.45 0.4 0.35 0.32Methionine + Cystine (%) 0.9 0.81 0.72 0.7Lysine (%) 1.2 1.08 0.95 0.92Threonine (%) 0.68 0.6 0.5 0.45Tryptophan (%) 0.21 0.19 0.17 0.14Arginine (%) 1.3 1.15 1.0 0.95Valine (%) 0.78 0.64 0.52 0.48Leucine (%) 1.2 0.9 0.8 0.75Isoleucine (%) 0.68 0.6 0.5 0.42Histidine (%) 0.37 0.28 0.25 0.21Phenylalanine (%) 0.7 0.65 0.55 0.46Vitamins (per kg of diet) 100% 70% 60% 40%Vitamin A (I.U) 8000Vitamin D3 (I.U) 3500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 4Riboflavin (mg) 5Pyridoxine (mg) 4Pantothenic acid (mg) 14Folic acid (mg) 1Biotin (µg) 100Niacin (mg) 40Choline (mg) 400Vitamin B12 (µg) 12Trace minerals (per kg of diet) 100% 70% 60% 40%Manganese (mg) 70Iron (mg) 20Copper (mg) 8Zinc (mg) 70Iodine (mg) 0.5Selenium (mg) 0.3Table 5.2 Low nutrient density diet specifications for broilers
  • 233CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.1Diet specifications and feed formulationsApproximate age 0-15d 16-30d 31-45d 46-56d 57d+Starter Grower #1 Grower #2 Finisher #1 Finisher #2Crude Protein (%) 20 19 18 16 15Metabolizable Energy (kcal/kg) 2850 2900 2950 3000 3000Calcium (%) 0.95 0.9 0.85 0.8 0.75Available Phosphorus (%) 0.45 0.41 0.36 0.34 0.3Sodium (%) 0.22 0.21 0.19 0.18 0.18Methionine (%) 0.42 0.38 0.33 0.30 0.28Methionine+cystine (%) 0.85 0.76 0.68 0.66 0.64Lysine (%) 1.13 1.02 0.95 0.92 0.90Threonine (%) 0.64 0.56 0.47 0.42 0.39Tryptophan (%) 0.20 0.18 0.16 0.13 0.11Arginine (%) 1.22 1.08 0.94 0.89 0.85Valine (%) 0.73 0.60 0.49 0.45 0.42Leucine (%) 1.13 0.85 0.75 0.71 0.67Isoleucine (%) 0.64 0.56 0.47 0.39 0.35Histidine (%) 0.35 0.26 0.24 0.20 0.18Phenylalanine (%) 0.66 0.61 0.52 0.43 0.39Vitamins (per kg of diet) 100% 80% 70% 60% 40%Vitamin A (I.U) 8000Vitamin D3 (I.U) 3500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 4Riboflavin (mg) 5Pyridoxine (mg) 4Pantothenic acid (mg) 14Folic acid (mg) 1Biotin (µg) 100Niacin (mg) 40Choline (mg) 400Vitamin B12 (µg) 12Trace minerals (per kg of diet) 100% 80% 70% 60% 40%Manganese (mg) 70Iron (mg) 20Copper (mg) 8Zinc (mg) 70Iodine (mg) 0.5Selenium (mg) 0.3Table 5.3 Diet specifications for very heavy broilers
  • 234 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.1Diet specifications and feed formulations1 2 3 4 5 6Corn 533 559Wheat 568 597Sorghum 523 542Wheat shorts 60 60 70 72 68 69Meat meal 40 50 42Soybean meal 342 295 334 281 283 230Fat 28.7 21.0 37.0 33.5 45.3 38.0DL-Methionine* 2.5 2.6 2.6 2.8 2.8 2.9L-Lysine 0.8 0.9 0.4 0.3 1.1 1.1Salt 4.4 3.9 4.6 3.9 3.9 3.3Limestone 15.8 12.0 16.0 11.2 16.2 12.5Dical Phosphate 11.8 4.6 11.4 2.3 10.7 3.2Vit-Min Premix** 1 1 1 1 1 1Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 22 22 22 22 22 22ME (kcal/kg) 3050 3050 3050 3050 3050 3050Calcium (%) 0.95 0.95 0.95 0.95 0.95 0.95Av Phosphorus (%) 0.45 0.45 0.45 0.45 0.45 0.45Sodium (%) 0.22 0.22 0.22 0.22 0.22 0.22Methionine (%) 0.61 0.62 0.56 0.57 0.60 0.61Meth + Cystine (%) 0.95 0.95 0.95 0.95 0.95 0.95Lysine (%) 1.3 1.3 1.3 1.3 1.3 1.3Threonine (%) 0.93 0.91 0.86 0.84 0.82 0.80Tryptophan (%) 0.30 0.30 0.30 0.29 0.32 0.31Table 5.4 Examples of high nutrient dense broiler starter diets* or eqivalent MHA** with choline
  • 235CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.1Diet specifications and feed formulations1 2 3 4 5 6Corn 613 646Wheat 630 665Sorghum 573 600Wheat shorts 31 30 60 64 64 65Meat meal 50 52 53Soybean meal 295 237 289 230 223 160Fat 26 16.4 44 34 49 37.3DL-Methionine* 2.4 2.5 2.5 2.7 2.7 2.9L-Lysine 0.8 0.8 0.3 0.2 1.1 1.1Salt 4.2 3.5 4.2 3.7 3.6 2.8Limestone 16 11.3 16 11.5 16.4 11.9Dical Phosphate 10.6 1.5 10 0.9 9.2Vit-Min Premix** 1.0 1.0 1.0 1.0 1.0 1.0Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 20 20 20 20 20 20ME (kcal/kg) 3100 3100 3100 3100 3100 3100Calcium (%) 0.92 0.92 0.92 0.92 0.92 0.92Av Phosphorus (%) 0.41 0.41 0.41 0.41 0.41 0.41Sodium (%) 0.21 0.21 0.21 0.21 0.21 0.21Methionine (%) 0.58 0.59 0.53 0.54 0.57 0.58Meth + Cystine (%) 0.88 0.88 0.88 0.88 0.88 0.88Lysine (%) 1.15 1.15 1.15 1.15 1.15 1.15Threonine (%) 0.85 0.83 0.78 0.76 0.73 0.7Tryptophan (%) 0.27 0.26 0.27 0.26 0.29 0.28Table 5. 5 Examples of high nutrient dense broiler grower diets* or eqivalent MHA** with choline
  • 236 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.1Diet specifications and feed formulations1 2 3 4 5 6Corn 693 726Wheat 714 779Sorghum 643 676Wheat shorts 50 50 50 23Meat meal 50 50 50Soybean meal 250 192 236 178 161 100Fat 23.7 13.1 38.5 27.9 43 29.8DL-Methionine* 1.7 1.8 1.8 2.0 2.0 2.2L-Lysine 0.8 0.8 0.3 0.2 1.2 1.2Salt 3.9 3.3 4 3.4 3.2 2.5Limestone 16 11.3 16.3 11.5 16.5 11.3Dical Phosphate 9.9 0.7 9.1 8.1Vit-Min Premix** 1.0 1.0 1.0 1.0 1.0 1.0Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 18 18 18 18 18 18ME (kcal/kg) 3150 3150 3150 3150 3150 3150Calcium (%) 0.89 0.89 0.89 0.89 0.89 0.89Av Phosphorus (%) 0.38 0.38 0.38 0.38 0.38 0.38Sodium (%) 0.2 0.2 0.2 0.2 0.2 0.2Methionine (%) 0.48 0.49 0.42 0.43 0.47 0.48Meth + Cystine (%) 0.75 0.75 0.75 0.75 0.75 0.75Lysine (%) 1.0 1.0 1.0 1.0 1.0 1.0Threonine (%) 0.78 0.76 0.69 0.67 0.63 0.78Tryptophan (%) 0.25 0.23 0.24 0.23 0.27 0.25Table 5.6 Examples of high nutrient dense broiler finisher diets* or eqivalent MHA** with choline
  • 237CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.1Diet specifications and feed formulations1 2 3 4 5 6Corn 745 783Wheat 772 812Sorghum 695 728Wheat shorts 50 50 50 60Meat meal 60 50 50Soybean meal 196 127 181 123 100 27Fat 25 12.6 40.4 30 45 34DL-Methionine* 2.0 2.2 2.2 2.3 2.4 2.6L-Lysine 2.2 2.2 1.7 1.6 2.7 2.7Salt 3.9 3.1 4 3.4 3.1 2.3Limestone 15.4 8.9 15.7 10.7 16 8.4Dical Phosphate 9.5 9.0 7.8Vit-Min Premix** 1.0 1.0 1.0 1.0 1.0 1.0Total (kg) 1000 1000 1000 1000 1000 1000Crude Protein (%) 16 16 16 16 16 16ME (kcal/kg) 3200 3200 3200 3200 3200 3200Calcium (%) 0.85 0.85 0.85 0.85 0.85 0.85Av Phosphorus (%) 0.36 0.39 0.36 0.37 0.36 0.38Sodium (%) 0.20 0.20 0.20 0.20 0.20 0.20Methionine (%) 0.49 0.50 0.43 0.44 0.48 0.49Meth + Cystine (%) 0.72 0.72 0.72 0.72 0.72 0.72Lysine (%) 0.95 0.95 0.95 0.95 0.95 0.95Threonine (%) 0.69 0.67 0.60 0.58 0.53 0.51Tryptophan (%) 0.21 0.20 0.21 0.19 0.24 0.22Table 5.7 Examples of high nutrient dense broiler withdrawal diets* or eqivalent MHA** with choline
  • 238 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programs5.2 Feeding programsa) General considerationsWhile nutrient requirement values anddiet formulations are fairly standardworldwide, there is considerablevariation in how such diets are scheduled with-in a feed program. Feed program is affected bystrain of bird, as well as sex and market age ormarket weight. Other variables are environmentaltemperature, local disease challenge and whetherthe bird is sold live, as an intact eviscerated car-cass, or is destined for further processing.Management factors such as stocking density, feedand water delivery equipment and presence ornot of anticoccidials and growth promoters,also influence feed scheduling.The underlying factors to such inputs forfeed scheduling, often relate to their influenceon feed intake. Predicting daily or weekly feedintake is therefore of great importance in devel-oping feed programs. Table 5.8 outlines expect-ed feed intake for male and female broilers to 63and 56 d respectively. In the first 20 d of growth,male and female broilers eat almost identical quan-tities of feed, and growth is therefore compara-ble. After this time, the increased growth of themale is a consequence of increased feed intake.Ten years ago, age in days x 4 gave an estimateof daily feed intake. Today, this estimate no longerholds true, since growth rate and feed intake haveincreased. For a male broiler chicken, daily feedintake of starter, grower, finisher and withdrawalcan be estimated by multiplying bird age indays by 4, 5, 4 and 3.5 respectively.The major factor influencing choice of feedscheduling is market age and weight. As a gen-eralization, the earlier that a bird is marketed, themore prolonged the use of starter and grower feeds.For heavier birds, the high nutrient dense starterand grower feeds are used for shorter periods oftime. Feed schedules for male and female broil-ers are shown inTables 5.9 and 5.10 respectivelywhileTable 5.11 outlines data for mixed-sex birds.Feed scheduling tends to be on the basis offeed quantity or according to bird age, andboth of these options are shown in Tables 5.9-5.11. The withdrawal diet is used for 5-10 ddepending on market age although it must beemphasized that scheduling of this diet is dic-tated by the minimum withdrawal time of spe-cific antibiotics, growth promoters and/or antic-occidials, etc.The need for strain-specific diets is oftenquestioned. Tables 5.12-5.14 outline the nutrientrequirements of the three major commercialstrains currently used worldwide. Since it is pro-hibitively expensive for breeding companies to con-duct research on defining needs of all nutrients fortheir strains at all ages, then their requirement val-ues are often based on information collectedfrom customers worldwide. The publishedrequirement values (Tables 5.12 – 5.14) are there-fore considered to be the most appropriate for theindividual strains under most commercial grow-ing conditions. With this in mind, there are no majordifferences in nutrient requirements for any spe-cific strain. In reality, the nutrient needs andfeeding program for a 42 d vs. 60 d Ross male aregoing to be much more different than are require-ments of a 42 d Ross vs. 42 d Cobb bird.
