Effects of dietary methionine on growth performance, meat quality and oxidative status of breast muscle in fast- and slow-growing broilers

D This experiment was conducted to investigate the effects of dietary methionine (Met) on growth performance, carcass traits, meat quality and oxidative status of breast muscle in fast- (Arbor Acres, AA) and slow- (Partridge Shank, PS) growing broilers from 1 to 42 d of age. The broilers were divided into a 2 x 3 factorial design with 6 replicates per treatment. Diets were formulated to contain low (LM, 0.35 and 0.31% during 1 to 21 and 22 to 42 d), adequate (AM, 0.50 and 0.44%) and high (HM, 0.65 and 0.57%) Met, respectively. The main effects showed that the AA broilers had superior (P < 0.05) growth performance and carcass traits compared with those of the PS broilers. The breast muscle of the AA broilers had lower (P < 0.05) drip loss and malondialdehyde (MDA) content but higher (P < 0.05) cooking loss and glutathione peroxidase (GPX) activity than that of the PS broilers. Compared with the LM diets, the AM and HM diets increased (P < 0.05) 42-d BW, ADG, eviscerated yield and breast muscle yield only in the AA broilers. The AA broilers fed the HM diets had higher (P < 0.05) pH but lower (P < 0.05) L*, cooking loss and ether extract content in breast muscle than those fed the LM diets. Compared with the LM diets, the HM diets resulted in strain-dependent changes (P < 0.05) in muscle oxidative status, with total antioxidant capacity (T-AOC) increased in the AA broilers, GPX activity increased and MDA content decreased in the PS broilers, and superoxide dismutase (SOD) activity increased in both strains of broilers. No differences were observed between the AM and HM diets except for T-AOC in breast muscle. In conclusion, the LM treatment negatively affected broiler growth performance, carcass traits, meat quality and oxidative status of breast muscle in a strain-dependent manner, particularly in the AA broilers, whereas the HM treatment had limited effects compared to the AM treatment.