Growel' Swine Nutrition Guide

Preface
The objective ofthe Swine Nutrition Guide
remains the same: to provide the reader with a
simple, easy-to-read source ofpractical information
on the nutrition of the pig. Fundamentally, the pig
has changed little since 1989 when the first edition
was released; ofcourse, genetic progress has been
impressive, but the list of nutrients required by the
pig and how they are used have remained much the
same.
What has changed over the past 6 years is the
tremendous growth in knowledge on how to define
nutrient requirements and how to provide these
nutrients more precisely and effectively with a
keener eye to economics. Perhaps even more
striking has been the rapid progress ofpork produc-
ers in their ability to take advantage ofthis informa-
tion and apply it "on the farm."
The target audience ofthe Swine Nutrition Guide
also remains the same: pork producers, workers in
agribusiness and extension, and students. The
common interest is information on how the pig uses
nutrients, how to determine the nutrient require-
ments of a given class of swine and how feedstuffs
can be most effectively employed in the diet. We
sincerely hope that the Guide continues to fill this
need - serving as a single source reference on these
topics.
The book is not intended to make all readers pig
nutritionists, but rather to provide an understanding
and appreciation for the importance ofa holistic
approach to the subject; the pig does not exist in a
vacuum and to be successful, feeding programs
must be designed with many factors in mind,
including genetics, the environment, herd health
and, ofcourse. economics.
The format of the second edition remains the
same as the first. Chapters l, 2 and 3 provide
background on the more fundamental aspects of
nutrition. Chapter 4 describes more than 40 com-
mon ingredients, including recommendations on
how they might be used in pig diets. Chapter 5 then
explains how to successfully formulate diets,
emphasizing a balanced approach to this sometimes
complex subject but also briefly explaining the
specific mechanics as well.
Chapters 6 to 9 discuss the day-to-day feeding of
various classes ofswine. Because nutrition cannot
be considered in isolation, other aspects of manage-
ment are also included. The authors have taken a
more factorial approach to the design offeeding
programs than in the first edition. This reflects
what we believe to be a growing trend in pig nutri-
tion - to define nutrient requirements on the basis of
specific traits and desired levels ofproductivity,
with economics being considered in all instances.
Chapter 10 considers the processing and manufac-
turing of pig diets, a step that is often taken for
granted - at considerable peril. Mixing and delivery
offeed to the pig represents the final step in the
nutrition continuum. Failure to manufacture diets
properly can erase any gains achieved through
improved diet formulation or ingredient selection!
Chapter 11 provides information on toxins or
antinutritional factors that may be present in feeds
and feedstuffs, either as a consequence of contami-
nation or due to the natural composition ofthe
feedstuff itself. A new chapter (12) on water has
been added to the second edition ofthe Swine
Nutrition Guide, discussing both nutritional and
quality issues.
We trust that the interests of the individual pig are
not lost in the pages ofthis book. Readers will note
that considerations ofpig behaviour creep into
many chapters as we learn more about this aspect of
the animal that we serve - and who has served us so
well. Our respect and affection for this creature, at
once both intelligent and stubborn, fun and frustrat-
ing, neat and messy, motivate us to again dedicate
the Swine Nutrition Guide to the pig.
J.F. Patience
P.A. Thacker
C.F.M. de Lange

Table of Contents
1. The Science of Nutrition I
What is Nutrition 1
The Role ofthe Computer . 3
The Future ofNutrition 4
2. Gastrointestinal Physiology 5
The Role of the Digestive Tract .. . 5
Types of Digestive Tracts 6
Eating and Swallowing 7
The Stomach .................................................................................................. 7
The Small Intestine . . . . 9
The Large Intestine ................ ...... . ..... ................................ ........... 12
3. Nutrients 15
What is a Nutrient ................................................... .... ...................... 15
Nutrient Availability 15
Nutrient Requirements .. . . . . 16
Energy 16
Amino Acids ........................ .. ........ .................... ................... 22
Minerals 31
Vitamins .... .. . 40
Essential Fatty Acids . . . ................................................ . ........... 48
Water 49
4. Ingredients 51
Ingredient versus Nutrient .. 51
Animal Sources 53
Blood Meal ....... ..... ................. .................................................. 54
Bone Meal 55
Feather Meal 55
Fish Meal .. .. 56
Fish Silage 57
Meat and Bone Meal .... 59
Whole Milk 60
Dried Skim Milk 61
Whey 61
Plant Sources .. . . . . . .. 63
Alfalfa 63
Barley 65
Barley: High Moisture 67
Barley: Hulless 69
Beet Pulp 71
Buckwheat 71
Canola Meal . . . .... 73

Canola Seed: Full Fat 74
76
78
80
80
82
84
Grain Screenings 84
Lentils 86
Molasses 87
Oats 87
Oats: Naked .... . . . 89
Oat Groats .. . . . 90
Potatoes and Potato Products ......... ........................... ...................... 90
Rye 92
Soybeans: Full Fat . . .. 93
Soybean Meal 96
Sunflower Meal . . . 97
Sunflower Seeds .... . . 98
Triticale ...... . . . . . 100
Wheat 101
Wheat Bran .......................................... ..................... ..................... 104
Wheat Shorts . . . 105
Wild Oat Groats . . . . . . 105
Fats and Oils . . . . . .. 107
Mineral Ingredients .. .. 112
Probiotics 113
Synthetic Amino Acids 115
Organic Acids 115
Feed Flavours ..................................... ................. ............................... 116
5. Diet Formulation 119
Define Objectives .... . 119
Define Requirements 121
Select and Characterize Ingredients 122
Diet Formulation 123
Evaluating Diet Quality 128
Conducting a Feeding Trial 131
Common Calculations and Conversions 132
6. Nutrition of the Breeding Herd 133
Feeding and Management of Replacement Gilts 134
Feeding the Sow During Gestation 137
Feeding the Sow Around Farrowing Time 151
Feeding the Sow During Lactation 154
Feeding the Sow at Weaning 161
Feeding Boars 162
Grain Dust .
Corn .
Corn By-Products .
Dried Bakery Product .
Fababeans .
Field Peas ..

7. Feeding the Suckling Piglet 167
The Importance ofColostrum . .. 167
The Need for Supplementary Iron 168
Water Requirements 168
Use of Milk Replacers I 69
Creep Feeding . . .... . . . . . . . . . 169
8. Feeding the Weaned Pig 173
Stresses at Weaning 173
Performance Targets 174
Maximizing Feed Intake I 74
Managing the Early-Weaned Pig 176
Nutrient Requirements ofthe Weaned Pig 177
Feeding Programs .. . . 178
Diet Composition . . . . .. 180
Diet Formulations . . . 183
Feed Additives ..... . . . . 183
The Pig's Environment 184
9. Feeding Management of Market Hogs 187
Goals for the Feeder Barn . 187
Lean Tissue Growth in Growing-Finishing Pigs 188
Feed Intake in Feeder Pigs ....................................... ............................ J 91
Feed Utilization in Feeder Pigs . . 192
Factors Affecting Nutrient Requirements in Growing-Finishing Pigs l 94
Nutrient Allowances and Diet Formulation . 196
Typical Diets ..................................................................................... ... 20 l
Feed Additives ..... . . 203
Phase Feeding 203
Split-sex Feeding 204
Feeding to Appetite Versus Restricted Feeding .. 206
Choice Feeding .. . .. . .. 207
Feeding of Pigs Housed Outdoors . . 207
Feed Separation . . . 208
Feed Wastage .. . 209
Monitoring Performance . .... 210
Meat Quality 213
10. Diet Processing and Delivery 215
Grinding . .... . . .... . 216
Mixing 219
Pelleting . .. . . . . . . . . . 220
Liquid Feeding 223
Drying Grains 224
High Moisture Grains 224
Mixing Feeds on the Farm 225
Processing Problems 226
Feeds Act and Regulation 227

11. Toxic Substances in Feeds 231
Toxicants Produced by Plants 231
Exogenous Microbes and Toxin Producers 235
Prevention ofMycotoxin Contamination 239
Treatment 239
Safety 240
12. Water 241
Requirements and Intake ... . 241
Gestating Sows . . . .. 242
Lactating Sows 243
Piglets .. . .... . .. 243
Weanling Pigs . 244
Water Delivery .. 244
Water Quality 245
Impact ofWater Quality . 248
Response to Poor Quality Water 249
Appendix I. Typical Nutrient Composition of Selected Feed Ingredients 253
Appendix II. Calibrating Proportioner-Type Mills 261
Conversion Factors ........ ........................................................................... 262
Glossary ......... ...... ............ ....................... . ........................................ 265
Index 271

List of Tables
3-1. Essential Nutrients in the Diet of the Pig 15
3-2. Proportions of Gross, Digestible and Metabolizable
Energy (Kcal/kg) in Common Ingredients 18
3-3. Fibre Content of Ingredients Used in Swine Diets 19
3-4. Digestibility of Ether Extract of Common Feedstuffs 20
3-5. Effect of Bushel Weight on Nutrient Content of Cereal Grains 21
3-6. Minimum Recommended Bushel Weightsfor Grains Used in
Swine Rations 21
3-7. Nitrogen Content of Amino Acids 24
3-8. Protein Estimation Adjusted for Corrected Nitrogen Factors
and Non-Protein Nitrogen Content 24
3-9. Amino Acid Profile ofVarious Protein Fractions in Com 26
3-10. Effect of Increasing Total Nitrogen (Crude Protein) on the Lysine
Content of Wheat and Oats 26
3-11. Average Apparent Availability ofAmino Acids(%) in
Common Ingredients 28
3-12. Suggested Optimum Amino Acid Balance in Protein
(Ideal Protein) for Swine 31
3-13. Approximate Mineral Composition of the Animal Body 32
3-14. Total Phosphorus Content and Phosphorus Availability
of Some Common Ingredients 33
3-15. Feed Grade Phosphate Sources 33
3-16. Calculating 'Salt' Values from Sodium or Chloride Assays in Swine Diets 35
3-17. Maximum Tolerable Limits and Supplemental Sources
of the Microminerals 37
3-18. Stability ofVitamins in Premixes and During Pelleting and Extrusion 43
3-19. Alpha-tocopherol Content of Feed Ingredients 45
4-1. Consistency ofVarious Protein Sources used in Swine Diets 52
4-2. Performance of Weanling Pigs Fed Diets Containing Graded
Levels offish Silage 58
4-3. Performance of Growing Pigs (25 to 55 kg body weight) Fed Diets
Containing Graded Levels of Oily Fish Silage (44% fat in the pure product) 58
4-4. Effect of Feeding Fish Silage on the Reproductive Performance of Sows 58
4-5. Replacement Scheme for Using Whole Milk in Swine Diets 61
4-6. Growth, Feed Intake and Carcass Characteristics of Pigs
(54-100 kg) Fed Alfalfa 64
4-7. Composition ofBarley Varieties and Performance of
Growing-finishing Pigs (approximately 20-95 kg body weight)
Fed Various Barley Varieties 65
4-8. Utilization of Frozen or Sprouted Barley (Bonanza) by Growing Pigs 67
4-9. Chemical Analysis of High Moisture and Dry Barley 68
4-10. Amount of High Moisture Grain Necessary to Supply the Same
Amount of Dry Matter as Regular Barley (90% DM) 69
4-11. Performance and Carcass Characteristics of Pigs Fed Acid-treated
High Moisture Barley (74.5% CM) or Regular Barley (85.8% DM) 69
4-12. Performance of Starter Pigs Fed Condor Hulless or Samson Hulled Barley 70
4-13. Performance of Growing-finishing Pigs Fed Diets Based on Hulled or
Hulless Barley 70
4-14. Performance of Growing Pigs (20-60 kg) Fed Diets Containing
Various Levels of Buckwheat in Combination With Barley 72

