Integrated Parasite Management for Livestock


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Integrated Parasite Management for Livestock

  1. 1. INTEGRATED PARASITE MANAGEMENT 800-346-9140 FOR LIVESTOCK LIVESTOCK SYSTEMS GUIDEAppr i e Technol Tr opr at ogy ansf f Rur Ar er or al eas ATTRA is the national sustainable agriculture information center funded by the USDA’s Rural Business -- Cooperative Service.By Ann Wells, DVMNCAT Agriculture Specialist Integrated Parasite Management for LivestockApril 1999Abstract Animals Immune SystemInternal parasites can be a major problem for (Low Dose Exposure)producers. With parasites developing resistance to alldewormers and more farmers producing livestock by Weather Cold“natural” methods, there is interest in looking for Humidity Foragesalternative ways to managing parasites problems. Height Soil SpeciesManagement is the most important thing to Dung Beetles By-pass Protein Phosphorusconsider. The whole system affects internal parasites. Earthworms Nematophagous FungiNutrition and pasture management can help preventproblems by improving the health of the animals.There are soil organisms that kill or prevent thedevelopment of internal parasites. Strategicdeworming means planning the timing whendeworming is done. This can also be an important dewormer on the market has had somepart of any management scheme. Little is known resistance built up to it by the internal parasitesabout the effectiveness of any alternative dewormer. that infest livestock. This resistance means thatChanges will have to done slowly while observing not all the worms are killed during deworming.their outcome. The surviving worms pass that genetic resistance on to offspring.Introduction The growing concern about the resistance ofInternal parasites are considered by some to be internal parasites to all classes of dewormers hasone of the most economically importantconstraints in raising livestock. Confinementand pasture-based animals are almost certain to ✼✼✼ Whats Inside ✼✼✼be exposed to worms at some point in their life. Introduction............................................................1Animals raised on the dry and arid rangelands Nutrition .................................................................2are much less likely to be infested. But if these Pasture Management ............................................2animals are brought to the more humid climates Immunity ................................................................4east of the Rockies, worms will be a major Soil Organisms .......................................................5problem for these animals. Effect of Ivermectin on Dung Beetles .................5 Strategic Deworming ............................................5Most producers are aware of the problems that Alternative Dewormers ........................................7worms cause, which range from decreased Conditions with Signs Similar to Parasitism.....8productivity of their animals to death. Animals Conclusion..............................................................8are usually routinely dewormed with different References...............................................................8commercial chemicals, by owners using a Enclosures...............................................................9variety of deworming schedules. Every ATTRA // Integrated Parasite Management Page 1
  2. 2. caused people to look for alternatives. As degraded or broken down in the rumen,dewormers lose their effectiveness, the livestock animals lose less weight than those animals thatcommunity fears increasing economic losses were not fed the increased level of by-passfrom worms. Much attention both in the protein. These researchers used fish meal asresearch community and on the farm is being their source of by-pass protein. However, theredevoted to discovering ways to prevent and are forages that also have an increased level oftreat internal parasites without relying on heavy by-pass protein because they contain tannins.doses of chemical dewormers. Many people These include birdsfoot trefoil and lespedeza.claim this treatment or that control measure The protein in native warm season grasses alsoworks, but there are more questions than has a higher level of by-pass protein. Phosphorus By looking at the whole farm as an interrelated system, it becomes There is also research that shows that when the apparent that there are parts of the phosphorus level of the diet was at a level of system that can be managed to .28% phosphorus on a dry matter basis, the decrease internal parasites and weight gain of lambs infected with parasites their effects. was increased by 40% over those lambs fed a low (.18%) phosphorus level diet (3).answers. There is no simple alternative way ofpreventing or treating worms. By looking at the Pasture Managementwhole farm as an interrelated system, it becomesapparent that there are parts of the system that Management of animals, pastures and anycan be managed to decrease internal parasites loafing areas is key to reducing the amount ofand their effects. These management internal parasite problems in livestock. Anadjustments not only postpone the day when understanding of the life cycles of the differentchemical controls no longer work, but they also parasites within the whole soil-plant-animalmay decrease costs and