LEUKOCYTE FUNCTIONS OF YOUNG DAIRY CALVES FED MILK REPLACERS SUPPLEMENTED WITH VITAMIN-A AND VITAMIN-E

Holstein calves (n = 44) were fed milk replacers from d 3 to 45 with l ow or high concentrations of vitamin A (7000 or 87,000 IU/kg) and vita min E (11.2 or 57 IU/kg) to examine the influence of vitamin concentra tions on vitamin bioavailability and leukocyte functions. Concentratio ns of alpha-tocopherol in plasma reflected increased vitamin E but wer e unaffected by increased vitamin A. Plasma retinol concentrations wer e greatest with high supplementation of vitamins A and E at wk 3; howe ver, at wk 6, plasma of calves fed high vitamin A and low vitamin E co ntained the most retinol. Increased supplementation of vitamin A impro ved fecal consistency compared with that for calves fed the low vitami n A diet at wk 3 and 4. At wk 3, calves that received increased supple mentation of vitamins E and A had enhanced neutrophil bactericidal act ivity compared with that of calves with increased individual vitamins. Lymphocyte DNA synthesis and chemotactic index were unaffected by die tary treatments. Results indicate that increased vitamin A in milk rep lacer 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.