  • 239CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsAge Male Female Age Male Female(d) Daily Cum.* Daily Cum. (d) Daily Cum. Daily Cum.1 13 13 13 13 33 159 2726 136 25552 15 28 15 28 34 163 2889 140 26953 18 46 18 46 35 167 3056 143 28384 21 67 21 67 36 170 3226 147 29815 24 91 23 90 37 172 3398 150 31316 25 116 25 115 38 174 3572 152 32837 27 143 26 141 39 176 3748 153 34368 32 175 32 173 40 178 3926 154 35909 37 212 37 210 41 180 4106 154 374410 42 254 41 251 42 182 4288 154 389811 47 301 46 297 43 184 4472 155 405312 53 354 52 349 44 185 4657 156 420913 59 413 58 407 45 186 4843 156 436514 66 479 65 472 46 187 5021 157 452215 74 553 70 542 47 188 5209 158 468016 80 633 76 618 48 189 5398 159 483917 85 718 81 694 49 190 5588 160 499918 90 808 86 785 50 191 5779 161 516019 95 903 91 876 51 192 5971 161 532120 100 1003 96 972 52 193 6164 162 548321 105 1108 102 1074 53 194 6358 163 564622 110 1218 106 1180 54 195 6553 164 581023 115 1333 110 1290 55 196 6749 165 597524 120 1453 114 1404 56 197 6946 165 614025 125 1578 117 1521 57 198 714426 129 1707 120 1641 58 199 734327 133 1840 123 1764 59 200 754328 137 1977 126 1890 60 201 774429 141 2118 130 2020 61 202 794630 145 2263 132 2152 62 203 814931 149 2412 133 2285 63 204 835332 155 2567 134 2419Table 5.8 Feed intake of male and female broilers (g/bird)* Cumulative
  • 240 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsFeedallocation(kg/bird)AgeBodyF:GStarterGrowerFinisherWithdrawalTotalFeed(d)Wt.(g)(kg)(age)(kg)(age)(kg)(age)(kg)(age)(kg)4224351.740.750-17d2.4518-36d1.0037-42d4.244325101.760.700-17d2.7218-37d1.0038-43d4.424425851.780.650-16d2.9517-38d1.0039-44d4.604526601.800.650-16d2.1317-33d1.0034-39d1.0040-45d4.794627351.820.600-16d1.8817-31d1.5032-40d1.0041-46d4.984728101.840.600-16d1.6217-30d1.9031-41d1.0541-47d5.174828851.860.600-16d1.4117-28d2.3029-42d1.0543-48d5.374929601.880.580-15d1.3216-28d2.5629-43d1.1044-49d5.565030301.900.560-15d1.5516-29d2.5530-44d1.1045-50d5.765131001.920.540-15d1.7016-30d2.6131-45d1.1046-51d5.955231701.940.520-15d1.8016-30d2.7331-46d1.1047-52d6.155332401.960.500-14d1.9015-31d2.8032-47d1.1548-53d6.355433101.980.480-14d1.9515-31d2.9732-48d1.1549-54d6.555533802.000.460-14d2.0015-31d3.1532-49d1.1550-55d6.765634502.020.440-13d2.1014-32d3.2833-50d1.1551-56d6.975735202.030.420-13d2.2014-32d3.3233-51d1.2052-57d7.155835902.040.400-13d2.3014-33d3.4434-52d1.2053-58d7.325936602.060.400-13d2.4014-34d3.5435-53d1.2054-59d7.546037302.080.400-13d2.5014-34d3.6435-54d1.2055-60d7.766138002.090.400-13d2.6014-35d3.6536-55d1.3056-61d7.946238702.110.400-13d2.7014-35d3.7536-55d1.3056-62d8.146339402.120.400-13d2.8014-35d3.8536-55d1.3056-63d8.35Table 5.9 Feed schedule for male broilers
  • 241CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsTable 5.10 Feed schedule for female broilersFeedallocation(kg/bird)AgeBodyF:GStarterGrowerFinisherWithdrawalTotalFeed(d)Wt.(g)(kg)(age)(kg)(age)(kg)(age)(kg)(age)(kg)3516421.730.50-14d1.6615-30d0.6831-35d2.843617041.750.50-14d1.7915-31d0.7032-36d2.983717651.770.50-14d1.8915-32d0.7333-37d3.123818271.790.50-14d2.0215-33d0.7534-38d3.273918881.820.480-13d2.2014-34d0.7835-39d3.444019491.840.480-13d2.3114-35d0.8036-40d3.594120121.860.450-13d2.4714-36d0.8237-41d3.744220751.880.450-13d2.6114-37d0.8438-42d3.904321351.900.450-13d2.7514-38d0.8639-43d4.064421941.920.430-13d2.8814-38d0.9039-44d4.214522521.940.430-13d2.4814-36d0.5037-39d0.9540-45d4.374623081.960.430-13d2.4414-35d0.7036-40d0.9541-46d4.524723631.980.410-13d2.3714-35d0.9036-41d1.0042-47d4.684824172.000.410-13d2.3214-34d1.1035-42d1.0043-48d4.834924702.020.410-13d2.2814-34d1.3035-43d1.0044-49d4.995025222.040.410-12d2.2313-34d1.5035-44d1.0045-50d5.145125732.060.400-12d2.1513-33d1.7034-44d1.0045-51d5.305226232.080.400-12d2.1113-33d1.9034-45d1.0546-52d5.465326722.100.400-12d2.0613-32d2.1033-46d1.0047-53d5.615427202.130.400-11d2.0412-32d2.2733-47d1.0548-54d5.815527702.160.300-11d2.0212-31d2.5632-48d1.1049-55d5.985628202.180.300-11d2.0012-31d2.7432-49d1.1050-56d6.14
  • 242 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsFeedallocation(kg/bird)AgeBodyF:GStarterGrowerFinisherWithdrawalTotal(d)Wt.(g)(kg)(age)(kg)(age)(kg)(age)(kg)(age)Feed(kg)4222551.810.600-16d2.5317-36d0.9237-42d4.084323231.830.580-15d2.7416-37d0.9338-48d4.254423601.850.540-15d2.9216-38d0.9539-44d4.374524561.870.540-13d2.3116-34d0.7535-39d0.9840-45d4.594625211.890.520-15d2.1616-33d1.1035-40d0.9841-46d4.764725861.910.510-15d2.0016-32d1.4033-41d1.0342-47d4.944826511.930.510-15d1.8716-31d1.7032-42d1.0343-48d5.124927151.950.500-14d1.8015-31d1.9332-43d1.0544-49d5.295027761.970.490-14d1.8915-31d2.0332-44d1.0545-50d5.475128361.990.470-14d1.9315-31d2.1632-45d1.0846-51d5.645228962.010.460-14d1.9615-32d2.3233-46d1.0847-52d5.825329562.030.450-13d1.9814-32d2.4533-47d1.1048-53d6.005430152.060.440-13d2.0014-32d2.6233-48d1.1349-54d6.215530752.080.380-12d2.0113-31d2.8632-49d1.1350-55d6.405631352.100.350-12d2.0613-32d3.0133-50d1.1351-56d6.58Table 5.11 Feed schedule for mixed-sex broilers
  • 243CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsStarter GrowerHubbard Ross Cobb Hubbard Ross CobbME (kcal/kg) 3000 3040 3023 3080 3140 3166CP (%) 22.0 22.0 21.5 20.0 20.0 19.5Ca (%) 0.95 1.0 0.90 0.90 0.90 0.88Av P (%) 0.44 0.50 0.45 0.40 0.45 0.42Na (%) 0.19 0.21 0.20 0.19 0.21 0.17Methionine (%) 0.50 0.53 0.56 0.45 0.46 0.53Meth + Cys (%) 0.90 0.97 0.98 0.83 0.85 0.96Lysine (%) 1.25 1.35 1.33 1.15 1.18 1.25Threonine (%) 0.81 0.87 0.85 0.75 0.70 0.80Finisher WithdrawalHubbard Ross Cobb Hubbard Ross CobbME (kcal/kg) 3150 3200 3202 3160 3220 3202CP (%) 19.0 18.0 18.0 18.0 17.0 17.0Ca (%) 0.87 0.85 0.84 0.82 0.76 0.78Av P (%) 0.37 0.42 0.40 0.34 0.37 0.35Na (%) 0.19 0.21 0.16 0.19 0.21 0.16Methionine (%) 0.42 0.43 0.48 0.39 0.42 0.44Meth + Cys (%) 0.80 0.80 0.88 0.75 0.79 0.88Lysine (%) 1.05 1.09 1.10 0.93 1.03 1.04Threonine (%) 0.72 0.72 0.73 0.69 0.70 0.70Table 5.12 Diet specifications for 2.5 kg broilersTable 5.13 Diet specifications for 2.5 kg broilers
  • 244 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsHubbard Ross CobbVitamin A (I.U) 7000 8270 12000Vitamin D3 (I.U) 3500 3030 4000Vitamin E (I.U) 40 50 30Vitamin K3 (I.U) 2.2 2.2 4.0Thiamin (mg) 4.0 2.4 4.0Riboflavin (mg) 6.0 7.7 9.0Pantothenate acid (mg) 11.0 12.7Niacin (mg) 45 51.8Pyridoxine (mg) 3.3 2.4 4.0Choline (mg) 750 - 400Folic acid (mg) 1.0 1.1 1.5Biotin (µg) 100 110 150Vitamin B12 (µg) 12 15.4 20Manganese (mg) 66 120 120Zinc (mg) 50 110 100Iron (mg) 80 20 40Copper (mg) 9.0 16 20Iodine (mg) 1.0 1.25 1.0Selenium (mg) 0.30 0.30 0.30Table 5.14 Vitamin-Mineral Premixes (starter or general)b) PrestartersIt is generally recognized that the neonate chickdoes not produce an adult complex of digestiveenzymes, and so digestibility is somewhatimpaired. This situation is further complicatedby the change in nutrient substrate of lipid andprotein in the embryo to quite complex carbo-hydrates, proteins and lipids in conventional starterdiets. So even though chicks grow quite rapid-ly in the first few days of life, there is the idea thatthis could be further enhanced by use of aprestarter. Prestarters therefore, either pre-con-dition the chick such that it can digest complexsubstrates and/or provide more (or more high-ly digestible) substrates until the chick’s enzymeproduction has ‘matured’.The role of the unabsorbed yolk sac in earlylife nutrition is open to debate. On an evolutionaryscale the yolk sac likely provides a source of ener-gy, water and perhaps, most importantly, IgAmaternal antibodies for the young bird. Most altri-cial birds have virtually no yolk sac, while pre-cocial birds have considerable yolk reserves athatch. The yolk sac in chicks weighs around 8-10 g depending on the size of the original eggyolk. It is often stated that the residual yolk willbe used more quickly if the chick is without feedand water. It seems that yolk utilization is unaf-fected by presence or not of feed with a lineardecline in yolk weight up to 3 d post-hatch. Byday 3, regardless of feed supply, yolk size is onlyaround 2-3 g. During this time there is an
  • 245CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsincrease in enzyme supply within the intestin-al lumen. Specific activity of individual enzymesactually declines over the first week of life,although this is compensated for by rapidincrease in secretory cell numbers. Early cell dam-age, especially in the duodenum will greatlyimpair digestion.While corn-soybean meal diets are regard-ed as ideal for poultry, there is evidence thatdigestibility is sub-optimal for the young chick.Parsons and co-workers show reduced AMEn andamino acid digestion in chicks less than 7-10 dof age (Figure 5.1).Figure 5.1 Age effect on AMEn and lysinedigestion of a corn-soy diet (Batal andParsons, 2002)With some 10% reduction in nutrient diges-tion compared to expected values, it is obviousthat our conventional starter diets are not idealfor young chicks.The idea in formulating prestarter diets is tocorrect any such deficiency, and so hopefullyincrease early growth rate and/or improve uni-formity of such early growth. Two types ofprestarter diets are used for broiler chickens. Thefirst option is to use greater than normal levelsof nutrients while the alternate approach is to usemore highly digestible ingredients. Accordingto Figure 5.1, if we increase nutrient supply by10-15%, it should be possible to correct any defi-ciency in digestibility, and so realize expectedAMEn and amino acid utilization. A potentialproblem with this approach is the acceptance thatnutrients will not be optimally digested andthat such undigested nutrients will fuel micro-bial overgrowth.An alternate approach is to use more high-ly digestible ingredients, with little change in levelof nutrients. Such prestarter diets are going tobe very expensive, since alternative ingredi-ents are invariably more expensive than arecorn and soybean meal. Table 5.15 showsingredients that could be considered in formu-lating specialized prestarter diets.Using these ingredients, it is possible toachieve 190-200 g body weight at 7 d, comparedto 150-160 g with conventional corn-soybeandiets. This improved early growth rate contin-ues during most of the subsequent grow-outperiod (Table 5.16).In this study, male broilers were 34% heav-ier than standard, when a highly digestibleprestarter was fed for the first 4 d. Because ofthe ingredients used in formulation, this prestarterwas twice as expensive as the conventionalcorn-soy starter diet. As shown inTable 5.16, theadvantage of using the prestarter diminisheswith age, although birds were still significantlyheavier at 42 d. Interestingly, the highly digestibleprestarter had no effect on uniformity of body
  • 246 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsMax.% inclusionCereals Rice 40Corn 30Glucose (cerelose) 5Oat groats 5Proteins Fish meal 5Fish protein concentrate 5Blood plasma 10Casein 8Soybean meal 20Alfalfa 4Fats Vegetable oil 4Additives Wheat enzymeMannanoligosaccharideProbioticLactic acidTable 5.15 Potential ingredients for highly digestible prestarter dietsTable 5.16 Effect of using a highly digestible prestarter to 4 d of age, ongrowth of male broilersAge (days)4d 7 d 21 d 33d 42dPrestarter (0-4 d) 117 190 820 1900 2670Conventional 87 150 700 1700 2450Difference 34% 21% 17% 12% 9%(Swidersky 2002, unpublished data)weight at any time during the trial. In this andother studies, we have seen no advantage to usingso called ‘mini-pellets’ vs. using good qualityfine crumbles.c) Low nutrient dense dietsBy offering low protein, low energy diets (Table5.2) it is hoped to reduce feed costs. However,it is obvious that the birds will necessarily con-sume more of these diets and that birds may alsotake longer to reach market weight. These twofactors result in reduced feed efficiency.Surprisingly, broiler chickens seem to perform quitereasonably with low nutrient dense diets, andin certain situations these may prove to be themost economical program. If diets of low
