Effects of vitamin E on immune function of dairy cows.

The effect of vitamin E supplementation on the immune function of dairy cows was studied. Twelve cows were assigned to 1 of the 2 experimental groups: control (no vitamin E supplementation), and vitamin E-supplemented. Supplementation of vitamin E started 4 weeks before and continued up to 8 weeks after parturition and included oral supplementation of vitamin E at the rate of 3,000 IU/cow/d. In addition, the same group of cows received 1 injection of vitamin E (5,000 IU), 1 week prior to the expected date of parturition. Data indicated that blood neutrophils isolated from control cows produced twofold less (P < 0.05) superoxide anion after parturition, compared with the corresponding value before parturition. Furthermore, blood macrophages isolated from control cows produced 15 and 35% (P < 0.05) less interleukin 1 (IL-1) and major histocompatibility (MHC) class-II antigens, respectively, after parturition, compared with the corresponding values before parturition. These data, collectively, indicate that functions of blood macrophages and neutrophils are depressed during the early postpartum period in control cows. In contrast, there were no differences in superoxide anion production by blood neutrophils, or in IL-1 production, and MHC class-II antigen expression by blood macrophages before and after parturition in cows supplemented with vitamin E. There were no differences in lymphocyte proliferation, or IL-1 production and MHC class-II antigen expression by mammary macrophages when control and vitamin E-supplemented cows were compared. We conclude that vitamin E prevented suppression of blood neutrophil and macrophage function during the early postpatum period.