Abstract: The objective of this study was to investigate the oxidative stability of meat from Sunit sheep fed on two different diets: pasture and forage supplemented with concentrate mixture. The amount of lipid oxidation products, thiobarbituric acid (TBA) value, antioxidant ability, antioxidant enzymes activities and the expression of antioxidant genes in Biceps femoris muscles from sheep slaughtered at 12 months of age were determined and compared between the two feeding groups. The results showed that TBA value of meat from grazed sheep was significantly lower than that of forage plus concentrate-fed sheep (P < 0.001). Hexanal, heptanal, nonanal, 1-octen-3-ol and 2,3-octanedione were the major lipid oxidation products in both meat samples and their values were lower in meat from grazed sheep than in forage plus concentrate-fed sheep (P < 0.05), indicating that the latter had a higher degree of lipid oxidation. As for antioxidant properties, total antioxidant capacity (T-AOC, P < 0.01) and cupric reducing antioxidant capacity (CUPRAC, P < 0.05) of grazed sheep were significantly higher than those of forage plus concentrate-fed sheep. The same was true for the antioxidant enzymes, superoxide dismutase (SOD, P < 0.001), catalase (CAT, P < 0.05) and glutathione peroxidase (GPx, P < 0.05). These observations suggest that meat from pasture-fed sheep has higher antioxidant enzymes activities and as a result, its lipid oxidation can be effectively inhibited. Furthermore, the gene expression of SOD (P < 0.001), CAT (P < 0.05) and GPx (P < 0.05) in pasture-fed sheep was significantly higher than in forage plus concentrate-fed sheep, while the opposite was true for the gene expression of lipoxygenase (P < 0.001). In conclusion, this study provides molecular evidence that antioxidant capacity in meat from pasture-fed sheep was better than in forage plus concentrate-fed sheep.

Key words: feeding pattern, Sunit sheep, lipid oxidation, antioxidant enzymes, gene expression