  • 247CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsenergy level are fed, the broiler will eat more feed(Table 5.17).In this study, only the energy level waschanged and the broiler adjusted reasonably wellin an attempt to maintain constant energy intake.Diet energy from 3300 – 2700 kcal ME/kg hadno significant effect on body weight, and this sug-gests the bird is still eating for its energy need.Obviously these data on growth rate are con-founded with the intake of all nutrients other thanenergy. For example, birds offered the dietwith 2700 kcal ME/kg increased their protein intakein an attempt to meet energy needs. Usingthese same diets, but controlling feed intake ata constant level for all birds (Table 5.18) showsthat energy intake per se is a critical factor in affect-ing growth rate.With low energy diets, therefore, we can expectslightly reduced growth rate because ‘normal’energy intake is rarely achieved and this fact isthe basis for programs aimed at reducing earlygrowth rate. However, live body weight is oftennot the ‘end-point’ of consideration for broilerproduction, since carcass weight and carcass com-position are often important. From the point ofview of the processor or integrator, these cheap-er diets may be less attractive. Carcass weightand meat yield are often reduced, and this is asso-ciated with increased deposition of carcass fat,especially in the abdominal region. Low proteindiets are therefore less attractive when one con-siders feed cost/kg edible carcass or feed cost/kgedible meat. This consideration of carcass com-position leads to development of diets that max-imize lean meat yield.Another concept for feeding broilers is truelow nutrient dense diets, where all nutrient con-centrations are reduced (in practice energy andprotein/amino acids are most often the onlyTable 5.17 Performance of broilers fed diets of variable energy contentBody weight (g) Feed intake (g/bird)Diet ME25 d 49 d 0 – 25 d 25 – 49 d 0 – 49 d(kcal/kg)3300 1025 2812 1468 3003 44713100 1039 2780 1481 3620 51012900 977 2740 1497 3709 52062700 989 2752 1658 3927 5586
  • 248 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsBody weight (g)Feed intake: bodyweight gainDiet ME25 d 49 d 0 – 49 d(kcal/kg)3300 825a 2558ab 1.84c3100 818a 2599a 1.82c2900 790b 2439b 1.94b2700 764b 2303c 2.05aTable 5.18 Performance of broilers given fixed quantities of feedTable 5.19 Response of male broiler to low nutrient dense finisherdiets (35 – 49 d)Diet nutrients Body wt. (g) Feed intake (g) Carcass wt. (g) Breast wt. (g)ME CP 42 d 49 d 35 – 49 d 49 d 49 d(kcal/kg) (%)3210 18.0 2420 2948 2583 2184 4182890 16.2 2367 2921 2763 2107 4042570 14.4 2320 2879 2904 2063 4002250 12.6 2263 2913 3272 2088 4021925 10.8 2170 2913 3673 2073 3901605 9.0 2218 2892 4295 2038 378nutrients changed in such a program). Examplesof such diets are shown in Table 5.2. With thistype of feeding program, one can expect slow-er growth and inferior feed efficiency, althoughthis should not be associated with increased fatdeposition. Depending upon local economic con-ditions and the price of corn and fat, this type ofprogram can be economical.The older the broiler chicken, the greater itsability to adapt to very low nutrient dense diets.When broilers are offered very low nutrientdense diets in the finisher period, they adapt quitewell and growth rate is little affected (Table5.19). In the 42-49 d period broilers adjustedalmost perfectly to the low nutrient dense diets,and growth rate was maintained by adjustmentto feed intake. With the lowest nutrient densediet for example, which is at 50% of the controllevel of nutrients, broilers exactly doubled theirfeed intake. The reduction in carcass and breastweight is likely a reflection of reduced intake dur-ing the 35-42 d period of adjustment. It is notlikely that 50% diet dilution is economical, yetthe data in Table 5.19 indicates that the broileris not eating to physical capacity, and givensufficient time for adjustment, can at least dou-ble its feed intake. In the 42-49 d period, broil-ers fed the diet of lowest nutrient density con-sumed over 300 g feed each day.d) Growth restrictionBroilers are usually given unlimitedaccess to high nutrient dense diets, or have
  • 249CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programslimited access during brief periods of darkness.It is generally assumed that the faster the growthrate, the better the utilization of feed, sincemaintenance nutrient needs are minimizedFigures 5.2 and 5.3 indicate the increase ingenetic potential of the male broiler over the last30 years. It is obvious that there has beenmajor emphasis placed on early growth rate, sincethe modern broiler is now at least 300% heav-ier at 7 d compared to hatch weight, while 20years ago. This value was closest to 200%.However,fastinitialgrowthratecanleadtoman-agement problems, such as increased incidence ofmetabolic disorders. Also, if early growth rate canbe tempered without loss in weight-for-age at 42 –56 d, then there should be potential for improvedfeed efficiency due to reduced maintenance needs.This concept is often termed compensatory gain.Figure 5.2 Male Broiler Growth over the last 30 YearsFigure 5.3 Percentage weekly increase in growth of male broilers.
  • 250 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsIf growth rate is to be reduced, then basedon needs to optimize feed usage, nutrient restric-tion must occur early in the grow out period (Table5.20). As the bird gets older, a greater propor-tion of nutrients are used for maintenance andless is used for growth. Therefore, reducingnutrient intake in, say the first 7 d, will have lit-tle effect on feed efficiency, because so little feedis going towards maintenance (Table 5.20). At8 weeks of age, a feed restriction programwould be more costly, because with say a 20%restriction there would likely be no growth,because 80% of nutrients must go towardsmaintenance. Early feed restriction programs there-fore make sense from an energetic efficiency pointof view, and are the most advantageous in pro-grams aimed at reducing the incidence of meta-bolic disorders.Table 5.20. Proportion of energy forgrowth vs. maintenancebenefits of improved feed efficiency are notrealized. This situation often happens when theperiod of undernutrition is too prolonged, or thedegree of undernutrition is too severe. A peri-od of undernutrition can be achieved by phys-ical feed restriction, diet dilution or by limitingaccess time to feed as occurs with some light-ing programs (see section 5.5).In early studies, we fed broiler chickensconventional starter diets to 4 days of age andthen the same diet diluted with up to 55% ricehulls from 6 – 11 days. After this time, theconventional starter was reintroduced, followedby regular grower and finisher diets. Table 5.21indicates the amazing ability of the broilerchicken to compensate for this drastic reductionin nutrient intake from 6 – 11 days of age.When broilers are fed limited quantities offeed through to market age, there is a pre-dictable reduction in growth rate (Table 5.22).When there is continuous feed restriction, feedefficiency is compromised, since there is nopotential for compensatory growth. When feedrestriction is applied only during early growth,then there is potential for compensatory growth(Table 5.23).(%) DistributionWeek Maintenance Growth1 20 802 30 703 40 604 50 505 60 406 70 307 75 258 80 20If birds grow more slowly in the first few weeksand achieve normal market weight for age,then the difference in the growth curves shouldbe proportional to the reduction in mainte-nance energy needs. Figure 5.4 shows an exam-ple of compensatory growth in female broilers,achieved by feed restriction from 4 – 10 d of age.If regular market weight-for-age is notachieved due to early life undernutrition, thenFigure 5.4 Compensatory growth curveexhibited by female broilers.
  • 251CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsTable 5.21 Effect of diet dilution with rice hulls from 6 – 11 days of age, oncompensatory growth of male broiler chickensTreatment Body weight (g) Feed:gain ME/kg gain21 d 35 d 42 d 49 d 21 – 35 d 0 – 49 d 0 – 49 dControl 733 1790 2390 2890 1.84 2.01 6.2150% dilution 6-11 d 677 1790 2380 2950 1.70 1.93 5.90Table 5.22 Effect of 5 – 15% feed restriction from 1 – 42 d on broiler growthFeeding system Body wt. (g) F:G Mortality (%) Carcass wt. (g)Ad lib 2401a 1.68 5.6b 1849a5% restriction 2201b 1.76 4.5ab 1716b10% restriction 2063bc 1.75 3.2ab 1625bc15% restriction 1997c 1.78 1.1b 1518cAdapted from Zubair and Leeson (1994)Adapted from Urdaneta and Leeson (2002)Table 5.23 Effect of feeding at 90% of ad-lib intake for various times, ongrowth and mortality of male broilersBody wt. (g) F:G Mortality (%)35 d 49 d (0 – 49 d) Total SDS AscitesAd-lib 1744 2967 1.75 11.7 8.3 1.75 – 10 d11696 2931 1.71 8.3 4.9 1.75 – 15 d 1725 2934 1.69 8.3 3.3 1.75 – 20 d 1727 2959 1.70 8.3 4.9 1.75 – 25 d 1734 2947 1.69 8.3 4.9 1.75 – 30 d 1676 2875 1.69 5.1 1.6 0190% of ad-libWith 10% feed restriction from 5 up to 25 daysof age, there was minimal effect on growth rate,although feed efficiency was improved. Thisimprovement in feed utilization is a conse-quence of reduced mortality and reduced main-tenance need due to slower initial growth.When feed restriction occurs in the mid-periodof growth (14 – 28 d) there is little effect on mor-tality and growth compensation is rarely achieved.The results of early feed restriction or under-nutrition on carcass composition are quite vari-able. The early work of Plavnik and co-workerssuggested that feeding to maintenance energyneeds from 4 – 11 d of age resulted in a markedreduction in carcass fatness and especially yieldof the abdominal fat pad. The reasoning behindreduced fatness was limited early growth ofadipose cells. We have not been able to con-sistently duplicate these results. However, in moststudies, even when body weight compensationis achieved, there are often subtle reductions incarcass yield and especially breast meat yield.
  • 252 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsA consistent result of early undernutrition isreduction in the incidence of metabolic disor-ders and especially SDS. Although such conditionsare less problematic than 5 –10 years ago theyoften still represent the major cause of mortal-ity and condemnations, and any reduction in mor-tality is of economic importance. It seems asthough early undernutrition can be economicalas long as final weight-for-age is not compromised.A practical problem with diet dilution or feedrestriction, is deciding on levels of anticoccidi-als and other feed additives. With diet dilution,birds will eat much more feed. If for example,feed intake is doubled due to a 50% dilution,should the level of anticoccidial be reducedby 50%? With 50% feed restriction on theother hand, does there need to be an increasein concentration of these additives? This generalarea needs careful consideration, and results maywell vary with the chemical compounds underconsideration due to potential toxicity at criti-cal levels.Where broilers are necessarily grown athigh altitude or when birds are exposed to envi-ronmental temperatures of <15˚C, mortalitydue to ascites is inevitable. Although the breed-ing companies have selected against this condition,mortality of up to 10% is still common in malebroilers grown under these adverse conditions.In these situations, mild feed restriction through-out rearing is often economical, where the 2 –3 d longer growing period is offset by much lowermortality. Table 5.24 gives examples of mild andsevere restriction programs for male broilers. Feedrestriction can start as early as 3 – 4 d. Table 5.24shows cumulative feed intake expected in the firstweek together with subsequent intakes each 2d. The cumulative intake data takes into accountthe intake on the odd days not shown.e) Heavy broilers/roastersIn relation to its mature weight, the broilerchicken is marketed at a relatively young age. At49 – 56 d, growth rate of the male bird is still lin-ear, even though maximum growth rate occursat 5 – 6 weeks of age. Modern strains of malebroilers are still able to increase their bodyweight by 450-500 g each week through to 11or 12 weeks of age. The breast yield of these olderbirds is maintained, and so very heavy broilersor roasters find ready niche markets. The majorchallenge in growing these heavy birds is pre-venting high levels of mortality. In a recentstudy in which broilers were offered ad-lib feedto a mature weight of around 8 kg, 70% mortalityoccurred in the male birds.Perhaps the most important consideration ingrowing heavy broilers is development of spe-cialized feed programs that are not merely ‘con-tinuations’ of conventional 0 - 49 d broiler pro-grams. Table 5.3 provides examples of diets forheavy broilers grown to 60 – 70 d of age. Thereseems to be no need for high nutrient dense dietsat any time during growout, and even single stagelow-nutrient dense diets give reasonable results(Table 5.25).
