<i>Faecalibacterium duncaniae</i> -derived metabolites protect intestinal epithelial integrity under inflammatory conditions in dairy calves

ABSTRACT Preweaning diarrhea and intestinal inflammation represent leading causes of morbidity and economic loss in modern dairy calf production systems, causing impaired growth performance, increased mortality, and substantial veterinary costs that collectively constrain farm profitability. Faecalibacterium duncaniae , a key butyrate-producing commensal bacterium, is consistently depleted in diarrheic dairy calves, yet its protective effects on the ruminant intestinal epithelium remain mechanistically understood. In this study, a long-term expandable ruminant colonic organoid model was used to investigate the effects of F. duncaniae -derived metabolites under inflammatory conditions induced by tumor necrosis factor-α (TNF-α). TNF-α stimulation caused epithelial injury characterized by elevated inflammatory cytokine expression, impaired barrier function, and increased epithelial permeability. Treatment with F. duncaniae cell-free supernatant markedly attenuated inflammatory responses, restored epithelial proliferation, and preserved tight junction integrity, as evidenced by reduced permeability and increased expression of barrier-related proteins. Transcriptomic analysis further indicated suppression of inflammation-associated signaling pathways, including chemokine signaling and NF-κB pathways, accompanied by enrichment of energy metabolism and epithelial repair pathways, thereby creating a molecular environment conducive to epithelial barrier improvement and repair. In addition, comparison with the bacterial culture medium and the single metabolite sodium butyrate (NaB) further supported the role of F. duncaniae -derived metabolites in barrier repair. Collectively, these findings demonstrate that F. duncaniae -derived metabolites protect intestinal epithelial integrity under inflammatory stress and provide mechanistic and translational support for microbiota-targeted nutritional strategies to improve gut health in dairy calves, thereby establishing a foundation for the development of postbiotic-based interventions aimed at reducing diarrhea incidence, decreasing antimicrobial dependence, and enhancing growth efficiency and long-term productivity in dairy systems. IMPORTANCE Dairy calves are highly susceptible to severe impacts from diarrhea and intestinal inflammation before weaning, leading to malnutrition, dehydration, and even death. The costs associated with enteritis, including mortality, productivity losses, and treatment expenses, have been rising annually. Therefore, the treatment and prevention of enteritis are of paramount importance. Faecalibacterium duncaniae , a beneficial bacterium that produces butyrate, plays a crucial role in maintaining gut health. However, its specific protective mechanisms in intestinal inflammation remain poorly understood. This study reveals the molecular mechanisms by which F. duncaniae metabolites protect the intestinal barrier under inflammatory stress, providing valuable insights into how microbiota-based nutritional interventions can enhance gut health in neonatal and preweaning dairy calves. These strategies may offer innovative approaches to managing calf intestinal diseases, improving their health and growth, and enhancing overall productivity in dairy farming.