EFFECT OF FORAGE TYPE AND SUPPLEMENTAL DIETARY VITAMIN-E ON MILK OXIDATIVE STABILITY

Twelve Holstein cows in each of two replicates were used to determine the effect of forage type and vitamin E supplementation on the oxidative stability of milk. Alfalfa or corn silage was fed ad libitum as the sole roughage, with a concentrate to milk ratio of 1:2.5. Half the cows on each forage were fed 7000 IU d-1 of dL-alpha-tocopherol acetate top-dressed on the concentrate in two feedings per day over a 4-wk period. Cows consuming the alfalfa silage had higher (P < 0.05) plasma vitamin E content, but there were no differences in milk vitamin E or flavor due to forage type. Supplementing the diets with vitamin E resulted in higher (P < 0.01) vitamin E content of plasma and milk and improved milk oxidative stability. There was an interaction (P = 0.03) between forage type and vitamin E supplementation for oxidative flavor score in week 2. Supplementing the corn silage diet with 7000 IU d-1 of vitamin E resulted in almost complete elimination of oxidized flavor in milk within 1 wk of starting supplementation. However, supplementing the alfalfa silage diet had no effect on flavor over the first 3 wk of feeding. It is apparent that the vitamin E content of milk is not the sole determinant of its oxidative stability.