Expression of Serum and Muscle Endocrine Factors at Antemortem and Postmortem Periods and Their Relationship with Pig Carcass Grade

Carcass weight and backfat thickness are primary yield grading factors. Insulin-like growth factor (IGF)-I/-II, transforming growth factor $\beta$1 (TGF-$\beta$1), and epidermal growth factor (EGF) regulate the proliferation and differentiation of cells including adipocytes. Also, interleukin (IL)-2/-6, cortisol, and dehydroepiandrosterone-sulfate (DHEA-S) are known to be related to muscle growth and fat depth. However, the relationships between endocrine factors and carcass grade have not been studied. Therefore, this study aimed to measure the concentrations of endocrine factors in serum and muscle, and to investigate the relationship of endocrine factors with carcass grade. A total of 60 crossbred gilts (Duroc${\times}$Yorkshire${\times}$Landrace) were used. Blood from the jugular vein was collected at antemortem (7 days before slaughter) and postmortem periods, and M. Longissimus was collected at 45 min and 24 h after slaughter. The concentrations of IGF-I/-II, EGF, TGF-$\beta$1, IL-2/-6, cortisol and DHEA-S were analyzed by radioimmunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA). In general, IGF and EGF concentrations in serum and muscle of grade A carcasses were found to be higher than those of grade C carcasses at antemortem and postmortem periods, whereas the pattern of TGF-$\beta$1 concentration was reversed. In particular, the concentrations of muscle IGF-I (24 h postmortem) and serum TGF-$\beta$1 (antemortem) were significantly different between grades A and C (p<0.05). The present results indicate that serum and muscle growth factors affect carcass weight and backfat thickness, and indirectly suggest the possibility that carcass grade could be predicted by expression of serum and/or muscle growth factors.