Title : Dietary supplementation of bacillus subtilis modulates gut microbiota composition and fecal indole levels in cats
Abstract:
Gut microbiota homeostasis is closely linked to the overall health of cats, as dysbiosis often leads to digestive disorders, poor coat condition, and compromised mental well-being. Bacillus subtilis, a widely used probiotic, has shown potential in regulating intestinal flora balance in livestock and companion animals, yet limited research has systematically evaluated its effects on feline gut health and related physiological indicators. This study aimed to investigate the impacts of dietary B. subtilis supplementation on mental state, coat condition, gut microbiota composition, and key fecal metabolites (p-cresol, indole, and biogenic amines) in cats. A 30-day randomized controlled trial was conducted with twenty healthy adult domestic shorthair cats (2–4 years old, 3.5–5.0 kg), randomly divided into two groups (n=10 per group): the control group fed a basal diet, and the experimental group fed the basal diet supplemented with 0.5 g/kg B. subtilis (viable count≥1×10¹? CFU/g). Mental state was assessed via behavior observation (activity level, stress response), and coat condition was scored based on glossiness and smoothness. Fecal samples were collected on days 15 and 30 to analyze gut microbiota (quantified by qPCR) and metabolites (detected by HPLC). The results showed that by day 30, the experimental group exhibited significantly increased abundances of beneficial bacteria, including Bifidobacteria (p<0.01), Lactobacilli, and B. subtilis (p<0.05), while pathogenic microorganisms such as Clostridium perfringens (p<0.01) and Escherichia coli (p<0.05) were markedly reduced. Notably, fecal moisture content and indole concentrations were significantly decreased (p<0.05), and no significant changes were observed in p-cresol or biogenic amines. On day 15, Salmonella counts in the experimental group were already significantly lower than those in the control group (p<0.05). Additionally, the experimental group showed improved coat glossiness (p<0.05) and reduced stress-related behaviors. In conclusion, dietary supplementation with 0.5 g/kg B. subtilis effectively promotes the colonization of beneficial intestinal bacteria, inhibits pathogenic growth, optimizes fecal properties, and enhances the overall well-being of cats, providing experimental evidence for the application of B. subtilis in feline functional diets.