increase the overall system will help show the interrelationshipshealth of the animal. between these three components. Managing internal parasites is just like managing fleas inNutrition dogs and cats. The major part of the parasite life cycle is outside of the animal. This point willNutrition plays a major role in how well help the producer to choose managementanimals are able to overcome the detrimental strategies that reduce parasite levels on his oreffects of internal parasites. In fact, the signs of her farm and decrease the usage of chemicalparasitism can often be used as a symptom of dewormers. The same principle is used insome other problem, usually poor nutrition. In integrated pest management for vegetables andan article in the Journal of the American Veterinary other crops.Medical Association in 1943, researchers showedthat sheep placed on a high plane of nutrition Many farmers closely monitor their animals butwere able to reduce their worm burden pay little attention to the plants and soil. Pasturesignificantly and many of the sheep were even contamination by infective larvae is the primaryable to cure themselves (1). factor to deal with. If you start with an understanding of the interrelationship betweenBy-pass Protein the animal, the plants it eats and the soil on which those plants grow, then it becomesResearchers in New Zealand have been clearer how parasites infect the animal and howstudying the effects of by-pass protein on they can be managed so as not to cause as manyparasitized sheep (2). They have found that by problems. Everything a farmer does to his or herincreasing the amount of protein that is not animals, including the grazing management, ATTRA // Integrated Parasite Management Page 2
  3. 3. affects the manure, which affects the animal’s periparturient rise, which is the sudden releaseenvironment. For example, animals that of infective larvae and eggs within the ewe’scontinuously graze a pasture eat the grass into intestinal tract. This occurs right after lambing,the ground, while contaminating the soil with and is due to the ewe and doe’s immune systemso many parasites that nothing outside of becoming temporarily less effective. By treatingregular deworming with chemicals will control animals at this time, the exposure to newbornthem. By using controlled grazing methods that and young lambs (those most susceptible toallow pastures to rest and soil life to function parasites) is minimized.well, contamination can be reduced. Thisreduction occurs because soil organisms,including earthworms, dung beetles, and Other ATTRA Materials of Interestnematophagous fungi will destroy orkeep a lot of the parasite eggs and larvae Assessing the Pasture Soil Resourcefrom developing. Keeping the grass in a Matching Livestock & Forage Resourcesmore vegetative stage, and tall enough to Meeting the Nutritional Needs of Ruminants on Pastureprovide the animal with adequate forage, Nutrient Cycling in Pastureswill provide better nutrition to keep the Rotational Grazinganimal healthier, strengthening the Sustainable Pasture Managementimmune system to prevent the adult Beef Farm Sustainability Checksheetworms from producing eggs. Parasites do Contact ATTRA at (800) 346-9140 to order these and othernot cause as much harm to a healthy, well publications.nourished animal. The parasites that arepresent will not deplete the host as muchas in an animal that is malnourished. Parasite Good grazing management includes the use ofloads affecting wildlife generally do not cause clean pasture to minimize re-infection. Cleanthe death of the host, because the parasites need pasture is pasture that has not been grazed bythe host to survive. The same principle applies the host animal (in this case sheep and goats) forto livestock. 12 months, and therefore is not contaminated with worm larvae. It may be new pasture,Pasture contamination can be reduced through pasture grazed by livestock such as cattle ormanagement. Livestock will avoid manure piles horses which do not share parasites with sheepand the grass surrounding them. This behavior (goats do share parasites with sheep), or pasturealso helps them avoid eating larvae. The height that has been hayed, renovated, or rotated withof the pasture sward can affect parasites. The row crops. There is some killing of parasites onmajority of worm larvae crawl only one inch pasture during the winter due to freezing andfrom the ground onto plants, so not allowing thawing; however, snow cover insulates theanimals to graze below that point will cut down larvae. Summer is the time in the Southernon a lot of infestation. This is one reason sheep states when most larval kill will occur ontend to have more problems with internal pastures. Sunlight will kill them, and thisparasites. They eat much lower to the ground occurrence can be used to determine whichthan cattle do, picking up higher numbers of pastures can be used in the fall and into thelarvae. Therefore, it is important to monitor winter. Grazing down to 2-4 inches from thegrazing sheep closely so they don’t graze too ground allows more sunlight to get to thoselow. Larvae migrate from the manure no more larvae and increases their chances of drying outthan 12 inches from the manure pile. If livestock and being killed.are not forced to eat close to their own manure,they will eat fewer larvae. Warmth, oxygen and moisture are the three most important things that increase the chancesWith sheep and goats, the most important time that larvae will survive on pasture (4). Knowingto control pasture contamination is during the when your pastures are apt to be driest and ATTRA // Integrated Parasite Management Page 3
