COW CALF PRODUCTION MANAGEMENT UPDATE - SELENIUM AND IMMUNE FUNCTION IN CATTLE/

In North America, many soils and regions are considered to be deficien t in selenium; as a result, ruminants that consume grains and forage f rom these regions may be at risk of developing selenium deficiency. Su rveys of beef cattle conducted in the United States and Alberta indica te that 18% and 9% of cattle, respectively, are considered to be margi nally or severely : deficient in selenium. In animals, selenium is a c omponent of glutathione peroxidase. This cellular enzyme protects cell s from oxidative damage by-reducing hydrogen peroxide and organic pero xides. Glutathione peroxidase activity is considered to be the most im portant function of selenium in animals, in cattle, blood selenium con centration and blood glutathione peroxidase activity are used to asses s selenium status. Selenium supplementation can improve immune functio n. Research on the effects of selenium on immune response in ruminants has centered on neutrophil function, mastitis, humoral immune respons es, passive transfer of immunoglobulins, and lymphocyte function. Sele nium can be supplied by means of parenteral injection, addition to rat ions, supplements, or salt-mineral mixtures. In ruminants that are sel enium-deficient supplementation enhances the humoral and cellular comp onents of the immune system.