Increased Selenium Dosage Boosts Growth and Immunity in Lambs

In a new study published in the Journal of Animal Science, Oregon State University (OSU) researchers show that maximum selenium levels permitted by the U.S. Food and Drug Administration (FDA) may be too low for sheep to reach optimum growth and health.

Selenium is essential for cellular function in animals and aids development. Large selenium doses can be toxic, but too-low levels can impair growth and compromise the immune system.

“When sheep don’t grow to their potential or have weak immune systems, it can be a sign of insufficient selenium,” said Gerd Bobe, co-author of the study and an OSU professor. “Our research shows higher levels of selenium can result in healthier animals that grow bigger and that can improve returns at the marketplace for farmers and ranchers.”

A challenge is that the range between selenium deficiency and selenium toxicity can be narrow; current FDA regulations limit the amount of dietary selenium supplementation for animals grazing on selenium-scare soils to 0.7 mg per sheep per day or 3 mg per beef cattle per day.

In OSU’s experiments, pregnant ewes were given selenium doses up to five-times higher than the FDA’s allowed level – an amount of supplementation researchers determined to be not harmful to sheep. The element is carried into the bodies of offspring, helping young animals during development.

At the highest selenium doses, ewes gave birth to lambs that grew to be 4.3-pounds heavier than average after 60 days. Furthermore, survival was 15-percent higher in lambs receiving the highest amount of organic selenium supplementation. As farmers look to sell sheep at five to six months old, weight and health metrics are keys to profitability.

A new generation of OSU research is attempting to determine how much selenium and in what form is best for optimal growth and health of sheep and cattle.