Probiotic-fermented Pulsatilla alleviates Escherichia coli-induced diarrhea in calves by improving gut microbiota and amino acid metabolism.

ABSTRACT Escherichia coli-induced diarrhoea is a common form of diarrhoea in dairy cattle farming, which severely affects the taste and flavour of milk, leading to significant economic losses. Traditional microbial treatments have gradually become less effective due to antibiotic resistance, and prolonged use disrupts the balance of gut microbiota. This study investigates the mechanism by which probiotic-fermented Pulsatilla alleviates E. coli-induced diarrhoea in calves, focusing on its effects on gut microbiota, metabolites, and intestinal barrier function. The results indicate that probiotic-fermented Pulsatilla significantly improves the growth performance of calves, reduces pro-inflammatory cytokines (IL-6, TNF-α, IL-1β), and increases the levels of the anti-inflammatory cytokine IL-10. Furthermore, following the treatment with probiotic-fermented Pulsatilla, the abundance of Porcincola intestinalis, Bifidobacterium pseudolongum, and Limosilactobacillus reuteri in the gut increased, and metabolites such as Nicotinamide riboside, Baicalein, and Ginsenoside F2 were significantly elevated. Fecal microbiota transplantation experiments further confirmed that probiotic-fermented Pulsatilla alleviates diarrhoea by modulating the gut microbiota and improving amino acid metabolism. Therefore, probiotic-fermented Pulsatilla offers a promising new therapeutic strategy by improving gut microbiota balance and metabolism, significantly alleviating E. coli-induced diarrhoea in calves. Key words: Probiotic fermentation, Escherichia coli-induced diarrhoea, Calves, Gut microbiota, Amino acid metabolism