Effects of Live and Heat-Killed Brevibacillus Laterosporus BL1 on Serum Parameters, Intestinal Barrier Function, Cecal Microbiota, and Microbial Metabolites in Finishing Pigs

Intestinal health is critical for efficient swine production, yet effective intervention strategies remain limited. This study evaluated the impacts of dietary Brevibacillus laterosporus BL1 (live or heat-killed form) on finishing pigs, focusing on serum parameters, antioxidant capacity, intestinal barrier, cecal microbiota, and microbial metabolic profiles. Results demonstrated that relative to the control group (CON), B. laterosporus BL1 (both live and heat-killed forms) decreased serum pro-inflammatory cytokines, ameliorated serum lipids, and enhanced systemic antioxidant capacity. Moreover, the heat-killed form was comparable to the live bacteria in strengthening the intestinal barrier, as evidenced by improved intestinal morphology, upregulated barrier-related proteins (ZO-1, Muc-1, and Muc-2), decreased serum lipopolysaccharide levels, and raised intestinal anti-inflammatory cytokines (IL-10 and IL-22) and immunoglobulins (IgG and IgM). Further, metagenomic analysis of cecal digesta demonstrated that heat-killed B. laterosporus BL1 elevated the proportions of potentially beneficial genera Limosilactobacillus and Lactobacillus, while suppressed potential pathogens Clostridium and Terrisporobacter. Consistently, heat-killed B. laterosporus BL1 increased cecal levels of lactate, total short-chain fatty acids (SCFAs), acetic acid, and butyric acid, while decreasing the concentration of phenol, indole, skatole, and biogenic amines (total amines, methylamine, cadaverine, and putrescine). Thus, heat-killed B. laterosporus BL1 emerges as a promising agent for promoting overall physiological status and intestinal health in finishing pigs.