4-15.
4-16.
4-17.
4-l8.
4-19.
4-20.
4-21.
4-22.
4-23.
4-24.
Performance of Female and Castrated Male Pigs Fed Diets
Containing Equal Levels of Digestible Nutrients
Performance of Starter Pigs Fed Diets Containing Whole Canola Seed
Performance and Carcass Composition of Pigs Fed Diets Containing
Whole Canola Seed
Nutritional Value of Immature Com
for Starter Pigs Fed Corn-Soybean Meal Based Diets
Effect of Bushel Weight on Rate and Efficiency
of Growth and on Digestibility of Energy in Corn
Performance of Starter Pigs ( l 0-25 kg) Fed Graded Levels of Fababeans
Performance of Grower Pigs ( 16-45 kg) Fed Diets Containing Fababeans
Effect of Fababeans on Reproductive Performance
Performance of Pigs (27-95 kg) Fed Peas as a Replacement for Soybean Meal
Performance of Growing-finishing Pigs (25-90 kg) Fed a
Mixture of Peas and Canola Meal
73
75
75
77
79
81
81
81
83
83
4-25.
4-26.
4-27.
4-28a.
4-28b.
4-29.
4-30.
4-31.
4-32.
4-33.
4-34.
4-35.
4-36.
4-37.
4-38.
4-39.
4-40.
4-4 l.
4-42.
4-43.
4-44.
4-45.
4-46.
4-47.
4-48.
4-49.
4-50.
Comparison of the Composition of Grain Dust and Parent Grains 84
Chemical Composition of Five Samples of
Feed Wheat Screenings Compared to Wheat 85
Effects of Feeding Cull Lentils on Digestibility and Pig Performance (23-100 kg) 86
Effect of Substituting Oats for Com on the Performance of Weaner Pigs 88
Effect of Substituting Oats for Com on Grower Pig Performance 88
Comparison of Naked Oats and Other Cereal
Grains as an Energy Source for Weaner Pigs (25-56 days). 89
Performance of Market Hogs Fed Naked Oats (32-79 kg) 89
Effect of Enzyme Supplementation on the Performance of
Growing Pigs (20-98 kg) Fed Rye 93
The Effect of Heat Treatment on the Digestible Energy Content of Soybeans 95
Performance of Growing-finishing Pigs Fed Roasted Beans as the
Sole Supplemental Protein Source in Com-based Diets 96
Effect of Feeding Sunflower Seeds on the Performance of Weaner Pigs 99
Performance of Growing Pigs Fed Graded Levels of Sunflower Seeds 99
Trypsin Inhibition Levels in Spring Triticale I 00
Performance of Grower Pigs Fed Diets Containing Triticale, Wheat or Com l OI
Comparison of Hard and Soft Wheat in the Diet of Pigs from 61 - L2 l kg 102
Replacement of Hard Red Spring Wheat
with Soft Wheat in Pig Starter Diets l 02
Performance of Starter Pigs Fed Either Sprouted or Regular Soft Wheat I 04
Typical Specifications for Wheat and its By-products I 05
Performance of Starter Pigs (7-25 kg) Fed Various Oat Products 106
Estimating Iodine Value from Fatty Acid Composition of a Fat l 09
Digestible Energy Content of Selected Fat Sources 11 O
Summary of Responses to Supplemental Fat in Sow Diets 11 I
Fat Content - Common Feed Ingredients I I I
Typical Analysis(%) of Common Mineral
Ingredients Used in Swine Diets 112
a. Macrominerals 112
b, Microminerals 113
Performance of Starter Pigs Fed Diets Containing a Probiotic 114
Performance of Growing Pigs (23-38 kg) Fed Diets Containing a Probiotic 114
Effect of Organic Acid Supplementation on Starter Pig Performance 116
5-1.
5-2.
5-3.
Typical Ingredient Output from a Feed Formulation Program
Typical Nutrient Output from a Feed Formulation Program
Diet Composition from Pierson Square Calculation
124
125
127

5-4. Recommended Schedule for Feed Testing on a Farm Manufacturing Three Diets 129
5-5. Calculation of the Theoretical Nutrient Composition of a Feed 130
5-6. Examples of Conclusive and Inconclusive Test Results Based on ADG 132
6-1. Reproductive Efficiency ofAverage and Superior Swine Herds 133
6-2. Influence ofFeeding Level Following Mating on Embryo Survival in Gilts 136
6-3. Effect ofFeed Level in Early Gestation
on Plasma Progesterone Levels and Embryo Survival 136
6-4. Effect of Energy Intake (day 75 to I 05 of Gestation) on Mammary
Development in Gilts 137
6-5. Comparison of Sows Fed with Electronic Sow Feeders or in Gestation Stalls 139
6-6. The Influence of Dispensing Speed on the Behaviour and Feed Intake of
Sows Using the Slow Feeding System 141
6-7. Effect of Feeding Level During Last 23 days of Gestation on
Reproductive Performance 144
6-8. Components of Gestational Weight Gain 144
6-9. Feed Allowances for Dry Sows According to Body Condition Score 145
6-10. Metabolic Body Weights of Sows and Maintenance Energy Requirements 145
6-1 I. Energy Requirements of Sows (estimated) During Gestation 147
6-12. Daily Amino Acid Requirements for Maintenance of Gestating Sows 148
6-13. Daily Amino Acid Requirements {g/day) for Growth of Gestating Sows 148
6-14. Estimated Total Amino Acid Needs of Pregnant Sows Under
Various Conditions 149
6-15. Mineral Requirements of Gestating Sows 150
6-16. Vitamin Requirements of Gestating Sows 150
6-17. Effects of Folic Acid Supplementation of Diets Fed to Gestating Sows 150
6-18. Effect of injection of Beta-Carotene on Reproductive Performance of
Multiparous Sows 151
6-19. Effect ofVitamin E on Sow Productivity 151
6-20a. Examples of Gestation Diets 153
6-20b. Examples of Lactation Diets 153
6-21. Effect ofType of Fat Fed During Late
Gestation and Early Lactation on Sow Productivity 154
6-22a. Effect of Sow Feed Intake During Lactation
on Subsequent Reproductive Performance 154
6-22b. Effect of Feed Level on Milk Yield at 21 Days 155
6-23. Effect of Feed Intake During Pregnancy on Feed Intake During Lactation 155
6-24. Effect of Feeding Various Levels of Protein During Lactation
on Sow Feed Intake and Body Condition 156
6-25. Effect of Method of Feeding on Sow Feed
Intake and Weight Change During Lactation 156
6-26. Performance of Sows Fed Artificial Flavours During Lactation 157
6-27. Effect of Environmental Temperature on Feed Intake and Weight
Loss of the Sow and Weight Gain of the Litter 158
6-28. Estimated Daily Energy Requirements of Lactating Sows 159
6-29. Estimated Daily Amino Acid Requirements for Milk Production by the Sow 160
6-30. Estimated Total Daily Amino Acid Requirements of Lactating Sows 161
6-31. Effect of Feed and Water Deprivation.
Prior to Weaning, on Days to Successful Service After Weaning 161
6-32. Effect of Feed Intake During the Weaning to Remaining Interval
on the Reproductive Performance of Gilts and Sows 162
6-33. Nutrient Requirements of Developing Boars (20-100 kg) 163
6-34. Energy Requirements of Working Boars 164
6-35. Composition of Diets for Adult Boars 165

7-1 Effect ofWeaning Weight at 25-29 Days
ofAge on Piglet Performance to 78 Days ofAge 167
8-1. Recommended Weaning Age for Disease Elimination 174
8-2. Performance Targets for Pigs from 7 to 25 kg Body Weight 174
8-3. Nutrient Requirements of the Weanling Pig 176
8-4. Diet Composition Guidelines for the Weanling Pig 181
8-5. Sample Diets for Weanling Pigs 182
8-6. Effect of Medication on the Performance of Weanling Pigs in a High Health Herd 183
8-7. Recommended Floor Space Allowances for Weanling Pigs 185
9-1. Goals for the Feeder Barn 187
9-2. Saskatchewan Grading Table 190
9-3. Observed Lean Growth Rates in Growing-finishing Pigs in
Relation to Growth Rates and Carcass Lean Yield Content 191
9-4. Effect of Health Status on Performance in Growing-finishing Pigs 195
9-5. Estimated Available (apparent ilea! digestible) Lysine Requirements
for a Growing Pig at 50 kg Body Weight 196
9-6. Estimation of the Lowest Cost per Unit of Energy in Growing Pig Diets 197
9-7. Effect of Dietary Energy Density on the Voluntary Feed Intake
and Performance of Entire Male Pigs between 22 and 50 kg Body Weight 197
9-8. Recommended Allowances ofAvailable(apparent ilea) digestible)
Lysine in Relation to Lean Growth Potential and Body Weight
in Growing-finishing pigs 198
9-9. Estimated Change in the Balance in which Amino Acids are
Required by Growing Pigs with Average Lean Growth
Potentials and with Increasing Body Weights 199
9-10. Recommendations for Vitamin Fortification of Grower and
Finisher Diets 199
9-11. Recommendations for Mineral Levels in Grower and finisher Diets 200
9-12. Examples of Growout Diets based on Wheat and Barley 201
9-13. Examples ofGrowout Diets Based on Corn 202
9-14. Pig Response to Antimicrobials in Feed of Growing-finishing Pigs 203
9-15. Estimated Value of a One versus Two versus Three Phase Feeding
Program in Pigs with Average Lean Growth Potential 204
9-16. Performance of Barrows and Gilts Fed a Similar Diet 204
9-17. Effect of Sex and Dietary Lysine Level on Performance in Finishing Pigs 205
9-18. Estimated Effect of Level ofFeed Intake on Animal and Financial
Performance in Pigs with a Slightly Better than Average
Lean Growth Potential 207
9-19. Performance Data Comparing Shelter and Conventionally Raised
Feeder Pigs During the Summer, Fall and Winter 208
9-20. Effect of Feed Handling on Pig Performance 209
9-21. Effect of Floor feeding on Growing-finishing Pig Performance 209
9-22. Effect of Feed Form on Performance of ad libitum Fed Pigs 210
9-23. Calculation of Days to Market Based on Inventory Turnover 211
9-24. Estimated Performance of Feeder Pigs Based on Feed Intake and
Growth Curves Presented in Figure 9-11 213
9-25. Recommended Pen Floor Space Allowances for Growing Pigs 214
10-1. Effect of Fineness of Grind on the Performance ofWeanling Pigs
Fed Barley-based Diets 216
10-2. Effect of Fineness of Grind on the Performance of Finishing
Pigs Fed Barley-based Diets 216

