ANSC 420: Critical thinking in Animal Science Susan SchoenianSheep and Goat SpecialistWestern Maryland Research & Education CenterUniversity of Maryland Cooperative Extensionwww.sheepandgoat.com – firstname.lastname@example.org
Critical thinking is learning to think for yourself and to develop your own independent opinions, backed by sound reasoning and support. Critical thinking is the process of evaluating what other people say or write to determine whether to believe their statements.
Critical thinkers gather information from all senses, verbal and/or written expressions, reflection, observation, experience, and reasoning. . . .to form a solid judgment that reconciles scientific evidence with common sense.
(Internal) parasite control in small ruminants Lecture/Discussion topic
Ruminant Even-toed hoofed animal Cud-chewing 4 compartment stomach Bovidae (hollow horns) family Caprinea sub family Ovis aries (54 chromosomes) Capra hircus (60 chromosomes Small sheep, goat, cervids (deer) Small ruminants
Multi-purpose animals Meat Dairy Fiber Vegetation control Research and biomedical Hobby Youth projects (4-H, FFA) Pets Sheep and goats
More similarities than differences. Same problems, same opportunities Mostly the same diseases and health issues. Sheep vs. goats
Some large farms 200-300 females Over 500 Largest farm has 1,600 sheep for bleeding Only 4 certified dairy goat farms; no sheep dairies A lot of small fiber flocks Mostly small farms Average flock size is less than 30 A lot of niche marketing of lamb and wool products. Some commercial production Mostly hobby, 4-H, tax advantage Sheep and goats in Maryland 2002 Ag Census: 22,702 sheep (655 farms) and 9,601 goats (702 farms)
Parasite An animal or plant that lives in or on a host (another animal or plant) and obtains nourishment from the host without benefiting or killing the host. Internal parasite An organism which lives in an animal and derives its nutriment from the host animal oftencausing death or damage to the host. This term is usually reserved for worms.
Primary health problem affecting small ruminants in warm, moist climates like Maryland. Sheep are goats are more susceptible to the effects of internal parasites than most other livestock. Internal parasites (worms)
Close grazing Goats forced to graze Small fecal pellets Graze close to feces and each other. Slower to develop immunity Incomplete immunity (goats) Temporary relaxing of immunity at lambing/kidding. Lack of veterinary expertise Lack of FDA-approved drugs Worms have become resistant to most dewormers (drugs). Main parasite is a blood sucker and killer! Why more susceptible?
Many veterinarians will not work with farm livestock. Many veterinarians lack technical and/or practical knowledge of sheep and goat health issues. The cost of treating a sheep or goat often exceeds its value. There is often a disconnect between veterinarians and producers. Most sheep and goat producers learn to do their own veterinary work. They are often in violation of extra-label drug laws (they have no choice!). Lack of veterinary expertise
Three families (chemistries) of anthelmintics. Benzimidazoles Nicotinic agonists Macrolytic lactones 1-2 drugs in each family are FDA-approved for use in sheep. Valbazen® Levamisol ® Ivermectin ® and Cydectin ® Only two drugs are FDA-approved for use in goats. Safeguard ® Rumatel ® U.S. Organic standards do not permit deworming of meat animals. There is growing public scrutiny regarding the use of drugs in food animal production. Therapeutic Medical use Lack of FDA-approved drugs
Lack of anthelmintic efficacy • Overuse (therapeutic) and sometimes misuse (e.g. pour-ons and injectables, underdosing) has lead to the emergence of drug-resistant worms in all three anthelmintic classes. • Highest levels of resistance have been reported in the benzimidazoles and ivermectins. • Drug resistance is determined using a fecal egg count reduction test or DrenchRite® larval assay test. • Resistance is permanent (levamisole ?).
Slowing drug resistance The FAMACHA© system • A color eye chart showing varying degrees of anemia (symptom of barber pole worm infection). • Identifies animals that require deworming and those that do not. • Results in fewer animals being treated. • Results in more refugia (worms that have not been exposed to the drug). • Slows the development of drug-resist worms and prolongs the effectiveness of anthelmintics.
Non-chemical “dewormers” • Nematode-trapping fungus • Copper oxide wire particles • Condensed tannins (Sericea lespedeza) • Natural dewormers are currently be evaluated by researchers: • Garlic juice • Pumpkin seeds • Wormwood • Diatomaceous earth • Oregano oil (coccidiosis) • A vaccine is under development.
