Relationship of Dietary Selenium to Selenium in Plasma and Milk from Dairy Cows

Abstract

In a 13-wk trial Holstein cows in mid-lactation were fed four diets containing natural selenium alone or supplemented with .1, .2, or .5mg of inorganic selenium per kilogram of diet. Dietary selenium concentration averaged .334, .385, .456, and .772 mg/kg. Selenium plasma in wk 7 averaged .112µg/ml with no differences among treatments; milk selenium ranged from .040 to .046µg/ml and was higher in the two higher selenium diets. In wk 13 selenium in plasma and milk averaged .119 and .054 with no treatment differences. The 7 and 13 wk concentrations were higher than pretrial .084 and .033µg/ml for plasma and milk during which time dietary selenium concentration was .254 mg/kg. Selenium concentration increased linearly from about .08 to .120µg/ml of plasma and about .030 to .055µg/ml of milk as intake of selenium increased from about 2 to 6 mg/day. Increase in selenium intake from 6 to 12 mg/day resulted in little change in plasma and milk selenium. Moderate concentrations of dietary selenium (.3 to .7 mg/kg) do not result in toxic amounts of selenium in milk.