Dietary Energy Levels Affect Growth Performance through Growth Hormone and Insulin-Like Growth Factor 1 in Yak (Bos grunniens)

The objective of this study was to investigate the effects of different dietary energy levels on serum concentrations of growth hormone (GH) and insulin-like growth factor 1 (IGF-1), as well as gene expression of their associated binding proteins and receptors in yak. Fifteen adult male yaks with BW of 276.1 ± 3.5 kg were allotted in three dietary groups and were fed with low (LE), medium (ME), and high energy (HE) level diet having different NEg of 5.5 MJ/kg, 6.2 MJ/kg, 6.9 MJ/kg, respectively. The effects of these treatments on ADG, BW, ADFI, and feed conversion ratio were significant (p p p p p < 0.001) in ME and HE groups, except the LE group. In conclusion, our findings provide a first insight into the combined effect of GH and IGF-1 in controlling the metabolism and productivity of yak. It also showed that medium energy level diet contributed to promote growth performance of yak during the cold season.