Gut Microbiome and Metabolome Signatures Associated with Heat Tolerance in Dairy Cows

Heat stress significantly impairs dairy cow health and productivity, highlighting the need to understand the gut microbiome-metabolite interactions that contribute to heat tolerance. Here, we integrated metagenomic sequencing and untargeted metabolomics in twelve holstein cows selected from a previously phenotyped herd of 120 individuals, including six heat-tolerant (HT) and six heat-sensitive (HS) cows identified using entropy-weighted TOPSIS scoring. HT cows were enriched in genera such as <i>Faecalimonas</i> and <i>UBA737</i>, which were functionally linked to pathways of energy and lipid metabolism, whereas, HS cows harbored taxa associated with bacterial lipopolysaccharide and glycosphingolipid biosynthesis. A total of 135 metabolites were differentially abundant between groups. Among them, glycerol 2-phosphate and 24(28)-dehydroergosterol showed perfect classification performance (AUC = 1.000), and were mainly involved in membrane lipid remodeling and redox regulation. Integrated analysis revealed coordinated microbial-metabolite networks, exemplified by the <i>Faecalimonas</i>-LysoPS (16:0/0:0) and <i>UBA737</i>-Glycerol 2-phosphate axes, suggesting functional coupling between microbial composition and metabolic adaptation. Together, these findings demonstrate that HT cows harbor gut microbiota and metabolites favoring energy balance, membrane remodeling, and oxidative stress resilience, while HS cows display stress-related metabolic patterns. This study elucidates the microbial-metabolic mechanisms underlying thermal resilience and highlights potential biomarkers and metabolic pathways that could be applied in heat-tolerance breeding and precision management of dairy cattle.