Abstract
Studies demonstrated that Bacillus coagulans (B. coagulans) as a dietary additive enhanced broiler growth performance, yet its mechanisms of action modulation remained unclear. Therefore, this study investigated effects of dietary B. coagulans BCH0 (1 × 10(9) CFU/kg) on growth performance, intestinal morphology, gut microbiota, and ileal transcriptomics in Arbor Acres broilers using a completely randomized design. A total of 200 one-day-old broilers were allocated to control (Con, basal diet) and experimental (BCH0, basal diet + 1 × 10(9) CFU/kg B. coagulans BCH0) groups (10 replicates/group, 10 birds/replicate) over a 42-day trial. The results revealed that BCH0 significantly increased body weights (BW) at 21 and 42 days (p < 0.05), improved the average daily gain (ADG) during the starter (1-21 days) and overall phases (1-42 days), and reduced the ratio of feed intake to body weight gain (F/G) across all phases (p < 0.05). Duodenal morphology analysis indicated a BCH0 elevated villus height (+16.9%, p < 0.01) and villus height/crypt depth (V/C) (p < 0.01) and no significant differences in crypt depth (p = 0.46). In the ileum, the BCH0 group exhibited a significantly greater villus height (p < 0.01), crypt depth (p < 0.05), and V/C (p < 0.05) than the Con group. Microbiota analysis revealed no significant differences in α-diversity or β-diversity, but phylum-level shifts involved an increase in Firmicutes and a reduction in Actinobacteriota in the BCH0 group. At the genus level, dominance shifted from Romboutsia (Control group) to Lactobacillus (BCH0 group), accompanied by marked reductions in Turicibacter, Ldatus_arthromitus, and Rothia. Ileal transcriptomics identified 605 differentially expressed genes, with KEGG enrichment highlighting activated nutrient assimilation pathways (p < 0.05), including carbohydrate, mineral, fat, and protein digestion/absorption. These findings collectively demonstrated that B. coagulans BCH0 enhanced broiler growth through the synergistic modulation of beneficial microbiota, the upregulation of nutrient metabolism genes, and intestinal architectural optimization, supporting its role as a sustainable microbial additive for enhancing poultry productivity and gut health.