Part 3: Non-chemical options

Those who raise sheep and goats are in a constant battle against internal parasites. The most effective parasite control approach for small ruminants is to use a combination of chemical and non-chemical management tools.

Dr. Dahlia O’Brien, Virginia State University, said internal parasitism should be treated as a disease, so the first non-chemical approach in fighting parasite resistance is proper nutrition. Good nutrition supports the immune system and enhances disease tolerance.

Females in late gestation have decreased immunity, which makes them more susceptible to parasitism. Research has shown that ewes supplemented with higher protein for six weeks before lambing have significantly lower fecal egg counts (FECs).

“It’s the same with lambs and kids,” said O’Brien. “If we supplement young animals adequately, the effects of internal parasites will be reduced.”

Pasture management is helpful because few parasite larvae climb higher than six inches on a blade of grass. “Monitor forage height to make sure animals don’t graze too low,” said O’Brien. “We also know that larvae migrate about 12 inches from a manure pile, so by using the biology of worms and pasture management, we can ensure animals aren’t exposed to as many larvae on pasture.”

Rotational grazing plays a role in managing parasites. “In the height of parasite season, it takes about three to seven days from the time animals have passed eggs in manure until they hatch and become infective larvae that animals ingest,” said O’Brien. “Rotating every three days moves animals off pasture before larvae start to increase.”

When possible, maintain low stocking rates so animals are not forced to eat where they have defecated. While sheep and goats share parasites, other livestock such as cattle and horses don’t share parasite species and can be used to vacuum pastures – ingesting larvae that affect smaller ruminants.

Kids and lambs are most susceptible to parasites on pasture, followed by periparturient females, then older animals that should have a degree of immunity. Less susceptible animals are bucks and rams, open females and pets. If time is a limiting factor for checking FAMACHA scores, check at least the youngest, most susceptible animals.

With multi-species grazing, lead with the susceptible species and follow with cattle or horses. With a single species, allow more susceptible young animals to graze first, followed by older animals, which should be more resistant. A zero-grazing approach for young animals, which means confinement on a dry lot, also helps with parasite management.

Access to browse and bioactive forages such as Sericea lespedeza with high levels of condensed tannins may be beneficial. Harvesting hay from pastures can break the parasite reproduction cycle and increase forage quality aids in alleviating parasite issues through better nutrition.

“The presence of condensed tannins has been shown to reduce worm infection in sheep and goats,” said O’Brien, adding that tannins are effective against barber pole worm and Coccidia eggs. “It has been found to reduce FEC when grazed and when fed as a hay or pellets.”

Genetic selection plays a role in parasite management. “We know the ability to regulate worms is under genetic control,” said O’Brien. “Some animals are naturally resistant to worms, and some are more resilient. Resistance is the ability of the animal to limit infection. These animals consume the parasite but don’t establish inside the animal, have consistently low FEC and never have clinical signs.”

Resilient animals are those that withstand infection. They may have high FECs but have good FAMACHA scores, and few (if any) signs of parasite infection. “With tools like FAMACHA and the five-point check, you’re looking at clinical signs,” said O’Brien. “Both resistant and resilient animals will have no clinical signs. The only way to differentiate a truly resistant animal from a resilient animal is by FECs and FAMACHA.”

Some breeds are more tolerant of internal parasites. “Spanish and myotonic goats are more resistant,” said O’Brien. “Hair sheep breeds tend to be more resistant than wool breeds, and the Texel breed is more resistant.”

Even in breeds that are considered less susceptible, animals should be evaluated on individual merit because some animals within every breed will be more resistant than others.

It’s important to keep genetics in mind: resistant dams and sires will most likely produce resistant offspring. When selecting females, FECs should be checked and considered as a cull factor. Ideally, purchased males will have parasite data indicating a degree of parasite resistance.

The 70/30 rule refers to the fact that about 30% of the herd or flock is responsible for shedding 70% of the parasite eggs. “If you can identify those animals and cull based on high FECs,” said O’Brien, “you’re helping to select more resistant animals to keep.”

While some sheep and goat owners rely on herbal dewormers, O’Brien said scientific data are inconsistent in supporting their effectiveness. This is largely due to inconsistency in the amounts and methods by which herbals are administered.

Ingredients in herbal dewormers vary, and common names don’t always refer to the same plants. Herbal products should always be used in combination with other integrated parasite management techniques.

A non-chemical treatment for sheep and goats is copper oxide wire particles (COWP), which are effective in controlling barber pole worm in sheep and goats. If other worm species are problematic, COWP may not be sufficient.

COWP can be used in conjunction with chemical dewormers for greater FEC reduction. The recommended COWP dose is 0.5 – 1 gram for kids and lambs, and 1 to 2 grams for adult animals. Although sheep are sensitive to copper, COWP can be effective if not overused.

The nematode-trapping fungi Duddingtonia flagrans, which has been available as BioWorma® in the U.S. since 2020, is becoming more widely used. When this naturally-occurring fungus is fed to animals, it survives the digestive process and is passed in manure. When parasite eggs hatch, the fungus traps the larvae and prevents development on pasture.

D. flagrans does not treat the parasite load in animals – it treats what’s on the pasture. “About 10% of the worm population is inside the animal and 90% is on pasture,” said O’Brien. “If we give a drug that’s 90% effective, it only deals with the 10% (of parasites) inside the animal.” D. flagrans fed to cattle, horses, sheep and goats averages about 70% effectiveness in reducing pasture worm loads.

O’Brien said drug resistance is not a death sentence, but strategic drug use and management practices are key. “By using a more holistic approach, we become a more sustainable and profitable industry,” she said, “especially if we use genetic selection to choose more parasite-resistant animals to make our flocks and herds stronger.”

More information regarding parasite management is available at wormx.info.

Find Part 1 here and Part 2 here.