Dietary β-carotene alleviated ETEC-induced intestinal barrier dysfunction and inflammation by reshaping gut microbiota and metabolic profiles in piglets

Enterotoxigenic Escherichia coli (ETEC) infection is a primary bacterial culprit responsible for post-weaning diarrhea and intestinal injury in piglets. β-carotene is a natural carotenoid exhibiting exceptional immunomodulatory properties; however, its protective efficacy against ETEC K88-induced intestinal injury remains largely unexplored. This study investigated the dose-dependent effects of dietary β-carotene on inflammatory signaling, mucosal barrier integrity, and colonic microbial fermentation in an ETEC-challenged porcine model. Piglets were allocated to a control group, an ETEC-challenged group, and three β-carotene treatment groups (40, 80, or 160 mg/kg). The results demonstrated that ETEC infection significantly decreased average daily gain, increased diarrhea incidence, and disrupted intestinal morphology. Conversely, dietary supplementation with β-carotene effectively mitigated these adverse impacts, with 80 mg/kg showing the greatest protective effect. Mechanistically, by neutralizing systemic oxidative stress through the upregulation of antioxidant enzymes, β-carotene effectively suppressed the TLR4/MyD88-mediated inflammatory cascade. This targeted suppression significantly reduced serum pro-inflammatory cytokines and restored host immunoglobulins. Furthermore, β-carotene reinforced the physical intestinal barrier by preventing the ETEC-induced reductions in tight junction proteins. 16S rRNA sequencing and colonic volatile fatty acid analyses revealed that β-carotene ameliorated microbial dysbiosis by enriching beneficial short-chain fatty acid-producing bacteria, and significantly increased colonic butyrate concentrations. Correlation analysis integrated these findings, revealing that the enriched beneficial taxa were positively correlated with SCFA production and barrier function, while exhibiting negative correlations with systemic inflammation and diarrhea. Collectively, our findings illuminate that β-carotene serves as a multi-target nutritional intervention to antagonize ETEC-induced injury through the synergistic modulation of the “microbiota-metabolite-immune” axis.