1. ANSC 420: Critical thinking in Animal Science
Susan Schoenian Sheep and Goat Specialist Western Maryland Research & Education Center University of Maryland Cooperative Extension –

2. 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.

3. 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.

4. (Internal) parasite control in small ruminants
Lecture/Discussion topic
(Internal) parasite control in small ruminants

5. Small ruminants Ruminant Small 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)

6. Sheep and goats Multi-purpose animals Meat Dairy Fiber
Vegetation control
Research and biomedical
Hobby
Youth projects (4-H, FFA)
Pets

7. Sheep vs. goats More similarities than differences.
Same problems, same opportunities
Mostly the same diseases and health issues.

8. Sheep and goats in Maryland
2002 Ag Census: 22,702 sheep (655 farms) and 9,601 goats (702 farms)
Some large farms
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

9. Internal parasite 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 often causing death or damage to the host. This term is usually reserved for worms.

10. Internal parasites (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.

11. Why more susceptible? 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!

12. Lack of veterinary expertise
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!).

13. Lack of FDA-approved drugs
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

14. 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 ?).

15. 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.

16. 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.

17. The internal parasites of sheep and goats
Stomach worms
Tapeworms
Lungworms
Liver flukes
Coccidia
Meningeal worm

18. The “other” parasites These parasites tend to cause less problems than the others
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.

19. Coccidia Eimeria sp. Single-cell protozoa Species-specific
Permanently damages lining of the small intestines.

20. Coccidia life cycle
2 to 3 weeks oxygen, moisture, warmth

21. Diagnosing coccidia
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*

22. 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

23. Prevention of coccidiosis
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

24. 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 goats 2 FDA-approved for sheep

25. Coccidiostats Inhibit growth but do not kill coccidia
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

26. Gastro-intestinal worms The barber pole worm and its relatives
Haemonchus contortus Barber pole worm
Ostertagia circumcincta Medium or small brown stomach worm
Trichostrongylus Bankrupt or hair worm

27. Barber Pole Worm Symptoms Is difficult to control because . .
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

28. Stomach worm life cycle
2-3 weeks
Eggs require warmth (60°F) and humidity to hatch to first stage larvae.

29. Infective larvae on pasture (if no treatment)
Lambing Rise
Spring Rise

30. Fecal egg counts Ewes Lambs Lambing Weaning F M A M J J A S O N D J F
Spring
Summer
Fall
Winter

31. 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.

32. 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.

33. 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.

34. 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.

35. 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.

36. 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.

37. Forage Chicory
Sericea Lespedeza
Birdsfoot Trefoil
Chicory, birdsfoot trefoil, and Sericea Lespedeza have been shown to reduce fecal egg counts and/or larval development.

38. 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.

39. “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.

40. Genetics and worms Two important traits: resistance and resilience
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 – percent

41. “Resistant” Breeds Some sheep and goat breeds are more resistant to worms.
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

42. “Resistant” Individuals Parasite 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.

43. Heritability of FEC and PCV
FEC (resistance)
PCV (resilience)
Ewes
0.31
0.15
Lambs
0.10
0.39
2004, Vanimisetti, Andrew, Zazac, Notter
Selection for parasite resistance is possible and will not adversely affect growth of lambs and fertility of ewes.

44. Comparison of Genetic and Non-genetic Control Strategies
Strategy
Reduction in FEC’s
Genetic Selection
69%
Protein supplementation
35%
Strategic deworming
28%
Experimental vaccine 0%
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.

45. 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 hours before administering a benzimidazole or ivermectin or administer two treatments 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.

46. 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

47. “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.

48. How We Select for Drug resistance Parents Next Generation
Drug Treatment
Susceptible
Resistant
Resistant

49. *South Africa recommends goats be treated at categories 3, 4, and 5
FAMACHA©
Treatment Recommendations Deworm 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
Clinical Category
Eye Lid Color
Packed Cell Volume
Deworm? 1
Red
> 28 No 2
Red-Pink
23-27 3
Pink
18-22 ? 4
Pink-White
13-17
Yes 5
White
< 12

50. % Lambs/ No. times treated
Using the FAMACHA© system to control internal parasites in grazing lambs
26.2%
41.7%
16.7%
7.1%
4.8%
1.2% 1 2 3 4 5 6
% Lambs/ No. times treated
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.
Western Maryland Research & Education Center, Keedysville, MD

51. Fecal Egg Counting Qualitative Analysis Quantitative Analysis
Shows presence or absence of eggs
Identify egg types
Shows general trends
Quantitative Analysis
Shows specific number of eggs per gram of feces (epg)
Use known quantity of feces and flotation solution.

52. What do fecal egg counts tell you?
Potential pasture contamination
Fecal egg counts are not mathematically correlated to worm numbers or the severity of parasitic disease.
Monitor and maintain low egg counts; deworm when appropriate to keep contamination of pasture low.
Determine the efficacy of anthelmintic treatment by comparing paired samples from the same animals (treatment and control group).

53. Next Wednesday’s farm visit
Small meat goat farm in Clarksburg (typical operation for Maryland)
Evaluate overall health management, with specific attention to the control of internal parasites (worms and coccidia).
Reduce morbidity and mortality
Minimize cost
Minimize use of drugs

54. Pasture and grazing management
Sanitation
Pasture and grazing management
Management
Internal parasites
Worms
Coccidia
Equipment and facilities
Genetics and selection
Feeding and nutrition