Effect of vitamins A and E on nitric oxide production by brood mononuclearleukocytes from neonatal carves fed milk replacer

This study evaluated the effects of dietary vitamin A and E on the in vitro capacity of blood mononuclear leukocytes from calves to produce nitric oxi de. Calves fed milk replacer received 100 IU/d of vitamin E as RRR-alpha-to copherol or RRR-alpha-tocopheryl acetate and 0, 1700, 34,000, or 68,000 IU of vitamin A as retinyl acetate. Leukocytes from calves produced greater am ounts of nitric oxide relative to leukocytes from adult cattle. The greater production of nitric oxide by calf leukocytes may be typical; of the immat ure neonatal immune system. Nitric oxide production by calves fed RRR-alpha -tocopherol and either 1700 or 34,000 IU of vitamin A was less than that of calves in other groups and was more typical of production by leukocytes fr om cows. Our data suggest that optimal amounts of dietary vitamins A and E prompt the maturation of this response toward one that is more typical of a dult cattle. Leukocytes from 1-wk-old calves produced less nitric oxide and were less responsive to stimuli than were leukocytes from older calves, a possible consequence of suppressive factors that were present in the ingest ed colostrum or in the circulation at birth.