Metabolomics analysis reveals potential response mechanisms to cold stress in Altay sheep

Understanding the mechanisms underlying cold tolerance in livestock is crucial for improving welfare and productivity in harsh environments. However, the complex regulatory responses to cold stress (CS) in sheep remain incompletely elucidated. This study investigated the cold adaptation mechanisms in Altay sheep (cold-adapted) compared to Turpan black sheep (heat-adapted) using serum antioxidant assays, histomorphometry of skin and rumen, and multi-tissue metabolomics under CS. Altay sheep exhibited significantly enhanced systemic antioxidant capacity under CS, evidenced by increased serum superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) (P < 0.01). Histologically, epidermal thickness (EP) and rumen basal layer thickness (RBL) were significantly greater (P < 0.01). Comprehensive non-targeted metabolomics analysis based on LC-MS revealed the multi-tissue metabolic coordination adaptation mechanism of Altay sheep under CS. A total of 629, 341, 1283, 1284, and 1351 differentially expressed metabolites were identified in tail fat, perirenal adipose tissue, rumen, small intestine, and feces, respectively. Notably, enhanced glycolytic flux in adipose tissue and elevated pyruvate levels emerged as key energy mobilization strategies. Concurrently, cold stimulation activated brown adipose tissue (BAT) thermogenesis, triggering mitochondrial reactive oxygen species (ROS) production. Significant enrichment of leukotrienes in feces indicated gastrointestinal oxidative damage. Notably, the upregulation of arachidonic acid, α-linolenic acid, methionine, and L-glutamine in the digestive tract of Altay sheep indicates their exceptional endogenous antioxidant reserve capacity. Additionally, critical pathways including TCA cycle, glucagon signaling pathway, unsaturated fatty acid biosynthesis, D-amino acid metabolism, and inflammatory mediator regulation of TRP channels, are associated with energy metabolism and immune regulation. These findings reveal potential serum biomarkers and metabolic pathways underlying cold adaptation, offering new insights into environmental adaptation mechanisms in sheep.