RESUMO
Vitamin E is known for its antioxidant properties and has been shown to modulate immune system in various species. An experiment with 240 one-day old Ross 308 male broilers was conducted to investigate the effects of 4 different levels of vitamin E [0, 10, 20 and 40 mg/kg] on performance and response of humoral immunity. Chicks at age of 15, 30 and 45 days were injected I.M. with 0.2ml of a 5% saline suspension of sheep red blood cell [SRBC]. Blood samples were collected from each bird at 7 and 14 days of the second and third challenge. Afterwards, the 2-mercaptoethanol sensitive [2MES, presumably IgM] and 2-mercaptoethanol resistant [2MER, presumably IgG], Anti-SRBC antibody titers were determined using a microheamagglutination technique. Then chicks were slaughtered and their bursa of fabricius and spleens were weighted. The results of this study suggested that vitamin E has no significant effect on performance of broiler chicks such as body weight, feed intake and feed efficiency. There was a significant difference on total anti-SRBC-titter, 2-mercaptoethanol sensitive antibody titer [2-ME sensitive], anti-New Castle disease virus titter [NDV] in group which was given 40 mg/ kg supplemented vitamin E compared to the control group [p<0.005]. 2-mercaptoethanol resistant antibody titter [2-Me resistant] and lymphatic organs [bursa of fabricius and spleen] weight were not under the effect of diet. Furthermore significant difference wasn't observed between treatments. These results indicated that supplementation of vitamin E increases humoral immune responses