  4. 4. coldest will help you manage them better for parasites from reproducing but rarely killsparasite control. Enclosures such as them. An example of an effective parasite"Alternative Approaches to Managing Small control program can be found in Tennessee.Ruminant Gastrointestinal Nematode Parasites" Dennis Onks, superintendent of the Highlanddiscuss pasture Rim Experiment Station in Springfield,management in more Tennessee, has not wormed the adult The three most importantdetail. Also enclosed is cattle on the farm in eight years. They are things for larvae survival:an article that wormed at weaning and then not again.discusses the They have never shown any signs of • Warmthdeworming effects of internal parasites and their condition is • Oxygencertain plants, such as excellent. These animals are on a high • Moistureplantain. The plantain plane of nutrition, have a low stress level,must be young for the and are strictly culled on production. Allanimals to eat it readily as it loses palatability these things work together to produce an animalwhen it becomes mature. that shows no signs of internal parasites.Cleanliness is a defense against parasites. Feed It is the young animal whose immune system istroughs and water sources located where they not fully mature and the animal whose immunecan be contaminated with feces will increase the system is compromised by disease, inadequatechances of livestock infestation. This is only one nutrition, or other stress, that is most adverselyreason not to water directly from ponds, or to affected by worms. Animals brought fromallow animals continuous access to water western rangelands, for example, where the aridsources. Feeders should be cleaned and conditions keep parasites from surviving, haveelevated. Calving and lambing areas, as well as no immunity and can easily be overwhelmed byother holding areas, should be clean and dry. worms.Prevent the transmission of infestations fromnew arrivals to the herd or flock by deworming Every farm is different. The parasite load of thethem before arrival and again three weeks later. animal depends on many variables − such as stocking density, time of year, the reproductiveSheep and goats are infested by the same state of the animal, etc. Good nutrition plays aspecies of worms. Cattle are mainly infested by big part in how well the animal’s immuneother species. The cattle parasite of most system mounts the proper defenses, and in theconcern is Ostertagia ostertagi, the brownstomach worm. The barber pole worm, Many people have found, and researchHaemonchus contortus, is a stomach worm that has shown, that adult animals rarelycan severely affect sheep. Enclosed is an articlethat discusses the life cycle and infective larval need to be wormed.stages of worms. animal’s overall ability to tolerate the presenceImmunity of some worms. Healthy and well-nourished animals will be able to develop resistance andWhile it is usually neither possible nor advisable resilience to worms and other parasites muchto completely eliminate internal parasites in better than thin animals that do not have goodsheep or other livestock, reduction of parasite availability of quality feed (3). Resistance is theload can be achieved. Many people have found, ability of an animal to prevent the establishmentand research has shown, that adult animals and maintenance of a parasite populationrarely need to be wormed (4). Most animals within the gastrointestinal tract. Somedevelop immunity against internal parasites, individuals and some breeds show morethough not to the level that is developed against resistance to parasitic infection than others.viruses and bacteria. This immunity keeps the Research to identify characteristics in such ATTRA // Integrated Parasite Management Page 4
  5. 5. individuals is a hot area. Culling susceptible Effect of Ivermectin on Dung Beetlesanimals can take advantage of this. Resilience isthe ability of an animal to reduce production There is concern today about the effects ofloss during a parasite infestation. Both of these ivermectin on soil organisms, especially dungtraits are being looked at as ways of selecting beetles. Research has shown that the use ofanimals that will be less susceptible to parasite ivermectin kills dung beetle larvae for up to 45effects. Animals that possess some genetic days through residue in the manure (6, 7).resistance or resilience can still be infected with Manure from livestock treated with ivermectinworms. Therefore, you must keep in mind that does not break down as fast, either. Otherthis is just one more measure that will help dewormers don’t appear to have the same effect.control worm problems, not a cure by itself. Also, the management system has to be taken into consideration. Ivermectin under someSoil Organisms circumstances will be no more detrimental than any other chemical dewormer. Soils with noThere are several soil organisms that can have dung beetles will not be any more adverselyan impact on parasites. Managing pastures to affected by the use of