Glutathione peroxidase and selenium in sheep. I. Effect of intraruminal selenium pellets on tissue glutathione peroxidase activities

Two groups of sheep, both on a diet deficient in selenium, were either treated with intraruminal selenium pellets (containing 5% elemental selenium, 95% iron) or remained as untreated controls. At 23 weeks after pellet administration, activities of the selenium-containing enzyme glutathione peroxidase were greatly increased in many of the tissues of treated animals compared with the untreated controls. Maximum activity of erythrocyte glutathione peroxidase was reached 20 weeks after pellet administration. The maximum activity was considerably greater than the activity at which selenium-responsive diseases, in particular selenium-responsive unthriftiness, occur. This, together with the greatly increased enzyme activities in other tissues several months after pellet administration, suggests that selenium status can be adequately maintained for long periods by treatment with these pellets. In contrast to monogastric species, it appears that in the ruminant the biological availability of elemental selenium released from pellets, as determined by tissue glutathione peroxidase activities, is similar to that reported previously for selenite.