High-energy diet improves growth performance, meat quality and gene expression related to intramuscular fat deposition in finishing yaks raised by barn feeding.

This research aimed to investigate the effects of dietary energy concentration (combined net energy, Nemf) on growth performance and meat quality of yaks raised by barn feeding. In all, 30 male yaks (3-year old and 114.57 ± 21.56 kg of body weight) were allocated to one of three isonitrogenous dietary treatments that had different Nemf concentrations (low 3.72 MJ/kg, middle 4.52 MJ/kg and high 5.32 MJ/kg, respectively). The yaks were fed for 120 days. The results showed that the final weight, average daily gain, dressing percentage, backfat thickness and loin muscle area were significantly improved (p < .05) with the increase in dietary energy concentration. However, an opposite trend of feed:gain ratio, cooking loss, driage, shear force and moisture content was found. A significant improvement (p < .05) of intramuscular fat content was observed in the high-energy group. Additionally, the proportion of polyunsaturated fatty acid was increased (p < .05) at the expense of the saturated fatty acids. The mRNA expressions of lipogenic genes fatty acid synthase, acetyl-CoA carboxylase, sterol regulatory element-binding protein 1, stearoyl-CoA desaturase, peroxisome proliferator-activated receptor γ, lipoprotein lipase and heart fatty acid-binding proteins increased (p < .05) in a dose-dependent manner. However, the mRNA expressions of lipolytic genes carnitine palmitoyltransferase-1 and hormone-sensitive lipase correspondingly decreased (p < .05) with increased dietary energy level. In summary, the growth performance, meat production and meat quality improvement of finishing yaks can be achieved by increasing the dietary energy concentration. The intramuscular fat accumulation of yaks was achieved through up-regulation of intramuscular lipogenic gene expression as well as fatty acid transport gene expression and down-regulation of lipolytic gene expression by promoting dietary energy concentration.