10-3. Effect of Particle Size on the Performance of Lactating Sows
Fed a Corn-based Diet 217
10-4. Impact of Fineness of Grind on Mill Productivity and Energy Efficiency 217
10-5. Effect of Screen and Hammer Wear on Grinding Effectiveness 218
10-6. Effect of Fineness of Grind of Corn on Incidence of Ulcers
and other Stomach Lesions in Swine 219
10-7. Effect of Fineness of Grind of Barley on the Incidence of Ulcers
and other Stomach Lesions in Swine 219
10-8. Impact of Mixing Time on Diet Uniformity and Performance of
Weanling Pigs 219
10-9. Impact of Mixing Time on Diet Uniformity and Performance of
Finishing Swine 220
10-10. Impact of Pelleting Corn-based Diets on Finishing Pig Performance.
Nutrient Digestibility and the Incidence of Ulcers 221
10-11. Effect of Pelleting Diets based on Canola and Cereal Grains on
Pig Performance 222
10-12. Effect of Pellet Fines on Performance of Finishing Pigs Fed a
Corn-based Diet 222
10-13. Effect of Pelleting and Fines on Performance of Newly-weaned
Pigs Fed Com-based Diets 223
10-14. Separation of Feeds Following Mixing on the Farm 226
10-15. Nutrient Guarantees Required for Swine Diets that are Exempt
from Registration Requirements 228
11-1. Phytate Phosphorus Content of Common Feedstuffs 232
11-2. Naturally-occurring Phytase in Common Feedstuffs 232
11-3. Results of Salmonella Assays Reported by the Veterinary
Diagnostic Laboratory at the Pennsylvania State University 235
11-4. Survey of Raw Materials Provided by Five Feed
Compounders in the U.K. 235
12-1. Nipple Drinker Flow Rates on Saskatchewan Farms 244
12-2. Recommended Nipple Drinker Flow Rates for Various Classes of Swine 245
12-3. Canadian Water Quality Guidelines for Livestock 245
12-4. Assays to Include in the Chemical Evaluation
of Water Used in Pig Production 246
12-5. Effect ofAeration and Seven Days Settling on Water Chemistry 247
12-6. Effect of Water Quality on the Performance
of Weanling Pigs Fed a Diet Containing Antibiotics 248
12-7. Effect of Water Quality on the Performance of
Weanling Pigs Fed a Diet Free ofAntibiotics 249
12-8. Effect of Pen Temperature and Water Quality on the
Performance of Newly-weaned Pigs 249

List of Figures
I-la. Cost of Production Budget: all costs
I-lb. Cost of Production Budget: variable costs only
2-1. Gastrointestinal Tracts 6
2-2a. Capacity of Gastrointestinal Tract 7
2-2b. Length of the Gastrointestinal Tract 7
2-3. Nutrient Digestion along the Gastrointestinal Tract of the Pig 12
3-1. Pig Response to Level of Nutrient in the Diet 16
3-2. Distribution of Dietary Energy 17
3-3. Relationship of Protein Content to Protein Type in Cereal Grains 26
3-4. Relationship between Amino Acid Level in Diet and Observed
Apparent and Calculated "True" Ilea! Amino Acid Digestibilities
(Figure 3-4a.), and the Relationship between Amino Acid Level in Diet
and Observed Recovery at Distal £1eum (total endogenous and
non-digested dietary aminoacids) (Figure 3-4b.) 29
3-5. Diagram Tllustrating What is Meant by the Term Amino Acid Balance
as it Relates to Evaluating Swine Diets 30
4-1. Flow Diagram Showing Choices in Selection
of Ingredients used in Practical Diets 53
4-2. Triglyceride 107
5-1. Determination of a Nutrient Requirement Showing the Pig Response to
increasing Nutrient Supply 122
5-2. Quality Control Procedures on the Farm 130
6-1. Effects of Feed Intake During Pregnancy on Sow Productivity 138
6-2. Diagram of Slow Feeding System for Sows 140
6-3. Diagram ofWoldrix Feeding System for Sows 141
6-4. Diagram of Hurnick-Morris System for Gestating Sows 142
6-5. Guides to Condition Scoring Sows, Including Photographs of
Representative Animals 146
6-6. Example of a Card for Monitoring Lactation Feed Intake 159
7-1. A Lactation Curve for a Sow 169
7-2. Digestive Enzyme Activity Pattern in Young Swine 170
8-1. Average Daily Gain versus Days to Market 173
8-2. Growth Curves for Pigs Demonstrating Good, Better and Best
Performance to IO Weeks ofAge 175
8-3a. Starter Feed Usage: Two Week Weaning 178
8-3b. Starter Feed Usage: Three Week Weaning 178
8-4. Relationship Between Dietary Energy Concentration and Body Protein
Gain in Weanling Pigs 178
9-1. Sigmoidal Growth Curve 188
9-2. Relative Proportions of Muscle Bone and Fat at Birth and 28 Weeks ofAge 188
9-3. Description of PI, P2, and P3 Fat Measurements 189

9-4. Typical Feed Intake Curve for Growing Pigs Consuming a Diet
with a DE Content of Either 3150 or 3400 kcal/kg. 192
9-5. Relationship between Feed lntake and Tissue Accretion Rates in Growing Pigs 193
9-6. Effect of Feed Intake on Lean Tissue Growth and Body Fat
Deposition in Finishing Pigs with Average ("average pig")
and High ("good" pig) Lean Tissue Growth Potential 193
9-7. Relationship between Feed Intake and
Performance in Growing Pigs where Energy Lntake Limits Lean
Growth (Figure a), and in Finishing Pigs Where Feed Intake
does not Limit Lean Growth (Figure b) 194
9-8. Effect of Dietary Lysine Levels and Pig Type on Lean Growth Rates 194
9-9. Change in Required Dietary Nutrient Levels in Relation to Body Weight 195
9-10. Feed Intake Curves of Barrows and Gilts Fed a Similar Diet and
Housed in Groups of 12 Pigs per Pen 205
9-l 1. Estimated Feed lntake and Growth Curves
Derived from a Limited Number ofDetailed Observations on
Feed Lntake and Body Weights in a Feeder Barn 212
10-1. Improvement due to Grinding on the Digestibility ofNutrients for
Two Sizes of Pigs 216
12-1. Water Balance in the Pig: Intake and Output 241
12-2. Typical Water Intake Pattern During the Post-weaning Period 244

DIET INGREDIENTS
BLOOD MEAL BONE MEAL
•• •
•
•
. •..., .
• •
FEATHER MEAL FISH MEAL FISH SILAGE (CAPELIN)
SKIM MILK POWDER WHEY POWDER ALFALFA: DEHYDRATED
MEAL
BARLEY BARLEY:HULLESS

BEET PULP
;-:_, '') 'I • I
. ' .. , ..· .. ,' _...,, . -c..·1;. •. . . , .. ,.' '!-' ','.,.� ,,, ·. --.••
. It ... •• > .,..• . ' .. ,li"J, .
• ; ,: ·�.� �.-•. • '{ y'·� '�I :.,': ....
.�----J' •;- .. , i;.'1_
•.Jo_�:·"" .:.,�.�... .: ; +-&-,. �
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. t t -. .. ", �� ...
CANOLA: FINE
SCREENINGS
CORN: DISTILLER'S
GRAIN
DRIED BAKERY PRODUCT
CANOLASEED
CORN
CORN: MOLDY
ERGOT
CANOLA MEAL
CORN:CRACKED
FABABEANS

FIELD PEAS (PRINCESS)
MOLASSES
DEHYDRATED
SOYBEAN SEED
FIELD PEAS (TIPU)
OATS
RYE
SOYBEAN MEAL
LENTILS (LAIRD)
OATS: NAKED (TARA)
RYE: WITH ERGOT
SUNFLOWER SEEDS

SUNFLOWER MEAL:
DEHULLED
WHEAT BRAN
L-THREONINE
TRITICALE
MHA LIQUID
L-TRYPTOPHAN
WHEAT
CANOLA OIL: CRUDE,
DEGUMMED
DL-METHIONINE
l
LYSINE HCI

1. THE SCIENCE OF NUTRITION
Despite major changes in the nature ofthe swine
industry in Canada, the cost offeed remains the
largest single expense involved in raising pigs.
Although the exact cost varies greatly depending on
grain and protein markets, the total feed bill for the
Canadian pork industry approaches one billion
dollars. Even modest savings would provide
benefits to the swine industry in the millions of
dollars.
At the farm level, feed represents slightly more
than 50% ofthe total cost ofproduction and about
75% of the variable costs (Figure 1-1). It surpasses
the next largest expense - fixed costs associated
with housing- by a factor ofthree. Simple logic
dictates that optimizing feed costs - selecting
feeding programs that maximize net income - is a
critical step in ensuring success in pork production.
Figure 1-la. Cost of production budget: all costs.
..
•II FEED 11
111111111 72% 11111111
11111
111111111111111111111111111111111111111111111111111111111
111111
Figure 1-1 b. Cost of production budget: variable
costs only.
It is our experience that much can be
accomplished to reduce feed costs and increase net
income. Linking nutrient supply to nutrient
requirements represents a reasonable, if not
essential goal, but it becomes difficult at the farm
level due to differences in genetics, housing, health
status and overall production objectives.
Recently, a sampling offarrow-to-finish
operations on the Canadian prairies suggested that
feed costs, expressed on a per pig sold basis, varied
by almost 100%! While the lowest feed cost may
not be associated with the highest profitability, it is
clear that such variability is inexplicable by normal
economic and biological principles. The obvious,
and correct conclusion is that nutrients are being
wasted; the source ofsuch waste varies from poor
feed presentation through to diet over- formulation.
Clearly, opportunities exist for significant cost
savings through the application ofincreased knowl-
edge in nutrition. The nutritionist must be able to
identify such opportunities and exploit them effec-
tively. The purpose ofthis book is to provide
practical information on the subject ofnutrition to
afford nutritionists, pork producers and their associ-
ates the capability to exercise greater control over
their feeding programs.
What is Nutrition?
What exactly is nutrition? It is the science that
studies the nutrients needed by animals: how much
ofeach is required in a healthy diet, how they can
be supplied in an economical fashion andhow the
body utilizes them for maintenance, growth and
production. Nutritionists are concerned with
improving the chemical analysis offeeds and
feedstuffs to better reflect their true value to the
animal. Information is drawn from other fields of
science, such as biochemistry and physiology, to
help us understand the basic processes in the body
that dictate the ultimate fate ofthe feed that animals
eat. The essence ofnutrition is to define the
nutrients required by the animal to perform at a

desired level, identify a suitable source ofthese
nutrients and match the two (requirement and
source) in a diet formulation.
This is not a simple task. Nutrient requirements
fluctuate according to many environmental, genetic
and physiological influences. For example, grow-
ing pigs with a maximum protein deposition rate
(Pdma.> of 170 grams per day will have a very
different requirement for essential amino acids than
those with a Pd of 150 grams per day. Sowsma.,
housed outdoors require more nutrients, and thus
more feed, than sows housed indoors. This is
particularly true during the winter.
Diets, therefore, cannot be formulated in a
vacuum; the total circumstances surrounding the
animal including its environment and the type of
farming operation involved must be considered. In
the same way that an engineer designs a barn with a
view towards the producer's management style and
his overall production objectives, the nutritionist
must formulate diets that will complement other
aspects ofthe farm. No single diet will suit all
farming operations.
Diets can not be formulated in a vacuum. Like designing
a barn, feed formulation must consider the total manage-
ment situation including genetics, housing, health, and of
course. economics.
The nutrients supplied by a given ingredient are
sometimes difficult to determine with precision, due
partly to the limitations ofthe chemical analyses
currently available and in part to the many factors
that influence how available these nutrients might be
to the animal.
t<>t> o 0
NUTRIENTS
I t» <>
0 I> 0
QUANTITY
EATEN
PER DAY
"-.. <> g<>o
i t» <> 0
MIXED DIET INGREDIENT A INGREDIENT B
Pig nutrition embraces three components: nutrient requirements, nutrient sources, and daily feed intake.
2

