Integrated 16S rDNA and Metabolomics Analysis Unveils Dietary Fiber-Induced Changes in Small Intestinal Microbiota and Metabolites of Pigs

Dietary fiber has proven beneficial for improving gastrointestinal function, its role in the small intestine has received comparatively less attention. In this study, ten Erhualian pigs (40 ± 0.86 kg) were randomly assigned to two groups: a basal diet and a 7% wheat bran-supplemented diet, respectively. Using 16S rDNA sequencing and LC-MS-based untargeted metabolomics, we observed significant shifts in small intestinal microbiota and metabolome. Five genera (<i>Terrisporobacter</i>, <i>Howardella</i>, <i>Romboutsia</i>, <i>Cellulosilyticum</i>, and <i>Intestinibacter</i>) showed a significant increase in abundance in pigs fed the high-fiber diet. In addition, 155 differential metabolites were identified between the two groups. Functional enrichment analysis revealed that these metabolites were particularly enriched in pathways of carbohydrate utilization and tryptophan catabolism. Correlation analysis revealed significant associations between specific microbial genera and bile acids including lithocholic acid and 23-Norcholic acid. These findings indicate that a high-fiber diet may promote tryptophan metabolism by genera such as <i>Clostridium_sensu_stricto_1</i>, <i>Terrisporobacter</i>, and <i>Romboutsia</i>, facilitating intestinal function and health. Overall, our findings provide new insights into the effects of dietary fiber on the microbial community and metabolome in the small intestine, and highlight the potential of certain bacterial genera as beneficial microbiota for promoting small intestinal health.