Gut Microbiota-Derived 5-Hydroxyindoleacetic Acid Alleviates Diarrhea in Piglets via the Aryl Hydrocarbon Receptor Pathway.

With the improvement in sow prolificacy, formula feeding has been increasingly used in the pig industry. Diarrhea remains a serious health concern in formula-fed (FF) piglets. Fecal microbiota transplantation (FMT) is an efficacious strategy to reshape gut microbiota and the metabolic profile for treating diarrhea. This study aims to investigate whether FMT from breast-fed piglets could alleviate diarrhea in FF piglets. The piglets were randomly assigned to the control (CON) group, FF group, and FMT group. Our results showed that FF piglets exhibited a higher diarrhea incidence, damaged colonic morphology, and disrupted barrier function. In contrast, FMT treatment normalized the morphology and barrier function. FMT suppressed the / pathway and production of proinflammatory cytokines. Additionally, FF piglets had a lower abundance of the beneficial bacterial genus compared to CON piglets. Following FMT administration, was restored. Meanwhile, 5-HIAA, a metabolite of tryptophan, and -responsive and were upregulated. Importantly, integrated multiomics analysis revealed a strong positive correlation between and 5-HIAA. In vitro, 5-HIAA supplementation reversed the LPS-induced disruption of tight junctions and production of proinflammatory cytokines in IPEC-J2 cells. In conclusion, FMT reduced diarrhea incidence and improved growth performance. The alleviative effect of FMT on diarrhea was associated with and 5-HIAA.