Submitted to: American Dairy Science Association Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/25/2000
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Fat-soluble vitamin status has been shown to influence broad aspects of the immune systems of a variety of animal species. Previous in vitro studies have shown that metabolites of VA and VE modulate the cellular composition and function of the bovine immune system. In the present study, effects of dietary VA and VE on the function and composition of blood leukocyte populations in neonatal calves were examined. Male, Holstein calves entered a 4-wk trial at less than/equal to 9 d of age and immediately after being transported for 34 h. During the study period, calves were fed a milk replacer providing 2000 (NRC level), 4000, or 34,000 IU VA/d and either 20 or 100 IU of VE/d. At 4 wk, the composition and function of peripheral blood mononuclear leukocyte (MNL) populations from calves (n=6/treatment group) were evaluated. Flow cytometric analysis of MNL populations indicated that percentages of B cells (P=.74) or T cells [i.e., CD4 (P=.22); CD8 (P=.43); and gamma/delta (P=.47) T cells] or expression of activation antigens [interleukin-2 receptor (P=.33) and MHC class II antigens (P=.13)] were unaffected by dietary VA and VE. Although DNA synthesis and secretion of IFN-gamma, nitric oxide, and polyclonal IgM by unstimulated and mitogen-stimulated MNL were unaffected by dietary VE, these variables were influenced by dietary VA. VE, but not VA, influenced neutrophil function (i.e. cytochrome C reductase activity. Serum Ig (G1, G, and M) concentrations and total numbers of blood leukocytes were unaffected by VA or VE. These results indicate that dietary VA and VE influence broad aspects of leukocyte function in vitro and suggest that bioavailability of these vitamins may alter immune competency and disease susceptibility of newborn calves.