EFFECTS OF REPLACEMENT OF NATIVE FAT IN COLOSTRUM AND MILK WITH COCONUT OIL ON FAT-SOLUBLE VITAMINS IN SERUM AND IMMUNE FUNCTION IN CALVES

Fat-soluble vitamins and their metabolites modulate immune function in a variety of animal species. The objective of the present study was t o determine the role of fat-soluble vitamins in colostrum and milk in the development of specific aspects of immune function in the calf dur ing the 1st wk postpartum. During this period, control calves (n = 6) were fed normal colostrum and milk, and calves in the treatment group (n = 6) were fed skimmed colostrum and skimmed milk supplemented with coconut oil. Treated calves did not experience the progressive increas e in concentrations of retinol, beta-carotene, alpha-tocopherol, 1,25- dihydroxyvitamin D, or retinoic acids in serum that was observed in co ntrol calves. Acquisition of passive immunity, which is indicated by c oncentrations of immunoglobulin G(1) in serum, was unaffected by treat ment. Composition and functional capacities of populations of blood mo nonuclear leukocytes that were collected from birth to 7 d postpartum were also unaffected by treatment. Major changes in the function and c omposition of mononuclear leukocyte populations from all calves occurr ed during the experimental period and were unrelated to the concentrat ions of fat-soluble vitamins in serum. Populations of blood mononuclea r leukocytes from calves were functionally hyporesponsive and composit ionally different from populations of blood mononuclear leukocytes fro m adult nongravid cows. These differences likely reflected the immatur ity of the immune system of the neonatal calf and may contribute to th e increased susceptibility of the calf to infectious disease.