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Researchers look at alternative dewormers to address parasite resistance

by Wyoming Livestock Roundup

“Because of anthelmintic resistance and increased interest from a lot of producers in alternative dewormers, researchers came together and said, ‘Let’s see if we can repeat these results in controlled experiments,’” said Virginia State University Cooperative Extension Small Ruminant Specialist Dahlia O’Brien.

In a presentation for sheep and goat producers through Maryland Extension, O’Brien discussed the current status of alternative deworming product research, as well as practical management strategies for reducing a flock’s susceptibility to internal parasites.

Mixed results

According to O’Brien, a flood of personal testimonies on the efficacy of various alternative products for deworming has been available in recent years, but very little conclusive research has been done.

“A lot of the information we have on herbal dewormers is anecdotal or hearsay, and there has been limited research to provide verification,” said O’Brien. “Even when producers can find research that supports the anthelmintic properties of individual herbs and natural plant products, the products are inconsistent.”

She illustrated this point by referencing a variety of studies on the use of garlic, papaya, pumpkin seeds and other herbal dewormers that all had conflicting results on the products efficacy in reducing fecal egg counts.

“I came across an article where sheep were inoculated with the Barber pole worm and then treated with papaya where fecal egg counts were reduced by 98 percent,” said O’Brien. “However, in control experiments conducted in Arkansas and Maryland, there was no effect from garlic or papaya on fecal egg counts.”

She commented that, because of the mixed results, she could not make a confident statement whether herbal products have any effect on fecal egg counts.

“What I will say is that herbal dewormers should always be combined with other integrated parasite management techniques,” said O’Brien. “It is important to know the status of drug resistance on our farm, so these techniques can be used in conjunction with an effective chemical dewormer.”

Copper use

Considerable research has been done on the use of copper oxide wire particles (COWP), which is commonly used to treat copper deficiency in sheep and goats, in parasite control programs.

“There’s overwhelming evidence that it reduces fecal egg counts in both sheep and goats,” said O’Brien.

She did caution that sheep are particularly sensitive to copper and can easily be intoxicated.

“Their margin of safety between required amount of copper and toxic level is extremely narrow, so we should be cautious when using any kind of copper product in our herd or flock,” she explained. “It’s best to know the copper status on our farm before we start using copper products.”

In multiple studies looking at using COWP to reduce fecal egg counts, researchers have found that it is effective against the Barber pole worm. It is suspected that the product changes the environment in the abomasum and causes physical damage to the larvae.

“COWP been tested in both sheep and goats, and it’s been tested in multiple locations. It’s been tested in young animals versus old animals and has been found to be effective in reducing fecal egg counts. Therefore, we can be more confident in recommending that COWP be included in an integrated parasite control program, specifically to control H. contortus,” asserted O’Brien.

Tannin feeding

Feeding animals plants containing concentrated tannins, such as sericea lespedeza and chicory, is another alternative option that researchers have found promising for use in parasite control programs.

In studies that looked at grazing or feeding hay to animals made from concentrated tannin plant species, O’Brien noted that there was considerable impacts on Barber pole worms and protozoan parasites.

“Feeding fresh, dried or preserved forms of sericea lespedeza has been shown to have some level of anti-parasitic activity against H. contortus,” she said. “Research has also shown that it is effective against protozoan parasites that cause coccidiosis in sheep and goats.”

Forage chicory is another species that has been evaluated and found effective in reducing fecal egg counts. However, producers should use discretion when feeding concentrated tannins, as extended feeding may result in adverse effects on the animal’s nutrition.

“Plants that contain condensed tannins appear to be very good choices in integrating in a parasite control system, but extended feeding can cause problems with trace mineral absorption,” commented O’Brien.

Emilee Gibb is editor of Wyoming Livestock Roundup and can be reached at

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