Probiotics are effective for improving poultry health. Probiotic Bacillus cereus strains are widely used to improve animal health by stimulating the immune system. In this study, we obtained a B. cereus 13 (BC13) strain that functions in acid, high-temperature, and bile salt resistance. It also degrades starch, cellulose, and other proteins. To better understand the probiotic effects of BC13, we added the strain to the diet of broilers and observed its effects. We found that BC13 significantly improved the growth performance of broilers. The levels of total antioxidant capacity, superoxide dismutase, and glutathione peroxidase were increased, and the concentration of malondialdehyde was reduced by BC13. Supplementation with BC13 enhanced immune function by increasing the levels of secretory immunoglobulin A (sIgA) in the jejunum mucosa
IgA, IgM, and IgG in the serum
mRNA levels of Zo-1, claudin and occludin of the jejunal mucosa
and increased villus height/crypt depth of the jejunum. Furthermore, BC13 improved the composition of intestinal microbes, especially at the genus level of Akkermansia. The addition of BC13 increased the levels of acetic, butyric, valeric, and propionic acids. These results emphasise the potential of BC13 as a probiotic dietary supplement to improve the antioxidant capacity, intestinal barrier function, and gut microbial composition to enhance body health.