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Animal scientist Kip E. Panter examines a forage sample in preparation for a selenium study in sheep to compare absorption, distribution and elimination profiles of two forms of selenium: organic and inorganic.

Lambs' Selenium Needs Scrutinized

By Marcia Wood
September 14, 2006

Just like people, sheep and lambs need selenium to stay healthy. But, for humans and grazing animals alike, the difference between healthful amounts of selenium--and harmful ones--is exceptionally small, leading to selenium's reputation as a "Jekyll and Hyde" nutrient.

Ongoing studies by Agricultural Research Service (ARS) scientists at the Poisonous Plant Research Laboratory in Logan, Utah, provide a new, more detailed look at how lambs absorb, use and eliminate selenium. The investigations should yield insights into selenium poisoning.

The ARS scientists are collaborating with colleagues at Utah State University-Logan.

Technician Kermit Price (left) and range scientist James Pfister examine herbarium specimens of seleniferous plants in preparation for field studies to determine why sheep graze high-selenium forages. Click the images for more information about them.

Improved strategies for sidestepping selenium-related deaths would benefit everyone concerned with the health of not only sheep, but also of other livestock such as cattle, horses and goats or wildlife, including deer and elk.

What's more, the increasing interest in selenium's cancer-fighting properties in humans suggests that the selenium experiments may also be of value in medical research, according to laboratory director Lynn F. James.

The Logan investigations are expected to reveal unknown details about precisely how selenium poisons an animal. The experiments should answer a key question: Are there significant differences in the animal's responses to two different forms of selenium, namely, organic and inorganic?

The plants that sheep nibble in pastures, meadows or rangelands may contain mainly organic selenium. Inorganic selenium is the form traditionally mixed into feed, or perhaps added to salt-lick-type mineral blocks, in parts of the United States where soils and the plants growing on them do not have enough selenium.

Read more about the research in the September 2006 issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief in-house research agency.