  • 253CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsAge(d)StandardProgram(g/b)SevereRestriction(g/b)MildRestriction(g/b)DailyCumulativeDailyCumulativeDailyCumulative834184311713217410492744425246258125838749351553651472524614676649116816806960075636189185777750858012010010538591796988221091266981108105119324118149710613161151416261241743112153812216582813220031231776130191330139227712920301392187321472566137229914724763415428711462586154278136159318815128871593098381633512155319516334224016738441593510167375442171418416238331714094441734529164416117344394617648801674494176479048180523717648441805147Table 5.24 Examples of mild and severe feed restriction programs aimed atreducing incidence of metabolic disorders
  • 254 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsDietCP:ME(%:kcal/kg)BodywtF:GMortalityProteinEnergyRelativefeed(g)(%)efficiencyefficiencycost0-21d21–49d49–70d70d0–70d0–70dkg/kggainMcal/kggain(perkggain)20:310018:310016:32004193a2.26b19.20.39c7.1ab10020:310018:290016:28004088ab2.55a16.70.44b7.3ab10120:310018:290018:29004077ab2.48a16.70.45ab7.2ab9720:310020:310020:31004046ab2.40ab12.50.48a7.4a10518:290018:290018:29004260a2.45ab13.30.39c6.9b8516:280016:280016:28003753b2.45ab10.80.39c6.9b85Table 5.25 Growth of male broilers to 70 d when fed diets of varyingnutrient densityLeesonetal.2000
  • 255CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programsOnly with the single diet of 16% CP at 2800kcal ME/kg fed from 0 – 70 d was there reducedgrowth rate. In this study a single diet of 18% CPand 2800 kcal ME/kg appeared to be the most eco-nomical. Carcass yield and breast meat yield werenot different for all but the 16% CP diet. As shownin Table 5.25, mortality declined as nutrientdensity declined, yet even with just 16% CPand 2800 kcal ME/kg there was over 10% mor-tality to 70 d. Regardless of diet nutrient densi-ty, we have been unable to reduce mortalitybelow 10% without recourse to using mashdiets. It seems as though regardless of nutrientdensity, the broiler is able to increase its intakeof pelleted feed, and this undoubtedly con-tributes to high mortality. In order to reduce mor-tality this voracious appetite has to be controlled,and this can be achieved quite easily by offeringmash, rather than pelleted diets (Table 5.26).grow-out. At the same time mortality wasreduced from 20% to 4%, and so feed efficien-cy was actually superior with the mash diet. Withlow nutrient dense diets growth rate is more great-ly affected by using mash diets, where 70 dmales are some 5 – 6 d behind schedule.Although there are logistical problems when usingmash diets in mechanized feeders and microbialcontrol may be more difficult, adapting feedtexture seems to have great potential in growingvery heavy male broilers.f) Feed withdrawalThe current major concern about feed with-drawal relates to microbial contamination dur-ing processing. Regardless of withdrawal time,the gut will retain some digesta, and this can con-taminate birds during transportation as well asthe scald water during processing. Also if the intes-tines are broken during evisceration there ispotential for contamination.Withdrawing feed 6 – 8 hr prior to catchingseems to be optimum in terms of the bird clear-ing the upper digestive tract and so reducing thechance of contamination and for ease of processinggizzards. The bird will lose weight during feed with-drawal, and this will average about 10 g/hrdepending on age and liveweight. A significantportion of this loss will be excreta evacuation bythe birds. The loss in eviscerated carcass weightis closer to 2 g/hr, with equal losses to breast andleg/thigh meat. Feed withdrawal does not seemto have major effects on blood or liver glucose orglycogen levels, and this may be the reason for therebeing fewer post-mortem changes such as PSE asoccurs with pigs and sometimes turkeys.In addition to the concern about gut fill at pro-cessing, there is now interest in the pathogen loadof the digestive tract. The ceca have a veryhigh bacterial load and some of these will beTable 5.26 Performance of malebroilers to 70 d when fed mash vs.pellet dietsFeeding high nutrient dense mash vs. pelleteddiets reduced growth rate by about 300 g to 70d, which represents just 2 – 3 d prolongedBody Wt. F:G3Mortality70 d (g) (%)High density1Mash 3850 2.31 4.2Pellets 4166 2.44 20.0Low density2Mash 3571 2.45 5.8Pellets 4111 2.50 12.51 20% CP:3100 Kcal/kg ME, starter (0-21 d);18% CP:3100 Kcal/kg ME, grower (21-49 d);16% CP:3200 Kcal/kg ME, finisher (49-70 d).2 18% CP:2900 Kcal/kg ME (0-70 d)3 Adjusted for mortalityAdapted from Leeson et al. 2000
  • 256 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.2Feeding programspathogens of concern regarding food safety. Ina recent study, broilers were held on the litter orin crates for 24 hr without feed and surprising-ly there was little change in pH of the cecal con-tents or the bacterial populations. In fact, therewere few lactic acid producing bacteria, whichis a situation that allows pathogens to flourish.Excessively long periods of feed withdrawalseem to actually increase the pathogen load inthe upper digestive tract. With 12 hr+ of feed with-drawal, there are often high counts ofCampylobacter in the upper digestive tract, andagain this is associated with a reduction in the pres-ence of lactic acid producing organisms. Withprolonged feed withdrawal, broilers are more like-ly to eat litter and this seems to be the source ofthe pathogens. Because problems are oftencorrelated with reduced populations of Lactobacillitype organisms, there is interest in offering birdslactic acid in the water during feed withdrawal.Water with 0.5% lactic acid has been shown toreduce the incidence of Salmonella andCampylobacter in the upper digestive tract by atleast 80%.A more serious concern arises if birds are acci-dentally without feed for 12 hr+ in the 2 - 3 d priorto feed withdrawal. Broilers again are seen toeat litter, drink excessive amounts of water andso produce very wet manure. Both sexes havebeen observed to lose up to 100 g body weightafter 18 hr of no feed being available. Coupledwith a potential growth of 70 – 80g in this peri-od, means that birds are at least 170 g behindexpected standard weight. There is some com-pensation when feed is reintroduced, with birdseating up to 300 g in the first 24 hr following refeed-ing. Depending upon time of feed outage rel-ative to eventual withdrawal, means the bird canhave excessive quantities of digesta throughoutthe intestine.The other aspect of late cycle broiler nutri-tion is potential for reducing nutrient levels,and particularly the inclusion of trace minerals,vitamins and various feed additives. Broilers seemmost responsive to total withdrawal of vita-mins, than to removal of trace minerals (Table 5.27).Table 5.27 Broiler growth and F:Gfrom 42 – 49 d in response to vitaminand trace mineral supplementationVitamins Minerals Growth(g) F:G+ + 564 2.41+ - 562 2.40- + 537 2.58- - 481 2.85Adapted from Maiarka et al. 2002Feed efficiency and growth are both com-promised by total withdrawal of vitamins from thefeed, and this effect is accentuated when trace min-erals are also removed. There is also concern withhigher mortality when vitamins and minerals arewithdrawn under heat stress conditions (Table 5.28).Table 5.28 Removal of vitamins and trace minerals fromheat-stressed (24-35˚C) broilersVitamins Minerals 35-49 d wt gain (g) F:G Mortality (%)+ + 1280a 2.66a 9.6- - 1240b 2.86b 13.2Adapted from Teeter (1994)
  • 257CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.3Assessing growth and efficiencyThere are inconsistent reports on the effectsof removing anticoccidials and growth promot-ers during the last 5 – 10 d. This situation prob-ably relates to health status of individual flocks,and level of biosecurity etc. Since many ionophoreanticoccidials seem to influence proliferation ofnecrotic enteritis, then if growth promoters are notused in a feeding program, removal of ionophoresfor an extended period can compromise birdhealth and performance.5.3 Assessing growth and efficiencya) Broiler growthWith yearly increases in genetic poten-tial, standards for growth rate becomequickly dated. Over the past 20years, there has been at least an annual increaseof 25g in body weight at 42 d of age, and in cer-tain periods we have seen gains of 30 – 50 g eachyear. This growth rate is fueled by feed intake. Withincreasing growth rate, there has been everincreasing efficiency of gain. It seems unlikely thatthe bird has increased its ability to digest protein,amino acids and energy from commonly used ingre-dients, and so, change in efficiency is simply a con-sequence of reduced maintenance need. Whilethere has to be a biological limit to growth rate,it is likely that management concerns will bethe issue that imposes a lower limit on market age.For example, there is now concern on the ‘matu-rity’ of the skeleton of female broilers destined forthe 1.75 kg market, where market age could be30 d or less within the next 5 – 7 years.Factors influencing feed intake have the sin-gle largest effect on growth rate. Birds eat morein cooler environments and vice-versa, althoughthis situation is confounded with humidity,acclimatization and stocking density. As a gen-eralization, maintenance energy requirementincreases by about 3% for each 1˚C decline inenvironmental temperature below 30˚C. Ifmaintenance represents 60% of total energyneeds, then feed intake is expected to change byabout 2% for each 1˚C change in temperature.Under commercial conditions stocking densityis going to be one of the major variables affect-ing growth and feed intake (Table 5.29).With a higher stocking density, birds eat lessfeed, presumably due to greater competition at thefixed number of feeders. However this slightlyreduced growth is often accepted since there isgreater liveweight production from the broiler house.It is generally assumed that broilers hatched fromlargereggswillgrowmorequicklythanthosehatchedfrom small eggs. As broiler breeders get older, theyproduce larger eggs and so broiler growth is oftencorrelated with breeder age. In a recent study, wehatched broilers from breeders at 28, 38, 48 and58 weeks of age, and grew them under standardconditions within the same broiler facility.Interestingly, the growth of female broilers was mosthighly correlated with breeder age (Table 5.30).Table 5.29 Influence of stocking density on broiler performanceDensity (birds/m2) 49 d B.wt. (g) Feed intake (g) kg/m210.5 2337b 4973b 23.4a13.5 2261a 4803a 28.9bAdapted from Puron et al. (1997)
  • 258 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.3Assessing growth and efficiencyThere was a significant linear trend over timeand from these data we can predict that bothliveweight and carcass weight will be influencedby differences in egg weight that result as a con-sequence of increased breeder age (Table 5.31).Larger eggs usually have larger yolks, and itis often suggested that yolk size is the factorinfluencing growth as shown inTables 5.30 and5.31. However, experimental removal of yolk mate-rial from an incubating egg has little effect on chicksize at hatch. Removal of albumen does howevercause reduction in chick size, and so perhaps itis the albumen content of large eggs that influenceschick size and subsequent broiler growth.However, a confounding effect is that yolk size doesinfluence the size of the residual yolk at hatch, andthis may have some effect on early growth ifchick placement is delayed.While growth rate is of prime economicimportance, uniformity of growth is becoming ofincreasing concern. With mechanized feeding sys-tems, small birds have difficulty reaching feed andwater as they are raised to best suit the flockmean growth rate. The current lack of uniformityhowever, seems to start as early as the first weekof age. Even in well-managed flocks, there is skeweddistribution of that body weight, with a prepon-derance of smaller chicks (Figure 5.5).Table 5.30 Broiler growth characteristics as affected by breeder ageBreeder age (wks)28 38 48 58Male broiler:49 d live wt. (g) 3186 3249 3221 32730 – 49 d F:G 1.88 1.80 1.86 1.9649 d carcass wt. (g) 2498 2562 2610 -Deboned breast wt. (g) 587 605 607 -Female broiler:49 d live wt. (g) 2595 2633 2667 27120 – 49 d F:G 2.11 1.95 2.01 2.0049 d carcass wt. (g) 1972 2028 2118 -Deboned breast wt. (g) 462 468 492 -Table 5.31. Change in broiler live weight and carcass weight per1 g increase in breeder egg weightLive weight Carcass weightMale broiler (49 d) + 5 g/g egg wt. +11 g/g egg wt.Female broiler (49 d) + 8 g/g egg wt. +14 g/g egg wt.Fig. 5.5 Distribution of chick weight in awell managed broiler flock.
  • 259CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.3Assessing growth and efficiencyWhen specific health problems occur, suchas ‘feed passage’ or ‘stunting-runting syndrome’then the weight distribution is heavily biasedtowards small chicks (Figure 5.6).There is a suggestion that yield of yolk andalbumen is not highly correlated with egg size.b) Feed efficiencyA measure of the efficiency of feed utiliza-tion is obviously of economic importance.Classical feed efficiency is calculated as feed intake÷ body weight, while the converse measure ofbody weight ÷ feed intake is often used inEurope. Feed is used by the bird for two basicreasons, namely for growth and for mainte-nance. In young birds most feed is used for growth(80%) and little is used for maintenance (20%)and so efficiency is very good. Over time effi-ciency deteriorates because the broiler has an ever-increasing body mass to maintain. Table 5.32shows expected changes in classical feed efficiencyrelated to age of bird.These data suggest that at around 1.75 kg bodyweight, feed conversion will increase by 0.01 unitsfor each day of growth or that conversion willincrease by 0.013 units for each 100 g increasein market weight. As the bird gets heavier,these units of change increase (Table 5.32).Over the years we have seen a steady declinein classical feed conversion from around 2.2 inthe early 1960’s to 1.75 today under certain sit-uations. This continually improving situation isdue to improved genetic potential, and the factthat more feed is directed towards growth (andless for maintenance) as days to market decline.Body weight is a consequence of feed intake,and so feed intake tends to be the main variablein assessing feed efficiency. Historically broilerswere grown to 45 ± 3 days and fed diets with ener-gy levels that were standardized across the indus-try. Under these conditions, the measure of clas-sical feed efficiency is useful, and should relatedirectly to economics of production. Today, theFig. 5.6 Distribution of chick weight in afloor unit with obvious health problems.In most flocks today there is a skewed dis-tribution of 7 d body weight with the unevennesscontributed by 12 – 15% of small chicks. Thistype of uneven distribution occurs even with hatch-es of eggs from individual breeder flocks. Thisearly loss in uniformity influences subsequent flockcharacteristics.Each 1 g change in 7 d body weight alters18 d body weight by 3 g (i.e. a chick that is 30g underweight at 7 d will be 90 g underweightat 18 d. By 49 d the correlation is 1 g @ 7 d5 g @ 49 d.It is well known that chick size is influ-enced by size of the hatching egg. A range of eggweights are set, but usually the extremely smalland very large eggs are discarded. The currentvariance therefore occurs within the range of set-table eggs. The effects seen in Figures 5.5 and5.6 are made worse when broiler flocks arederived from a number of different age breed-er flocks. However the problem is not fullyresolved when eggs are graded prior to setting.
