Dietary triple-strain <i>Bacillus</i> -based probiotic improves growth performance by modulating intestinal barrier function and gut microbiota in weaned pigs

This study aimed to investigate the effects of dietary supplementation with a triple-strain Bacillus-based probiotic (BP) on growth performance, intestinal barrier function, and gut microbial composition in weaned pigs. A total of 160 piglets (initial body weight, 8.0 ± 0.25 kg; 28 d of age) were randomly assigned to 4 treatments: a basal diet (CON) or the basal diet supplemented with 100 mg/kg [BP100, 4 × 107 colony-forming unit (CFU)/kg feed], 200 mg/kg (BP200, 8 × 107 CFU/kg feed), and 400 mg/kg (BP400, 1.6 × 108 CFU/kg feed) a triple-strain Bacillus probiotic containing Bacillus subtilis PB6, Bacillus subtilis FXA, and Bacillus licheniformis G3. Each treatment included 8 replicate pens with 5 pigs per pen. Over the 35-d feeding period (Phase 1: d 0-14; Phase 2: d 15-35), increasing dietary BP supplementation linearly improved average daily gain and feed efficiency (P < 0.05) and reduced the diarrhea index by up to 49.3% relative to the CON (P < 0.05), whereas average daily feed intake was unaffected. Apparent nutrient digestibility increased, whereas organic matter, gross energy, and nitrogen excretion decreased linearly with increasing BP supplementation (P < 0.10). Dietary BP supplementation linearly increased villus height, villus height-to-crypt depth ratio, goblet cell numbers, and tight junction protein expression, while reducing crypt depth in the small intestine (P < 0.05). In addition, increasing dietary BP supplementation linearly increased colonic Lactobacillus abundance and the concentrations of acetic acid, propionic acid, butyric acid, and total short-chain fatty acids, with the greatest values observed in the BP400 (P < 0.05). In conclusion, dietary BP supplementation improved growth performance in weaned pigs by enhancing intestinal morphological development and barrier integrity, increasing nutrient digestibility, and modulating the composition and metabolic activity of the gut microbiota. These findings highlight the potential of BP as an effective functional feed additive to mitigate weaning stress through improvements in intestinal barrier function and modulation of gut microbiota.