II. Integrated parasite management (IPM)Controlling internal parasites without or before you need to use anthelmintics: host immunity, grazing and pasture management, nutrition, management, and genetics.

Boer goat grazing chicory

Key points of parasite control

• The goal is not to eradicate worms, but to reduce their adverse effects in practical and economical ways.

• The interaction between parasites, the environment, animals, and management decisions is complex.

• Drug resistance is a serious challenge to effective parasite control.

Parasite infection in sheep and goats

• Parasite infection is normal in sheep and goats.

• The number of worms found in individual animals varies, with essentially all animals having some worms (and coccidia).

• It is rare to find animals uninfected.

Parasite infection in sheep and goats

• The nematode population in a flock is over dispersed.

• A majority of the nematodes are in a minority of the animals.

• The 80-20 rule: 20 percent of the animals shed 80 percent of the worm eggs.

Parasite infection in sheep and goats

• The risk and severity of parasite infection varies by . . .

1. Season2. Year (weather)3. Geographic

location (climate)4. Farm5. Production system6. Animal

Integrated parasite management (IPM)

• Whole farm or systems approach to managing internal parasitism.

• Applying best management practices to minimize the effects of parasites and the need for deworming.

• Holistic worm management.

There is no one way or “magical” recipe for controlling parasites.

Integrated parasite management

• Host immunity• Pasture and grazing

management• Nutrition• Management• Genetics• Anthelmintic treatment

Host immunity

• Sheep and goats have several defense mechanisms for dealing with internal parasites:

1. Immune exclusion2. Self-cure3. Immunity

a) Innateb) Acquired

IMMUNE EXCLUSION• Ingested larvae fail to

establish in heavily infected animals.

SELF-CURE PHENOMENON• Adult nematodes are

spontaneously expelled when there is a massive larval invasion over a very short exposure period.– Usually observed after

a heavy rain.

Why does it occur (?)• Increase in

abomasal pH• IgE mediated

hypersensitivity

Immunity (2 kinds) The ability to resist a particular disease.

INNATE (inborn, natural)

• Infection is limited during the initial exposure.

• Immunity that occurs naturally as part of an individual’s genetic make-up.

ACQUIRED• Immunity that is not

inherited.• Immunity that is acquired

during life.• Immunity that results from

exposure to the disease.

St. Croix lambs

Crossbred lambs

Immunity• Develops with advancing age and

parasite exposure.– Not until >4 months of age,

depending upon breed and nematode species.

• Preventative anthelmintic treatments interfere with the development of immunity.

• Adults are generally immune to parasites, but under stress can break down.

• Goats show the weakest degree of immunity of any livestock.

Periparturient egg riseRelaxation of immunity around the time of parturition

• Lasts for about 4 weeks• May occur earlier (in

pregnancy) if animals are underfed or under stress.

• Primary source of infection for new crop of lambs and kids.

• Cause (?) Hypothesis:Lactation after pregnancy– Increasing prolactin levels– Reduction in IgA antibodies associated

with transfer of maternal antibodies in colostrum

“Spring” periparturient egg rise• If lambing and kidding

occur in the spring, it will coincide with the maturation and egg production from previously arrested worm larvae.

• Management strategies1. Deworm all females prior to

parturition with an anthelmintic that is effective against hypobiotic larvae.

2. Increase protein level of ration during late gestation.

3. Selective deworming using FAMACHA© system and Five Point Check©.

Pasture and grazing managementThe “cornerstone” of effective parasite control.

• Clean or safe pastures• Pasture rest/rotation• Stocking rates• Alternative forages• Browsing• Plant height• Plant morphology• Plant moisture• Mixed species grazing

Clean or safe pastureA pasture that is FREE from parasites.

1. A pasture that has never grazed by sheep or goats.

2. A pasture that is grazed once per year by sheep and/or goats.

3. A pasture that has not been grazed by sheep or goats for 6 to 12 months.

4. Pasture that has been grazed by cattle or horses for past 6 to 12 months.

5. Pasture in which a hay or silage crop has been removed.

6. A pasture that has been renovated with tillage.

7. A pasture that has been rotated with row crops.

8. Burnt pasture.9. Annual pastures.

Cleaner, safer pastures are usually a more practical option.

Newly planted dwarf pearl millet

Pasture rest/rotationThe primary method for creating safer (less contaminated) pastures.

• Parasite infection is driven by stocking rates and duration of grazing periods.

Overgrazing → parasitism

• The higher the stocking rate, the more the pasture gets infected and the more likely livestock are to ingest infective worm larvae.

• The longer the grazing period, the more the pasture gets infected and the more likely livestock are to ingest infective parasite larvae.

Rotational grazing• There is no “one-size fits all”

pasture rotation schedule. There are many variables to manage:– Climate– Season– Rainfall– Number of paddocks– Size of paddocks– Number of livestock– Susceptibility of livestock– Forage type and quality– Supplemental feed

• There is often a trade-off between parasite control and good pasture management.

General recommendations

• It takes approximately 60 days for a highly contaminated pasture to become lowly contaminated with worm larvae.

• “Take half, leave half”

• Don’t graze below 4 inches (10 cm).

Plant height

• It is estimated that 80 percent of infective worm larvae are found in the first 2 to 3 inches of the ground surface.

• Do not graze pastures below 4 inches.

• Overgrazing is one of the primary causes of internal parasitism in small ruminants.

Alternative forages

• Forages containing condensed tannins and sesquiterpene lactones.

– Sericea lespedeza– Chicory – Birdsfoot trefoil– Artemisia spp.

Chicory

How do they work (?) – reduce egg hatch and development of larvae.

