Sheep appear to 'self-medicate'

Pretend you're a lamb with an acid stomach. You sample some special feed dosed with an antacid, and the condition clears up. Not baaaaad, you decide. Five months later, you have the ailment again. What happens then?

You hoof it over to the same medicine you took the first time.

The seemingly improbable ability of livestock to self-medicate is described in a study by Utah State University researchers that was published in the May edition of the journal Animal Behavior. The authors are Juan Villalba, research assistant professor; Frederick D. Provenza, professor; and Ryan Shaw — all of USU's department of forest, range and wildlife sciences.

"The animal learns the association," Villalba said. The sheep discovers that with a certain medicated food, it will get "relief from heartburn, with the antacid."

The scientists carried out experiments over eight months at USU's Green Canyon Ecology Center, Logan. They used 20 lambs that were divided into a control group and a "treatment" group, each with 10 animals.

Both groups were given medicines to familiarize them with the tastes.

The animals were fed food that caused discomfort, such as too much grain that caused heartburn, food with tannins that affected digestion, and food with oxalic acid that reduced calcium intake. All of these substances were similar to things that might be eaten in the wild, like greasewood.

The treatment group was quickly offered identifiable medicine that would cure or ease the particular ailments. This amounted to conditioning. "The animals have the right associations at the right times," so that they learn.

The control group was given the same ailment-inducing feed and medicine but not with the same time association. They did not learn that the medicine could help them.

The conditions were induced, and preference tests were given to both groups, to check whether they would go for the correct treatment grains. Animals from the treatment group were more likely to eat the particular medicines that helped their condition than those in the control group.

Five months later the experiment was repeated, with similar results.

Those in the treatment group remembered the medicines that would help them and chose the right ones. However, the control group "never changed their patterns," Villalba said.

"This is the first demonstration of multiple state-specific medicine preferences in animals," says the report in Animal Behavior.

Villalba said the sheep in the treatment group learned medicine helped them. But the purpose of the study was not to show animal intelligence.

Its purpose was to determine whether livestock can receive medicine and learn to "self-medicate, so their welfare is much better in the wild and on the range," he said.

"It's really an important management tool," according to Villalba, both for domestic and wild animals.

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