摘要Background Diarrhea remains a major health concern in both young animals and humans.Prevotella spp.,a domi-nant commensal genus in the healthy porcine gut,becomes increasingly abundant following weaning,suggesting a potential role during this critical transitional period.However,its involvement in post-weaning diarrhea remains poorly understood.Here,we aim to elucidate the role and underlying mechanisms of Prevotella in alleviating diarrhea in weaned piglets.Results To model unsanitary housing conditions,piglets were housed in uncleaned pens containing residual fecal matter from previous occupants and exposed to cold stress by maintaining the ambient temperature at 19 ℃,below the optimal 28 ℃.Under these conditions,piglets were orally administered either a blank medium(CON,n=10×2)or Prevotella copriat 1 × 108 CFU(Pc,n=10×2)on d 1,3,and 5.After 28 d,cold stress induced a diar-rhea incidence of 33.45％in the CON group,while P.copri supplementation significantly reduced the diarrhea rate to 19.73％.Treatment with P.copri markedly improved intestinal morphology in the small intestine,decreased serum levels of lipopolysaccharide(LPS)and intestinal fatty acid-binding protein(i-FABP),and enhanced total antioxidant capacity(T-AOC)and catalase(CAT)activity.Quantitative PCR and 16S rRNA gene sequencing revealed that P.copri significantly increased the colonic abundance of Prevotella,reshaping both the composition and functional profile of the gut microbiota.Moreover,P.copri enhanced the modularity and robustness of microbial ecological networks.Untargeted metabolomic profiling of colonic contents revealed a significant enrichment of metabolites involved in the arachidonic acid pathway following P.copri supplementation.In parallel,untargeted metabolomics of P.copri culture supernatants identified differential metabolic pathways including metabolic pathways,biosynthesis of sec-ondary metabolites,and biosynthesis of antibiotics.In vitro assays demonstrated that P.copri-derived metabolites inhibited the growth of three common porcine intestinal pathogens.Furthermore,both P.copri metabolites and ara-chidonic acid enhanced intestinal barrier integrity and suppressed TNF-α-induced inflammation and apoptosis in Caco-2 cells through activation of the AHR-Nrf2 signaling pathway.Conclusions These findings highlight the role of P.copri in maintaining gut homeostasis and provide new insights into microbiota-based interventions for early-life intestinal disorders.