SELENIUM SUPPLEMENTS FOR GRAZING SHEEP .1. A COMPARISON BETWEEN SOLUBLE SALTS AND OTHER FORMS OF SUPPLEMENT

Sodium selenite was administered to grazing ewes at various stages of pregnancy and lactation, and in varying quantities by mouth and by subcutaneous injection. Other ewes received elemental Se and Fe:Se ruminal pellets. Growth rates of lambs were not significantly affected by the treatments but large differences in the Se content of blood were observed in both ewes and lambs. Elevations in Se status in lambs born to ewes dosed orally with sodium selenite were short, and it is suggested that ewes should be dosed in late pregnancy and their lambs dosed early in life. Subcutaneous injection was generally more efficient than oral dosing and Fe:Se pellets were the most reliable form of supplementation; elemental Se given alone had no effect on Se status. In a second experiment, pregnant ewes were given Fe:Se pellets and access to selenized salt; lambs born to ewes receiving both forms of supplement grew more rapidly. However, increases in blood Se content were very variable in ewes and their lambs given access to selenized salt, and this form of supplementation was not recommended. © 1990.