From Bench to Barn: Functional Characterization and Meta-analysis of a Bacillus Velezensis Consortium in Swine Nutrition

Growing demand for antibiotic alternatives has intensified interest in probiotics to enhance gut health, mitigate pathogenic infections, and support growth. This study investigates the mechanistic basis and efficacy of a Bacillus velezensis consortium in swine health and nutrition. This study was carried in 2 perspectives; 1) In vitro experiment used cell-free supernatant (CFS) derived from probiotics cultures, assays of pathogen inhibition, transepithelial electrical resistance (TEER), RT-qPCR, and proteomics to evaluate its impact on swine pathogen control and immune modulatory effect of porcine IPEC-J2 gut epithelial cell line, 2) A meta-analysis of 4 in vivo studies (average initial body weight (BW) of 6.9 ± 1.3 kg, contributing 680 data points) evaluated the effect of feeding a B. velezensis consortium to pigs from weaning to day 42 post-weaning on growth performance. Pigs were fed corn or corn-wheat or rice-corn-based diets with soybean meal, fish meal (1 study), whey, wheat bran, or wheat middlings. Diets were fed as mash in 2 phases (1-14 and 14-42 days). All studies had 1) a nutrient-adequate control diet containing no added antibiotic growth promoters and pharmacological level of Zn; 2) the control diet supplemented with a 3-strain Bacillus velezensis probiotics providing 3.0 × 108 cfu/kg of feed. Pigs were weighed individually, and feed intake was recorded per pen at day 14 and 42 to calculate average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR). Data were analyzed using Fit Model platform of JMP 16.1 with the study as a random effect. In vitro, CFS of B. velezensis consortium exhibited broad-spectrum antimicrobial activity by significantly inhibiting Enterotoxin Escherichia coli (ETEC) strains across F4+F18⁻ (84.8 ± 5.3%, P < 0.05), F4⁻F18+ (60.4 ± 7.2%, P < 0.05) and F4⁻F18⁻ phenotypes (73.8 ± 6.2%, P < 0.05). CFS achieved >88% inhibition against Clostridium perfringens (P < 0.05), Compared to medium control, CFS IPEC-J2 cell coculture significantly preserved epithelial barrier integrity (+ 19.5% higher TEER value, P < 0.05), markedly upregulated tight junction proteins (ZO-1, + 26.1%, P < 0.001) and mucins (MUC13, + 46.6%, P < 0.05; MUC20, + 12.9%, P < 0.05). In vivo, the BW of pigs increased (9.9 vs 10.1 and 24.0 vs 24.5 kg; P < 0.05) on day 14 and 42 with supplementation of probiotics, respectively. Feeding B. velezensis consortium improved ADG (P < 0.05) by 7.6, 2.4 and 3.0%, and FCR by 8.0, 3.7 and 3.2% for days 1-14, 14-42 and 1-42, respectively. Diarrhea scores were observed to be either normal (score 1; normal feces) in both treatments or improved in probiotics-supplemented diets compared to control. In conclusion, B. velezensis consortium effectively suppresses pathogens, strengthens epithelial barriers, and boosts growth, making it a strong candidate for swine gut health and nutrition.