Enhancing poultry health and food safety with probiotics: A study on Bacillus velezensis against Salmonella Heidelberg in broilers.

The growing concern over antibiotic use and foodborne pathogens such as Salmonella Heidelberg (SH) highlights the need for effective alternative strategies in poultry production. This study evaluated the probiotic potential of Bacillus velezensis (BV) to control SH colonization and modulate gut microbiota and metabolism in broilers. In vitro, BV exhibited inhibitory activity against SH. In vivo, a total of 100 one-day-old broiler chicks were randomly assigned to four treatments (n = 25/group): NC (negative control), PC (positive control, challenged with SH), BV-Neg (BV supplementation without SH challenge), and BV-SH (BV supplementation with SH challenge). Birds were orally challenged at 4 days of age with 0.2 mL of SH (6 × 109 CFU/mL). Cecal SH counts, microbial diversity, and fecal metabolomic profiles were evaluated at 7, 14, 21, and 28 days. Data were analyzed using ANOVA, chi-square tests, and multivariate approaches, including principal component analysis (PCA) and multivariate analysis of variance (MANOVA), with significance set at P < 0.05. BV supplementation significantly reduced SH colonization in the cecum at 28 days, with a reduction of 3.53 log CFU/g (∼99.9%) compared to the positive control (P < 0.01), indicating a time-dependent probiotic effect. Microbial diversity was influenced by treatment and age, with BV-supplemented and SH-challenged groups showing higher diversity than NC (P < 0.05). Metabolomic analysis identified 60 analytes across multiple metabolic classes, with BV increasing beneficial compounds such as fatty acyl glucosides, lignin, artemisinin, and taurodeoxycholic acid, while reducing metabolites associated with SH infection. Overall, BV demonstrated a cumulative effect in reducing SH colonization and modulating gut microbiota and metabolism, supporting its potential as a probiotic strategy to improve poultry health and food safety.