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FosteringParasiteResistance

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This presentation by Susan Schoenian and Jeff Semler was given in a small ruminant workshop at the 2013 PASA Conference in State College, PA.

This presentation by Susan Schoenian and Jeff Semler was given in a small ruminant workshop at the 2013 PASA Conference in State College, PA.

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  • 1. STRATEGIES, TECHNIQUES ANDEXPERIENCE TO FOSTER PARASITERESISTANCE & RESILIENCE SUSAN SCHOENIAN & JEFF SEMLER UNIVERSITY OF MARYLAND EXTENSION
  • 2. GASTRO-INTESTINAL PARASITES Gastro-intestinal parasites are the primary health problem affecting sheep and goats in warm, moist climates and areas with summer rainfall. Sheep and especially goats are more susceptible to the effects of internal parasites than other farm livestock. Goats are not natural grazers, nor well-adapted to moist climates.
  • 3. GASTRO-INTESTINAL PARASITES• Sheep and goats share the same internal parasites (except for coccidia).• Not all parasites are pathogenic or equally pathogenic.• Close grazing facilitates the ingestion of infective worm larvae (L3).• Grazing near fecal pellets also facilitates ingestion of infective worm larvae (L3).
  • 4. GASTRO-INTESTINAL PARASITES • Sheep and especially goats are slow to develop immunity to internal parasites and experience a relaxation of immunity around the time of parturition (known as the “periparturient egg rise”). • Worms have developed varying degrees of resistance to ALL of the dewormers (anthelmintics). • Drug resistance is inevitable! Worms will eventually develop resistance to any new dewormer, quicker if we over-use it or use it improperly (like we’ve done in the past!).
  • 5. SHEEP AND GOATS CAN BE AFFECTED BY AVARIETY OF INTERNAL (AND EXTERNAL) PARASITESAND IT IS NORMAL FOR THEM TO HAVE SOMEWORMS IN THEIR GUTS AND EGGS IN THEIR FECES.1. Helminths (worms) 1) Roundworms I have worms! (gut, lung, meningeal) 2) Trematodes (tapeworms) 3) Cestodes (flukes) Me, too!2. Protozoa (single cell) 1) Coccidia
  • 6. PRIMARY PARASITES AFFECTINGSHEEP AND GOATS• Roundworms, especially Haemonchus contortus • Coccidia (Eimeria spp.) (barber pole worm). • Other parasites (e.g. meningeal worm) can be• Also, Trichostrongylus a problem on individual spp. and Teladorsagia farms or in some years. (Ostertagia). Barber pole worm Coccidia “nodules” in small intestines Image from Novartis Image from ScienceDirect
  • 7. MOST ECONOMICALLY-DEVASTATING PARASITEIS USUALLY HAEMONCHUS CONTORTUS. 2012 2010 100 100 80 80 60 60 40 40 20 20 0 0 6/2 6/28 7/26 8/22 6/7 7/1 7/29 8/25 Haemonchus Trichostrongylus Other Haemonchus Trichostrongylus Other 2011 2009 100 100 80 80 60 60 40 40 20 20 0 0 6/3 7/7 8/4 9/1 6/6 7/1 7/16 7/30 8/13 8/26 9/10 9/26 Haemonchus Trichostrongylus Other Haemonchus TrichostrongylusLARVAE ID (PERCENT HAEMONCHUS IN RED) FROM WESTERN MARYLAND PASTURE-BASED MEAT GOAT PERFORMANCE TEST.
  • 8. THE BARBER POLE WORM ISAN INCREDIBLE PARASITE!• Very pathogenic: kills a lot of sheep and goats, especially weanlings.• Difficult to control • Simple, direct life cycle • Prolific egg layer • Undergoes hypobiosis (inhibited developmental stage)• Adaptable: from the Tropics to the Artic.
