The potency of α- and γ-tocopherol, and their combination, in reducing dietary induced oxidative stress in vivo and improving meat lipid stability in broilers

The objective of this study was to investigate the roles of alpha-and gamma-tocopherol, and their combination, in the prevention of oxidative stress in vivo and on lipid oxidation of meat in broiler chickens. One day-old chicks were included in a 30 day trial and divided into five experimental groups, the negative control (Cont-, n = 10) received 5% palm fat, while other four groups (positive control, Cont+, n = 10; TOC alpha, n = 10; TOC gamma, n = 8 and TOCa gamma, n = 8) received 5% linseed oil that was vitamin E-stripped. Cont + and Cont- were given 10 mg/kg a-tocopheryl acetate to cover basic needs, group TOC alpha 67 mg/kg RRR-alpha-tocopherol, group TOC gamma 67 mg/kg RRR-gamma-tocopherol and group TOCa gamma 33.5 mg/kg each of tocopherols. Oxidative stress in vivo was evaluated by means of a Comet Assay to measure lymphocyte DNA damage, by plasma, breast and thigh malondialdehyde (MDA) formation, and by measuring antioxidant capacity of plasma. The tocopherols in plasma, breast and thigh muscles, the fatty acid composition of both muscles and their lipid stability under different storage conditions (6 days at 4 C, 2 and 4 months at -20 C) were also analysed. Both forms of vitamin E were able to reduce the lymphocyte DNA damage, while the results of other analyses evaluating oxidative stress indicated that only a-tocopherol and the combination of both tocopherols are effective in its prevention. This seems to be a consequence of a-tocopherol being preferentially retained in the organism. Its concentrations in plasma and muscles reflected the feeding regimen, while gamma-tocopherol's concentrations were only slightly elevated in both groups supplemented with gamma-tocopherol. The fatty acid composition of the diet was reflected in the fatty acid composition of both muscles. The lipid stability of muscles in groups receiving linseed oil was compromised, but lower MDA values in groups TOC alpha and TOCa gamma under some of the storage conditions proved the ability of alpha-tocopherol and the combination of both tocopherols (TOCa gamma) to improve it.