Bacillus probiotic blend modulates ileal microbiome to improve growth performance and prevent necrotic enteritis in broiler chickens

The intensification of poultry production has led to an increased prevalence of necrotic enteritis (NE), a costly disease caused by Clostridium perfringens , traditionally managed through antibiotic use. However, concerns over antibiotic resistance have driven the search for alternative solutions. This study evaluates the efficacy of a three-strain Bacillus probiotic blend as an alternative for preventing NE in broiler chickens. The three Bacillus strains, Bacillus subtilis ATCC PTA126786, B. velezensis ATCC PTA127064, and B. velezensis ATCC PTA 127065, were selected based on their probiotic attributes, especially their ability to inhibit the growth of C. perfringens and other poultry pathogens. Our results from in vivo experiments showed that dietary supplementation with the probiotic blend significantly reduced NE-associated mortality and improved growth performance metrics such as average daily gain and feed conversion ratio. Metagenomic analyses of ileal contents of chickens supplemented with the Bacillus blend revealed a significant reduction in the abundances of C. perfringens , Enterococcus cecorum , and Eimeria acervulina following NE challenge, despite modest changes in overall microbiome composition. Importantly, the observed probiotic efficacy was strongly associated with the Bacillus strains colonization in the gut, as measured by the Bacillus genome recovery in ileal content samples. These findings highlight the potential of Bacillus -based probiotics as an effective alternative to antibiotics in poultry production, contributing to improved animal health and sustainability.