Metabonomic identification of serum biomarkers related to heat stress tolerance of sheep.

Heat stress is considered as a limiting factor for sheep production; it is necessary to screen for sheep breeds with heat tolerance. This study was to compare the serum metabolomes of Hu sheep and Dorper sheep and identify potential biomarkers related to heat stress. The results revealed that the respiratory rate, heart rate, and rectal temperature of Dorper sheep were significantly higher than those of Hu sheep. Compared to Dorper sheep, the serum activities of total antioxidant capacity and glutathione peroxidase in Hu sheep were significantly higher, while the concentration of malondialdehyde was lower. Metabolomics analysis identified 107 differential serum metabolites. The pathways enriched from the altered serum metabolites between the two breeds were mainly involved in protein metabolism, carbohydrate metabolism, and lipid metabolism. The levels of antioxidant- and energy-related metabolites were higher in the serum of Hu sheep than that of Dorper sheep; however, the levels of lipid catabolism- and inflammation-related were higher in the serum of Dorper sheep. The results indicate that Hu sheep had better heat stress resistance capability than Dorper sheep. Moreover, high levels of metabolites in the serum of Hu sheep are potential biomarkers for heat stress tolerance, including l-methionine, s-adenosylmethionine, and nicotinuric acid.