  • 260 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.3Assessing growth and efficiencyWeight Change in F:G per Daily change incategory 100 g body wt. F:G1.75 kg 0.013 0.0102.50 kg 0.015 0.0143.50 kg 0.017 0.016Table 5.32 Adjustments to feed efficiency based on body weight or ageTable 5.33 Performance and economic considerations of feeding broilersdiets of varying nutrient densityMean diet energy1Relative feed 45 d male body wtFeed:GainRelative feed(kcal/kg) cost (kg) cost/bird3000 100 2.7 2.10 1003100 105 2.7 2.00 993200 114 2.7 1.90 1023300 123 2.7 1.80 1051 all other nutrients tied to energyindustry grows birds over a vast range of ages/mar-ket weights, and there is now considerable vari-ation in diet nutrient density. The fact that a clas-sical feed efficiency of 1.9 is achieved with a certainflock, has to be qualified in terms of sex ofbird, market age and diet nutrient density. Thelowest numerical feed efficiency may thereforenot be the most economical (Table 5.33).As nutrient density increases, feed conversionpredictably declines. However, body weight isunaffected. Since high nutrient dense diets costmore, the feed cost per bird will only be reducedif birds eat correspondingly less feed. In thisexample, the most economic situation ariseswith mean energy level at 3100 kcal/kg, even thoughclassical feed efficiency is not optimized. Socalled ‘broiler growth models’ today should be ableto identify the most profitable diet, given feed price,broiler prices, expected performance, etc. The dietis ultimately least-costed in the traditional way, butthis prior selection is often referred to as ‘maxi-mum profit formulation”. A more useful meas-ure of feed utilization is efficiency of energy use.When efficiency is based on energy, the energylevel of the diet is irrelevant, and so this major vari-able is resolved. Table 5.34 indicates expectedenergy efficiency in male and female broilers.Table 5.34 Energy efficiency inbroilersEnergy intakeMcal/kg gainMarket age (d) Male Female35 - 5.3542 5.39 5.8349 5.84 6.2856 6.30 6.8063 6.63 -Assesssment of efficiency can be taken furtherthan the level of individual bird production to accom-modate such factors as feed cost, carcass yield andstocking density. In the future we may evenhave to consider manure management in ourassessment of production criteria (Table 5.35)
  • 261CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.4Nutrition and environmental temperatureCriteria Measurement CommentsEnergy efficiency Energy intake: weight gain Energy is the most expensive nutrient, andso this value is important. To some extent,values are independent of feed intake.Feed cost Feed cost: weight gain Takes into account the fact that the mostexpensive diet is not always the most profitable.Carcass yield Energy intake: carcass wt. Takes into account the fact that birds of similarEnergy intake: breast meat weight may not always yield the same amountFeed cost: carcass wt. of edible carcass.Feed cost:breast meatBird placement Feed cost/kg bird/sq. meter Optimizes the use of the building e.g.: higherfloor space/yr nutrient dense diets give faster growth rate,Economic return/sq. meter therefore more crops per year.floor space/yrEnvironment Nitrogen excretion/bird Future considerations for environmentalPhosphorus excretion/bird stewardship.Table 5.35 Future considerations in assessment of efficiency of feed usage inbroiler production5.4 Nutrition and environmental temperaturea) Bird responseMost broiler farms will be subjected toheat stress conditions for at least partof the year. The terms heat stress orheat distress are used to describe the conditionsthat affect broilers in hot climates. Becausebirds must use evaporative cooling (panting) tolose heat at high temperatures, humidity of theair also becomes critical. Consequently, a com-bination of high temperature and humidity is muchmore stressful to birds than are situations ofhigh temperature coupled with low humidity.Other environmental factors, such as air speedand air movement, also become important. Itis also becoming clear that adaptation to heat stresscan markedly influence broiler growth. Forexample, broilers can tolerate constant envi-ronmental temperatures of 38˚C (100˚F) andperform reasonably well. On the other hand, mostbroilers are stressed at 38˚C (100˚F) when fluc-tuating day/night temperatures exist. In the fol-lowing discussion, it is assumed that fluctuatingconditions occur, because these are more com-mon and certainly more stressful to the bird.A market weight broiler produces about 5 –10 kcals energy each hour. This heat, which isgenerated by normal processes in the body,must be lost to the environment by convec-tion, conduction and/or evaporation. The broil-er will conduct heat from its body to whateverit touches, assuming that these objects (litter, etc)are at a lower temperature than is body temperature(41˚C). The broiler will also convect heat awayfrom its body, through circulating air, again
  • 262 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.4Nutrition and environmental temperatureassuming that the air temperature is less than bodytemperature. The balance of heat production andheat loss is such that body temperature is main-tained at around 41˚C.Interestingly, under thermoneutral condi-tions, body temperature has little influence onperformance. However, as body temperature getsmuch above 41.5˚C for broilers under heat dis-tress, then there is good correlation between risein body temperature and decrease in perform-ance. Much above 42˚C mortality is inevitable.In order to dissipate more and more heat, evap-orative cooling has to be increased. Water bal-ance and evaporative water loss of the broiler undernon-heat stress conditions changes over time.In the first week of life, about 35% of total waterintake is excreted through evaporative losses.By seven weeks of age, this amount increases to70%. This increased emphasis on evaporative waterloss with age is one of the reasons why the olderbird has more problems in balancing its heatload during heat stress, because evaporative sys-tems are so heavily relied upon under normal con-ditions. The bird does not have sweat glands, andso at high temperatures, evaporative cooling is theonly effective means of greatly increasing heat loss.As the bird pants under heat stress conditions, watervapour is lost in the exhaled air with each breath.Some heat is lost in raising the temperature ofexhaled water vapour, from ambient (drinking watertemperature) to that of body temperature. However,this heat loss is insignificant in relation to the heatloss needed to evaporate water. About 0.5 kcalsof energy are lost for each gram of water evapo-rated during breathing. A market weight broilerproducing 200 kcals heat energy per day needsalmost 400 grams water loss by evaporation.This is an extreme case, because other heat dis-sipation mechanisms are also active and the birdalso loses some water via the urine. However, thissimple calculation does emphasize the need forincreased water intake during excessive heatstress. Unfortunately, the situation is made worseby the fact that cooling mechanisms, such aspanting, generate significant quantities of body heat.In fact, it has been calculated that panting intro-duces an extra 20 – 25% heat load on the bird.The major heat load in the body arises fromthe digestion and metabolism of food. A simpleway of avoiding heat stress, therefore, is toremove feed. Under less stressful conditions, weare interested in maintaining growth rate closeto genetic potential, and this means feeding atclose to normal physical intake. However, dif-ferent nutrients produce different quantities ofheat during metabolism. For example, themetabolism of fat is most efficient, and metab-olism of protein is least efficient in this respect.Unfortunately, the metabolism of all nutrient isfar from being 100% efficient, and so even fordietary fats, there will be some heat evolved dur-ing normal metabolism.This means that diet formulation can be usedto advantage in trying to minimize heat load.Unfortunately, the major heat load is going to bea consequence of feed intake per se (Table 5.36).
  • 263CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.4Nutrition and environmental temperatureFeed/day0 g 50 g 100 g 150 g24˚C environment:Heat production 192 204 212 236Sensible loss 160 168 180 192Evaporative loss 44 40 44 48Balance -12 -4 -12 -435˚C environment:Heat production 196 220 240 248Sensible loss 88 112 96 132Evaporative loss 72 88 92 96Balance 36 20 52 20Table 5.36 Energy balance of a 2 kg broiler (kcal/bird)Adapted from Wiernusz and Teeter, (1993)Table 5.37 Male broiler feed intake at 15-30˚CMale broiler (g feed/bird/day)Age (d) 15˚C 20˚C 25˚C 30˚C14 78 72 65 5921 120 110 100 9028 168 154 140 12635 204 187 170 15342 240 220 200 18049 264 242 220 194At 24˚C, the broiler is in near perfect balance,with heat production being similar to heat dis-sipation. At 35˚C, the broiler is in severe pos-itive energy balance, where heat dissipation can-not match the heat load generated by feedmetabolism. In this situation, the broiler has toquickly correct the balance, and the easiestsolution is to reduce heat load by voluntary reduc-tion in feed intake. Such changes in feed intakewill occur very quickly, certainly within hours,because the birds must maintain the balance atclose to zero. Table 5.37 shows the expectedfeed intake of male broilers housed at varyingenvironmental temperatures.Broilers will acclimate to warm conditionsand can perform reasonably well at constant tem-peratures as high as 36˚C. However, if broilersare normally held at 25˚C a sudden change intemperature to 36˚C may prove fatal, and willcertainly influence growth rate. There is someresearch to suggest that intentionally subjectingyoung broiler chicks to high temperaturesenables them to better withstand subsequent heatstress conditions when they are older. Such accli-mated birds seem to show less of an increase intheir core body temperature when later (up to 4– 6 weeks) exposed to high temperatures. Heatacclimatized birds do seem to drink more
  • 264 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.4Nutrition and environmental temperaturewater and eat more feed under heat stressconditions. Therefore, because acclimatizedbirds are prepared to eat more feed, this inducesa greater heat load, so this can counterbalancethe effect of prior acclimatization. For prioracclimatization to be useful therefore, it seemsnecessary to combine this with some degree offeed restriction if maximum benefits are to beachieved. It is likely that the confounding effectof ‘increased’ feed intake by acclimatized birdsis responsible for variation in results of trials andfield studies of early life heat stress acclimatization.The general growth response of male broil-ers of 500-2500 g body weight to a range of envi-ronmental temperatures is eloquently shownby the data of May et al. (1998).500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500Beginning weight, gAdapted from May et al, 19981009590858075706560Gain/day,g23C25C27C29C31CFig. 5.7 Effect of environmental temperature on daily growth of male broilers.
  • 265CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.4Nutrition and environmental temperatureb) Potential nutritionalinterventionNutritional intervention to limit the effects ofheat stress include change in levels of nutrients,change in ingredient composition, time of feed-ing and in extreme situations, removal of feed.In terms of nutrients and ingredients, thelevel of crude protein should be minimizedand the level of supplemental fat increased to prac-tical maximums. It is usually not economical touse constraints for crude protein that increase over-all diet cost by more than 5 – 8%. In general,economical reductions in crude protein level arein the order of 2 – 3% (e.g. 22 20% CP). Amajor problem related to metabolism of proteinsis the heat increment related to transamination(rearrangement), deamination (breakdown), andexcretion of nitrogen as uric acid in the urine.It follows therefore, that amino acid balance with-in a diet is as important as the total level of crudeprotein. With 4% excess CP in a diet (due to usingpoorer quality ingredients, while trying to achievethe level of limiting amino acids), the bird’sheat output is increased by 8 – 10%. Protein qual-ity, therefore, becomes critical in these diets.Because energy intake is often the limitingfactor to growth during heat stress, it is tempt-ing to recommend high-energy diets that con-tain high levels of supplemental fats. Unfortunately,the broiler is still eating to its energy requirement,so simply increasing the energy concentrationof a diet does not ensure a major increase in ener-gy intake. Broilers will tend to eat more ener-gy with higher energy diets, so it can be usefulto consider such a formulation change althoughin itself this change will not correct growthdepression.Acid:base (electrolyte) balance in the broil-er is altered at high temperatures because of theassociated effect of increased carbon dioxide lossdue to panting. There has been considerableresearch in this area, investigating the potentialof maintaining normal anion:cation balanceduring heat-stress. However, the general con-sensus at this time is that acid:base balanceper se is not a major factor influencing eithergrowth rate or survival of broilers in heat stressconditions. This is not to say that adding elec-trolytes to the feed or water is ineffective, rather,their mode of action may be other than by alter-ing or maintaining acid:base balance.It seems as though the benefit of addingelectrolytes to the feed or water is simply to increasethe bird’s water intake which in turn fuels evap-orative cooling. Various studies have been con-ducted in which broilers have been given min-eral supplements in the water, producing arange of anion-cation balance. For example, both(NH4)2SO4 and NaHCO3 are effective water sup-plements used in trying to combat heat stress, yettheir ion balances are very different. The ben-eficial effects of these supplements seem moreclosely correlated with their effects on water intake.Adding a mineral salt, such as KCl increas-es water intake and evaporative heat loss ofthe bird. A common treatment and/or preven-tative measure during heat stress, is to add NaClat 0.5% to the birds’ drinking water. For broil-ers eating 100 g of feed containing 0.2% Na (0.5%salt) each day, means that birds consume 30%of their daily Na from feed and 70% of Nafrom treated water. The level of water supple-mentation should therefore, represent a signif-icant increase in the birds’ Na (or K) intake.Maintaining or stimulating water intake seemsto be a key factor in maintaining growth rate ofolder broilers subjected to hot environments. Inthis regard, the use of drinker equipment is a fac-tor (Table 5.38)