Sericea lespedeza Lespedeza cuneata (high tannin variety)

• Warm season legume that grows in acidic soils with low fertility and is tolerant of drought.

• Goats readily eat.Sheep will eat.

• For control of barber pole worm only.

• Effective when consumed as– Fresh forage– Loose or ground hay– Pelleted supplement

Images from scsrpc.org

Browsing

• Goats that are allowed to browse (their natural grazing behavior) have fewer parasite problems.

• Browse should be managed to provide continuous nutrition for goats.

• Sheep will also browse.

Plant morphology

• There are lower numbers of larvae on non-grass plants, e.g. legumes, forbs.

• Non-grass plants reduce parasite survival on pasture or reduce larval migration up plant.

• Management strategies– Include legumes in pasture

mixes (e.g. 30%).– Plant alternative forages.

Red clover

Plant moisture

• Delay grazing until after dew has lifted or the grass has dried after a rain.

• Dry conditions force the larvae to stay at the base of the plant. • Parasites need moisture!

Mixed or multi-species grazing

• Parasites are mostly host-specific.– Worms rarely transmit from

one species to another.– Cattle and horses have

different parasites than sheep and goats.

• Complementary grazing habits– Goats → browse– Sheep → forbs– Cattle → grass

NutritionThere is an interaction between parasites and nutrition.

• Livestock are far more capable of coping with parasites if their nutritional needs are being met.

• Animals on low protein diets are more susceptible to infection because they produce less IgA.

Nutritional control of parasites

• Improved protein nutrition.• Increased body protein

reserves.

• Feed periparturient females protein at 130% of requirements.

• Provide supplemental protein to grazing livestock, especially at-risk animals and during periods of poor forage quality.

• Manage pastures so that they are grazed in a vegetative state.

Management options

• Sanitation• Biosecurity• Zero grazing• Timing of lambing

and kidding• Weaning age

Sanitation• Dry, well-bedded pens

• Clean floors and surfaces

• Feeders which prevent contamination and wastage. Do not feed on ground.

• Clean water that is free from fecal material.

• Discourage congregation on pasture.

BiosecurityDon’t introduce drug-resistant worms to your farm

• Quarantine new animals for 30 days

– In a pen away from rest of flock/herd.

– No fence line contact

– Deworm with anthelmintics from 2-3 drug chemistries, e.g. • Cydectin® + levamisole• Valbazen® + Ivomec®

+ levamisole

Zero grazingconfinement, dry lot, feed lot, elevated floors

• Can maintain animals relatively “worm-free” under zero grazing conditions.– Coccidiosis is still a risk.

• Primary source of infection (and re-infection) is removed: grazing.

• Pens should be kept dry.

• Feeders and waterers need to be kept clean.– No feeding on pen floor or

ground.Dairy goats in China

Season of lambing and kidding

• Parasite problems can be minimized by lambing and kidding at different times of the year, so that lambs and kids are not on pasture when weather conditions are most conducive to parasite development.

• There can be other advantages to lambing and kidding at different times of the year (e.g. marketing, predator risk).

Weaning

• The influence of weaning on resistance to worms is not clear and is probably more dependent on nutrition. However, . . .

– If lambs or kids will face a substantial parasite challenge, do not wean before 3(-4) months of age.

Genetic aspects of parasite control

• Some animals mount a significant response to internal parasite infection, while others do not.

• Some animals do not mount a noticeable response to internal parasite infection, but they suffer no obvious loss of production.

• There is significant within and between breed variation in parasite resistance and resilience.

Two genetic traits

RESISTANCE• Ability to prevent infection

from establishing.• Quantified by fecal egg

counts.• Moderately heritable

– h2 ranges from 0.22 to 0.63– Avg. h2 is 0.25

RESILIENCE (tolerance)

• Ability to limit damage caused by parasites

• Quantified by clinical signs: packed cell volume (barber pole worm), dag scores, etc.

• Less heritable than resistance, ~ 0.1

Resistance and resilienceBoth traits are equally important!

• There is a cost to parasite resistance as resources are directed away from production traits.

• Resilient animals may still carry significant parasite loads and be a source of contamination to the pasture and other animals.

• Correlation between two traits– No correlation between worm

resistance and resilience in New Zealand studies.

– Positive correlation between two traits in Australian work.

– Low (positive) or no correlation in Western Maryland Pasture-Based Meat Goat Performance Test.

(More) resistant breedsSHEEP1. Hair sheep of Caribbean or

North African heritage St. Croix Barbados Blackbelly Katahdin

2. Gulf Coast Native

GOATS• Kiko• Spanish• Myotonic

Naturally-selected resistant breeds of sheep and goats have developed resistance over a much longer term (decades and perhaps centuries) than short-term (few years) genetically-selected resistant lines within breed.

St. Croix sheep

Breeding for worm resistanceWithin breed selection

RESISTANCE• Cull animals with high fecal egg

counts.• Don’t select replacements with high

fecal egg counts.• Don’t use rams or bucks with high egg

fecal counts.• Include fecal egg counts in a selection

index.• Select animals based on a minimum

standard for parasite resistance.• Use EPD’s to select for parasite

resistance.• Use gene markers to select for parasite

resistance.

RESILIENCE• Cull animals that require

frequent deworming.• Don’t select replacements that

require frequent deworming.• Don’t use a ram or buck that

requires frequent deworming.

Make sure you are comparing animals in the same contemporary group (i.e.

similar breed, age, and management).

Thank you for your attention.

Any questions?

Susan Schoeniansschoen@umd.edu

www.sheepandgoat.com

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