ivermectin in livestockfavor populations of beneficial soil organisms than by other dewormers. Farmers usingwill decrease parasite levels on pastures. controlled grazing methods and working toOxygen is the primary requirement for worm improve the health of their soil are the ones whoeggs and larvae to survive and develop. will be most affected by using ivermectin. OneEarthworms have been shown to ingest worm way to use ivermectin while working toeggs and larvae, either killing them or carrying improve soils is to have a sacrifice area wherethem far enough below ground to keep them animals are kept until the majority of thefrom maturing. Dung beetles ingest and ivermectin is excreted from them. The pour-ondisperse manure, taking it to their burrows, thus formulations of ivermectin affect dung beetlekeeping eggs and larvae from developing. There larvae for the least amount of time, theare also nematophagous fungi that produce sustained release formulation for the longest“traps” that engulf and kill parasitic larvae. period of time (6).These fungi are more delicate than other fungi,so there are rarely great numbers of them in the Strategic Dewormingsoil. If the soil is depleted or out of balance,other, more dominant microorganisms will There will be times when chemical dewormersreplace these fungi. Research in New Zealand are the best treatment. The situation, time ofand the Netherlands is in progress using year and location will help determine whichnematophagous fungi to determine if they can chemical dewormer to use. These dewormingsbe fed to cattle or other ruminants to kill larvae should be strategically carried out in order toin manure piles and the surrounding soil (5). reduce the number of times needed. There areThis research is in its infancy and a marketable three main classes of wormers--theproduct is years away. benzimidazoles, such as fenbendazole or Safeguard  (white); the imidazothiazoles, suchThe amount of time that feces remain on the as levamisole (yellow); and the avermectins, ofpasture has an effect on the number of parasite which ivermectin (clear) is a member. Rotatinglarvae that survive and mature. Anything that these three classes yearly is an accepted rule forhastens the breakdown of the feces will lessen decreasing resistance buildup by the parasitesthe number of larvae. This can include the soil themselves. It is critical to reworm three weeksorganisms mentioned above, mechanical later, especially with newly weaned animals.dragging of pastures, poultry or other animal This kills those worms that were ingested anddisturbance and the consistency of the feces matured following the initial deworming. Thisthemselves. has been shown to significantly reduce pasture ATTRA // Integrated Parasite Management Page 5
  6. 6. contamination. Strategic deworming is days, check the egg count again. There shoulddiscussed in detail in the enclosure "Alternative be at least an 85 percent kill. You may need toApproaches to Managing Small Ruminant consult your veterinarian about the mostGastrointestinal Nematode Parasites." effective dewormers for your area. If parasites become resistant to a particular family ofIt does little good to deworm livestock and dewormers, then you will have to switchreturn them to the same infected pasture. Do not families. Alternating families of wormers is adeworm and immediately move animals to a good way of slowing resistance to theclean pasture. All the dead worms, with very dewormer. Many people alternate every timeviable eggs in them, will be passed to they worm. Research does not recommend this.contaminate the pasture. Instead, deworm, hold Instead, use the same dewormer for a wholeanimals in their same location for 12-24 hours, year before switching. The enclosure "Is Parasiteand then move them to a clean pasture. Control Possible?" discusses dewormerAppropriate management minimizes Strategies discussed in theenclosures include calving or lambing on clean To implement any type of integrated parasitepasture, weaning calves and lambs to clean control program it is essential to know whenpasture (with cows and ewes grazing the loads will be highest, such as at lambing; whereinfested pastures in the fall), and pasture the young animals stay at those highest eggrotation between cattle and sheep. There are production times; how pastures can be dividedseveral ways to utilize multiple animal species and how long they can be rested in order to letto control the worm population. One technique eggs and larvae die. If the producer has somethat appears to work well is dividing your farm idea of how much parasite infestation exists,in half, with cattle on one half and sheep on the this will also help in determining whether, andother half. Midway through the grazing season, how often, chemical deworming should beswitch halves of the farm. Having one species of given. Some scientists and producers say thatlivestock follow another one will have a benefit. rotationally grazed pastures do not aid inThe different livestock species will break up parasite control, because the rest period ismanure of other species and will not avoid those usually not long enough to break the life cyclesareas of pastures. This will break the life cycles of parasites. This is true. Most pastures areof the parasites because their natural host will rested between 21-30 days during the