  • 266 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.4Nutrition and environmental temperatureBirds were always heaviest when using the opentrough drinkers, and nipple height also influ-enced growth. At 30˚C, the difference in growthfor birds using open trough vs. nipples is greatly ac-centuated. The actual reason behind better growthwith open trough drinkers is not fully resolved. Itis likely that birds drink more water, but they alsomay immerse their wattles in open trough drinkersand this aids evaporative cooling. However,nipple drinkers are often preferred, since litter con-dition is easier to manage. Nipple height is alsocritical for optimum water intake. As a rule-of-thumb nipple height should be at 10 cm at dayof age, and then increase by 5 cm per week.In situations when broiler mortality is the mainconcern, the best recourse is to remove feed, soas to reduce heat load on the bird. The time ofpeak mortality due to heat stress is usually in lateafternoon, which does not always coincide withthe hottest time of the day. The late afternoon peri-od does, however, coincide with the time of peakheat of digestion and metabolism for birds eat-ing substantial quantities of feed in the early-midmorning period. Consequently, it is often rec-ommended to withdraw feed prior to antici-pated time of peak environmental temperature,to minimize the heat load of the bird.A common management scenario is toremove feed at 10 a.m. and re-feed at 5 p.m. Sucha system assumes having some supplemental lightsso that they can eat at cooler times of the day.Table 5.39 summarizes recommendations for feedformulation and feeding management for heatstressed broilers.Table 5.38 Broiler growth at 25˚C vs 30˚C using open trough or nippledrinkers (g/bird)Water system 25˚C 30˚C28 d 49 d 28 d 49 dOpen trough 1424a 3275a 1349d 2632dLow nipple 1411b 3199b 1336e 2395eMedium nipple 1400b 3164b 1333e 2300fHigh nipple 1385c 2995c 1303f 2104gAdapted from Lott et al. (2001)
  • 267CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.5Nutrition and lighting programsStrategy ActivityFeed formulation 1. Reduce crude protein by 2 – 3%.2. Maintain levels of Meth + Cys, Lysine and Threonine.3. Increase diet energy by direct substitution of 2% fat for 2% of major cereal.4. Add 250 mg Vitamin C/kg diet.5. Use only highly digestible ingredients.6. Select appropriate anticoccidials.Feed management 1. Withdraw feed 10 a.m. – 5 p.m.2. Ensure adequate feeder space and drinkers.3. Manage nipple height according to bird age.4. Add 0.5% salt to the drinking water.5. Keep drinking water as cool as possible.Bird management 1. Increase air flow at bird level.2. Maintain litter quality.3. Use lower stocking density.4. Do not disturb birds at time of peak heat distressTable 5.39 Strategies for reducing the impact of heat stressLighting programs are now used routine-ly in growing broilers, and in someEuropean countries it is mandatory to givebroilers a period of darkness. An extendedperiod of darkness each day seems to reduce theincidence of SDS and leg problems, and inwinter months may help to control ascites in heav-ier males. The major advantage to these lightprograms is a period of rest and/or tempering ofgrowth rate, which both seem to improve livability.There may also be some subtle effects of lightthat influence the bird’s metabolism. In addi-tion to influencing sex hormone output inmature birds, light also affects the pineal glandat the base of the brain, and this is responsiblefor production of another hormone, namelymelatonin. Melatonin is produced during longperiods of darkness, and is the hormone respon-sible for shutting down the reproductive systemin wild birds during the fall. Broilers subjectedto long periods of darkness will produce moremelatonin, and this is thought to be involved insome way with the beneficial effects of such lightprograms. Adding synthetic melatonin to the dietof broilers does cause a calming effect, but doesnot seem to have any influence on mortality. Themain feature of a lighting program for an imma-ture bird such as the broiler is simply that duringdarkness, birds are more reluctant to eat, and sothis controls growth rate.If one visits 20 different broiler farms, it is pos-sible to see 20 different lighting programs.However, all have the common feature of impos-ing a long period of darkness that lasts for at least8 hours. Differences occur in the ages at whichthe light restriction is initiated and the pattern ofreturning to a longer daylength.5.5. Nutrition and lighting programs
  • 268 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.5Nutrition and lighting programsBroilers are reluctant to eat in the dark, andso the major ‘activity’ during darkness is simplysitting. However, some birds will attempt to eatand drink at this time and this disturbance cancause scratching and downgrading of the carcass.Such problems, which lead to infection, will bemore prevalent with high stocking densities,and when longer (> 8 hr) periods of darkness areused after 22 – 25 days of age. The shorter theperiod of light the greater the reduction in feedintake, and so the greater the control overgrowth. If birds are kept on constant short daysto 49 d (i.e. no compensatory step-up) thengrowth rate will be reduced. On average, for each1 hour of darkness, broiler growth will bereduced by 20 g. Therfore, keeping birds on con-stant 12 hr vs. constant 24 hr from 1 – 49 d, willreduce growth by about 240 g. However, thereduced growth will be accompanied by reducedmortality. In practice, it is more common to step-up the hours of light after 2 – 3 weeks, and thisallows for growth compensation.There is little doubt that short-day lighting pro-grams are most beneficial for male broilers.They are particularly successful for males grownto heavier weights and less useful (and perhapsdetrimental) to lightweight females. Table 5.40shows typical research results for 49 d malebroilers.While broilers will be smaller during theperiod of extended darkness, they are able to com-pensate by 49 d. Mortality is reduced, and espe-cially the incidence of leg disorders. Although oftennot statistically significant, there is usually aslight reduction in breast meat yield for broilerson reduced daylength as shown in Table 5.40.As previously mentioned, there are manydifferent light programs, and selection depends onsex of bird, diet nutrient density, pellet quality, mar-ket weight and whether or not blackout or open-sided housing is used. In addition, the extendedperiod of darkness may be less severe or shortenedsomewhat in the summer vs. winter, since hot weath-er also reduces growth rate, and the two combinedcan cause delay in grow-out. Table 5.41 summarizesthe factors influencing choice of light program. Table5.42 shows examples of lighting programs takingthese factors (Table 5.41) into account.Light intensity can also influence bird activ-ity and feed intake. The higher the intensity,usually the greater the bird activity and so this canlead to more maintenance costs, and poorerfeed efficiency. Higher body weights and betterfeed efficiency have been recorded at 5 vs. 150lux. Light intensity after brooding should be at 2– 5 lux, which is the minimal intensity for the stock-person to adequately inspect birds and equipment.Table 5.40 Effect of step-down, step-up lighting for male broilersTreatment49 d B. wt.F:GMortality Leg problems Breast yield(kg) (%) (%) (%)23L:1D 2.86 1.85 8.5 20.0 24.8Step-down:Step-up 2.82 1.86 3.0 9.5 24.2Adapted from Renden et al. (1996)
  • 269CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.5Nutrition and lighting programsParameter Consideration for light:dark schedule1. Strain of bird Earlier fast growth means need for earlier introduction ofreduced daylength.2. Diet nutrient density With higher nutrient density there is more benefit to a longerand more extended period of darkness.3. Pellet quality The better the pellet quality, the greater the need for light control.4. Market weight For older, heavier birds, delay step-up schedule.5. Open sided vs. blackout housing Open-sided housing dictates the maximum period of darkness.With blackout housing there is absolute control over duration andintensity of light period.6. Season Less severe programs in hot weather because growth-rate isalready reduced.Table 5.41 Factors influencing choice of light programTable 5.42 Examples of light programs for birds grown to 42 or 56 d in eithersummer or winter, in open or blackout houses (hours light/day)Age (d) Black out Open-sidedSummer Winter Summer Winter42 d 56 d 42 d 56 d 42 d 56 d 42 d 56 d0 – 5 23 23 23 23 23 23 23 235 – 8 14 12 12 10 Natural Natural Natural Natural8 - 12 14 12 12 10 Natural Natural Natural Natural12 – 16 14 12 14 12 14 Natural Natural Natural16 – 20 16 14 14 12 16 14 14 Natural20 – 24 16 14 16 14 16 14 14 1424 – 28 18 16 16 14 18 16 16 1428 – 32 18 16 18 16 18 16 16 1632 – 36 18 16 18 16 18 16 16 1636 – 40 18 18 18 16 18 18 18 1640 – 44 18 18 18 18 18 18 18 1644 – 48 - 18 - 18 - 18 18 1848 – 52 - 18 - 18 - 18 - 1852 - 56 - 18 - 18 - 18 - 18
  • 270 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.6Nutrition and gut healthThere is little information available on theeffect of color (wavelength) of light on broilers. Itseems as though wavelengths above 550 nm (pur-ple-orange-red colors) cause reduced growth rate.On the other hand, shorter wavelengths, at the blue-green end of the spectrum produce increasedgrowth rate. These effects are quite subtle (5% max-imum) yet it is conceivable that light color couldbe used to either slow down or speed up growthrate at specific times during grow-out. Currentlybulbs that produce light at a specific wavelengthe.g. red or green, are very expensive.Intermittent lighting is another option formanaging broilers, although unlike the step-down step-up programs described previously, thissystem is intended to stimulate growth rate.Short cycles of light and dark are repeatedthroughout the day, the most common being eightcycles of 1 hr light:2 hrs darkness. The idea behindthe program is that birds will eat during thelight period and then sit down during the 2 hrdark cycle and be ready to eat again whenlights return. Obviously adequate feeder spaceis essential with the program and it is onlyviable with black-out housing (Table 5.43).With intermittent lighting, it is assumed thatenergy efficiency will be improved, since birdsare inactive for 66% of the day. In the studydetailed in Table 5.43, there was greater overallheat production for birds on the 1L:2D pro-gram, and so increased growth was simply a fac-tor of increased feed intake.5.6 Nutrition and gut healthBacterial and parasitic infections of thegastro-intestinal tract are an ever presentthreat to broilers grown on litter floors. Themicrobial status of the tract is kept in balance byuse of anticoccidials in conjunction with so-called growth promoters. The mode of action ofgrowth promoters has never really been fullyexplained, yet when they are excluded from thediet, bacterial overgrowth can occur. The role ofgut health in broiler performance has suddenlybecome topical because of current or pending leg-islation concerning use of antibiotics in poultrydiets. With the current pressure on antibiotic usein animal diets, it seems less likely that newproducts will be developed, and so one sce-nario is that at most, only currently registered prod-ucts will be available.We are greatly hampered in the study ofgut health by not knowing, with any great pre-cision, the normal microflora present in healthybirds. It has been suggested that, at best, con-ventional culture techniques are isolating 50%of the species of bacteria present in the gut. Newertechniques involving DNA fingerprinting ofmicrobes may give us a better understanding ofthe complexity of the microflora, and in partic-ular, how they change in response to various dietTable 5.43 Male broiler growth with intermittent vs. continuous lightingBody weight (g)Lighting 21 d 42 d 56 d 0 – 56 d F:GContinuous 717 2393 3459 2.071 hr L: 2 hr D 696 2616 3637 2.03NS * ** NSAdapted from Ohtani and Leeson (2000)
  • 271CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.6Nutrition and gut healthtreatments. On the other hand, we are awareof the major pathogens, and as a starting pointin maintaining gut health, it is more promisingin the short-term to concentrate on their control.The chick hatches with a gut virtually devoidof microbes, and so early colonizers tend to pre-dominate quite quickly. The enzyme system andabsorptive capacity of the newly hatched chickis also quite immature. As previously describedin section 5.2b, selection of ingredients eaten bythe chick in the first few days of life will undoubt-edly influence microbial growth and perhapsmicrobial species. Any undigested nutrientswill be available to fuel microbial growth in thelower intestine and ceca – if these happen toinclude pathogens, then the chick will be dis-advantaged. The ‘normal’ gut microflora devel-ops quite quickly, and so microbial numbers andspecies present on the hatching tray, in thehatchery, during delivery, and the first few daysat the farm will likely dictate early colonization.While ‘dirty-shelled’ eggs may hatch quite well,they do provide a major source of microbial col-onization for the hatchling.The Nurmi concept of manipulating gutmicrobes relies on early introduction of non-path-ogenic microbes. Ideally, these microbes will helpprevent subsequent pathogenic colonizations.Today, there is not an ideal culture for such a com-petitive exclusion product, which is again afactor of our not knowing the profile of a healthymicroflora. In the past, undefined cultures havebeen used with reasonable success, but now reg-ulatory agencies are insisting on dosing birds onlywith accurately defined cultures. It seems thatif competitive exclusion (CE) is to be successful,cultures must be administered as soon as pos-sible, and time of placement at the farm may betoo late. However CE is undoubtedly going tobe one of the management tools routinely usedin broiler production.Rapid early development of the intestinalepithelium is also another prerequisite for nor-mal digestion. The villi and microvilli growrapidly in the first few days, and any delay in thisprocess is going to reduce nutrient uptake.Presence of pathogens, mycotoxins and ani-mal and plant toxins will all delay microvilli devel-opment. Selection of highly digestible ingredi-ents, devoid of natural toxins where possible, istherefore important for rapid early gut development.As the epithelium develops within the microvil-li, where mucus is secreted and this acts as animportant barrier against pathogenic coloniza-tion and also auto digestion from the bird’sown digestive enzymes. Some bacteria areable to colonize because they are able to break-down this protective mucus layer. Heliobacterpylori, the bacteria that causes gastric ulcers inhumans, secretes urease enzyme that destroysthe protective mucus coating, thereby making thestomach wall susceptible to degradation byhydrochloric acid and pepsin. It would beinteresting to study the gut microflora of birds fedhigh urease soybean meal.In addition to capturing digested nutrients, theepithelium of the gut also secretes large quanti-ties of water that aid in digestion. For eachgram of feed ingested, up to 2 ml of water maybe infused into the gut lumen, and this will sub-sequently be resorbed in the lower intestine. Ifthe epithelium is damaged by pathogens or tox-ins, then it can become a net secretor of water,and this contributes to diarrhea type conditions.Some strains of E. coli can also secrete toxins thatdisrupt water balance and contribute to diarrhea.Rancid fats also contribute to diarrhea by caus-ing sub-lethal injury to the microvilli epitheliumWithout the use of antibiotic growth promoters,the incidence of necrotic enteritis and coc-cidiosis are often the main production con-cerns. It now seems obvious that one of the major
