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

摘要

Simple SummaryYak is always in a malnutrition condition under pure grazing in the cold season. Many studies have suggested that provision of supplementary feed to yak cannot only be an effective approach to avoid weight loss, but also improve productivity. Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) could improve yak productivity. In current work, we evaluated the effects of different energy feedstuffs on the serum concentration of GH, IGF-1, and relative hepatic expression of their associated binding proteins and receptors, as well as growth performance of yak. The results indicated that average daily gain (ADG), body weight (BW), feed conversion ratio, serum IGF-1 concentration, and relative expression of IGF-1 and IGFBP-3 were increased with an increase in dietary energy level, while serum GH concentration and hepatic growth hormone (GHR) expression were decreased. Serum IGF-1 concentration, relative hepatic expression of IGF-1, and insulin-like growth factor binding protein 3 (IGFBP-3) showed positive correlation with ADG, but serum GH concentration and GHR expression were negatively correlated with ADG. Yak offered with medium energy diet (NEg: 6.2 MJ/kg) displayed better growth by gaining 0.883 kg/d and showing a superior feed conversion ratio during experiment.