The internal parasites of sheep and goats • Stomach worms • Tapeworms • Lungworms • Liver flukes • Coccidia • Meningeal worm
Tapeworms Tend to be non-pathogenic No beneficial effect of treatment Lungworms Difficult to diagnose Liver fluke Not thought to be a problem in Maryland Meningeal worm Parasite of the white tail deer (sheep and goats are abnormal hosts) Requires intermediate host (snail, slug) Causes neurological damage. The “other” parasitesThese parasites tend to cause less problems than the others
Single-cell protozoa Species-specific Permanently damages lining of the small intestines. CoccidiaEimeria sp.
Coccidia life cycle 2 to 3 weeksoxygen, moisture, warmth
Affects mostly young lambs and kids, 1 to 6 months of age. Diarrhea is the most common symptom. It often contains blood or mucous. Other symptoms: loss of appetite, rough hair coat, poor growth, ill thrift, loss of body condition, dehydration. Fecal egg flotation* Diagnosing coccidia
Treating coccidiosis • Amprolium (Corid)* • Sulfa drugs* • Must individually treat each animal. • Must treat each animal in pen. • Cannot reverse permanent damage. * Not FDA-approved for goats
Some level of “infection” is normal. Most fecal tests will be “positive” for coccidia eggs. Young animals require low level of exposure to develop immunity. Prevention starts with good sanitation and management. Clean pens Feed and water that is free from fecal matter Avoid overstocking Prevention of coccidiosis
Prevention of coccidiosis • Coccidiostats aid in the prevention of coccidiosis and can be put in the feed, mineral, or drinking water. • Monensin (Rumensin®1) • Lasalocid (Bovatec®2) • Decoquinate (Deccox®12) • Oregano oil (experimental) • Amprolium (Corid) Feed/mineral Drinking water 1 FDA-approved for goats2 FDA-approved for sheep
Reduce coccidia in the environment Start 30 days before lambing/kidding Continue through weaning Include in lamb and kid rations Have many other beneficial effects Feed efficiency, rate-of-gain, aid in prevention of toxoplasmosis and bloat Can be toxic to equines CoccidiostatsInhibit growth but do not kill coccidia
Gastro-intestinal wormsThe barber pole worm and its relatives • Haemonchus contortusBarber pole worm • Ostertagia circumcincta Medium or small brown stomach worm • Trichostrongylus Bankrupt or hair worm
Barber Pole Worm Rough hair coat Symptoms • Pale mucous membranes • Edema (bottle jaw) • Not diarrhea (scours) • Sudden DEATH • Fecal egg flotation (?) Is difficult to control because . . • Short, direct life cycle • Prolific egg producer • Can go into “hypobiotic” (arrested) state during winter to survive. • Can survive on pasture for a long time. Weight loss, unthrifty Bottle jaw Pale membranes
Stomach worm life cycle 2-3 weeks Eggs require warmth (60°F) and humidity to hatch to first stage larvae.
Infective larvae on pasture(if no treatment) Lambing Rise Spring Rise
Fecal egg counts Ewes Lambs Lambing Weaning F M A M J J A S O N D J F Spring Summer Fall Winter
Integrated Parasite Management (IPM) Goal is not to create parasite-free animals. It is normal for sheep and goats to have parasites. Goal is to prevent clinical disease and production losses.
Parasite control begins with good management and common sense • Good sanitation • Feeders which prevent wastage and contamination. • Clean water, free from fecal matter. • Not overstocking pens and pastures. • Isolation and deworming of new animals. The primary cause of internal parasitism is overstocking.
Use “clean or safe” pastures What is a safe pasture? • New pasture • Pasture that has been renovated with tillage • A pasture that has not been grazed by sheep or goats for the past 6 to 12 months. • Pasture grazed by horses and/or cattle for the past 6 to 12 months. • Pasture in which a hay or silage crop has been removed. • Pasture that has been rotated with row crops. • Burnt pasture • Severely overgrazed pasture???? Cleaner, safer pastures are a more realistic goal for most producers.
Graze multiple species • Sheep and goats share the same internal parasites, but they are different from the parasites that affect cattle and horses. • Producers who graze multiple species of livestock report fewer parasite problems. • Cattle and horses“vacuum” sheep/goat pastures. • There are other benefits to mixed species grazing, such as complimentary grazing habits.
Pasture Rest and Rotation • Pasture rotation is a recommended strategy for controlling internal parasites because it allows the use of safe or safer pastures. • BUT, intensive rotational grazing generally does not help to reduce parasitism unless rest periods are long enough. • In a rotational grazing system, ideally, sheep/goats should not be returned to the same pasture for 2 to 3 months. • Due to increased stocking rates, management intensive grazing may increase internal parasite problems in sheep and goats.