  • 272 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.6Nutrition and gut healthmodes of action of growth promoters is controlover necrotic enteritis caused by Clostridium per-fringens. The association between coccidiosisand necrotic enteritis may be as simple as coc-cidial oocysts damaging the gut epithelium andso allowing for greater adhesion of clostridial bac-teria. There is no doubt that judicious use ofionophore anticoccidials or coccidial vaccinesare important in the control of necrotic enteritis.There has been a significant increase in theincidence of necrotic enteritis (NE) in Europe fol-lowing removal of growth promoting antibi-otics. Unfortunately, broiler diets in Europeare often based on wheat as the major cereal andit is well documented that clostridia multiply andcolonize more quickly when the diet containsmuch more than 20% wheat. An interesting obser-vation in Europe is that clostridia are now col-onizing the upper digestive tract as well as thenormal site of adhesion in the small intestine.Coupled with increased incidence of NE, socalled ‘dysbacteriosis’ is now common inEuropean broiler operations, and representsabnormal microbial overgrowth in the absenceof antibiotic growth promoters. This latter con-dition does not seem to be related to diet com-position or ingredient selection. Necrotic enteri-tis is also more common if the diet contains pectinscontributed, for example, by ingredients such asrye. While rye is not a common component ofbroiler diets, such findings indicate that diges-ta viscosity, and associated maldigestion, areideal for bacterial proliferation. There is a suggestionthat clostridial growth is greatly reduced in dietscontaining wheat that is processed through aroller mill, rather than a conventional hammer mill.Table 5.44 summarizes suggestions for trying tominimize the incidence of necrotic enteritis in birdsfed diets devoid of antibiotic growth promoters.Table 5.44 Actions to reduce the incidence of necrotic enteritis in broilersAction Effect1. Minimize feed changes Change in ingredient/nutrient composition isassociated with change in gut microflora2. Use highly digestible ingredients Undigested nutrients fuel bacterial overgrowth3. Minimize the use of wheat (< 20% Increased digesta viscosity leads to greater clostridialideally) activity. Enzyme addition important4. Process wheat through a roller mill Change in digesta viscosity?5. Use only quality fats and oils Rancid fats injure the microvilli6. Ensure low level of urease/trypsin Urease can destroy protective mucus barrierinhibitor in soybean meal7. Use ingredients with minimal levels of Toxins can destroy epithelial cells in the microvillimycotoxins, especially up to 28 d of age8. Use appropriate ionophore anticoccidials Coccidiosis predisposes clostridial growthor coccidial vaccines
  • 273CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.7Metabolic disordersAnother approach to maintaining gut healthis microbial reduction in feed and water. Thereis no doubt that high temperature pelleting ( 80˚C)can inactivate pathogens such as salmonella.However, ‘sterile’ feed is an ideal medium for sub-sequent bacterial colonization (since there is nocompetition for growth) and so a practical prob-lem is to prevent subsequent recontaminationbetween the time feed leaves the mill and is deliv-ered to the feed trough. Organic acids, such aspropionic acid, can help prevent such reconta-mination, and where allowed by regulatoryagencies, formaldehyde is especially effectiveagainst colonization by salmonella.Drinking water is another potential routeof bacterial infection. Many farms utilize somesystem of water sanitation, such as chlorine at3 – 4 ppm. While such sanitizers hopefullyensure a clean water supply at the nipple, theyhave no effect on gut health. Of more recent inter-est is the use of organic acids, such as lactic acid,as both a sanitizer and to manipulate gut pH.Adjusting water pH from regular levels of 7.2 –7.5, down to pH 5 with products such as lacticacid are claimed to reduce pathogen load in youngbroilers. In a recent study, we observed improvedgrowth with using drinking water at pH 5 vs. pH7.5. Interestingly, at pH 4, produced by simplyusing more organic acid, we observed fila-mentous yeast growth in the water lines, and thisimpacted water intake by clogging nippledrinkers. Yeast are always present in poultry facil-ities and thrive in acid environments.The other alternate dietary intervention forpreventing bacterial overgrowth is use of manan-oligosaccharides. Many pathogens such as E. coliattach to the gut epithelium by small appendagescalled fimbriae. These fimbriae actually attachby binding to mannose sugar receptors. If man-nose sugars are included in the diet, they also attachto these binding sites and effectively blockattachment by many strains of E. coli andSalmonella. Commercial products such asBioMos®, which is derived from the outer cellwall of Saccharomyces yeast, is often used aspart of an alternative strategy to antibiotics.Such products seem most efficacious whenused on a step-down program, such as 2 kg, 1kg and 0.5 kg per tonne in starter, grower andfinisher diets.5.7 Metabolic disordersThere has been a steady decline in theincidence of classical metabolic disor-ders as a consequence of genetic selectionfor liveability. Metabolic disorders such as ascites,Sudden Death Syndrome (SDS) and leg disorderscollectively still account for the majority of mor-tality and morbidity in healthy flocks, although thetotal incidence is now closer to 2 – 3 % vs.4 – 5% just 10 years ago. In male broilers, SDSwill usually be the major cause of mortality start-ing as early as 10 – 14 d of age. At high eleva-tions, and/or in cool climates ascites can still beproblematic and often necessitates tempering ofgrowth rate as a control measure.a) AscitesAscites is characterized by the accumulationof fluid in the abdomen, and hence the basis forthe common name of ‘water-belly’. Fluid in theabdomen is, in fact, plasma that has seepedfrom the liver, and this occurs as the end resultof a cascade of events ultimately triggered by oxy-
  • 274 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.7Metabolic disordersgen inadequacy within the bird. For various rea-sons, the need to provide more oxygen to the tis-sues leads to increased heart stroke volume,and ultimately to hypertrophy of the right ven-tricle. Such heart hypertrophy, coupled with mal-function of the heart valve, leads to increased pres-sure in the venous supply to the heart and sopressure builds up in the liver, and there isoften a characteristic fluid leakage.Because of the relationship with oxygendemand, ascites is affected and/or precipitatedby such factors as growth rate, altitude (hypox-ia) and environmental temperature. Of these fac-tors, hypoxia was the initial trigger some yearsago, since the condition was first seen as amajor problem in birds held at high altitude, wheremortality in male broilers of 20 – 30% was notuncommon. Today, ascites is seen in fast grow-ing lines of male broilers fed high nutrient densediets at most altitudes and where the environmentis cool/cold at least for part of each day. Mortalityseen with ascites is dictated by the number of ‘stres-sors’ involved and hence the efficacy of thecardio-pulmonary system to oxygenate tissues.Although growth rate per se is the major fac-tor contributing to oxygen demand, the com-position of growth is also influential, because oxy-gen need varies for metabolism of fats vs.proteins. Oxygen need for nitrogen and proteinmetabolism is high in relation to that for fat,although it must be remembered that the chick-en carcass actually contains little protein ornitrogen. The carcass does contain a great dealof muscle, but 80% of this is water. On the otherhand, adipose tissue contains about 90% fat, andso its contribution to oxygen demand is pro-portionally quite high. Excess fatness in birds willtherefore lead to significantly increased oxygenneeds for metabolism. At high altitude, these effectsare magnified due to low oxygen tension inthe air. Interestingly, broilers grow more slow-ly at high altitude, and comparable slowergrowth (4 – 5%) at sea level would virtually elim-inate the incidence of ascites. Regions of highaltitude invariably have cool night time tem-peratures (< 15˚C) and no one has really quan-titated the effects due to altitude per se vs. coolnight temperatures.Keeping birds ‘warm’ is perhaps the singlemost practical way of reducing the incidence ofascites. As environmental temperature changes,there is a change in the bird’s oxygen requirement.If one considers the thermoneutral zone fol-lowing the brooding to be 24 – 26˚C, then tem-peratures outside this range cause an increasein metabolic rate, and so increased need for oxy-gen. Low environmental temperatures are mostproblematic, since they are accompanied by anincrease in feed intake with little reduction ingrowth rate. While there is an increased oxygendemand at high temperatures due to panting etc.,this is usually accompanied by a reduced growthrate, and so overall there is reduced oxygendemand. Under commercial farm conditions,cold environmental conditions are probablythe major contributing factor to ascites. Forexample, at 10 vs. 26˚C, the oxygen demand bythe bird is almost doubled. This dramaticincrease in oxygen need, coupled with the needto metabolize increased quantities of feed,invariably leads to ascites.Manipulation of diet composition and/orfeed allocation system can have a major effecton the incidence of ascites. In most instances,such changes to the feeding program influenceascites via their effect on growth rate. However,there is also a concern about the levels of nutri-ents that influence electrolyte and water balance,the most notable being sodium. Feeding high lev-els of salt to broilers (> 0.5%) does lead toincreased fluid retention, although ascites invari-ably occurs with diets containing a vast range of
  • 275CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.7Metabolic disorderssalt, sodium and chloride concentrations. Apartfrom obvious nutrient deficiencies, or excessesas in the situation with sodium, the majorinvolvement of the feeding program as it affectsascites revolves around nutrient density andfeed restriction. Ascites is more common whenhigh energy diets are used, especially whenthese are pelleted. Dale and co-workers grewbirds on high energy diets designed to promoterapid growth and likely to induce ascites. Therewas no correlation between 14 d body weightand propensity of ascites, although birds fed 30003100 kcal ME/kg rather than 2850 2950kcal ME/kg had twice the incidence of ascites.When diets of varying nutrient density are used,there is a clear relationship of energy level andincidence of ascites (Table 5.45).Because feeding program, nutrient density andgrowth rate are all intimately involved in affect-ing the severity of ascites, then there is invariablydiscussion on the possible advantages of feedrestriction. The goal of such programs is toreduce the incidence of ascites without adverse-ly affecting economics of production. It isexpected that nutrient restriction programs willreduce final weight-for-age to some degree,and obviously there is a balance between thedegree of feed restriction and commerciallyacceptable growth characteristics. Using feedrestriction or restricted access time to feed,ascites can be virtually eliminated in male broil-ers (Table 5.46).Although low energy diets have little appar-ent effect on growth rate, there is often reductionin ascites. Using high energy diets with accessat 8 h/d is perhaps the most practical way of con-trolling ascites in problem situations. As shownin Table 5.46, elimination of ascites is at thecost of a 200 g or 2 d delay in growth rate. A 2– 3 d delay in market age sounds quite a reasonabletrade-off for a major reduction in ascites. However,careful economic analysis must be carried out todetermine the real cost of such decisions. A oneday delay in market age can be accepted if mor-tality is reduced by at least 2.5%.Another factor to consider in diet formula-tion is the balance and the quality of the protein.Excess nitrogen must be removed from the body,and this is an oxygen demanding process. Thereis a potential to reduce the oxygen demandthrough minimizing crude protein supply whilemaintaining essential amino acid levels in aTable 5.45 Effect of diet nutrient density and composition on incidence ofascites at 49 dDiet ME Crude protein Added Fat Ascites mort.(kcal/kg) (%) (%) (%)2950 23 0 8.82950 23 4 8.73100 24 4 15.82950 21 0 9.02950 21 4 8.53100 22 4 12.0Adapted from Dale and Villacres (1986)
  • 276 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.7Metabolic disordersDiet treatment Weight gain Mortality (%)(g) Total AscitesHigh energy (3000 3300) 2616a12.8 3.8Low energy (2900 3100) 2607a11.3 1.4High energy (8 h/d) 2422b8.7 0.6High energy (90% ad lib) 2452b9.0 0.2Table 5.46 Incidence of ascites in male broilers fed restricted quantities offeed or limited access time to feedAdapted from Camacho-Fernandez et al. (2002)diet. If we consider two diets providing the samelevel of available amino acids, but with 20 vs.24% crude protein, then there will be a need forbirds to deaminate an extra 4% CP in the high-protein diet. If birds consume 130 g feed/d, thismeans an extra 5 g/d of protein for catabolism.Such protein catabolism will likely result inuric acid and fat synthesis, and these are calculatedto need 2 and 1 litres of oxygen per day respec-tively. Therefore, catabolism of an extra 5 g crudeprotein each day means a 3 litre increase in oxy-gen demand, which represents about an 8%increase relative to the bird’s total requirements.There is an obvious incentive to minimize crudeprotein per se, because its catabolism merelyimposes another stress on the oxygen demandof the bird.There has been recent interest in themetabolism of two specific amino acids with poten-tial to influence incidence of ascites. Arginineis a precursor of nitric oxide, which acts as a potentvasodilator. Feeding more arginine shouldtherefore lessen the effects of increased pressurewithin the cardiovascular system. Feeding an extra10 kg arginine/tonne does, in fact, cause a dra-matic reduction in pulmonary arterial pressure.Unfortunately synthetic arginine is prohibitive-ly expensive and no natural ingredients are suf-ficiently enriched to supply such high levels inthe diet. Groundnut and cottonseed meal are per-haps the richest sources of arginine, at around4%. Taurine is an amino acid rarely consideredin poultry nutrition. It is required by cats wheredeficiency causes heart defects somewhat sim-ilar to those seen with ascites. However, addingtaurine to broiler diets has no effect on growthrate or cardio-pulmoary physiology, and with meatmeal in the diet ‘deficiency’ is unlikely to occur.If ascites mortality is sufficiently high, thefollowing diet changes may be considered:• Low energy feeds throughout the entire lifecycle e.g.:Starter (2850 kcal ME/kg)Grower (2950 kcal ME/kg)Finisher (3100 kcal ME/kg)• Use mash rather than pelleted feeds.Do not use too fine a mash diet, since thisencourages feed wastage and causesdustiness at broiler level.• Consider skip-a-day feeding from 7 – 20 dof age. Longer periods of restricted feedingmay be necessary where ascites levels arevery high. Water management becomesmore critical with this system.