It is also a challenge to determine the intake of
diets, since feed intake will obviously dictate
nutrient intake. The physical capacity ofthe gas-
trointestinal tract plays a role, particularly in nurs-
ing sows, weanling pigs and growing pigs. The
importance of feed intake in practical nutrition is
becoming increasingly apparent, in part because of
the considerable variation that exists among farms -
in the order of30% in the grow out period, for
example. Measuring true feed intake is being
viewed as increasingly important, although it tends
to be a time consuming process.
Palatability is another factor. However, people
will often make the mistake ofascribing human
tastes to the pig. Yet, the pig will eat many things
that humans will not, while some components ofthe
human diet are met with disdain by the pig! Great
care should be taken to avoid altering the diet to
improve what we might think is its palatability. The
pig may have very different opinions on the subject,
and the producer may end up with a more expen-
sive, but no more desirable diet.
The Role of the Computer
In the past 15 years. the computer has become an
indispensable tool to the professional nutritionist for
formulating diets. Farmers who choose to manufac-
ture their own diets now have the added option of
using feed formulation programs designed for the
home computer. Time will tell ifpork producers
choose this option, or decide to leave diet formula-
tion to professional nutritionists working for the
feed industry, provincial extension services or
private consultants.
The use ofthe computer in formulating diets has
met with considerable skepticism, focusing on the
mechanical and unfeeling way with which it com-
bines feedstuffs into a diet. This ignores the incred-
ible power the computer brings to the whole area of
diet formulation. Certainly, the computer is only as
good as the nutritionist operating it and mistakes
can be made. However. the chances oferror are far
more likely with manual calculation. For all their
faults, computers are notably less prone to mistakes
than their human masters! Dependency on the
3
computer has led to errors in diet formulation, but
invariably these can be traced to human mistakes in
programming.
Photo 1 - 1.
The computer can be an enormously useful tool to help
monitor the performance of the breeding herd. It is not a
replacement for good management; itjust makes it easier
and more effective.
The computer has allowed the nutritionist to
move ahead with much greater speed. A balanced
diet contains 40 or more known nutrients. Using
manual calculation methods, it would be impractical
to consider more than three or four nutrients at a
time. With computers. all nutrients can be moni-
tored simultaneously and least-costing programs
focus on a dozen or more ofthe most critical
nutrients. The computer also demands much more
of its nutritionist master in terms ofprecise infor-
mation on nutrient composition, availability, re-
quirements and cost. Researchers have responded
by developing knowledge to accommodate this
expanded need. Finally, computers are being used
increasingly in the development and application of
growth simulation models, with the result that
specific feeding and management programs can be
generated for individual farms. Clearly, in every
respect, the livestock farmer has been a beneficiary
ofthese developments.

The Future of Nutrition
What does the future hold for the science of
nutrition? Already, the advent ofbiotechnology is
having an effect. Reduced costs ofsynthetic amino
acids means that we will have more options for
balancing diets, and that our dependency on con-
ventional protein sources such as soybean meal and
canola meal will diminish.
Both improved crops and superior genetic quality
of pigs will alter the way in which we formulate
diets. The most exciting development, however,
will be a vastly improved ability to understand how
the pig grows and uses nutrients. This knowledge
will be oftremendous benefit because it will expand
our ability to match the pig's diet with its needs for
growth and production. It will allow us to
formulate diets for very specific conditions, such as
the growth of lean as opposed to fat in the carcass;
and to integrate environment, disease and genetics
into the final ration. The costly waste ofexcess
nutrients will be eliminated and pork production
will become a much more efficient process.
The rise of the environment as a key issue in pork
production, and the role ofthe diet in determining
the nutrient content ofslurry, dictates that nutrition
and the environment will be intimately linked in the
future. Indeed, diet formulation with a view to
minimizing nutrient waste not only benefits the
environment, but it often leads to reduced produc-
tion costs. It has forced us all to question bow we
balance diets and design feeding programs, particu-
larly with respect to amino acid (nitrogen) and
phosphorus supply.
CROP
The pig plays an integral part in the environment.
4

2. GASTROINTESTINAL PHYSIOLOGY
The science ofnutrition is closely linked to other
scientific disciplines, one ofthe most important
being physiology. Gastrointestinal physiology is
the study ofthe stomach, the small and large intes-
tines and related tissues. It is a subject that helps us
better understand nutrition.
The Role of the Digestive Tract
Before feed can be used by the pig, it must first
be absorbed from the digestive tract into the body.
From a physiological point of view, the material
contained in the digestive tract is considered to be
outside the body. There are very good reasons for
this. Some parts ofthe undigested food are actually
toxic to the body; the intestinal wall acts as a barrier
to prevent, or at least attempt to prevent, the entry
ofunwanted compounds. For example, some intact
proteins can cause an allergic reaction in the animal.
The proteins in the diet are therefore broken down
into their constituent parts called amino acids,
before being allowed to enter the body.
The breakdown of food into simpler and smaller
compounds is called digestion. Digestion not only
converts proteins into amino acids, but it also
breaks carbohydrates down into sugars such as
glucose or fructose. Fats in the diet are converted
into their constituent parts, largely free fatty acids,
monoglycerides and related compounds. Minerals
are also separated into individual elements. Salt is
an example. Salt is chemically known as sodium
chloride and is broken down into its individual
molecules of sodium and chloride. Although not
digested, some vitamins must be modified in the
gut to facilitate their transfer across the gut wall.
All ofthese processes are required in order to
prepare the nutrients for absorption. The enzymes
involved in the digestion offeed are represented
below. The dual processes ofdigestion and ab-
sorption are discussed in more detail later in this
chapter.
e,oSE
Q
Feed ingredients must be broken down in the gastrointestinal tract into individual nutrients such as protein into amino
acids or starch into glucose.
5

Types of Digestive Tracts
There is an old saying that "You are what you
eat!" In actual fact, all animals must cat according
to what "they are". Each member of the animal
kingdom has a digestive tract that determines the
type of diet best suited to the animal and dictates
how it should be fed. For example, cattle and other
ruminant animals have a complex stomach which
includes four distinct segments each of which has a
specific function. The rumen is the largest of these
and functions as a large fermentation vat containing
both bacteria and protozoa. The action of these
microbes serves to degrade many feed components
and convert them into more simple compounds.
This fermentation process allows the cow to take
advantage ofthe "bugs" that can break down fibre
or roughage into products that, upon entering the
intestinal tract, can be digested and absorbed.
Pigs differ from cattle in that they possess only a
simple stomach. The pig must depend on its own
digestive abilities because it cannot depend on
microbes in a rumen to do thejob for it. The pig is
able to compensate for this, to some extent, because
"bugs" do live in its large intestine and help to
digest fibre after it leaves the small intestine.
Bacterial digestion is believed to provide a signifi-
cant amount ofenergy to the pig, somewhere in the
range of20 percent of its maintenance energy
requirement.
Stomach Small lnttttlne
Figure 2-1. Gastrointestinal Tracts.
6
As a result ofthe differences in the digestive
tracts ofcattle and pigs, their diets are also differ-
ent. The ruminant digestive tract lends itselfto the
use of feeds with a high fibre content while that of
the pig utilizes more easily digested. low-fibre feeds
such as grains.
All animals with a simple stomach are not alike
in terms of nutrition. Chickens and pigs both have
simple stomachs but differ in many areas.
Small lnlesllne
When one considers all ofthese differences, it is
easy to understand why the digestibility of lower
quality feedstuffs such as barley or oats, is higher in
swine than in poultry, while the digestibility of
higher quality or more easily digested feed ingredi-
ents such as corn or fish meal, is higher in poultry.
The reason appearers to be that the combination of
rate ofpassage and mixing, which occurs in the
intestinal tract ofthe chicken, maximizes the use of
highly digestible ingredients, but reduces its ability
to extract nutrients from feedstuffs requiring more
prolonged digestion.

PIGS DIFFER FROM CHICKENS
* The pig has a stronger sense of
taste, so palatability is ofgreater concern
with swine than with poultry.
* Poultry have a shorter intestinal
tract but compensate by moving digesta
back and forth within it more effectively
than pigs and thus enhance nutrient ab-
sorption.
* The rate ofpassage ofmaterial
throughout the gut ofthe pig is slower
than that of the chicken. This helps the
pig increase its nutrient absorption.
E3 SMALL INTESTINE (18.3 M)
D CECUM (0.2 M) � COLON (5.0 M)
Figure 2-2b. Length of the Gastrointestinal Tract.
Adapted from E.T. Moran, 1982.
* Chickens have a smaJler total
Figure 2-2a. Capacity of the Gastrointestinal Tract.
capacity in the large intestine than pigs,
and thus the contribution ofmicrobial
fermentation is reduced.
The physiology of the gastrointestinal tract ofthe
pig plays an important role in determining what
constitutes a good or bad diet. Figure 2-2 illustrates
the size and capacity ofvarious segments ofthe
gastrointestinal tract in the fully grown pig.
Secondly, chewing mixes saliva into the food.
The saliva lubricates the material to make swallow-
ing easier. It also contains digestive enzymes which
initiate the breakdown ofthe food bolus. For
example, an enzyme called amylase, which helps to
break down starches, is a component of saliva. The
amount ofstarch digestion occurring in the pig due
to salivary enzymes is not substantial. It has been
estimated that the quantity of salivary amylase is
less than 0.001 percent that ofpancreatic amylase.
The Stomach
Once food enters the stomach, the next phase of
digestion begins. The stomach serves as a large vat
in which food is mixed with acid and digestive
enzymes plus a substance called intrinsic factor.
Because the stomach secretes acid into itself, its
structure must be such that it does not digest itself!
Mother nature works in wonderful ways, and in this
case, the stomach also produces a mucous-like
substance that lines the stomach and helps prevent
acid from damaging it.
Eating and Swallowing
Digestion offood actually begins in the mouth
where chewing accomplishes at least two important
objectives. The grinding action ofthe teeth serves
to break down food particles into smaller pieces to
facilitate swallowing and to increase their exposure
to digestive enzymes.
33.5%
29.2%
D CECUM (1.6 L)
� COLON (8.7 L)
[ill STOMACH (8.0 L)
§ SMALL INTESTINE (9.2 L}
7

Acid secreted in the stomach serves to alter the
structure of food proteins making them more
accessible to digestive enzymes and initiating the
action ofcertain digestive enzymes. For example,
the stomach secretes a compound called
pepsinogen. When pepsinogen is exposed to the
acid of the stomach, it is converted into pepsin, a
very potent enzyme involved in the digestion of
proteins.
The intrinsic factor is an interesting compound
also secreted by the stomach. It is absolutely
critical in the prevention ofa disease called perni-
cious anemia, which is due to a vitamin B12
defi-
ciency. The intrinsic factor must bind to the
vitamin B12
supplied by the diet ifthe vitamin is to
be absorbed. Supplements ofthe vitamin will not
prevent pernicious anemia ifthe intrinsic factor,
which cannot be added to swine diets, is not present
to allow for its absorption.
The secretory activity ofthe stomach must not be
underestimated. For example, in one study, 40 kg
pigs were found to secrete four to eight litres of
total fluid per day.
A major role ofthe stomach is to control the rate
ofentry offood into the small intestine and thus
contribute to a more gradual supply ofnutrients
from the gut. After a single meal, the stomach can
mete out digesta to the lower gut over a period of
18 hours or more.
It has been postulated that in the young pig, the
formation ofthe 'milk clot' in the stomach is
critical in slowing the entry offood into a relatively
immature small intestine. The problem with diets
containing little or no milk is that clotting is im-
paired and transit time is increased. An excessive
rate of passage of food into the small intestine
overloads the system. The problem is compounded
by the reduced digestive abilities ofthe small
intestine ofthe young pig. This is extremely
important to consider at the time of weaning. Once
poorly digested material overwhelms the gut,
undesirable bacterial fermentation begins and
scouring results. lt is recommended that recently
weaned pigs fed non-milk diets should be limit-fed
for five to seven days to help prevent scouring.
8
In summary, the stomach ofthe pig secretes acid,
pepsinogen and intrinsic factor which all contribute
to the digestion and absorbtion offood. The stom-
ach also acts as a regulator offood entry into the
small intestine, helping to prevent either overloading
or deprivation.
The stomach ofthe pig is susceptible to ulcers,
especially in the esophageal region. Ulcers are
common in growing and adult swine, although most
producers do not recognize the problem until death
occurs. Symptoms ofbleeding ulcers include dark
feces and anemia, both due to the loss ofblood into
the intestinal tract. Animals with a chalky, white
colour may also have a bleeding ulcer. Ulcers can
impair growth in swine and in severe cases, result in
death. Detailed information on ulcers is surprisingly
limited, but it is suggested that economic losses are
greater with subclinical ulcers which reduce animal
performance, than from death loss itself.
The cause ofgastric (stomach) ulcers is not really
known. Many factors are associated with them but
more research needs to be carried out in this area.
CURRENT THEORIES ON THE
CAUSES OF ULCERS
* Some suggest that "stress" is involved but
this has not really been studied nor quantified.
* Diet type may be involved with wheat and
corn showing more ofa connection with ulcers
than barley or oats. This may be due to their
different fibre contents.
* Pelleted diets may also contribute to ulcers
and yet the number of animals fed pelleted diets
without apparent problems suggest that it is not
the sole cause. The fine grind required to manu
facture firm pellets is probably more of a factor
than the pelleting process itself.
* Other dietary factors that may be involved
include fineness ofgrind, the presence of milk
proteins, high fat content, especially of unsatu
rated, long-chained triglycerides and deficiencies
in thiamine and vitamin E.
* Ulcers also appear to be a greater problem in
minimum disease herds, possibly because other
health problems are reduced or because animal
performance is higher.

