Scientists first recognized selenium as a potentially toxic mineral, then in 1957 identified the element (Se) as an essential nutrient for humans and many animals. They discovered that selenium is critical to proper enzyme function and cellular antioxidant systems and involved in muscle contraction and immune function and is important for reproduction.

Because both the element and its salts are toxic even in small doses, selenium may be the most regulated trace mineral used in dairy animal supplements. The U.S. Food and Drug Administration (FDA) regulates the maximum supplemental level of selenium at 0.3 ppm. There are also regulations about the forms of selenium allowed.

FDA approval, new Se era

Prior to 2003, the only legal forms of selenium were sodium selenite and sodium selenate. But that year, the FDA approved selenium yeast as a legal form of selenium in the U.S., solely based on data submitted on Sel-Plex®. To this day, no other selenium yeast has been reviewed by the FDA.

Ruminants do not efficiently absorb the common forms of inorganic selenium (selenite and selenate). Research suggests that absorption of selenite by dairy cows is the range of 17-50%. Poor absorption of inorganic selenium is likely due to the ruminal environment, where oxidized selenite or selenate is, in large part, reduced by ruminal microbes to insoluble and unavailable elemental selenium, which is excreted via the feces.

The major advantage of an organic selenium source — such as Sel-Plex — is its improved absorption and retention in the body. Selenoamino acids incorporated into body proteins provide a reserve of stored selenium when demand for selenium is high, particularly during disease challenges and gestation.

Reproductive function

Maternal transfer of organic selenium through the placenta and colostrum improves the ability of the calf to survive and thrive. Also, organic selenium supports normal reproductive function, udder health, and postpartum health.

Ongoing research links Sel-Plex supplementation with increased Se concentration in milk and improved cow health and fertility. Learn more here.

Supported by more than 27 years of research, Sel-Plex remains the most researched and proven form of organic selenium to benefit dairy herd health and performance.