Effects of Bacillus subtilis KD1 on broiler intestinal flora.

A novel Bacillus subtilis KD1 strain was isolated and identified from healthy broilers, and its phylogenetic classification was subsequently analyzed. To evaluate its probiotic availability, its growth characteristics and tolerance for the gut environment were evaluated in vitro. The results suggest that B. subtilis KD1 is superior in secreting neutral protease and is highly tolerant of gastric acid and bile salt. In the logarithmic growth phase, the neutral protease reached a maximum of 1,369.3 U/mL. When all live bacteria had become spores in the broth, B. subtilis KD1 was freeze dried and fed to broilers at 10(9), 5 × 10(9), and 10(10) bacilli/kg of feed. The animal trial results suggest that the addition of the new strain significantly improved intestinal flora by increasing lactobacilli and reducing Escherichia coli (P < 0.05) as compared with the control; hence, B. subtilis KD1 is a promising probiotic organism in broilers.