Tibetan sheep, a vital livestock species adapted to the extreme hypoxia, low temperatures, and intense radiation of the Qinghai–Tibet Plateau, rely on gastrointestinal microbiota for ecological balance and host nutrition, metabolism, and immunity. However, the possible associations of gut microbiota and metabolites with seasonal phenology remain unclear. Integrating biochemical, metagenomic, and metabolomic analyses, this study investigated seasonal variations in serum indices, microbial communities, and metabolites to inform enhanced breeding strategies. Analysis of forage nutritional composition showed that warm-season forages had significantly higher concentrations of dry matter (DM), crude protein (CP), and ether extract (EE) ( p 0.01), whereas cold-season forages were characterized by significantly greater levels of neutral detergent fiber (NDF) and acid detergent fiber (ADF) ( p 0.01). Correspondingly, serum analysis revealed significantly higher warm-season concentrations of alanine aminotransferase, total cholesterol, creatinine, and urea nitrogen compared with the cold season ( p 0.01). Gut microbiota composition shifted seasonally, with Bacteroides dominating in warm seasons and Bacillus predominating in cold seasons. Functional metagenomics indicated cold-season enrichment in pathways related to carbon metabolism, ABC transporters, aminoacyl-tRNA biosynthesis, pyruvate metabolism, DNA replication, and methane metabolism ( p 0.01). Metabolomics identified elevated warm-season microbial metabolites (His-Met, leucylleucine, luteolin 7-glucoside, ursolic acid; p 0.05) and higher cold-season compounds (melatonin, glabrol, prostaglandin E2; p 0.05), with KEGG enrichment linking these to steroid hormone biosynthesis, fatty acid metabolism, bile acid synthesis, and propanoate pathways. These findings suggest possible associations between seasonal extremes and: (1) modulation of nutrient metabolism (e.g., secondary bile acids and short-chain fatty acids); (2) activation of stress-response pathways (e.g., pentose phosphate pathway, ABC transporters, and DNA replication); and (3) immune regulation mediated by bioactive metabolites. Cold-season enrichment in DNA repair and energy-production pathways may be associated with responses to oxidative stress, whereas warm-season shifts in lipid metabolism are consistent with increased nutrient availability. Fluctuations in key metabolites—such as elevated melatonin in cold seasons and elevated ursolic acid in warm seasons—likely reflect adaptations related to thermoregulation and antioxidant defense. This work provides foundational insights into microbiota–host interactions under extreme environmental conditions, supporting the optimization of supplementation, probiotic use, and sustainable husbandry on the Qinghai–Tibet Plateau.
An et al. (Tue,) studied this question.