Effect of dietary fat and vitamin E on α-tocopherol in milk from dairy cows

Abstract

Diets with different fat treatments and with 25, 125, or 250 IU of supplemental vitamin E (all-rac α-tocopheryl acetate)/kg of dry matter (DM) were fed for 28 d to midlactation Holstein cows to determine factors affecting concentrations of α-tocopherol in milk. Diets contained no supplemental fat or 2.25% added fat from roasted soybeans or tallow. Vitamin E treatment had no effects on production, but fat supplementation increased milk yield (37.2 vs. 35.1 kg/d). Cows fed RSB ate more DM (24.0 vs. 21.9 kg/d) and produced more milk fat than cows fed tallow. Supplemental fat increased plasma concentrations of α-tocopherol and cholesterol. Increased intake of α-tocopherol linearly increased concentrations of α-tocopherol in plasma but the rate of increase was 1.9 times greater when fat was fed. Plasma α-tocopherol concentrations were linearly related to concentrations in milk, but a change in plasma α-tocopherol resulted in a smaller change in milk α-tocopherol when fat was fed than when it was not. Fat treatment did not affect plasma α-tocopherol expressed relative to plasma cholesterol (mg α-tocopherol/g cholesterol) or relationships between plasma α-tocopherol/g of cholesterol and milk α-tocopherol. These data suggest that concentrations of α-tocopherol in milk are a function of the α-tocopherol enrichment of the plasma lipid fraction and enrichment of that fraction is saturable.