Interactive effects of α-tocopheryl acetate and zinc supplementation on the antioxidant and immune systems of broilers.

1. A total of 1440 one-day-old Ross 308 male broilers were allocated to 12 dietary treatments to evaluate dose-dependent effects of α-tocopheryl acetate (α-TOA) combined with zinc (Zn) supplementation on humoral and cellular immune responses, antioxidant enzymes, serum and hepatic contents of vitamins and minerals in broilers. 2. Three levels of supplemental α-TOA (0, 150 and 300 mg/kg) and 4 levels of Zn (0, 100, 200 and 400 mg/kg) were combined as a completely randomised design as a 3 × 4 factorial arrangement. 3. Concentrations of serum α-tocopherol and selenium were influenced by the interaction of α-TOA and Zn. The interaction of α-TOA and Zn affected malondialdehyde (MDA) concentration in serum and liver (p < 0.05). Incremental amounts of supplemental Zn augmented the effects of α-TOA in reducing serum and hepatic MDA concentrations. 4. The interaction of α-TOA and Zn on antibody titres (p < 0.05) was such that increasing level of Zn at each α-TOA level led to a linear enhancement in antibody titre. Moreover, dietary supplementation with α-TOA and Zn resulted in an increase in relative weight of lymphoid organs (thymus, bursa, spleen; p < 0.05) along with an increase in humoral and cellular immune responses (p < 0.05). 5. In conclusion, α-TOA with Zn showed interactive effects in improving oxidative stability and humoral immune responses, which could result from their impact on the concentrations of antioxidant vitamins and minerals in tissues.