Effect of Antioxidant, Protein, and Energy on Vitamin A and Feed Utilization in Steers1

Abstract

Yearling steers, prefed dehydrated alfalfa, were then fed two levels of protein (11–19%), two levels of energy (70–81 therms/ 100 lb.), and two levels of the antioxidant, Ethoxyquin (0 and 0.0125%) in a 23 factorial study. For the first 70 days, when no diets contained vitamin A or carotene, hepatic vitamin A expenditures were accelerated by increasing the protein and energy but significantly reduced by Ethoxyquin. Thereafter, vitamin A was added to all diets for the remainder of the study. Increasing the dietary protein reduced growth and increased feed/ gain. Increasing energy did not alter growth but reduced daily feed consumption and consequently reduced feed/gain. While the dressing percent of all groups were within 0.2%, only half the number of carcasses from steers fed high protein-high energy diets graded U. S. choice when compared to other diets. It is speculated that this effect was not due to differences in total carcass fat but to the distribution of fat in the muscle.