Photo 2 - I.
Cross section of the intestinal tract, showing the villi
extending into the lumen of the gut(top). The mus-
cles of the gut, which allow it to mix and move its
contents, appear at the bottom of th� photo. The
micro-vllli, too smaJI to be seen in this photo appear
opposite.
An outbreak of ulcers can be treated by adding
coarse fibre to the diet. Oats appear to be particu-
larly effective. The inclusion of 10% whole oats
even in pelleted diets is beneficial, although pellet
quality will suffer. If oats are added, adjustments
need to be made to the diet to account for the drop
in energy. In some cases, long hay can be offered to
affected pigs to increase the fibre level in their diet.
but this is generally impractical in barns with liquid
manure systems. A coarser grind ofthe total grain
in the diet may also prove helpful. The topic of
grinding is covered in more detail in Chapter I 0.
9
Photo 2 - 2.
A more powerful microscope shows the micro-villi
(top) typical ofthe small intestine. The dark oblong
structures below the micro-villi are called
mitochondria; they act like little power plants to
drive the many activities of the gut.
The Small Intestine
The small intestine works in conjunction with a
number oftissues to achieve its objectives of
digestion and absorption ofas much food as possi-
ble. For example, it accepts digestive enzymes
from the pancreas to supplement those it manufac-
tures itself. Tt gets bile from the liver to assist in the
absorption of fats and fat soluble vitamins. Many
hormones produced throughout the body regulate
the activity ofthe small intestine in relation to
feeding, appetite and other external signals. As
well there are internal stimuli, such as gut fill and
the presence ofcertain materials in the gut which

also help to regulate its activity. It is quite clear
then that the small intestine does not work in
isolation, but is influenced by many other tissues in
the body. Once food enters the small intestine from
the stomach, digestion speeds up and absorption
begins. More enzymes are added to the digesta, as
well as mucous, buffers and bile. Some of the
enzymes are produced locally by the intestine;
others arrive from the pancreas.
Specific enzymes have specific roles to play.
Carbohydrates, such as starches and sugars, are
broken down by the action ofenzymes which are
very specific with respect to the carbohydrates they
will attack. Amylase breaks down starches such as
those found in grains. Sucrase degrades sucrose
(table sugar) and lactase degrades the 'milk sugar',
lactose.
Proteins are digested by a totally different set of
enzymes. Proteins must be broken down into
amino acids before crossing the intestinal wall.
Protein digestion begins in the stomach but be-
comes much more effective in the small intestine.
Examples ofprotein-degrading enzymes include
trypsin, chymotrypsin, elastase and
carboxypeptidase. The protein-degrading
(proteolytic) enzymes attack proteins at very spe-
cific locations in their structure.
Fats in the diet must also be digested before
being absorbed. An enzyme called lipase, derived
from the work lipid which is another name for fat,
breaks fats into smaller parts which are then com-
bined with bile salts to form a compound that can
cross the intestinal barrier. Bile salts are produced
in the liver and are an absolute necessity for proper
fat digestion.
lt can be seen that a very competent system has
been devised to allow the pig to digest the various
components in the diet. Failure of any part of this
system will result in impaired utilization of food. It
is a complex system, with details far beyond the
scope of this book. lt is important, though, to
recognize that digestion is not a simple matter and
that what and how we feed the pig, how we house
it, how old it is and how healthy it is can all influ-
ence the final outcome of the digestive processes.
10
The structure ofthe small intestine is uniquely
designed to accomplish its objectives ofdigestion
and absorption of nutrients. The walI is heavily
muscled which permits the intestine to expand and
contract in a rhythmic manner to move material
along its length and to assist in mixing enzymes,
bile and other secretions into its contents. The
process also ensures that material ready for absorp-
tion is brought into contact with the absorptive cells
found along the intestine surface. The constant
mixing motion is absolutely critical ifthe process of
absorption is to be efficient.
The small intestine is designed to maximize
absorption. The surface consists offiner-like
projections called villi which increase the surface
area ofthe gut and thus increase its absorptive
capacity. Along the villi are further projections,
called microvilli which also increase surface area
and thus, the absorptive capacity ofthe small
intestine.
Another interesting feature ofthe small intestine
is the way in which the absorptive cells grow. They
are called enterocytes and are formed at the base of
the villi and then migrate up along its surface as
they mature. The maturation process is important
because the more mature these cells are, the greater
is their content ofdigestive enzymes. The migra-
tion ofenterocytes along the surface ofthe villi
from the base to the tip, ensures that the mature
cells receive maximum exposure to the contents of
the intestine; meanwhile, the immature cells located
at the base ofthe villi are protected rom the physi-
cal forces offood moving along the length ofthe
intestine. Once the enterocytes reach the tip ofthe
villi, they are sloughed offinto the lumen ofthe
intestine, to be digested and absorbed. These
sloughed offcells, together with enzymes secreted
into the intestine, constitute what are cal1ed endog-
enous protein. This endogenous protein has been
estimated to represent anywhere from 25 to 75% of
the protein digested and absorbed by the gut. The
diet makes up the remainder.
The cells have a very briefexistence even under
conditions ofgood health. The life expectancy of
an enterocyte in a one week old piglet is only two to
four days. Sometimes the enterocytes do not reach

Moving through
the lumen, feed Is
digested and absorbed
Into the body of the
pig. Muscles surround
the Intestinal tissue;
their contraction
moves the dlgesta
along the tract and
helps mix In digestive
enzymes.
DISCARDED CELLS
!1
Folds in the
intestine are lined
with projections called
villi. The villi
increase the surface
area, thus enhancing
both digestion and
, absorption.
-,
'>1--.
'�� ' "-.�� <',<
."" , "� '$� '..o
":/ o 0}
-,
BLOOD VESSELS
��2----/
The individual villus consists of
cells that form at the base and migrate
to the tip, where they are sloughed off
Into the lumen of the intestine. As the
cells migrate they mature, Increasing
their ability to break-down and absorb
nutrients from the lumen of the gut. It
takes a cell 2-5 days to move from the
base to the tip. Each day, literally
billions of cells are discarded along the
length of the pig's gastrointestinal
tract. The villi are also the site of
absorption, where nutrients pass
through the cells to enter the blood
stream.
THE SMALL INTESTINE OF THE PIG
NUTRIENTS ABSORBED INTO BLOOD
11

maturity, but are sloughed off into the intestinal
lumen prematurely. As a result, the 'oldest' cells in
the system arc still immature. Ifthis happens, the
digestive ability ofthe small intestine is impaired
due to the absence ofmature cells and their rich
source ofdigestive enzymes.
Several things have been shown to influence the
lifespan of absorptive cells. Research suggests that
one ofthe factors responsible for the post-weaning
lag in the young pig is a reduction in the length of
the villi. This results in a greater proportion of
immature intestinal cells with reduced digestive
capacity. Diet composition and feeding behaviour
may also affect the Iifespan of the cells. For exam-
ple, even a few days off feed wiU lower the rate of
cell turnover and impair the intestine's ability to
produce new cells.
"' 100
CD
.c..0 80Ill
.c
<
ell
60
'i 40
iii
CD
Cl
20
0
*- 0
Duodenum Ileum
- O,yMa!ter
- En11gy
- Nlltogan
To1•1 Tract
Figure 2-3. Nutrient Digestion Along the Gastrointes-
tinal Tract of the Pig.
What does all this mean in the day-to-day feeding
of pigs? A very relevant example is the post-
weaning Jag mentioned above. The stress ofwean-
ing with an associated drop in feed intake, appears
to have a negative effect on the structure ofthe villi
and thus, the function ofthe smaU intestine. Re-
moving milk form the diet impairs clot formation
and increases the flow ofmaterial from the stomach
into the small intestine. The small intestine is
unable to handle the material presented to it result-
ing in digestive upset. A further drop in feed intake
compounds the problem. Poor sanitation which
leads to increased stress from disease makes the
situation even worse. Various feeding regimes
designed to minimize this problem wilJ be dis-
cussed in Chapter 5.
Another feature ofthe small intestine and the
stomach which is relevant to practical nutrition is
their overall capacity. Size plays an important role
in determining the amount of food a pig can eat. It
has been estimated that the capacity of the small
intestine represents a major Limiting factor in young,
growing pigs and that among individual animals,
the length of the intestine is correlated with Lean
tissue growth. As a result, young pigs are fed a very
concentrated diet that maximizes the quantity of
digestible nutrients per unit of feed and thus, the
amount ofnutrients consumed per day by the
animal.
The Large Intestine
The large intestine plays an important role in the
processes ofdigestion and absorption. Figure 2-2
shows how the digested portion offood increases as
it passes along the intestinal tract. By the time the
digesta leaves the first part ofthe small intestine
called the duodenum, much of it remains to be
absorbed. Even as the food passes throught the last
segment ofthe small intestine called the ileum,
digestion and absorption still occur.
The major role ofthe large intestine, which
consists ofthe cecum and colon, is to absorb water
and certain minerals called electrolytes. Bacteria in
the large intestine break down undigested food and
help to extract more nutrients, especially energy,
from the feed ingredients. Complex carbohydrates,
supplied by fibre (roughage) in the diet, are con-
verted by the bacteria into volatile fatty acids.
These volatile fatty acids can be absorbed and used
as an energy source by the pig. The ability to utilize
more fibrous ingredients increases in older animals.
Sows for example, can utilize alfalfa hay more
efficiently than weanlings.
The B-vitamins, as well as vitamin K, are pro-
duced by these same bacteria. It is not clear,
though, to what extent the vitamins can be absorbed
12