  • 9. SYMPTOMS IN THE ANIMAL HAEMONCHOSIS1. Hyperacute (< 1 week) • “Sudden death” • No obvious signs2. Acute (> 1 week) • Anemia • Edema (bottle jaw) • Weight loss Voracious blood-sucker! • Loss of body condition • Anorexia • Loss of stamina • Diarrhea3. Chronic (sub-clinical) • Loss of performance
  • 10. GENETICS OF PARASITES:TWO TRAITSRESISTANCE RESILIENCE• Prevent parasitic disease • Tolerate (perform, remain from establishing. healthy) despite parasite burden (could still have• Quantified by fecal egg high egg count). counts (FECs), which are an estimate of the • For barber pole number of worms in the worm, quantified by packed animal’s gut. cell volume (PCV) and estimated by FAMACHA© EPG: eggs per gram (of feces) eye anemia scores. PCV - percent; FAMACHA© - 1-5
  • 11. ABOUT FECAL EGG COUNTS (EPG)• They are “relative”: a “snapshot” in time. McMaster slide• A single egg count is not necessarily a good measure of the parasite burden in an individual animal; however, it is a measure of pasture contamination.• Fecal egg counts include all strongyle-type eggs: Haemonchus, Trichostrongylus, and Teladorsagia: you must hatch eggs to identify strongyle species by worm larvae.• Worms vary in their egg-laying You can learn to do your own FECs. ability.
  • 12. ABOUT PACKED CELL VOLUME (PCV)• Is proportion (%) of blood represented by red blood cells. McMaster slide• Also known as blood hematocrit.• 25 to 35 percent is normal in sheep/goats.• Is usually lower for goats.• Is estimated by FAMACHA© scores. Score Color PCV Tx? 1 Red > 28 No 2 Red-Pink 23-27 No 3 Pink 18-22 ? 4 Pink-White 13-17 Yes 5 White < 12 Yes
  • 13. OTHER IMPORTANT MEASUREMENTSOF PARASITE RESILIENCE• Body condition (1-5)• Dag score (fecal soiling, 0-5)• Coat condition• Weight gain Dagginess Weight loss Poor body condition
  • 14. HERITABILITY (H2) OFRESISTANCE AND RESILIENCE RESISTANCE RESILIENCE • Moderately heritable • Low heritability ~0.25 ~ 0.10 (higher for Katahdins) • Less variability: • Extremely variable: coefficient of variation coefficient of variation usually between 20 is often over 100 and 40 percent. percent. Fecal egg counts are the standard for improving parasite resistance in sheep. Heritability (h2) is the proportion of phenotypic variation due to genetics.
  • 15. GENETIC RELATIONSHIP BETWEENRESISTANCE AND RESILIENCE• Resistance and resilience are usually positively correlated, Year Correlation though measurement numbers 2007 0.29 may be negatively related. 2008 0.42 2009 0.18 e.g.  FEC PCV and 2010 0.27  FEC  FAMACHA© Score. 2011 0.14• In the Western Maryland Genetic correlations range from -1 to +1 and are an indication of the amount of Pasture-Based Meat Goat variation that two traits share. Performance Test, FEC and FAMACHA© scores have had In New Zealand, they found no correlation between parasite positive correlations, but they resistance and parasite resilience. have not been very strong.
  • 16. IN OUR BUCK TEST, WE USE FECALEGG COUNTS (FEC) TO EVALUATEGENETIC RESISTANCE TO PARASITES.NOT TO MAKE DEWORMING DECISIONS.
  • 17. WE USE FAMACHA© SCORES TOESTIMATE PACKED CELL VOLUME…AND MAKE DEWORMING DECISIONS.
  • 18. TWO WAYS TO SELECT FORPARASITE RESISTANCE AND RESILIENCE BETWEEN BREED WITHIN BREED• Some breeds are naturally • There is as much variation more resistant and resilient to within a breed as between internal parasites (round- breeds. worms) than others. • The 80-20 rule: it is estimated• This is well-documented in that 20-30 percent of the flock sheep; not very well- or herd is responsible for documented in goats causing 70 to 80 percent of the (mostly anecdotal). pasture contamination• Resistant breeds tend to be (fecal egg outlay). those with tropical origins or • Parasite resistance (FECs) is a landrace breeds that have moderately heritable trait. naturally adapted to their environment (“survival of the fittest”).
