Strategic Parasite Control in Small Ruminates
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Parasites directly affect animal health, animal productivity, and the financial health of a farm. Sheep and goat producers generally feel the economic impact of gastrointestinal parasite burdens the most. Overuse and misuse of dewormers (anthelmintics) has reduced their effectiveness. Dewormer resistance means a particular dewormer loses its ability to effectively kill the parasites (worms). This is extremely problematic because the worms survive even after deworming. Resilience, the ability of an animal to tolerate parasitic infections, also contributes to increased parasite burdens. Unfortunately, both an animal’s ability to resist parasite infections and resilience are only moderately heritable (passed from parents to offspring). A key to controlling dewormer resistance is using a multistep approach focused on pasture management, animal selection, strategic deworming, and deworming alternatives.
A Multistep Approach
There are no quick fixes or silver bullets to parasite burdens; however, integrated, multistep approaches can be added to any production system. Following are a few suggestions for implementing strategic deworming:
- Quarantine new animals for at least 30 days
- Because resistance is moderately heritable, select parasite-resistant dams and sires
- Remember: 20 percent of the herd accounts for 80 percent of the parasite load
- Cull persistently infected animals
- Select animals with low fecal egg counts (FEC)
- Understand that resilient animals can carry heavy parasite loads without showing any significant symptoms
- Consider more resistant breeds, such as Katahdin, St. Croix, Spanish, Myotonic, and Kiko. **Remember, there are no truly resistant breeds, just breeds with increased resistance.
- Improve nutrition to reduce production losses from parasite infections
- Increase protein in diets to improve animals’ abilities to fight parasites
- Maintain body condition scores of at least 3 on a 1-5 scale
- Consider an animal’s stage of production. Energy demands are greatest during lactation. Also, lactation can be a stressful period
- Stocking density refers to the number of animals per acre
- Optimal density is no more than 6-8 goats per acre or 5-6 sheep per acre***Number of animals per acre varies farm to farm and is largely dependent on forage availability, forage species, and nutrition program.
- Maintain pasture height greater than 4 inches
- Incorporate multi-species grazing
- Rest pastures: 60 days is best
- Avoid overgrazing
- Implement leader follower grazing. Susceptible animals graze before less susceptible animals (lambs before dry ewes)
- Realize goats are browsers and will graze on shrubs, bushes, and low hanging trees
- Offer feed and hay off the ground to avoid feces contamination
- Practice rotational grazing to improve pasture forage health and reduce parasite load
- Deworming every 30 days
- Deworming the entire flock/herd
- Frequently rotating dewormers
- Using dewormers past expiration
- Using non-oral dewormers
- Dosing goats with sheep dosages
- Overgrazing and overstocking
To Increase Dewormer Effectiveness:
- Withhold feed for 24 hours. This slows the rate of passage through rumen.
- Try: 12 hours no feed, deworm, followed by 12 hours no feed.
- Use one dewormer class until ineffective.
- Double-up dewormer classes: White dewormer + ivermectin***Using multiple dewormers is off label use and your veterinarian should be consulted before you implement this strategy.
The five-point check helps determine which animals should be dewormed. It is vital to understand that not all animals need deworming treatment. This is called strategic deworming, deworming only the animals that need treatment.
- Eyes – FAMACHA©: visual score on lower eyelid membrane color. 1-5 score; 1 = bright red, 5 = pale white. Only used for Barber Pole Worm.
- Back – Body Condition Score (BCS): subjective measurement of body fat covering. 1-5 score; 1= emaciated, 5 = obese, 3 = ideal.
- Rear – Dag Score: fecal staining at tail base. 0-5 score; 0 = clean, 5 = heavy soiling. Not all parasites cause diarrhea.
- Coat (goats): Rough, broken, dull = unhealthy coats. Nose (sheep): Increased nasal discharge.
- Jaw – Bottle Jaw: swelling under chin. Edema: lack of dietary protein. Soft and cool to the touch
If there is still doubt after the five-point check, then fecal egg counts (FEC) can be done. Fecal samples are collected from animals to perform FEC to determine animals with high worm egg counts. FEC can also be used to determine the effectiveness of dewormers. FEC should not be the only tool for making deworming decisions. The fecal egg reduction test (FERT) may be done to determine dewormer effectiveness or if dewormer resistance has occurred. This test requires completing a FEC before and after deworming (10-14 days later). If a 90 percent reduction in FEC doesn’t occur, there is some level of dewormer resistance.
As resistance to chemical dewormers continues to grow, deworming alternatives have increased in popularity. Two proven alternatives are:
- Copper Wire Particles (COWP): take caution with sheep.
- Condensed Tannins (Sericea Lespedeza): decreases adult parasite reproduction rates and decreases FEC.
There has been significant research on deworming alternatives, but few methods are proven. Deworming alternatives (non-chemical anthelmintics) should not be used in place of strategic deworming methods, but can be used in conjunction with your current parasite control program. Seek guidance from your local veterinarian or county N.C. Cooperative Extension office.
It is important to implement a parasite control program. Applying a multistep approach will aid in safeguarding animal health and reducing financial losses from parasite infections. Talk with your veterinarian to help customize your herd health program.