The difference of castration timing of Korean Hanwoo bulls does not significantly affect the carcass characteristics.

It is already well known that castration improves marbling quality but exact timing of castration is still highly debated in beef cattle production industry. After castration, blood hormonal changes occur in steer and objective of this study was to investigate the effects of growth hormone (GH) levels on adipocyte differentiation in stromal vascular cells (SVCs) and transdifferentiation into adipocytes in C2C12 myoblasts. Total GH concentrations were measured via enzyme-linked immunosorbent assay (ELISA) in 24 male calves and 4 female calves. Cell proliferation, cellular triglyceride (TG) accumulation, and the cell's lipolytic capability were measured in C2C12 myoblasts and SVCs. Myogenic, adipogenic, and brown adipocyte-specific gene expression was measured via real-time polymerase chain reaction (PCR) using SYBR green. Serum GH levels were the highest in late-castrated calves. Treatment with 5 ng/mL GH resulted in greater TG accumulation as well as increased CCAAT-enhancer-binding protein (C/EBP)α and peroxisome proliferator-activated receptor (PPAR) expression compared to that after treatment with 15 ng/mL GH. Treatment with 5 ng/mL GH also resulted in lower myogenin (myo)G and myoD expression compared to that after treatment with 15 ng/mL GH. The expression of bone morphogenetic protein (BMP) 7 after treatment with 5 ng/mL GH was higher than that after treatment with 15 ng/mL GH. But carcass characteristics data showed no significant difference between early and late castrated steers. Therefore, our results indicate that castration timing does not seem to be inevitable determinate of carcass qualities, particularly carcass weight and marbling score in Hanwoo beef cattle.