Supplementation with free methionine or methionine dipeptide improves meat quality in broilers exposed to heat stress

This study aimed to evaluate the effect of methionine dipeptide supplementation on the meat quality of broilers subjected to heat stress. A completely randomized 3 × 2 factorial design with four repetitions of each treatment was used. Three diets, unsupplemented (U), supplemented with methionine (M), and supplemented with methionine dipeptide (MM), were fed to 96 broilers subjected to thermal comfort (TC) or heat stress (HS, 32 °C for 24 h) conditions antemortem. Meat quality parameters, total antioxidant capacity (TAC), protein and lipid oxidation, and ryanodine receptor type 3 (RYR3) gene expression in breast muscle of 35-day-old broilers were evaluated. Methionine supplementation (M and MM) enhanced the nutritional quality of breast meat. Diet had a significant effect on breast meat pH, color (a*), and nitrogen and lipid contents. Interaction effects of diet and HS on TAC and protein oxidation were not observed. Diet and HS influenced lipid oxidation of breast meat after 7 days of refrigerated storage. High RYR3 expression was observed in breast meat of broilers subjected to heat stress and fed the U diet. No differences were observed between M and MM diets in any of the parameters evaluated. The results showed that both sources of methionine (M and MM) can be supplemented in broiler diets with beneficial effects on breast yield and meat nutritional quality. In addition, HS has made chickens more susceptible to biomolecule oxidation, and MM can potentiate chicken TAC. Further study is needed to better understand the effects of MM on broilers.