Seasonal dietary shifts drive gut microbiome plasticity and metabolic adaptation in wild yaks on the Qinghai-Xizang Plateau.

The gut microbiota in different diets helps hosts to obtain sufficient nutrients from food, which is important for wild yaks in the Qinghai-Xizang Plateau to adapt to different seasons. The relationship between the host diet and the gut microbiota in different seasons is important for exploring the adaptation of these wild yaks to their environments. This study used wild yaks as a model organism. Using high-throughput sequencing and liquid chromatography-mass spectrometry, we investigated their seasonal diet, gut microbiota composition and function, and short-chain fatty acid profiles. The inter-season differences in them were compared, and relationships among these differences were explored. Wild yaks in summer had a diet higher in Polygonaceae and lower in Rosaceae compared to their diets in autumn and winter. The broadest dietary niche width (8.8449) was detected in autumn, and the lowest diet niche overlap (0.3751) was found between summer and winter. Co-occurrence network analyses revealed that microbial interactions were more complex in autumn, likely due to transitional dietary adjustments, whereas summer and winter exhibited simpler but more robust interactions. The abundance of Firmicute increased in winter, suggesting enhanced energy extraction from low-quality forage. Specific taxa, such as Alistipes_A in autumn and Romboutsia in winter, were linked to key metabolic pathways, including carbohydrate degradation and short-chain fatty acid production. The study highlights the critical role of gut microbiota plasticity in facilitating wild yaks' adaptation to the extreme and variable conditions and provides the basis for explaining the harsh environment adaptation of wild herbivores in the Qinghai-Xizang Plateau.