  • 19. (MORE) RESISTANT BREEDSSHEEP GOATS• Landrace hair sheep Not • Kiko 1) St. Croix • Boer 2) Barbados Blackbelly • Spanish • Nubian 3) American Blackbelly • Swiss dairy • Myotonic• Composite hair x wool 1) Katahdin• Medium wool 1) Gulf Coast Native Florida Native St. Croix: the most• Dorper - not resistant, but resistant maybe more resilient. breed in US.• Others (?)
  • 20. WITHIN BREED SELECTIONANY BREED (OR POPULATION) CAN BE SELECTEDFOR IMPROVED PARASITE RESISTANCE. 2012 Western Maryland Pasture-Based Meat Goat Performance Test Avg. FEC 2358 epg80:20 rule: Fecal egg counts are not evenly dispersed in a herd or flock.
  • 21. Selection for parasite resistance in Australia
  • 22. Selection for parasite resistance in Australia
  • 23. Selection for parasite resistance in Australia
  • 24. HOW TO SELECT FORPARASITE RESISTANCE• The immune system needs to be stimulated by a worm challenge before genetic differences can be expressed.• Measure fecal egg counts when animals are between 6 and 12 months of age.• No sooner than 6 weeks after weaning.• A high worm load is needed to do the best job of separating resistant vs. susceptible animals; • Avg. FEC of 500-1000 epg for barber pole worm • Less than 10% of animals should have zero egg counts.
  • 25. PROTOCOL FOR MEASURINGRESISTANCE IN KATAHDINSSource: NSIP, David Notter, Virginia Tech, 2004
  • 26. HOW TO SELECT FORPARASITE RESISTANCE• Take all samples on same day.• Store samples in a cool place to prevent eggs from hatching.• Compare animals in same contemporary group.• Compare individual FECs to group average.• Heritability will be higher if more than one FEC is used for comparison.
  • 27. 2012 Western Maryland Pasture-Based Meat Goat Performance Test 1 2 3 4 5 Top 10 6 7 8 9 10 10 9 8 7 6 Bottom 10 5 4 3 2 1 All goats were triple-dewormed (moxidectin + levamisole + albendazole) on 6/2. Twelve days later, the average fecal egg count was near zero.
  • 28. HOW TO SELECT FORPARASITE RESILIENCE• Many criteria can be used a) Packed cell volume b) FAMACHA© score c) Time from fixed point that deworming is required d) Number of times dewormed during specific time period. e) Body condition score f) Dag scores (scour worms) g) Growth rates• Cull animals that require frequently deworming.• Select animals that do not require deworming and whose parents don’t require deworming.
  • 29. 2012 Western Maryland Pasture-Based Meat Goat Performance Test 1 2 3 4 5 Top 10 6 7 8 9 10 10 9 8 7 6Bottom 10 5 4 3 2 1 All goats were triple-dewormed (moxidectin + levamisole + albendazole) on 6/2. For the next 8 weeks, the average FAMACHA© score improved and no goat required deworming.
  • 30. WE WANT BOTH RESISTANCEAND RESILIENCE!• You don’t want have to Let me out! deworm your stock, but you also don’t want to have animals that deposit a lot of eggs onto the pasture.• Heavily-contaminated pastures lead to clinical parasitism, as there are almost always susceptible animals in Fecal egg counts are a measure the herd or flock. of pasture contamination.
  • 31. IT IS MOST IMPORTANT THAT THEMALE BE RESISTANCE TO PARASITES There are large differences between sires for resistance.
  • 32. WHAT WILL HAPPEN IF YOU DON’TPAY ATTENTION TO PARASITES?• Eventually all the dewormers will stop working on your farm. Kiko x Boer• You will need to feed more so that your animals can tolerate parasitic burdens.• You’ll want to raise your sheep and goats in complete confinement so that they are not exposed to much infective worm larvae.• You’ll have to stop raising sheep and especially goats.• Your compost pile will get full. Top-performing buck from 2011 Test Avg. FEC: 232 epg; Avg. FAM: 1.7; ADG ratio: 181%
  • 33. QUESTIONS?THANK YOU FOR YOUR ATTENTION. Kiko and crossbred bucks from 2012 test.

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