Selenium status in cattle

Interpretation of laboratory results

Abstract

Selenium may affect a wider range of metabolic functions than only those associated with nutritional myodegeneration, but there is controversy regarding the type of problems that may be associated with suboptimal selenium status in cattle. An animal's nutritional requirement for selenium and vitamin E depends on age, physiological stage and species. In cattle, low selenium status becomes critical near calving when cows are more susceptible to intramammary infections, retained placenta, or infections in the neonate. Analysis of serum samples (n=204) submitted to the Iowa State University Veterinary Diagnostic Laboratory between January 2000 and July 2001, showed a mean (ñSD) serum selenium value of 68.4ñ17 ppb for adult Holstein cows in the Iowa and Wisconsin areas. Because cattle receiving higher levels of selenium and vitamin E than typically recommended may show improved immunocompetence, the levels found in this survey can be considered adequate for reproductive performance, but marginal for optimal resistance to mastitis pathogens or for adequate transfer of selenium to the suckling calf. This report also contradicts previous claims that selenium deficiency contributes to stillborn/weakborn calves. Studies relating selenium concentrations in blood and serum to common clinical conditions of cattle attributed to poor selenium status are reviewed; methods of supplementation are also addressed.