Integrated Rumen Metabolomics and Metagenomics Reveal Microbe-Metabolite Signatures Associated with Heat Tolerance in...

Heat stress impairs dairy cow productivity and rumen function, but rumen metabolic features associated with natural heat tolerance remain unclear. This study generated rumen fluid metabolomic data and integrated them with previously generated metagenomic abundance data from the same heat-tolerant (HT) and heat-sensitive (HS) Holstein cows selected from a cohort of 120 cows using an entropy-weighted TOPSIS model. Untargeted LC-MS identified 116 differential metabolites, including 66 enriched in HS cows and 50 enriched in HT cows. The HS cows showed higher levels of nucleotide-related metabolites, whereas HT cows were enriched in thiamine, L-malate, and argininosuccinic acid. Pathway enrichment mainly involved nucleotide metabolism, pyrimidine metabolism, pyruvate metabolism, and thiamine metabolism. Reanalysis of metagenomic data identified 12 differential microbial taxa, including HT-enriched Prevotella and Ruminococcus flavefaciens. Spearman correlation analysis revealed phenotype-associated microbe-metabolite associations, and ROC analysis based on the discovery dataset suggested that uridine 5'-monophosphate, thiamine, L-malate, and argininosuccinic acid had exploratory potential to distinguish HT and HS cows. These findings provide exploratory evidence that rumen microbe-metabolite associations are related to natural heat tolerance in dairy cows.