Multi-omics profiling reveals the role of gut microbiota and associated metabolites in postweaning oxidative stress in Holstein dairy calves, particularly in relation to amino acid synthesis and metabolism

To investigate the relationship between post-weaning oxidative stress (OS) and gut microbiota in dairy calves, 332 Holstein calves were enrolled and weaned uniformly at 64 d of age. Based on plasma oxidative stress index (OSI) measured at 3 d post-weaning (67 d of age), 10 calves with the highest OSI (post-Hos) and 10 with the lowest OSI (post-Los) were selected for subsequent analyses. Fecal samples collected at the same time point were subjected to 16S rRNA gene sequencing, metagenomic sequencing, and LC-MS untargeted metabolomics analysis. No significant differences in fecal score (FS) were observed between groups on weaning day, although a trend toward incraeased FS was noted in post-Hos calves after weaning (P = 0.075). Microbiota analysis revealed that post-Los calves were enriched in f__Lachnospiraceae, o__Lachnospirales, and f__Barnesiellaceae, whereas post-Hos calves showed enrichment of o__Oscillospirales, f__Oscillospiraceae, and g__Ruminococcaceae_UCG-005, with the latter showing a trend of higher abundance (P = 0.064). Spearman correlation analysis identified multiple genera, particularly Barnesiella and Muribaculum, significantly associated with OSI. Metagenomic functional profiling indicated enhanced pyruvate metabolism and caprolactam degradation pathways in post-Los calves. Metabolomics detected 240 differential metabolites between the 2 groups, significantly enriched in 19 KEGG pathways, notably those related to amino acid metabolism and arginine biosynthesis. Collectively, these findings demonstrate that OS levels in post-weaning calves are associated with distinct alterations in gut microbial composition, functional capacity, and metabolic profiles, with microbiota-involved arginine biosynthesis likely playing a role in this association. This study provides correlational evidence suggesting that modulating amino acid metabolism may represent a potential strategy for alleviating weaning-induced OS.