Vitamin E Status of Dairy Cows Fed Stored Feeds Continuously or Pastured during Summer

Parameters indicative of vitamin E status were monitored for over 4 yr in dairy cows to determine if feeding cows only stored feeds could cause deficiency of vitamin E. Low-E cows were fed stored feeds all year whereas the pastured cows grazed during summer. A third group pastured only while dry also was monitored the 4th yr. There were no signs of deficiency of vitamin E although vitamin E of low-E cows was lower than that of cows pastured. Vitamin E (total tocopherols) in milk from low-E cows remained below 25 mg/g fat except during October and November when new crop hay and silage contained more vitamin E than feeds stored longer. Vitamin E of milk from pastured cows increased to about 50 mg/g fat but declined to less than 30 mg/g fat by winter. Pasturing cows only during dry periods elevated vitamin E in milk only slightly and not as much as in lactation. Susceptibility of milk to oxidized flavor was related inversely to vitamin E. There were no differences between low-E and pastured cows in incidence of retained placentas or reproductive efficiency. Long feeding of only stored feeds had no adverse effects on health and production by lactating cows; however, milk quality was reduced by increased susceptibility to oxidized flavors.