Vitamins A and E in Steer Fattening Rations on Pasture

Abstract

A series of three experiments were conducted to determine the value of vitamins A and E when added to concentrate mixtures for steers on pasture. Levels of 25,000 I.U. of vitamin A significantly (P<.01) increased rate of gain of steers during two winter experiments but not during a summer trial. Vitamin E significantly increased weight gains during one winter trial but not the other. Neither vitamin A nor E had a significant effect upon steer performance during a summer feeding trial. The response to the vitamins appeared to be related to the level of carotene and KNO3 in the forage. Supplemental vitamin A or E increased vitamin A and copper in liver tissue. There was less growth response to vitamin A when it was fed in combination with vitamin E. The relationship of other nutrients, such as copper, may be a factor in the effect of supplemental vitamins A and E.