Abstract
Bacillus-based probiotics are recognized as safe and effective alternatives to antibiotic growth promoters in poultry production. This study evaluated the effects of Bacillus subtilis PS-216 on broiler performance, gut health, and meat quality. Broilers received PS-216 spores continuously via drinking water (2 × 10(9) spores/L; SW) or feed at low (2 × 10(6) spores/kg; SF1) or high (2 × 10(9) spores/kg; SF2) concentrations. Parameters were assessed at days 23 and 44, including growth performance, lymphatic organ weights, cecal microbiota composition, short-chain fatty acid (SCFA) profiles, and meat quality. All treatment groups demonstrated significant performance improvements compared to controls: body weight increased by 7.4-8.1% and feed conversion ratio improved by 3-11%. Thymus weight increased by approx. 22% across all groups, indicating immunomodulatory effects. Microbiota analysis revealed beneficial shifts including increased butyrate-producing taxa (Selenomonadales, Clostridium sensu stricto) and reduced stress-associated Anaeroplasma. The SF2 group showed enhanced cecal butyrate and acetate concentrations at day 23, with sustained butyrate elevation at day 44. Additionally, meat quality improvements were observed, particularly reduced electrical conductivity and improved breast meat color distribution in the SF2 group. Feed supplementation at 2 × 10(9) spores/kg (SF2) provided the most comprehensive benefits across all measured parameters. These findings demonstrate that B. subtilis PS-216 enhances broiler performance through beneficial microbiota modulation and immune function improvement, supporting its potential as a sustainable alternative to antibiotic growth promoters in commercial poultry production.