by the large intestine. lf the vitamins are excreted
in the feces and re-eaten, they will then contribute
to the vitamin nutrition of the pig. Some people
believe that pigs housed on fuJly-slatted floors
which have Jess exposure to manure, have a higher
requirement for dietary vitamins. There is very
little scientific evidence to support this. The pru-
dent approach is to ensure that the diet is properly
supplemented with preformed vitamins to meet the
requirements of the pig. In this way, the pig is not
dependent on microbial fermentation to supply even
a portion of its vitamin requirements.
Some of the information in Figure 2-2 must be
interpreted with great care. It suggests that nitrogen,
and thus protein, is absorbed by the large intestine.
It is true that nitrogen is absorbed, but unfortu-
nately, not as amino acids. Thus, ifan essential
amino acid is not absorb from a feed by the end of
the small intestine, it will not be absorbed intact.
The large intestine does not have the ability to
absorb essential amino acids but rather absorbs
nitrogen as a simpler compound called ammonia.
Nutritionists who are measuring the proportion of
lysine or other amino acids digested from a given
feedstuffwill collect digesta as it leaves the small
intestine rather than collect the feces. This is done
quite painlessly by surgically placing a collecting
tube in the intestinal tract of the pig. Ifnutritionists
use feces to determine amino acid digestibility, their
results will be incorrect. The bacteria in the large
intestine break down lysine and other amino acids
and are also able to manufacture amino acids from
non-protein nitrogen.
Summary
It appears that about 20% ofthe intestinal tissue
turns over (is replaced with new tissue) every day!
In the pancreas, up to 75% of the tissue is replaced
daily. This compares with muscle which turns over
at a rate of 2 to 3% per day. It has been estimated
that 25% of the protein turnover in the total body
occurs in the gastro-intestinal tract.
Studying the physiology ofthe stomach, intes-
tines and related tissues in the pig provides ex-
tremely useful information on how the pig digests
and absorbs feed, and how different conditions
13
impair this activity. Simply stated, for best per-
formance, the pig should be fed a diet that is suited
to its digestive abilities. Since these abilities change
with age, the better quality and more expensive
ingredients should be used with the younger pig
than with the adult sow or boar.
Additional Reading and References
Lloyd, L.E., B.E. McDonald and E.W. Crampton.
1978. Fundamentals ofNutrition. W.H. Freeman
and Co., San Francisco. 466 pp.
Low, A.G. 1989. Research into the digestive
physiology ofpigs. In. (E.J. van Weerden and J.
Huisman, eds.) Nutrition and Digestive Physiology
in Monogastric Farm Animals. pp. 1 - 15, Pudoc,
Wageningen.
Moran, E.T., Jr. 1982. Comparative Nutrition of
Fowl and Swine: The Gastrointestinal System,
University ofGuelph, Guelph.
McDonald, P., R.A. Edwards and J.F.D.
Greenhalgh. 1973. Animal Nutrition. Oliver &
Boyd, Edinburgh.
Pond, W.G. and K.A. Korpet. 1978. The Biology
ofthe Pig. Cornell University Press, Ithaca.
371 pp.
Whittemore, C.T. 1987. Elements ofPig Science.
Longman Handbooks in Agriculture, Harlow.
181 pp.
Whittemore, C.T. 1993. The Science and Practise
of Pig Production. Longman Group, U.K. Ltd.,
Harlow. 661 pp.

3. NUTRIENTS
Although diets are mixed using ingredients,
what really matters to a pig are the nutrients
contained in those ingredients. The relative
proportions of barley, wheat, soybean meal, and
other feedstuffs in a diet are determined on the basis
ofthe nutrients they provide to a pig. When a
nutritionist formulates a diet for pigs, no less than
41 essential nutrients are considered.
The essential nutrients can be divided into
categories ofminerals, amino acids, vitamins, fatty
acids, energy, and water (Table 3-1 ). If a diet is to
be properly balanced, the nutritionist must know the
pig's requirement for each nutrient and the amount
supplied by each ingredient.
Table 3-1. Essential Nutrients in the Diet of a Pig.
In this chapter, the utilization ofnutrients by
pigs and means to estimate the available nutrient
levels in pig feed ingredients are discussed. For
information on nutrient allowances in diets for the
various classes of pigs, the reader is referred to
chapters 6 - 9. Water, which can also be classified
as a nutrient, is addressed in chapter 12.
What is a Nutrient?
Knowing the difference between a nutrient and
an ingredient, or feedstuff, is critical when
formulating a diet. A nutrient is a chemical
substance that is supplied by the diet and which pigs
need to stay alive. Nutrients perform specific
functions in the body and their absence or
deficiency will result in reduced productivity, health
problems and, possibly, death.
An ingredient or feedstuff is the material used to
supply nutrients. For example, barley and com are
ingredients which contain amino acids, energy, and
other nutrients. They can supply a pig with some of
the nutrients it needs. A balanced diet mixes
ingredients, such as com or barley, that supply the
nutrients in proper proportions. The pig has no
specific requirement for individual ingredients - it
does not need barley or com, specifically, in its diet,
for it can obtain the necessary nutrients from other
ingredients, such as canola or soybean (or in some
countries, even green bananas!). A pig may prefer
to eat one ingredient over another, but ingredients
have no unique role in a pig's diet. Selecting the
type of feedstuffs to supply nutrients is much less
critical than making certain the necessary nutrients
are supplied from the feedstuffs chosen.
15
Amino Acids Minerals Vitamins Other
* These amino acids are considered semi-essential
nutrients because they can be derived from methionine
and phenylalanine, respectively. Other nutrients, such as
vitamin C, linolenic acid, fluorine, chromium, nickel, lead
silicon, tin, and vanadium, may be essentiaJ in a pig's diet,
however, deficiencies are extremely unlikely and/or
requirements for these nutrients have not been clearly
established.
Nutrient Availability
Availability refers to the pig's ability to digest,
absorb, and utilize nutrients from a given
ingredient. Very few nutrients are 100% available.
A nutrient may be present in an ingredient but not
available to the pig for both mechanical (e.g.,
processing methods) and physiological (e.g.,
digestive functions, age, state of health) reasons.
Defining the availability for each nutrient in each
ingredient is a difficult task because availability
Arginine Macro Vitamin A Energy
Histidine Calcium Vitamin D Linoleic
Isoleucine Chloride Vitamin E Acid
Leucine Magnesium Vitamin 812
(Omega-6
Lysine Phosphorus Biotin fatty acids)
Methionine Potassium Choline Water
Phenylalanine Sodium Folic Acid
Threonine Sulphur Menadione
Tryptophan Niacin
Valine Micro Pantothenic Acid
Cystine* Cobalt Pyridoxine
Tyrosine" Copper Riboflavin
Iodine Thiamine
Iron
Manganese
Selenium
Zinc

5
Figure 3-1. Pig Response to Level of Nutrient in the
Diet.
10
o..L.�---�------.....-..1,--.--r--.-....,....-r....,............,
o 2 4A s s
Nutrient Level In the Diet
*As the requirement (point A) is approached, the rate of
improvement per unit of nutrient decreases.
: .c
g_ 3
••a: 2
CII
a: 1
How docs the nutritionist work around this
problem? In many cases, sufficient information is
available to permit at least an educated guess. Diets
will often include more than one basal grain and
more than one protein supplement. Thus, the
nutritionist 'hedges his position' across a number of
ingredients, such that underestimating one might be
compensated by overestimating another. This
approach is not a totally desirable one, but until
more precise data becomes available, it is probably
the most practical one.
varies from ingredient to ingredient and is
influenced by many factors.
Nutrient Requirements
What is meant by the word 'requirement' from a
nutritionist's perspective? Traditionally, a
requirement has been defined as the amount ofa
given nutrient a pig requires to maximize
performance. Producers need to understand the
criteria used to determine requirements because
how the requirements are determined can influence
the way producers use nutritional information.
One ofthe frustrations in defining a requirement
is that maximum performance may occur at
different nutrient levels depending on the response
criteria being considered. For example, maximum
growth rate may require more or less ofan amino
acid than maximum feed efficiency. The amount of
a given nutrient required to maximize the immune
response may differ from the amount required for
maximum feed intake. Ifcarcass merit is used to
evaluate nutrient requirements, conclusions may
differ from those reached using growth rate.
Thus, requirement defines the level needed to
achieve maximum performance but not necessarily
maximum profit. Each situation must be evaluated
to determine the best (most profitable) feeding
strategy.
Although we would all like to have neat, simple
tables defining an absolute value, they are not
realistically possible. Some compromise must
occur. The compromise does not diminish the value
or importance ofnutrient requirement tables, it
merely emphasizes the importance ofunderstanding
their origin. Three excellent publications that
provide useful requirement guidelines are the
National Research Council's Nutrient Requirements
ofSwine (1988), the Agricultural Research
Council's The Nutrient Requirements ofPigs
(1981), and the Australian Agricultural Council's
Feeding Standardsfor Australian Livestock - Pigs
(1987).
Typically, in the case ofessential amino acids
and many minerals, the requirement is determined
by feeding a range oflevels ofthe nutrient and
determining the lowest concentration that
maximizes growth rate, feed efficiency, or some
other response criteria. The key word here is
'maximize'. Often, the pig's response to increasing
levels ofa nutrient becomes progressively smaller
as the requirement level is approached (Figure 3-1);
consequently, the cost of the last I 0% improvement
is much higher than the first 10%.
Energy
According to the definition given earlier, energy
is not truly a nutrient. Energy is a characteristic of
the organic nutrients (carbohydrates, fats, amino
acids) that are normally present in the pig's diet.
The energy released by burning a substance in a fire
is the same as the energy obtained by the body
when it metabolizes energy in a cell. The amazing
point is that, unlike an open fire which releases all
its heat, the body is able to 'capture' the energy that
is supplied by the diet and convert at least part of it
16

into forms the cell can use for various purposes.
Energy, due to the amount required, is generally the
most expensive 'nutrient' in the pig's diet.
Consequently, nutritionists focus considerable
attention on energy in feed formulation and feeding
management in order to minimize feed cost without
compromising performance.
energy is called net energy (NE). NE is the best
estimate ofthe amount ofuseful energy that is
supplied by feed ingredients.
Metabolizable Energy - Heat Increment= Net
Energy
Figure 3-2. Distribution of Dietary Energy.
Some scientists have attempted to use this
information on heat increment to practical
advantage by designing diets around heat
increments. The pig is a warm-blooded animal and
must maintain a constant internal body temperature
irrespective ofthe temperature ofits surroundings.
Normal metabolism generates heat that is used in
body temperature regulation. Ifa pig is chilled, it
must eat more feed to keep warm or else it will lose
weight or gain it at a slower rate. The heat
increment is used to provide some ofthis required
heat, so heat increment in a diet is desirable. The
pig will need less heat to maintain a constant body
temperature in hot weather and will actually lower
its feed intake to reduce the production of metabolic
body heat if it is in danger of becoming heat
stressed; in this case, heat increment in the diet is
detrimental. Obviously, in these two instances, pigs
will require diets with different heat increments.
The quantity ofheat increment varies depending on
the nature ofthe diet.
Production
Net energy
I
Metabolizable energy
I
IDigestible energy
I
Gross Energy
I
Maintenance
IFecal energy
Urinary energy
Heat increment
A portion of metabolizable energy is lost when
the pig uses the nutrients in the feed as heat, i.e. heat
losses during eating, digestion and actual nutrient
metabolism. This portion is called the heat
increment. Once the heat increment is used up out
of ME, the energy actually available to the pig for
maintenance and growth is left. This amount of
Gross Energy - Fecal Energy = Digestible Energy
_Some ofthe digestible energy is lost in the pig's
unne or released as gas from its gastro-intestinal
tract. Much ofthe energy lost in the urine results
from the excretion ofunneeded nitrogen
compounds, such as urea. The amount ofdigestible
energy remaining in the pig after these losses is
called metabolizable energy (ME).
Digestible Energy - (urine energy loss+ gas energy
loss)= Metabolizable Energy
Energy Components
The total quantity ofenergy contained in a
feedstuffcan be partitioned into different
components based on how the pig will use the
energy (Figure 3-2). Ifan ingredient, such as barley
or wheat, is burned completely, the amount of
energy released is called gross energy (GE). The
gross energy content can be determined by the
bomb calorimeter. GE is thus the total amount of
energy contained in the grain; ifthe pig could digest
and utilize 100% ofthe energy, that is how much
would be available. The pig, however, digests or
absorbs only a portion of the gross energy. The
energy absorbed by the intestinal tract and actually
available to the pig is called the digestible energy
(DE). The DE content of any feedstuffcan be
determined by measuring the quantity offood
(energy) consumed and subtracting the energy lost
in the feces (calculated by weighing the feces and
analysing their composition).
17