  • 277CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.7Metabolic disorders• Consider limit-time feeding, such that birdshave access to feed for 8 – 10 hours eachday. Extra care is needed in water manage-ment so as to prevent wet litter.• Use no more than 21% crude protein instarter diets, 19% in grower and 17% infinisher/withdrawal.b) Sudden Death SyndromeSudden Death Syndrome (SDS) has beenrecognized for over 35 years. Also referred toas Acute Death Syndrome or ‘flip-over’, SDS ismost common in males and especially whengrowth rate is maximized. Mortality may startas early as 10 – 14 d, but most often peaks ataround 3 – 4 weeks of age, with affected birdsinvariably being found dead on their back.Mortality may reach as high as 1 – 1.5% inmixed sex flocks, and in male flocks the conditionis often the major single cause of mortality,with death rates as high as 2% being quitecommon. The economic loss is therefore sub-stantial. Confirmation of SDS by necropsy isdifficult as no specific lesions are present. Birdsare generally well-fleshed with partially filled cropand gizzard. There seems little doubt that anynutritional or management factors that influ-ence growth rate will have a correspondingeffect on SDS. Sudden Death Syndrome can vir-tually be eliminated with diets of low nutrient den-sity although these may not always be eco-nomical in terms of general bird performance.Research data suggests that diets based on pureglucose as an energy source result in muchhigher incidence of SDS compared to birds fedstarch or fat-based diets. It seems likely that someanomaly in electrolyte balance is involved in SDSand that there is a genetic predisposition to thisin terms of heart arrhythmia. In part, this is dueto the fact that metabolic changes occur rapid-ly after death, and hence blood profiles taken fromSDS birds will likely vary depending upon sam-pling time following mortality. SDS can bereduced or eliminated by nutritional or man-agement practices that reduce growth rate.Obviously, such decisions will have to be basedon local economic considerations. At this time,there is no indication of a single causative fac-tor, and diet manipulation other than that relat-ed to reduced growth rate, is usually ineffective.c) Skeletal disordersMost broiler flocks will have a proportion ofbirds with atypical gait, although growth rate maybe unaffected. There is now greater incidenceof birds with twisted toes, yet again this is in birdsthat achieve standard weight-for-age. Most legproblems likely have a genetic basis, althoughseverity of problems can be influenced by nutri-tional programs. The most common skeletal abnor-malities seen in broilers are tibial dyschon-droplasia (TD) and rickets. The fact that legproblems are more prevalent in broilers (andturkeys) than in egg-type birds, has led to the spec-ulation of growth rate and/or body weight ascausative factors. On this basis, one is faced withnumerous reports of general nutritional factorsinfluencing leg problems. For example, it has beensuggested that energy restriction in the first fewweeks halves the number of leg problems in broil-ers, while reduced protein intake results infewer leg abnormalities. Similarly, restricting accessto feeder space also seems to result in fewer legdefects. However, most recent evidence suggeststhat body weight per se is not a major predisposingfactor to leg problems. From experiments involv-ing harnessing weights to the backs of broiler chick-ens and poults it is concluded that severity of legabnormality is independent of body weight andthat regular skeletal development is adequate tosupport loads far greater than normal body
  • 278 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.7Metabolic disordersweight. There seems to be some disparitybetween the effects on skeletal development of(1) limiting the incidence by reducing the planeof nutrition and (2) failing to aggravate the prob-lem by artificially increasing body weight. Thisapparent dichotomy suggests that it is the rate ofgrowth rather than body weight per se that is apredisposing factor.In addition to the confounding effect ofgenetics on skeletal development, there is alsosome effect of steroid hormones. Castratedturkeys have a higher incidence of leg abnormalitiesthan do intact toms or those treated with testos-terone. It is suggested that androgens act to fusethe epiphyses and shafts of long bones. Theremay well be major sex differences in the hormonalcontrol of skeletal development related to the bal-ance of androgens:estrogens. However, theeffect of androgens:estrogens per se on skeletaldevelopment in the relatively juvenile broiler oftoday is perhaps questionable due to the fact thatlittle sex differentiation in tibiotarsal length is seenuntil after 5 weeks of age.It is often suggested that use of low proteindiets reduces the incidence of leg disordersalthough this is likely a consequence of reducedgrowth rate. Diets high in protein can interferewith folic acid metabolism and in so doing,increase the incidence of leg problems. However,in recent studies involving folic acid deficient diets,we were unable to show an effect with 22 vs. 30%crude protein diets. In studying factors influencingskeletal development in broiler breeders andLeghorns, we have shown that while early skele-tal development was little influenced by mineraland vitamin fortification, shank and keel lengthscould be increased by feeding diets of higher pro-tein content (22 vs. 16% CP). It is also conceivablethat the ratio of amino acids:non-protein nitro-gen may be of importance in the developmentof bone organic matrix. Evidence for this con-cept comes from experiments involving syn-thetic amino acids and purified diets. The bird’snitrogen requirement for optimum organicmatrix development is often greater than the appar-ent requirement for growth. The wry neck con-dition sometimes seen in broiler breeders, andespecially males, may also be related to disruptedamino acid metabolism. While not directly a skele-tal abnormality, the condition seems to be relat-ed to the metabolism of tryptophan or niacin.During incubation, wry neck arises in the embryobecause of greater muscle pull on one side of theneck, which together with pressure from theamnion, causes the ‘apparent’ skeletal deformity.Certain feed ingredients have been associatedwith leg disorders. Much of the early work in thisarea centered on brewer’s yeast and its ability toreduce leg disorders. With current interest in pro-biotics and other yeast-based additives, thisidea may receive renewed attention. There areisolated reports of certain samples of soybean mealcontributing toTD in broilers although this maysimply be a factor of acid:base balance of the diet.It is realized that feedstuffs contaminated withcertain mycotoxins can induce or aggravateskeletal problems. Grains contaminated withFusarium roseum have been shown to causeTD.Aflatoxin and ochratoxin both decrease bonestrength, and this may be related to vitamin D3metabolism. Under such field conditions birdssometimes respond to water soluble D3 admin-istered via the drinking water, regardless of thelevel and source of D3 in the diet. Attempts atreducing leg problems by minimizing microbialcontamination of the litter have met with avarying degree of success. Adding sorbic acidto the diet, or treating litter with potassium sor-bate improves leg condition only in isolatedtrials. A number of fungicides used in grain treat-ment can also themselves lead to leg problems.The presence of tetramethylthiuram significantly
  • 279CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.7Metabolic disordersincreases the incidence of TD, while tetram-ethylthiuram disulphide causes the ‘classical’ con-dition of irregular penetration of blood vesselsinto the cartilage, which is a precursor to TD.High chloride levels induceTD, although sincethere are no major shifts in plasma ions withTD,it is concluded that the problem is not simply relat-ed to defective calcification. The occurrence ofcrooked legs seems to be greater when chicks arefed diets with a narrow range of cations:anionsand the incidence ofTD and bowed legs appearsto increase with increase in anion content of thediet. There may be a relationship between ionbalance and vitamin D3 metabolism. Increasingthe chloride content of the diet from 10 to 40mEq/100 g was reported to markedly enhancecartilage abnormalities when the cation (Na+, K+)content of the diet was low. Thus, with excessCl-, chicks become acidotic, although the con-dition can be corrected with dietary sodiumand potassium carbonates, suggesting that ifthe diet is high in Cl-, then it must be balancedwith equimolar concentrations of Na++ K+in theform of readily metabolizable anions. Workersfrom France have indicated that liver homogenatesfrom acidotic chicks lose 50% of their capaci-ty to synthesize 1,25-cholecalciferol which is theactive D3 metabolite. This possibly infers arelationship between acid:base balance TD,and vitamin D3 metabolism.In certain situations, a deficiency of D3 willmimic both Ca and P deficiency situations.While Ca deficient chicks are usually hypocal-cemic and hyper-phosphatemic, D3 deficiencyinvariable results in hypocalcemia and hypo-phos-phatemia. In the D3 deficient chick a greater rel-ative P deficiency is caused by parathyroid hor-mone. In situations of D3 repletion, the skeletonseems to respond much more slowly than doesthe intestine, since the immediate effect of re-feed-ing D3 is better ‘absorption’ of the diet Ca.There is also evidence to suggest that D3 isinvolved with collagen synthesis, where thematuration of collagen crosslinks seems D3dose related. While 1-25 (OH)2D3 is unlikelyto be available to the feed industry, nutritionistsnow have the option of using , 25(OH)2 commonlyreferred to as Hy-D®. Since the synthesis of,25(OH)2 normally occurs in the liver, then prod-ucts such as Hy-D® are going to be most ben-eficial when liver function is impaired for what-ever reason.While deficiencies of most vitamins have beenassociated with leg problems, pyridoxine has per-haps received the most attention. There is over-whelming evidence to suggest that low levels leadto skeletal abnormalities and/or that supple-mentation reduces the incidence. It has beenhypothesized that pyridoxine may exert its ben-eficial effect via involvement with zinc home-ostasis and in particular the formation of picol-inic acid which is involved in intestinal zincabsorption. There is an apparent synergismbetween zinc, B6 and tryptophan involved in theprevention of leg weakness. The situation withpyridoxine is further complicated through the effectof diet protein as previously described withfolic acid. Common to many other diet situations,pyridoxine deficiency manifests itself through epi-physeal lesions consisting of uneven invasion ofirregular blood vessels into the maturing growthplate. Presumably the higher level of diet pro-tein increases the metabolic requirement forpyridoxine through such processes as transam-ination and/or deamination. While deficienciesof many vitamins can therefore, precipitate legproblems in broilers, there is also evidence to sug-gest that certain vitamin excesses may be detri-mental. Very high levels of vitamin A in the dietincrease the incidence of rickets, while impairedbone formation has been observed with excessdietary vitamin E. It must be pointed out how-ever, that all these reported effects of vitamin excess
  • 280 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.7Metabolic disorderson bone metabolism relate to dietary levelsgrossly in excess (5 – 10 times) of normal feed-ing levels and hence would only be practical-ly encountered under unusual circumstances.As with vitamins, deficiencies, or excessesof a vast range of minerals, can also influencebone development. The effect of abnormal lev-els and/or ratios of calcium:phosphorus arewell documented. Confusion sometimes existswith respect to diagnosis of calcium or phosphorusdeficiencies, and accurate on-farm diagnosisof phosphorus deficiency vs. calcium excess isdifficult, and immediate recommendations of dietchange can be misleading prior to complete dietanalysis. Identical lesions for the two conditionsare seen suggesting that excess calcium forms insol-uble Ca3(PO4)2 in the intestine, thereby induc-ing phosphorus deficiency.Table 5.47 shows nor-mal levels of minerals in bone ash, and sovalues which are much different to these are acause for concern.Table 5.47 Normal mineral contentof bone ashcollagen secretion and this can be restored byadministration of Fe2+ or Fe2+ with Mn2+, butnot by Mn2+alone. The agent seems to block thesynthesis of hydroxylysine and within this mech-anism there seems to be a step requiring Fe2+.Copper metabolism has always been suspect instudies of leg problems, since there are certainsimilarities between the cartilage of copperdeficient birds and those with TD. However,attempts to correct TD with supplements of Cuhave invariable proved disappointing.Solubilization studies indicated that dystrophiccartilage (TD) is not deficient in cross-linked col-lagen, a situation often seen with classical cop-per deficiency.Skeletal disorders are sometimes seen inthe first few days after hatching and so it is pos-sible that metabolic disorders are initiated dur-ing incubation. Skeletal mineralization starts ataround the eighth day of incubation, and atthis time the yolk serves as a source of calcium.Shell calcium is not utilized until about the12th day of incubation, although during thecourse of embryonic development, the embryowill take up some 120 mg Ca from the shell.Culturing developing embryos in a mediumdeficient in calcium quickly results in grossskeletal abnormalities. There have been noreports linking breeder eggshell quality withbone formation in broiler offspring. Similarly, therehave been relatively few reports of the effect ofbreeder nutrition and management on skeletaldevelopment of the embryo. There seems littledoubt that more common leg problems, such astibial dyschondroplasia (TD) are inherited tosome degree and hence pedigree has a poten-tially confounding effect on studies of leg abnor-malities. TD is related to a major sex linkedgene, the recessive of which is associated witha higher incidence ofTD.This situation suggestsa large maternal component, and therefore, femalelines would greatly influence the expression.Calcium 37%Phosphorus 18%Magnesium 0.6%Zinc 200 – 250 ppmCopper 20 ppmManganese 3 – 5 ppmIron 400 – 500 ppmThe effect of manganese deficiency on the inci-dence of perosis is obviously well documentedalthough some evidence suggests that interac-tion with iron may be a complicating factor.Administration of hydralazine, a manganesesequestering agent, causes leg defects very sim-ilar to those seen in classical manganese deficiency,and in fact, successful Mn treatment has beenrecorded in these situations. Hydralazine blocks
  • 281CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENSSECTION 5.8Carcass compositiond) Spiking mortalitySpiking mortality affects young broiler chicksbetween the ages of 7 and 21 days, and is char-acterized by severe hypoglycemia. All affectedbirds exhibit extremely low blood glucose lev-els, which account for many of the observed signsof spiking mortality, including huddling andtrembling, blindness, loud chirping, litter eating,ataxia and rickets. Mortality rates of around 1%are observed daily for three to five days. Chicksthat survive, experience long-term stunting andgrowth reduction. There are now field observationsof an increasing occur