Astragalus polysaccharides modulate gut microbial interaction and bile acid metabolism of postpartum dairy cows

Gut microbiota is a symbiotic ecosystem, yet how polysaccharides regulate gut microbial interactions and the related host co-metabolism in dairy cows, particularly regarding bile acids, remain unclear. In postpartum cows, Astragalus polysaccharides (APS) supplementation reduced key biomarkers of metabolic stress, including β-hydroxybutyrate, triglycerides, interferon-γ, and TNF-α. Although fecal microbial diversity did not show significant changes, APS markedly altered interactions within the gut microbiota, improving cohesion and stability of co-occurrence network, such as a higher clustering coefficient, greater core modularization, and enhanced robustness, with reduced average path length and vulnerability. APS elevated bile acids such as tauroursodeoxycholic acid, independent of changes in related taxa abundance. Moreover, microbial functional gene networks exhibited strong correlations with bile acid metabolism after APS treatment. These findings demonstrate that APS enhances microbial network stability and bile acid–related host co-metabolism, alleviating postpartum metabolic stress in dairy cows.