Alternative forages • Livestock that browse have fewer parasite problems. • Livestock grazing tall-growing forages will have less parasite problems. • 80% of parasites live in the first 2 inches of the vegetation. • Grazing some high-tannin forages may reduce the effects of parasitism.
Forage Chicory Sericea Lespedeza Birdsfoot Trefoil Chicory, birdsfoot trefoil, and Sericea Lespedeza have been shown to reduce fecal egg counts and/or larval development.
Nutritional Management • Animals on a high plane of nutrition and in better body condition are better able to withstand worm burdens. • Nutrition in early pregnancy (fat stores) can affect the immune response to internal parasites. • Sheep receiving higher levels of protein prior to lambing have lower fecal egg counts. • Supplementing lambs with protein has been shown to reduce fecal egg counts.
“Zero” grazing • Sheep/goats raised in confinement or dry lot (zero grazing) have fewer stomach worm problems. • Sheep/goats put in confinement or dry lot do not usually get re-infected with stomach worms. • Coccidiosis could still be a problem.
Genetics and wormsTwo important traits: resistance and resilience Resistance • Ability of host to limit infection • Assessed by fecal egg counts (FEC) Resilience • Ability of host to withstand challenge and/or infection, and thus maintain health and productivity. • Assessed by blood hematocrit/packed cell volume (PCV) and eye anemia score. Moderately heritable – 20-40 percent
Sheep Gulf Coast Native Hair sheep Barbados Blackbelly St. Croix Katahdin Royal White (?) Select populations of other breeds(?) NOT Traditional wooled breeds Dorper Goats Spanish/Brush Myotonic/Tennessee Kiko Pygmy? Savannah???? NOT Boer goats Dairy goats Angora goats “Resistant” BreedsSome sheep and goat breeds are more resistant to worms.
“Resistant” IndividualsParasite resistance varies between individual animals of the same breed type. • 20-30 percent of flock shed most of the parasite eggs. • Focusing deworming on susceptible animals will significantly reduce pasture contamination. • Culling worm-susceptible animals will increase flock resistance and reduce pasture contamination.
Heritability of FEC and PCV 2004, Vanimisetti, Andrew, Zazac, Notter Selection for parasite resistance is possible and will not adversely affect growth of lambs and fertility of ewes.
Comparison of Genetic and Non-genetic Control Strategies Australia, 2002 • Monitor sheep, run in the plots after the end of the experiment had lower FEC’s when run in the plots previously grazed by supplemented sheep (35%) or selected sheep (46%). • The largest and most persistent effect on FEC’s and worm contamination of pasture was achieved by genetic selection.
Maximize the effect of a single treatment • Give proper dose;do not underdose. • Dose orally (all formulations) • Put dewormer in back of mouth behind tongue. • Restrict feed 12-24 hours before administering a benzimidazole or ivermectin or administer two treatments 12-24 hours apart. • Use higher dose for goats than listed on label. Goats usually require 1.5-2X the sheep/cattle dose. (Consult with veterinarian for proper dose for goats). • Use two different drugs.
Slowing Down Drug Resistance • DO NOT overuse drugs, especially Levamisole and Moxidectin. • DO NOT introduce resistant worms to your farm • Isolate new animals and deworm them aggressively • DO NOT underdose • Weigh animals or dose for heaviest animals in group. • DO NOT rotate dewormers after each treatment • Rotate dewormers annually • Rotate among drug families • Use specific dewormers for specific situations. • DO NOT treat everybody • Leave some animals untreated
“Refugia” – in refuge from the drug What is refugia? • Worms not exposed to drug;therefore still susceptible to treatment. The goal • Increase the population of susceptible worms. How? • Selective treatment – leave some animals untreated. • After deworming, do not move animals to a clean pasture. You do not have to deworm every animal.
How We Select for Drug resistance Parents Next Generation Drug Treatment Susceptible Resistant Resistant
FAMACHA© Treatment RecommendationsDeworm adults at scores 4 and 5*Treat lambs and kids at categories 3, 4, and 5 *South Africa recommends goats be treated at categories 3, 4, and 5
1.2% 6 1.2% 5 4 4.8% 7.1% 3 2 16.7% 1 41.7% 0 26.2% Using the FAMACHA© system to control internal parasites in grazing lambs • 84 hair x wool crossbred lambs, 3 months old • June 10-Sept 30 (112-day grazing period) • Lambs scoring 3, 4, or 5 on the FAMACHA© scale were dewormed with moxidectin or levamisole • Lambs gained 0.3 lbs. per day, 57 lbs. → 87 lbs. % Lambs/No. times treated Western Maryland Research & Education Center, Keedysville, MD