Effects of dietary vitamin E type on the growth performance and antioxidant capacity in cyclophosphamide immunosuppressed broilers
Reactive oxygen species and free radicals play multiple roles in some immune-pathological events. Vitamin E, as a very potent antioxidant, perhaps deceases the potentially negative effects of such oxidative stress to prevent immune-pathological damage to broilers. Therefore, the current study investigated the effects of dietary natural (D-α-tocopherol) and synthetic (DL-α-tocopherol acetate) vitamin E on the growth performance and antioxidant capacity in cyclophosphamide (CY) immunosuppressed broilers. 192 one-day-old male Arbor Acre broilers were randomly distributed into 4 groups: 1) non-CY-challenged control; 2) CY-challenged control; 3) CY-challenged group+20 IU DL-α-tocopherol acetate per kg feed; and 4) CY-challenged group+20 IU D-α-tocopherol per kg feed. The maize-soybean basal diet in the control group contained α-tocopherol (7.12 mg/kg). Broilers were intramuscularly injected with 80 mg/kg body weight of CY or sterile saline at 16, 17, and 18 d of age. CY decreased (P < 0.05) the average daily gain and average daily feed intake, but vitamin E did not alter the growth performance of broilers before or after CY injection (P > 0.05). The decreased absolute weight of the spleen, thymus and bursa, serum interleukin 2 (IL-2), and interleukin 6 (IL-2) concentrations in CY-treated broilers were alleviated by vitamin E (P < 0.05). The decreased relative weight (g/kg body weight) of the bursa in the CY-treated broilers was increased by natural vitamin E (P < 0.05). The CY-induced increases in malondialdehyde (MDA) content and decreases in total antioxidant capacity (T-AOC), glutathione, vitamin C, and α-tocopherol levels, and total superoxide dismutase and glutathione peroxidase activities in both serum and the liver were attenuated by vitamin E (P < 0.05). Additionally, natural vitamin E increased α-tocopherol and T-AOC levels and decreased MDA content in the liver of CY-treated broilers (P < 0.05) when compared to the synthetic form. In summary, both synthetic and natural vitamin E supplementation improved lymphoid organ weights, serum IL-2 and IL-6 levels, and antioxidant capacity of immunosuppressed broilers induced by CY. Especially, natural vitamin E was superior to the synthetic form and enhanced α-tocopherol and T-AOC levels, reduced MDA concentration in the liver, and alleviated the immune damage of the bursa.