growingnot be present. season, which is also the length of time it takes for infective stage larvae to develop. The goalThere are many claims of different dewormers then is to lower the number of infective larvaethat they will increase the weight of animals by that are ingested by the animal. If even oneso many pounds. It is up to the producer to thing can be done to lower these parasitedetermine if this increased poundage is numbers, it will help reduce the need foreconomically justified. Animals and worms chemical dewormers. One such technique washave developed together. Getting rid of all demonstrated by Dr. Louis Gasbarre (8). Heworms all the time is not essential for the health showed that by deworming adult dairy cattleof the animal, is rarely cost effective and can after they have been rotated through all theactually be detrimental since the immune farm’s paddocks (which took nineteen days), allsystem of the animal is an important defense the larvae that survived the winter on themechanism in managing parasite effects. pastures were eaten by the cattle and then killed by the deworming. This deworming was doneMake sure that your dewormer is effective. If before the larvae had matured to egg-producingyou are concerned that it isn’t, have a worms. This eliminated the need for threeveterinarian check the egg count in the feces of additional dewormings on that particular farm.about 15 animals before treatment. After 10 ATTRA // Integrated Parasite Management Page 6
  7. 7. Managing the length of time animals remain on counts, instead of realizing that it is the naturala pasture is also important to remember. This is cycle. I haven’t talked to any producer whojust one other item that has to be figured in uses DE without significantly changing andwhen doing pasture planning for a season. then watching their management. Using DE isDon’t let those pastures be grazed too short! not just a simple substitute for a chemical dewormer. This is another problem with theAlternative Dewormers scientific research that has been done on DE. Researchers have simply substituted DE forMost alternative dewormers have not been their conventional wormer and done everythingshown by scientific research to have any effect else exactly the same. This is componenton numbers of worms. Diatomaceous earth (DE) research, whereas to really prove that DE has anhas been promoted by some for controlling effect, systems research needs to be done, usinginternal and external parasites in livestock. the same or similar management techniques thatAlmost pure silica, DE is the finely ground producers use. This type of research is muchfossilized remains of diatoms, tiny sea more difficult to do. If you still want to use DE,organisms that accumulate on the sea floor and one dosage that I’ve seen used is ten to twentycan be mined from deposits. The diatom pounds per ton of mineral supplement. Everyremains have microscopic cutting edges that are animal must be fed a dose every day to besaid to pierce the outer protective layer of effective.parasitic worms and insects, causingdehydration and death. There is little scientific must know if their animalsdata on the effectiveness of DE for internal even have worms in order to knowparasites, but researchers have seen a decrease whether control measures are needed,in flies on animals when using DE. I haveenclosed a report from The Leopold Center are effective, or how to effectivelyabout a project that showed no statistical change them.difference between the use of DE and thecontrol group. I have talked to Dan Morrical, Deworming alternatives exist in herbal and folkSheep Extension Specialist at Iowa State, who medicine used for centuries in other cultures.told me that they had a hard time even getting Herbs such as garlic work not by killing thethe lambs infested with worms, which was worms, but by making the intestinal tractnecessary to test to the effectiveness of DE. I healthier. Since worms and other intestinalbring up this point to make you aware that parasites have evolved to thrive in thefarmers must know if their animals even have unhealthy digestive tract, anything that willworms in order to know whether control make that environment healthier will bemeasures are needed, are effective, or how to detrimental to their survival. Dr. Susan Wynneffectively change them. (9), writing in the Journal of American Holistic Veterinary Medical Association, discussesMany producers have claimed that they have alternative dewormers in great detail and pointshad good results with DE, but their out that much more research needs to be done tomanagement is usually very good. They may be determine the effectiveness of herbs and othergiving credit to the DE when they should be natural substances traditionally used asgiving it to themselves. Although I have dewormers. Her article also states that manynothing to back me up, I’ve often wondered if it herbs can be toxic to animals, so great careisn’t the minerals in the DE that provide the should be taken in giving them. There arebenefit. Worm egg count also naturally falls at veterinarians who use herbs as part of a parasitethe end of summer and the beginning of fall. control program. The AHVMA (10) has a list ofPeople who are doing fecal egg counts (FEC) veterinarians practicing complementary andmay be thinking the DE is lowering the egg alternative medicine in every state. ATTRA // Integrated Parasite Management Page 7
