Bacillus subtilis Improves Immunity and Disease Resistance in Rabbits

Probiotics such as <i>Lactobacillus</i> and <i>Bifidobacterium</i> have been successfully used to promote growth and prevent diseases. Previous reports have demonstrated that <i>Bacillus subtilis</i> (<i>B. subtilis</i>) was a potential probiotic for animals. In this research, 180 <i>B. subtilis</i> were isolated from the soil, identified, and investigated <i>in vitro</i>. Furthermore, five <i>B. subtilis</i> were selected and mixed to investigate their effect on growth performance, immune response, intestine microbiota, and disease resistance in rabbits. Rabbits with a diet of 10⁶ CFU g^-1 mixed <i>B. subtilis</i> exhibited the best growth performance and higher serum IgG and IgA than controls (<i>P</i> < 0.05). Moreover, dairy with <i>B. subtilis</i> can promote the balance of intestinal flora. The major proinflammatory factor and β-defensin were upregulated compared with the controls. After 7 weeks of feeding, the survival rate of the rabbits fed with <i>B. subtilis</i> was significantly higher than those in the control groups postinfected with <i>Escherichia coli</i>. At the same time, this study detected higher expression of β-defensin and reduced bacteria contents of the heart and cecal contents from the diet mixed with <i>B. subtilis</i> compared with the control groups. In conclusion, dietary supplementation with <i>B. subtilis</i> for rabbits could improve growth performance, intestinal homeostasis, and immune organ index and enhance innate immune response as well as disease resistance. These findings showed that the induction of β-defensin by <i>B. subtilis</i> might be an interesting new therapeutic strategy to strengthen innate defense mechanisms.