Effect of high dietary levels of α-tocopherol acetate on immune response of light and heavy weight male broiler breeders

The objective of this study was to investigate the effect of overdosing dietary α-tocopherol acetate (α-TOH) on immune response of heavy weight roosters. A total of 60 roosters (Ross 308) of light (LW, n = 30) and heavy weight (HW, n = 30) were kept in individual cages. Roosters were randomly allotted to ten treatment groups in a 2 × 5 factorial design. Each group received a basal diet supplemented with graded levels of α-TOH (0, 100, 200, 300, 400 mg/kg diet) for 10 weeks (from 25 to 35 week of age). Blood samples were collected at the fifth and tenth weeks of the experiment. Afterwards, humoral immune system function was evaluated by sheep red blood cell (SRBC) hemagglutination assay (HA) (at 35 weeks of age) and hemagglutination inhibition (HI) tests including antibody response to Newcastle disease viruses (NDV) and avian influenza viruses (AIV) (at 30 and 35 weeks of age). Cell-mediated immune response was evaluated by the cutaneous basophil hypersensitivity (CBH) test. A positive linear relationship was observed between incremental levels of dietary α-TOH and both humoral and cell-mediated immunity (P ≤ 0.05), with the highest immune parameters recorded for dietary supplementation of 400 mg/kg α-TOH (P ≤ 0.05). The results showed that CBH was significantly higher in LW roosters in comparison with HW roosters (P ≤ 0.05). However, the interaction of BW and α-TOH doses did not have any significant effect on immune responses (P ≥ 0.05). In conclusion, dietary supplementation of α-TOH at higher levels (four times more than the strain nutrients recommendation) had beneficial effects on the immune response of both HW and LW male broiler breeders.