Metabonomic Responses of Grazing Yak to Different Concentrate Supplementations in Cold Season

SIMPLE SUMMARY: The current study employed the nuclear magnetic resonance (NMR) spectroscopy combined with multivariate data analysis to evaluate the effects in supplementation of highland barley (HLB), rapeseed meal (RSM) and HLB plus RSM on serum metabolites in grazing yaks. The findings of the study explored that supplementation with HLB, RSM and HLB plus RSM significantly alleviated the weight loss of growing yak in cold season, and HLB and HLB plus RSM were better than feed RSM. We found that different concentrate supplementations can partially change the metabolic consequences, such as promoted synthesis of lipids and proteins, and supplementation with HBL plus RSM was more effective in promoting lipid and protein deposition and improving energy supply efficiency. The findings of the current experiment may help to explain the body weight changes by supplementation with different concentrates via metabonomic responses. ABSTRACT: Supplementation plays an important role in reversing the weight loss of grazing yaks during cold season. However, little is known about the effect of supplementation on the serum metabolites of grazing yaks. The objective of this study was to explore the effects of supplementary feeding on average daily gain (ADG) and serum metabolites with nuclear magnetic resonance (NMR)-based metabolomics method in growing yaks during cold season on the Qinghai-Tibetan plateau. Twenty 1.5-year-old female yaks (91.38 ± 10.43 kg LW) were evenly divided into three treatment groups and a control group (CON) (n = 5 per group). All the yaks were released to graze during daytime, whereas the yaks in the treatment groups were supplemented with highland barley (HLB), rapeseed meal (RSM), and highland barley plus rapeseed meal (HLB + RSM) at night. The whole experiment lasted for 120 days. Results indicated that the ADG of growing yak heifers was increased by concentrate supplementations, and ADG under HLB and HLB + RSM group was 37.5% higher (p < 0.05) than that with RSM supplementation. Supplementary feeding increased the plasma concentrations of total protein (TP), albumin (ALB), and blood urea nitrogen (BUN) of those in the CON group, and concentrations of BUN were higher in the RSM group than in the HLB and HLB + RSM group. Compared with the CON group, serum levels of glutamine, glycine, β-glucose were lower and that of choline was higher in the HLB group; serum levels of lactate were lower and that of choline, glutamate were higher in the HLB + RSM group. Compared with the HLB + RSM group, serum levels of glycerophosphoryl choline (GPC) and lactate were higher, and those of choline, glutamine, glutamate, leucine, N-acetyaspartate, α-glucose, and β-glucose were lower in the HLB group; serum levels of citrate, GPC and lactate were higher, and those of 3-Hydroxybutyrate, betaine, choline, glutamate, glutamine, N-acetylglycoprotein, N-acetyaspartate, α-glucose, and β-glucose were lower in the RSM group. It could be concluded that concentrate supplementations significantly improved the growth performance of growing yaks and supplementation with HBL or HLB plus RSM was better than RSM during the cold season. Supplementation with HBL or HLB plus RSM affected the serum metabolites of grazing yaks, and both treatments promoted lipid synthesis. Supplementation of yaks with HBL plus RSM could improve energy-supply efficiency, protein and lipid deposition compared with HLB and RSM.