Integrated metabolome and immunity analysis of immune-physiological responses in dairy cows under heat stress condition.

OBJECTIVE: This study aimed to investigate the metabolic changes and immune responses in Jersey dairy cows under heat stress (HS). The focus was on understanding HS-induced alterations in metabolism and immunity compared to HS-free cows. METHODS: Proton nuclear magnetic resonance spectroscopy-based metabolomics was performed on rumen fluid, serum, and milk samples which were collected through single sampling from HS-free (n = 9) and HS-exposed (n = 8) Jersey cows. Immune cell proportions and functions in peripheral blood mononuclear cells (PBMC) were analyzed to identify heat-sensitive immunological changes. Correlation analysis was conducted to link immune indicators with serum metabolites. RESULTS: Metabolomics revealed potential HS biomarkers in biofluids: nicotinate and phenylacetate in rumen fluid; isopropanol in serum; and glycine and trehalose in milk. HS increased B cell and CD4+ T cell populations, as well as Th17 cells and IL-17A expression in PBMCs. Twenty-three metabolites correlated strongly with five immune indicators, with nine metabolites exhibiting a positive correlation and fourteen a negative correlation. CONCLUSION: HS alters the both metabolism and immune cell function in Jersey dairy cows. These findings provide key information for the development of diagnostic methods for HS and nutritional intervention strategies to mitigate HS for dairy cows.