The vitamin needs of growing cattle mostly concern vitamin A, D and E. The most important vitamin is vitamin A. Feed 20,000 to 30,000 I.U. of vitamin A per head daily. Vitamin D supplementation is not needed if cattle have access to sunlight. Adding 2 to 5 I.U. of vitamin E per pound of high-grain ration devoid of roughage has improved feedlot performance.
Vitamin A: A vitamin A deficiency in feedlot cattle may result in reduced feed intake, reduced gain, and poor feed conversion. These symptoms may become more pronounced in cattle that are almost ready for market at the onset of hot weather.
Vitamin E: Supplying cattle with 500 IU per day of vitamin E during the last 100 days on feed can increase shelf-life of beef at the grocery store.
B-Complex Vitamins: B-complex vitamins such as riboflavin, niacin, pyridoxine, biotin, folic acid and B12 are normally synthesized in the rumen at a sufficient rate to meet the needs of non-stressed cattle. Vitamin B12 synthesis may be low if cobalt is deficient in the diet.