ABSTRACT
The classic nutritional research of Schwarz and Foltz (1957), showing that selenium (Se) is the critical element in factor 3 that prevents liver necrosis in rats, began the work that subsequently proved Se to be an essential nutrient for man, cattle, other grazing ruminants, and all vertebrates examined to date. Subsequently, Muth (1963) and Hogue et al. (1962) reported that Se and vitamin E administration can prevent white muscle disease in young ruminants. In recent years, several Se-responsive conditions have been described in cattle, and these have been reviewed (Maas, 1983). The Se-responsive conditions in cattle include nutritional myodegeneration (white muscle disease), retained placenta, abortions, neonatal weakness, diarrhea, ill thrift, infertility, and immune system deficits. Relationships between vitamin E and Se were observed; however, the biochemical basis for the action of Se was only speculated upon. Minimum dietary requirements of cattle for Se were developed from feeding and response trials. In 1973 Rotruck et al. published work outlining a basic biochemical mechanism that accounts for the role of Se as an essential nutrient. That work (Rotruck et al.,1973) showed that Se is a component of glutathione peroxidase (GSH-Px; EC 1.11.1.9) in erythrocytes. Selenium-deficient rats were found to have low GSH-Px activity and signs of Se deficiency. Most of a dose of radioactive 75Se was present in the GSH-Px activity of erythrocytes
of test animals. The same workers purified Se-containing GSH-Px from sheep erythrocytes.
