Goat bile acid and Clostridium butyricum exert a synergistic effect in enhancing the therapeutic efficacy against diarrhea induced by Escherichia coli infection

The goat industry has emerged as one of the major livestock sectors in China, with an annual production exceeding 300 million head. Bacterial diseases in goat pose significant threats to the sustainability and productivity of goat farming. Clinically, antibiotic treatments in ruminants are associated with considerable side effects, raising concerns about food safety. Therefore, the development of antibacterial functional feed additives has become an urgent priority for the industry. Bile acids are endogenous molecules synthesized in the liver through cholesterol metabolism and serve critical physiological roles, including hepatobiliary protection, reduction of oxidative stress, and enhancement of intestinal barrier function. They exert antimicrobial effects against pathogenic Escherichia coli ( E. coli ) primarily through direct mechanisms—such as disruption of the phospholipid bilayer of the bacterial cell membrane, leading to intracellular content leakage and subsequent bacterial cell death. Indirectly, bile acids promote the secretion of water and electrolytes in the intestine and modulate the gut microbiota composition, thereby creating an intestinal environment unfavorable for pathogenic bacterial survival. Clostridium butyricum ( C. butyricum ) contributes to intestinal health by maintaining gut microecological stability and reinforcing the intestinal barrier.Upon entering the intestinal tract, C. butyricum produces the antimicrobial agent butyric acid, which lowers the intestinal pH and thereby inhibits the growth of pathogenic E. coli . One of its core functions is to promote the proliferation and repair of intestinal epithelial cells and enhance the expression of tight junction proteins, facilitating the restoration of the intestinal barrier damaged by E. coli infection, and ultimately alleviating diarrhea and systemic inflammation at their source. Goat bile acid and C. butyricum exhibit strong potential for the treatment of E. coli -induced diarrhea. While goat bile acid excels in direct pathogen suppression, C. butyricum specializes in repairing and restoring intestinal homeostasis. Their combination offers a comprehensive therapeutic strategy that spans acute pathogen control to long-term mucosal recovery, presenting a highly promising biological alternative for reducing or replacing antibiotic use—particularly in cases involving antibiotic-associated dysbiosis and antimicrobial resistance.In this study, a mouse model of E. coli infection was first established to investigate the protective effects of dietary supplementation with goat bile acid and C. butyricum in infected mice, aiming to determine the optimal infection dose for the E. coli -induced diarrhea model and to identify effective therapeutic doses of goat bile acid and C. butyricum . The results demonstrated that concurrent supplementation with 200 mg/kg goat bile acid and 0.1 g/mouse of C. butyricum freeze-dried powder significantly alleviated infection-related damage and conferred protective benefits. Based on these findings, a diarrheal lamb model was further developed to evaluate the protective efficacy of the same interventions against E. coli infection in a clinically relevant large animal model. Dietary co-administration of 50 mg/kg goat bile acid and 5 g/lamb of C. butyricum freeze-dried powder was shown to enhance antioxidant capacity, reduce intestinal inflammatory responses, improve jejunal architecture, strengthen intestinal barrier function, and increase gut microbiota diversity in infected lambs. Notably, the combination regimen outperformed goat bile acid monotherapy. This study demonstrates that dietary supplementation with both goat bile acid and C. butyricum effectively protects lambs against E. coli infection and holds promise for practical application in ruminant health management.