The solution proposed by some scientists is to
feed a diet high in heat increment (rich in fibre)
when the pig is likely to be chilled. When the pig is
likely to be heat stressed, a diet low in heat
increment (rich in fat) is recommended. Under
Canadian conditions, this feeding approach means
feeding a high-fibre diet to dry sows in chilled
conditions, such as in outside housing in winter or
in a cool gestation barn (especially barns equipped
with individual stalls where sows cannot huddle to
keep warm). A high fibre diet is never fed to
weanling pigs, lactating sows, or growing pigs
because growth rate would suffer. In the heat of
summer, lactating sows and growing pigs should
receive a diet rich in fat to help maintain energy
intake. Ofcourse, these suggestions must be
considered in the context ofcost and economic
benefit.
Although net energy is the best estimate ofhow
much useful energy is supplied by a diet, it is rarely
used as a system for formulating swine diets in
North America because of the difficulty in routinely
and accurately determining the heat increment of
feeding when different ingredients are fed to pigs.
NE systems are used more commonly in European
countries, where a larger variety of ingredients are
used to formulate swine diets.
Table 3-2 shows the GE, DE, ME, and NE
content in selected pig feed ingredients. Most of
the ingredients listed are very similar in GE content.
There are, however, some important differences in
DE content, both expressed in absolute values as
well as in fractions ofGE content. In fact, barley
contains more GE but Jess DE than com. This
clearly indicates that it is more accurate to
formulate pig diets based on a DE basis rather that
on a GE basis.
The proportion ofdigested energy lost in the urine
is fairly constant for all grains and all protein
sources, but differs between these classes of
ingredients. This difference is due in part to the
urinary energy lost during excretion ofnitrogenous
waste products. Because ofthe differences between
protein sources and grains, there are theoretical
advantages to using ME values in preference to DE
values to formulate feed. However. note that many
of the published ME values have merely been
derived mathematically from DE. Direct assays
(analyses) ofME are difficult since measuring the
amount ofenergy excreted in the urine poses a
number of logistical problems. Whether DE or ME
is used, be certain that both requirement and
nutrient values are expressed in the same system.
The values in Table 3-2 demonstrate that the
differences in NE content between feedstuffs tend
to be larger than the differences in DE content. For
example, in a DE system. corn contains 12% more
energy than barley. In a NE system, this difference
increases to 15%. For ingredients with extreme
compositions such as alfalfa and wheat shorts (high
in fibre) or soybean oil (high in fat), these differ-
Table 3-2. Proportions of Gross Energy (GE), Digestible Energy (DE), Metabolizable Energy (ME) and Net
Energy (NE) in a Sample of Ingredients.
GE DE ME NE DE:GE ME:DE NE:ME
Alfalfa Meal 3830 1880 1705 540 .49 .91 .32
Barley 4395 3120 3040 1980 .71 .97 .65
Corn 3945 3490 3380 2270 .88 .97 .67
Wheal 3965 3360 3200 2215 .85 .95 .69
Wheat Shorts 4060 3025 2835 1795 .75 .94 .63
SBM 47% 4260 3680 3385 1760 .86 .92 .52
Soybean Oil 9395 7560 7280 5500 .80 .96 .76
Derived from: Ewan, 1989; Energy metabolism offarm animals. EAAP publication No.. 43. Pudoc Publishers,
Wagcningcn,The Netherlands.
18

ences are even more apparent. This again illustrates
that, in theory, it is more accurate to formulate diets
using an NE rather than DE or ME system.
Energy is measured in units ofeither calories (cal)
orjoules (J). The term used in this book is the
kilocaloric, equal to 1000 calories. Thejoule is
more common in Europe and is becoming more
popular in Canada, but is not yet universally
accepted. One calorie equals 4.184 joules.
hemicellulose, and lignin, which are essentially
indigestible by swine. ADF consists only of
cellulose and lignin. ADF and NDF were
developed to evaluate forages for ruminant species.
They have also been found valuable by swine
nutritionists but tend to underestimate the total fibre
ofcereaJ grains.
Table 3-3. Fibre Content of Ingredients Used in Swine
Diets.
Energy Sources Ingredient
Dietary energy is derived from three sources:
carbohydrates, fats, and amino acids. The term
carbohydrate includes simple sugars and starches,
such as table sugar or the starches found in flour,
which are all highJy digestible. Carbohydrates also
include more complex compounds, such as fibre,
which is difficult to digest, and thus a poor energy
source.
Content(%)
Dietary Crude
Fibre NDF ADF Fibre
Barley 19 15 5 4
Corn 9 8 2 2
Peas 16 10 7 5
Soybean meal 24 15 9 8
Wheat 11 10 3 2
Defining the term fibre has been a source of
controversy for decades. For the purposes of this
book, fibre is defined as the portion of carbohydrate
in a diet that cannot be digested by the enzymes
produced by a pig. Pigs, like ruminants, rely on
bacteria that are present in the digestive tract to utilize
dietary fibre. The pig does not have a requirement
for fibreperse, although it provides a texture in diets
that helps digestive processes. Fibre is used to evaluate
ingredient quaJity because it is associated with reduced
DE content and impairedutilization ofother important
nutrients. Therefore. from a nutrient perspective, fibre
has a generally negative impact onanimal feed quality.
Measuring fibre in feed ingredients is an area of
active research. Table 3-3 defines the fibre content of
some common ingredients. The complex nature of
fibre is illustrated by the number of fibre values
defined. Dietary fibre is a Swedish tenn that includes
lignin (a highly indigestible carbohydrate found in
such feedstuffs as straw) plus all complex sugars not
found in starch.
The detergent system, developed by P.J. van Soest
in the United States, differentiates between two
kinds offibre: acid detergent fibre (ADF) and
neutral detergent fibre (NDF). NDF includes
material in the plant cell wall, notably cellulose,
Adapted from: Graham 1988. Anim. Plant Sci. 1 :76-80.
There are large differences in the values obtained
by these measurements, although they all attempt to
define the same component of feed ingredients -
indigestible carbohydrate. Most Canadian feed
testing laboratories report crude fibre, although acid
detergent fibre and neutral detergent fibre
measurements are gaining popularity.
The ether extract (fat) content ofa feedstuffor
diet is important because fat is rich in energy. All
other factors being equal, the higher the fat content
in a diet, the more digestible energy it will contain.
Determining fat content provides some insight into
how much energy is present. Fat content is
estimated by determining the portion ofthe sample
that is soluble in petroleum ether. This procedure is
a standard one, but misses some important
compounds. such as energy-rich phospholipids. In
barley, for example, these phospholipids represent
as much as 25% ofthe total fat in barley grain and
contribute to its total energy.
Ether extract will also include such components
as waxes and pigments, which are of little
nutritional value. For this reason, the digestibility
19

Feedstuff
Alfalfa meal
Barley
Com
Soybean meal
Meat meal
Wheat
Wheat bran
Percent
Digestibility
54
86
80
80
93
52
58
Estimating Energy Contents in Feeds and
Feed Ingredients
Evaluating the content ofenergy and other
nutrients in feed ingredients is an important step in
formulating diets for swine. Without knowing the
amounts of nutrients supplied by individual
ingredients, one cannot, with any degree of
certainty, put together diets that will satisfy the pig's
needs. Unfortunately, there is a considerable
amount ofvariation in available energy contents
between different samples of one feedstuff. For
example, recent research at the Prairie Swine Centre
demonstrated that DE content varied by as much as
l0% between various samples ofsubstandard
wheat, with the poorest sample similar to that in
regular barley. This demonstrates the use of
average book values is not sufficient to estimate
nutrients in specific samples offeed ingredients.
However, it is simply too expensive and time-
consuming to evaluate the nutritional value of
feedstuffs in feeding trials. There is thus a need for
rapid, inexpensive, and practical tests for use in
day-to-day diet formulation. Laboratory (chemical)
evaluation can be ofgreat assistance in meeting this
need. World-wide research has attempted to
develop chemical and alternative tests that give the
true nutrient composition of ingredients and mixed
diets, and accurately reflect the true feeding value.
Table 3-4. Digestibility of Ether Extract of
Common Feedstuffs.
ofthe ether extract varies among grains as they vary
in the relative proportion of phospholipids and
waxes (Table 3-4).
What is the solution? Some nutritionists use
di ITcrent solvents in place of petroleum ether to
extract the fat of feed grains thus developing a more
complete analysis. Common alternative solvents
include diethyl ether, and a 2: 1 mixture of
chloroform and methanol. Different solvents arc
used to answer different questions. As in most
analyses, there is no complete test for all answers.
Adapted from: Animal FeedstuffTable. 1991. Centraal
Veevoederbureau, Runderweg 6, 8219 PK Lelystad, The
Netherlands.
Amino acids supply energy only when they are
not used for protein synthesis. Animals prefer to
use amino acids to produce body protein. Amino
acids supplied in excess ofthe animals'
requirements for the synthesis of body protein or
other nitrogenous compounds are degraded and
used as an energy source. Since protein is a very
expensive energy source, excess amino acids should
not be added to a diet intentionally to help meet the
pig's energy requirements. Much cheaper energy
sources, such as carbohydrates, are preferred
wherever applicable in a diet. In addition, some of
the energy derived from amino acid degradation is
required for the excretion (through urine) of
nitrogenous compounds that are derived from
amino acids. This requirement reduces the amount
of available energy that can be derived from
degraded ammo acids.
An example ofthe progress made in this area is
the use ofnear infra-red analyses (NTRA) to
evaluate feed samples. Nutrient levels are estimated
based on the feed sample's absorption of specific
wavelengths of infra-red light. However, in order to
properly calibrate NIRA equipment, large numbers
ofsamples which enclose the entire range of
samples to be tested and with known nutrient
contents and availabilities arc required. An
alternative means to estimate available energy
content in ingredients, as well as in complete feeds,
is to chemically determine the content ofvarious
nutrients that supply energy (fat, protein, various
fractions ofcarbohydrates such as starch sugars and
specific fibres) as well as GE, and to use this
information to predict its available energy content.
For example, the following equation, developed by
French researchers. can be used to estimate the DE
content in complete pig diets.
20

