Studies on selenuim in the nutrition of sheep

Abstract

In an area where the selenium concentration in the pastures appeared barely adequate, and where growth rate of lambs was commonly poor, experiments were conducted with 300 lambs during four successive years, to study the effects of supplements of selenium, cobalt, selenium plus cobalt, and vitamin E. The absence of any effect of treatment with selenium (or the other supplements) on growth rate, wool production, or level of glutamic-oxalacetic transaminase in the serum indicated that selenium deficiency did not affect the sheep during the experimental period. The toxic effects of regular oral doses of large amounts of selenium (up to 600 ¦gSe/kg/day) were studied on 50 mature wethers for periods up to 15 months. Food consumption and body weight increase were depressed by 200 ¦gSe/kg/day, and food consumption by 300 ¦g, while some mortality occurred at 400 ¦g. The selenium concentration in the blood and the tissues increased with rate and duration of intake; that in the tissues fell gradually after dosing with selenium was discontinued. No pathological changes were observed in the tissues of the sheep that survived the selenium treatment. It is unlikely that the amounts of selenium required to prevent selenium deficiencies in sheep will prove toxic to the animals.