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Ravell Call, Deseret News
Utah State University's Juan Villalba works in the lab where fecal matter from sheep is analyzed to check for parasites. He has learned that sheep can be trained to eat the right foods to help cure their ailments and keep them healthy in Logan, Wednesday, Sept. 7, 2011.

LOGAN — When Juan Villalba scoops up some alfalfa pellets, his sheep know food is coming and begin bleating and prancing with excitement.

While they don't look particularly remarkable, these sheep could end up helping to solve a growing global crisis that is threatening livestock worldwide: drug-resistant parasites.

Recent scientific studies have shown the number of livestock parasites that have grown resistant to pharmaceuticals has been steadily rising. Internal parasites have been attributed to weakening and even killing livestock animals, such as sheep, goats and cows. Such infestations can create negative impacts on economies and food availability, in particular with meat and dairy.

An associate research professor of foraging behavior at Utah State University, Villalba attributes the growth in drug-resistant parasites to conventional farming methods. "Producers treat all of the herd, whether they're sick or not," he said. The result is similar to concern doctors have to the overuse of antibiotics, which have given rise to drug-resistant diseases in humans.

In one of the first studies of its kind, Villalba is experimenting with using pastures as a natural pharmacy, where farm animals treat their own illness by eating certain plants with medicinal compounds. Researchers at USU have identified several plants which contain tannins, saponins and other natural compounds that can kill internal parasites.

More than a dozen sheep are penned in a covered area that Villalba calls "the cafeteria." Villalba is training his sheep to be discerning eaters. Lets face it, medicine doesn't taste all that good to animals either. Typically medicinal plants tend to taste bitter to them.

Villalba is training sick sheep to associate eating medicinal plants with feeling better. When the animals are placed in a pasture that contains those plants, the sheep have been observed seeking out those plants when they don't feel well.

"By offering animals choices, we allow them to build their diet as a function of their own needs," he said. As the animals recover, they then stop eating the medicinal plants.

Think of it as providing livestock with their own personal medicine cabinet. Villalba has about nine acres of test pasture in which he has grown fields containing a mix of medicinal plans and alfalfa. He is currently researching what mix of plants is best for sheep.

"The drugs that we use to treat worm infections aren't working anymore," said James Miller, parasitologist and professor at Louisiana State University. Miller said the problem is global and serious; particularly among sheep and goat populations. "Producers are going out of business. They're losing animals and they're losing productivity," he said.

Miller said Villalba's research could help farmers find a natural alternative to using drugs. While medicinal plants won't fully cure parasites, they can reduce infections to manageable levels.

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Other studies have shown that wild animals have learned to treat their illness by eating certain medicinal plants. A study of monkeys at Kyoto University in Japan showed that monkeys in the wild sought out medicinal plants in the forest, but only when they were sick.

Villalba said most livestock animals have those same skills and other studies have shown that they pass that behavior on to their offspring through observation. "Behavior can be a really powerful tool, if you understand how it works," he said.

E-mail: gfattah@desnews.com