Exploring the potential mechanisms by which feeding regimes affect muscle fibre composition and meat quality in Sunit sheep using TMT-labeled quantitative proteomic

To investigate the molecular mechanisms influencing sheep meat quality and muscle fiber characteristics under different feeding regimes, biceps femoris (BF) muscle samples were collected from a traditional grazing group (TGG) and a concentrated feeding group (CFG). The meat quality indicators, muscle fiber characteristics and proteome of sheep under different feeding regimes were studied. It was found that CFG improved growth performance and carcass traits (increased final body weight by 10.8 %, average daily gain by 30.8 %, carcass weight by 14.8 %, carcass length by 9.6 % and dressing percentage by 10.6 % respectively), reduced meat quality reducing meat quality (increased shear force by 11.6 %) in Sunit sheep, as well as reducing the proportion of oxidative muscle fibers in the BF. 82 differentially abundant proteins (DAPs) were identified. Bioinformatics analysis of the DAPs revealed reduced Ca2 + release in TGG meat (PVALB and CASQ2 have higher activity), decreased activity of glycolysis-related enzymes (ALDOA, ALDOB, and ALDOC), and higher expression levels of proteins involved in oxidative muscle fiber formation (ACTB, ACTN1, TNNT1, TNNC1, MYL4 and MYL3). These findings suggest that TGG meat exhibited lower glycolysis activity and a higher proportion of oxidative muscle fibers compared to CFG meat. These findings provide a foundation for deeper comprehension of the molecular processes through which proteins regulate the quality of meat and the characteristics of muscle fibers.