  8. 8. Conditions with Signs Similar to Parasitism pursuit of parasite control, using alternative and more management-intensive methods.Keep in mind that there are other conditionsthat can mimic the signs of parasites. It is easy to References:assume that any unthrifty or thin animal with arough hair coat or diarrhea is wormy. Internal 1) Whitlock, J.H., et al. 1943. The relationship ofparasites may be present, but the clinical signs diet to the development of Haemonchosis inare secondary or a symptom of some other, sheep. Journal of the American Veterinarymore insidious disease or condition. Any Medical Association. January. p. 34-35.stressful condition, such as a weather extreme, 2) Stear, M.J., K. Bairden, et al. 1997. How hostscan cause borderline clinical parasitism to control worms. Nature. September 4. p. 27.become severe. If animals do not have enoughforage or other feed in the fall so that they go 3) Barrell, G.K., (ed.) 1997. Sustainable control ofinto winter in good condition, this lack of internal parasites in ruminants. Animalcondition will cause additional stress on the Industries Workshop. Lincoln University,animal in other ways. This animal will be more Canterbury, New Zealand. June. 280 p.apt to show extreme clinical signs of parasitism,including blood loss and death, than an animal 4) Dr. Craig Reinemeyer Department of Comparative Medicinewhich might have some internal parasites but is 2407 River good physical condition and is on a high Knoxville, TN 37901-1071plane of nutrition. In this case, poor nutrition is (423) 974-5727the cause of the animal’s disease and worms arethe symptom. 5) Waller, P.J. and Margaret Faedo. 1996. The prospects for biological control of the free-livingFescue toxicosis is often blamed when animals stages of nematode parasites of livestock.are actually wormy. These two conditions can Volume 26, No. 8/9. p. 915-925.also work together, and it can be hard to 6) Herd, R.P., et al. 1996. Persistence of ivermectindetermine which one is the main culprit. Fescue in plasma and feces following treatment of cowstoxicosis is especially blamed when bringing with ivermectin sustained-release, pour-on oranimals from the western states. While that injectable formulations. International Journalindeed may be a problem, the farmer needs to for Parasitology. Vol. 26, No. 10. p. 1087-1093.look at the time of year the animals have beenplaced on fescue, what their overall body 7) Strong, L., et al. 1996. The effect of faecallycondition is, and also check for the presence of excreted ivermectin and fenbendazole on theworm eggs in the feces. insect colonisation of cattle dung following the oral administration of sustained-release boluses. Veterinary Parasitology. Volume 62. p. 253-266.Conclusion 8) McBride, Judy. 1998. An ounce of preventionThere is no one thing that can be given or done equals pounds of milk. Agricultural replace chemical dewormers. It will take a January. p.10-11.combination of extremely good managementtechniques and possibly some alternative 9) Wynn, Susan G. 1996. Anthelmintic therapy intherapies. Do not think you can just stop holistic veterinary practice. Journal of thedeworming your animals with chemical American Holistic Veterinary Medicaldewormers. It is something you will need to Association. February-April. p. 15-19.change gradually, observing and testing animals 10) American Holistic Veterinary Medicaland soil, in order to monitor your progress. Association (AHVMA)Alternative parasite control is an area that is 2214 Old Emmorton Roadreceiving a lot of interest and attention. Bel Aire, MD 21015Programs and research will continue in the (410) 569-0795 ATTRA // Integrated Parasite Management Page 8
  9. 9. Enclosures: Kidd, Randy. 1993. Control parasites organically? The New Farm. November-December. p. 7, 11. Adams, Mary. 1997. Natural product evaluated for efficiency in deworming sheep. Leopold Letter. Mitchell, Linda. 1996. Clean grazing for parasite Spring. p. 4-5. control. New Farmer & Grower. November. p. 8-11. Anon. 1996. “Medicine” plants key to worm control. Scarfe, A. David. 1993. Alternative approaches to CashMirror. March. p. 6. managing small ruminant gastrointestinal nematode parasites. In: Proceedings of the 1993 American Dairy Bowen, Joan. 1994. Economics of parasite control; Goat Association National Convention. Portland, OR. more isn’t necessarily better. sheep! December. p. 15. p. 37-44. Griffith, Charles. 1997. Forage. Ag News & Views. November. p. 1. By Ann Wells, DVM Hawker, Lisa Stormes. 1995. Is parasite control NCAT Agriculture Specialist possible? National Lamb & Wool Grower. July. p. 28- 30. April 1999 Herring, Chris. 1994. Ask the vet. The Fiberfest Magazine. Summer. p. 27-28.THE ATTRA PROJECT IS OPERATED BY THE NATIONAL CENTER FOR APPROPRIATE TECHNOLOGY UNDER A GRANT FROMTHE RURAL BUSINESS-COOPERATIVE SERVICE, U.S. DEPARTMENT OF AGRICULTURE. THESE ORGANIZATIONS DO NOTRECOMMEND OR ENDORSE PRODUCTS, COMPANIES, OR INDIVIDUALS. ATTRA IS LOCATED IN THE OZARK MOUNTAINSAT THE UNIVERSITY OF ARKANSAS IN FAYETTEVILLE AT P.O. BOX 3657, FAYETTEVILLE, AR 72702. ATTRA STAFFMEMBERS PREFER TO RECEIVE REQUESTS FOR INFORMATION ABOUT SUSTAINABLE AGRICULTURE VIA THE TOLL-FREENUMBER 800-346-9140. ATTRA // Integrated Parasite Management Page 9