Faecal Microbial and Metabolic Profiles Covary With Dietary Plant Composition in Tibetan Sheep Across Contrasting Grasslands

ABSTRACT Alpine meadows (AM) and desert steppes (DS) are major grassland types in northern Qiangtang that support ecosystem functioning, livestock production and pastoral livelihoods. However, how Tibetan sheep coordinate dietary, microbial and metabolic responses across these contrasting forage environments remains unclear. We used vegetation surveys, organic matter intake (OMI) estimation, faecal DNA metabarcoding, 16S rRNA gene sequencing and untargeted metabolomics to compare female Tibetan sheep grazing AM or DS. The DS had lower forage biomass and concentrations of several nutrients, whereas DS sheep had higher OMI, lower dietary plant diversity and greater representation of Rosaceae ( p < 0.05). Faecal bacterial communities differed between groups. Plant‐family composition, rather than dietary alpha diversity, was associated with bacterial variation; Rosaceae and Tamaricaceae showed the strongest associations ( r 2 = 0.929 and 0.836, respectively; p = 0.001). Selected bacterial genera were associated with Rosaceae (Mantel R = 0.59, p = 0.001). Among 3819 detected metabolites, 1177 differed between groups and were mainly enriched in flavonoid‐ and phenylpropanoid‐related pathways (adjusted p < 0.05). These findings reveal coordinated associations among diet, faecal microbiota and metabolites and identify plant‐family composition as a key correlate of habitat‐related microbial and metabolic variation.