DE (Kcal/kg of dry matter)*= 4168 - (9. lx Ash)+
( 1.9 x Crude Protein)+ (3.9 x Ether Extract) - (3.6
x NDF)**
*The contents ofthe chemical constituents in the diet are
expressed in grams per kg of dry matter.
**NDF - Neutral Detergent Fibre
In Chapter 4, various equations will be presented
that can be used to predict DE content in specific
samples ofmain feed ingredients.
Table 3-5. Effect of Bushel Weight on Nutrient
Content of Cereal Grains.
Bushel Crude Crude Ether
Weight Protein Fibre Extract
kg (lb) -%-
23 (5 I) 9.2 8.5 2.4
22 (49) 10.4 7.6 1.8
20 (45) 10.6 8.9 2.5
19(42) 11.0 9.6 2.5
Table 3-6. Minimum Recommended Bushel Weights
for Grains Used in Swine Rations.
Guidelines for minimum bushel weights ofgrains used in
swine diets. [f grains below these standards are used,
adjustments in energy content should be made.
Table 3-6 offers guidelines for minimum bushel
weights ofcereal grains destined for use in swine
diets.
Energy Requirements
A pig requires energy for almost all its body
processes. Amino acids cannot be converted to
muscle proteins and feed cannot be digested or
wastes eliminated without energy. Body
temperature cannot be maintained , gestating sows
cannot produce a fetus, nor can nursing sows
produce milk without energy. Clearly, energy is
fundamental to all life.
43
50
55
48
56
60
Bushel Weights (lb)
Standard Minimum
Grain
Barley
Com
Wheat
A common misconception is that bushel weight
is a good indicator of a cereal grain's nutrient
quality, and DE content in particular. Premiums are
sometimes paid for grains that exceed normal
bushel weights, e.g., 23 kg (50 lb) barley or 26 kg
(58 lb) com. Unfortunately, like many of the .
factors used in the grading ofgrains, bushel weight
is not a good indicator of feed value. Test weight
can be affected by many factors, such as the shape
and surface dimensions ofindividual kernels, which
do not necessarily reflect nutrient content.
Research results show very clearly that energy
concentration ofgrains does not fall in proportion
with bushel weight. The energy content oftypical
50 lb of barley is no different than that of48 lb or
even 46 lb of barley. In a recent study at Prairie
Swine Centre, there was no relationship between
DE content and bushel weight in wheat samples that
varied in density between 53 and 63 lb/bushel. In
the case ofvery low bushel weights, energy values
do appear to fall; therefore, very low bushel weight
grains should be used only in diets where energy
concentration is not critical (gestating sows or
growing pigs over 60 kg body weight) and even
then the concentration ofother nutrients needs to,
be adjusted to reflect changing energy levels.
The rise in crude fibre coinciding with falling
bushel weight is often put forward as an argument
favouring the use of bushel weight as an indicator
ofgrain quality. However, the rise in crude fibre,
which is low in energy, appears to be offset by a
similar rise in fat, which is high in energy (Table 3-
5). Interestingly, bushel weight has been used as an
indicator of flour yield, but even this relationship is
suspect.
A pig's requirement for energy will be determined
by a number of factors. The pig's size is important
because energy needed for maintenance is directly
related to body size. It 'costs' more in terms of
energy to maintain a 250 kg sow than a 180 kg sow.
The pig's productive state is also an important
factor. A lactating sow requires more energy than a
gestating sow since she is producing large quantities
of milk. A pig that is gaining weight requires more
21

energy than one that is not growing. As described
previously, the environment in which a pig is
housed is also critical. In cold temperatures or wet,
drafty conditions, energy required to maintain body
temperature rises. Jf pigs can huddle with each
other, their energy requirements in cold weather are
lower than if they arc penned individually.
The amount of energy required in feed is
determined by considering both quantity offeed
consumed per day and amount ofenergy required
per day. This principle is important. For example,
a man working at a job that involves considerable
physical exertion has a high energy requirement per
day. In theory, this requirement could be met by
eating an enormous quantity of lettuce or other
bulky, low energy, foods. In practice, this approach
will not work because the man simply cannot
physically consume enough lettuce to meet his
energy needs. If he is given a diet of meat and
potatoes, i.e., high energy foods, he can easily
consume enough food to meet his daily energy
needs. The message here is that gut capacity plays
an important role in formulating diets.
The same principle applies to pigs. Ifthe
concentration ofenergy in the diet is too low, the
pig may be unable to consume sufficient amounts to
meet its energy needs. A gestating sow is fed less
than her appetite demands to prevent excess weight
gain. Her stomach capacity is more than sufficient
to meet her energy needs with most practical diets.
Conversely, the lactating sow has a very high energy
requirement to support milk production and
maintain her body condition in preparation for the
subsequent breeding period. Ifshe is fed a low
energy diet, she will be unable to consume
sufficient energy per day, will lose body weight, and
produce less than her maximum potential ofmilk.
Pigs up to about a 60 kg body weight ( 130 lb)
being fed traditional ingredients may be in danger
ofgrowth retardation because their gut capacity is
insufficient to accommodate the energy required for
them to grow quickly. In pigs with extremely high
(lean) growth potential, such as boars, energy intake
may limit growth up to higher body weights.
However, in most finishing pigs of 60 kg or heavier
body weight, gut capacity no longer places a limit
on growth, assuming normal ingredients are used.
Because of limitations in gut capacity relative to
energy needs, diets with a high concentration of
energy should be fed to younger pigs and lactating
sows. These are called high nutrient density diets.
Lower energy grains, such as oats, are too low in
energy to support maximum growth rate.
Refer to the specific chapters on feeding various
classes ofpigs for further information on energy
requirements. Any general requirement must
consider many variables, such as environmental
temperature, desired performance, body size, and
some score of genetic capacity.
Amino Acids
Amino acids are the building blocks ofprotein,
meaning that all proteins are made up of individual
amino acids linked together like beads in a
necklace. In nature, there are about 22 amino acids
that can link together to form proteins. Pigs can
produce some of them from other substances; but
they cannot synthesize 10 amino acids so they must
be provided by the diet. These 10 amino acids are
called the 'essential amino acids' (Table 3-1). If
they are not present in the diet, or are present in
insufficient quantities relative to need, the animal
will be unable to grow properly.
In addition to the 10 essential amino acids, there
are two so-called semi-essential amino acids,
cystine and tyrosine, that can be synthesized only
from essential amino acids, methionine and
phenylalanine, respectively. The term 'total sulphur
amino acids' (T.S.A.A.), refers to the sum of
methionine plus cystine. Pigs require T.S.A.A. in
addition to the requirements for methionine. This
requirement indicates the importance ofmonitoring
both methionine and cystine levels in swine feeds.
At least 50-55% ofthe total T.S.A.A. requirements
must be supplied by methionine. In the same
manner, phenylalanine must supply approximately
55% of the animals' requirements for phenylalanine
plus tyrosine. The sum ofphenylalanine and
tyrosine is also referred to as "total aromatic amino
acids". Phenylalanine and total aromatic amino
acids are rarely deficient in practical diets.
Consequently, under practical conditions, tyrosine is
much less important than cystine.
22

When the pig eats protein as part of its diet. the
intestinal tract breaks down protein into individual
amino acids. These amino acids are then
transported into the blood and carried to various
tissues where they are used for a variety of
purposes. The most obvious function is to form
muscle protein. However, a host of other proteins
in cells are just as important since they support a
wide range ofessential body functions. Enzymes,
such as those that help to digest food in the gut, or
those that help ensure that overall metabolism in
tissues flows smoothly, are proteins. There are also
carrier proteins that transport nutrients from one
side of the cell wall to the other. Haemoglobin in
the blood is a protein; it transports oxygen from the
lungs to the tissues to support cell metabolism. The
blood also contains many other proteins, such as
those which transport certain vitamins or minerals.
Milk contains proteins to nourish newborn piglets.
Immunoglobulins circulating in the blood protect
animals against specific forms ofdisease.
Although protein synthesis is important,
individual amino acids also perform other
functions. For example, tryptophan is converted
into serotonin, a chemical called a neuro-
transmitter, that is involved in the transmission of
signals by the nervous system. It is this function
that has prompted some people to recommend
tryptophan supplements as a calming influence in
the diet. Tryptophan can also be converted to the
vitamin niacin. thereby reducing, but not
eliminating, the need for niacin in the diet.
Estimating Protein and Amino Acid
Contents in Feeds and Feed Ingredients
The crude protein content is an estimate of the
amount ofprotein present in a feed ingredient or
mixed diet. Since amino acid analysis is very
expensive and time-consuming, crude protein has
been adopted as a more practical indicator of feed
value. Direct analysis for amino acids will become
a much more common procedure in the future.
Crude protein is usually measured using the
Kjeldahl method. According to this very old, but
simple and accurate method, feed is digested in acid
and the quantity oftotal nitrogen in the sample is
determined. The total nitrogen value is then multi-
plied by the 'Kjeldahl' factor of6.25 to generate the
crude protein value.
The crude protein content of feedstuffs must be
interpreted with great care for three main reasons:
The true Kjeldahl factor varies from ingredient to
ingredient; not all ofthe nitrogen in a feed sample is
associated with true protein; and total protein is a
very rough estimate ofthe amino acids present.
The first point The true Kjeldahl factor varies
from ingredient to ingredient. The Kjeldahl factor
of6.25 assumes that the protein in the sample
contains 16.0% nitrogen. This assumption is not
necessarily true. As mentioned previously, protein
consists of individual amino acids. The proportion
of nitrogen in each amino acid varies from 7.7 to
32.2 (Table 3-7) so the actual amount ofnitrogen
present in a protein will depend on the relative
proportions ofeach amino acid in the protein. As
the proportion of amino acids change, so will the
average proportion ofnitrogen in the final protein.
Com protein contains I 6.0% nitrogen while the
protein in wheat or barley contains about 17.2%
nitrogen. Therefore, the correct factor for wheat
and barley is 5.83. Using 6.25 for these two cereals
will overestimate protein content by about 7%.
However, the standard Kjeldahl factor is neces-
sary because the proper nitrogen correction value is
not always known. For example, ifa pork producer
submits a mixed feed for analysis, what value
should be used to adjust nitrogen to crude protein?
A universally accepted standard is required and
6.25 has become that accepted standard.
23

Table 3-7. Nitrogen Content ofAmino Acids.
Amino Acid % Nitrogen
.Methionine 9.4
Cystine 11.6
Lysine 19.2
Tryptophan 13.7
Phenylalanine 8.5
Leucine 10.7
lsoleucine 10.7
Threonine 11.8
Valine 12.0
Histidine 27.1
Arginine 32.2
Glycine 18.7
Asparagine 21.2
Aspartic Acid 10.5
Serine 13.3
Glutamine 19.2
Glutamic Acid 9.5
Proline 12.2
Alanine 15.7
Tyrosine 7.7
The second point: Not all ofthe nitrogen in a
feed sample is associated with true protein. Some
ofthe nitrogen in feed ingredients is in the form of
non-protein nitrogen. There are compounds that
contain nitrogen but are not protein. Including them
in the crude protein calculation will overestimate
the quality ofthe ingredient. The information in
Table 3-8 summarizes these two points. It provides
the 'corrected' Kjeldah1 factor, two crude protein
values (one obtained from the standard Kjeldahl
factor, one from the corrected factor) and the
corrected crude protein value adjusted for non-
protein nitrogen.
The third point: Total protein is a very rough
estimate ofthe amino acids present. Total protein,
even adjusted for non-protein nitrogen and using the
corrected Kjeldahl factor, is not a perfect indicator
ofamino acid content. For example, in cereal
grains lysine contributes to approximately 4% of
corrected protein, while in soybean meal this value
exceeds 7.5%. As lysine is generally the first
limiting amino acid in pig diets, this means that
protein in soybean meal is close to two times more
valuable than cereal grains in meeting the pig's
amino acid requirements.
Table 3-8. Protein Estimation Adjusted for Corrected Nitrogen Factors and Non-protein Nitrogen Content.
Corrected Crude Protein (CP) Non-protein Corrected
Feedstuff Factor N x 6.25 N x Corrected Nitrogen Protein
Factor (% ofCP)
(%)
Barley 5.83 10.6 9.89 18.2 8.09
Canola Meal 5.53 37.7 33.36
Com 6.25 8.5 8.50 22.2 6.61
Milk, Fresh 6.38 3.3 3.40 11.1 3.01
Oats 5.83 10.8 9.79 25.0 7.34
SBM 5.71 47.5 43.40 18.4 35.41
Wheat 5.83 13.5 12.59 16.7 10.49
Wheat Bran 6.31 15.5 15.65 20.0 12.52
Source: unknown.
24

Growel' Swine Nutrition Guide

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Growel' Swine Nutrition Guide