Expression profiles of myostatin and calpastatin genes and analysis of shear force and intramuscular fat content of yak longissimus muscle

The main objective of this study was to reveal the expression profiles of two negative regulators, myostatin (MSTN) and calpastatin (CAST) genes, of skeletal muscle growth in highland yaks (Bos grunniens). mRNA levels of both genes were quantified in different yak tissues by semi-quantitative RT-PCR to reveal the tissue expression pattern, and real-time quantitative RT-PCR was employed to compare the mRNA levels of MSTN and CAST in longissimus muscles of yaks at different ages and adult Yellow cattle. Intramuscular fat (IMF) content, tenderness and pH of longissimus muscle of yaks at different ages and of adult Yellow cattle were also measured. The results showed that MSTN and CAST expressions have tissue specificity and both exhibited a high level in longissimus muscle and a low level in adipose tissue. Yak calves had lower mRNA levels of both MSTN and CAST in longissimus muscle compared with adult yaks. The analysis of meat quality traits of longissimus muscle showed that the shear forces of raw longissimus muscle of yak calves were significantly lower than those of adult yaks and Yellow cattle, no significant difference was found between adult yaks and Yellow cattle of similar age. IMF content in longissimus muscle was lower in yaks than in Yellow cattle. Although yaks were smaller in body size than Yellow cattle, adult yaks showed lower levels of MSTN and similar level of CAST mRNA in longissimus muscle compared to Yellow cattle. These data indicate that the expression of both MSTN and CAST in longissimus muscle differs between adult yaks and yak calves, and the yak longissimus muscle shows a lower IMF content compared to cattle.