Dietary Administration of theBacillus subtilisEnhances Immune Responses and Disease Resistance in Chickens

Bacillus subtilis(B. subtilis) has a variety of proposed beneficial effects for chickens, including growth promotion and disease prevention. In this study, chickens were fed a diet containingB. subtilisfor 21 days and growth performance, intestinal morphology, intestinal microbiota, immune responses, and disease resistance were investigated. After 21 days of feeding, chickens fed a diet containingB. subtilishad higher body weights. The concentrations of serum immunoglobulins IgA and IgM were significantly increased byB. subtilisin the diet. Moreover, chickens fed withB. subtilishad greater villus height (VH), shallower crypt depth (CD), and a higher VH/CD ratio in the jejunum than chickens fed a standard control diet. Diet withB. subtiliscan balance intestinal microbiota, facilitate an increase in beneficial bacteria, and inhibit the pathogenic bacteria after 21 days of feeding. After anEscherichia coli(E. coli) challenge, the survival rate of chickens fed withB. subtiliswas 66.67%, which was significantly higher than the controls. TheE. colicontents in spleens and lungs from chickens fed a diet withB. subtiliswere lower than those in controls. In addition,B. subtiliscan trigger the toll-like receptor 4 and cause induction of proinflammatory cytokine (Il1 beta,Il6, andIl8) production to develop innate immune responses in chickens. In conclusion, diets containingB. subtiliscan improve growth performance, serum immunoglobulin levels, the intestinal villus-crypt system, intestinal homeostasis, immune responses, and disease resistance againstE. coliin chickens.