Leukocyte functions of young dairy calves fed milk replacers supplemented with vitamins A and E.
Holstein calves (n = 44) were fed milk replacers from d 3 to 45 with low or high concentrations of vitamin A (7000 or 87,000 IU/kg) and vitamin E (11.2 or 57 IU/kg) to examine the influence of vitamin concentrations on vitamin bioavailability and leukocyte functions. Concentrations of alpha-tocopherol in plasma reflected increased vitamin E but were unaffected by increased vitamin A. Plasma retinol concentrations were greatest with high supplementation of vitamins A and E at wk 3; however, at wk 6, plasma of calves fed high vitamin A and low vitamin E contained the most retinol. Increased supplementation of vitamin A improved fecal consistency compared with that for calves fed the low vitamin A diet at wk 3 and 4. At wk 3, calves that received increased supplementation of vitamins E and A had enhanced neutrophil bactericidal activity compared with that of calves with increased individual vitamins. Lymphocyte DNA synthesis and chemotactic index were unaffected by dietary treatments. Results indicate that increased vitamin A in milk replacer did not affect plasma vitamin E concentrations, benefited fecal scores regardless of vitamin E concentrations, but was only beneficial to bactericidal activity of neutrophils in conjunction with increased vitamin E.