High dietary concentrations of methionine reduce the selenium content, glutathione peroxidase activity and oxidative stability of chicken meat

Three experiments (EXP) were conducted using two hundred seventy male chicks Ross 308 in each (90 cockerels per treatment; 3 replications, 30 chickens per pen) for 42, 38 and 35 days. The basal diets (treatment 1) for three EXPs contained the identical ingredients, and the concentration of selenium (Se), methionine (Met) and total sulphur amino acids (TSAA) in the control diet was 0.11 mg/kg, 5.65 g per kg and 9.25 g/kg, respectively. Chicks in dietary treatment 2 were fed a basal diet supplemented with 0.3 mg/kg of Se (EXP 1, 2 and 3) and in dietary treatment 3 they were fed a basal diet with the addition of 0.3 mg/kg of Se and 1 g/kg (EXP 1 and 2) or 2.5 g/kg of dl-methionine (EXP 3). In EXP 1, sodium selenite and in EXP 2 and 3 Se-enriched yeast were used as sources of supplemental selenium, respectively. The results indicated that the addition of Se or Se and Met into the diet of broilers did not significantly affect the final live weight of chickens and the feed consumption. Moreover, the concentration of Met (P = 0.004), Cys (P = 0.01) and tyrosine (P < 0.001) in breast muscle increased with an increase in dietary Met content, and the isoleucine concentration decreased (P < 0.001). Moreover, the addition of inorganic and organic sources of Se increased the Se content of breast meat (P < 0.001). On the other hand, the addition of Met decreased the concentration of Se (P < 0.001) in breast meat and reduced glutathione peroxidase activity and oxidative stability of raw breast muscle (P = 0.019, P < 0.001) and breast meat stored for 3 days (P = 0.016, P = 0.006) in EXP 2 and 3.