Seasonal Dynamics of Skin Microbiota and Metabolites in Transhumant-Grazed Altay Sheep

To explore the seasonal variation patterns of the skin microecology of Altay sheep under transhumant grazing conditions, skin swabs were collected from 60 free-grazing Altay sheep at seasonal transition nodes in the Altay region. Metagenomic sequencing combined with untargeted metabolomics was used to characterize their bacterial community structure, functional pathways, and metabolite profiles. The results showed that the skin microecology of Altay sheep presented obvious seasonal variation patterns. In spring, 35 of the 39 highly abundant bacteria were environmentally derived, five proliferation-related pathways were significantly enriched, and the levels of five metabolites associated with microbial community regulation and skin barrier defense were elevated. In summer, the abundance of three skin symbiotic bacteria increased, the activities of eight pathways mainly related to biofilm formation were significantly enhanced, and the contents of five metabolites primarily associated with membrane lipid homeostasis and selective bacteriostasis increased. In autumn, the abundances of nine radiation-resistant and cold-tolerant strains increased, together with the elevated abundance of two opportunistic pathogens; five repair-related pathways were active, and the levels of four anti-inflammatory and repair-associated metabolites were synchronously increased. In winter, the abundance of two cold-tolerant strains increased, the activities of pathways related to nitrogen metabolism and energy synthesis were enhanced, and one lignan compound was identified as the key metabolite. These findings elucidate the seasonal dynamic patterns of the skin microecology of Altay sheep and provide a theoretical basis for research on the adaptive mechanisms and seasonal health management of Altay sheep and other sheep in alpine regions.