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

ANSC 420: Critical thinking in Animal Science

Susan SchoenianSheep and Goat Specialist

Western Maryland Research & Education CenterUniversity of Maryland Cooperative Extensionwww.sheepandgoat.com – [email protected]

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

Small ruminants

• 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)

Sheep and goats

• Multi-purpose animals1) Meat

2) Dairy

3) Fiber

4) Vegetation control

5) Research and biomedical

6) Hobby

7) Youth projects (4-H, FFA)

8) Pets

Sheep vs. goats

More similarities than differences.

Same problems, same opportunities

Mostly the same diseases and health issues.

Sheep and goats in Maryland

• 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

2002 Ag Census: 22,702 sheep (655 farms) and 9,601 goats (702 farms)

Parasite

Internal parasiteAn 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.

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 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.

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!

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!).

Lack of FDA-approved drugs• Three families (chemistries) of

anthelmintics.1) Benzimidazoles2) Nicotinic agonists3) Macrolytic lactones

• 1-2 drugs in each family are FDA-approved for use in sheep.

1) Valbazen®2) Levamisol ®3) Ivermectin ® and Cydectin ®

• Only two drugs are FDA-approved for use in goats.

1) Safeguard ® 2) 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 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 resistanceThe 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

The “other” parasitesThese 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.

CoccidiaEimeria sp.

• Single-cell protozoa• Species-specific• Permanently

damages lining of the small intestines.

Coccidia life cycle

2 to 3 weeksoxygen, moisture, warmth

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*

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

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

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) 1 FDA-approved for goats2 FDA-approved for sheep

Feed/mineral

Drinking water

CoccidiostatsInhibit 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

Gastro-intestinal wormsThe barber pole worm and its relatives

Haemonchus contortus Barber pole worm

• Ostertagia circumcincta Medium or small brown stomach worm

• Trichostrongylus Bankrupt or hair worm

Barber Pole Worm

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. Bottle jaw

Pale membranes

Weight loss, unthrifty

Rough hair coat

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 RiseSpring Rise

Fecal egg counts

JMF AM J A S O N D J

Spring WinterFallSummer

F

Lambing

Weaning

Ewes

Lambs

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.

Chicory, birdsfoot trefoil, and Sericea Lespedeza

have been shown to reduce fecal egg counts

and/or larval development.

Birdsfoot Trefoil

Forage Chicory

Sericea Lespedeza

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

“Resistant” BreedsSome sheep and goat breeds are more resistant to worms.

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” 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

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.

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.

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.

Parents How We Select forDrug resistance

Res

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Su

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Next Generation

Res

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Drug Treatment

FAMACHA©

Clinical Category

Eye Lid Color

Packed Cell

VolumeDeworm?

1 Red > 28 No

2 Red-Pink 23-27 No

3 Pink 18-22 ?

4 Pink-White 13-17 Yes

5 White < 12 Yes

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

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.

Western Maryland Research & Education Center, Keedysville, MD

26.2%

41.7%

16.7%

7.1%

4.8%1.2%1.2%

0

1

2

3

456

% Lambs/No. times treated

Fecal Egg Counting

Qualitative 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.

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).

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

Internal parasitesWorms

Coccidia

Sanitation

Feeding and nutrition

Pasture and grazing management

Genetics andselection

Equipment and facilities

Management