Isolation and characterization of B acillus subtilis CH 16 strain from chicken gastrointestinal tracts for use as a feed supplement to promote weight gain in broilers

Spore‐forming bacterial strains were isolated from chicken gastrointestinal tracts to develop a heat‐stable feed supplement that promotes weight gain in broilers. Seven Bacillus strains having more than 90% sporulation were screened from the isolates and identified to be closely related with Bacillus subtilis and Bacillus licheniformis . Of the seven strains, B. subtilis CH 16 was selected to develop a feed supplement for broilers, because it formed 100% heat‐stable spores, grew rapidly at 42°C and quickly formed a biofilm. In large‐scale trials in broilers ( n  ≥   1150 per group), the group fed CH 16 (3 × 10 6   CFU  g −1  pellet) showed higher average daily gain ( ADG  = 61·16) and lower food conversion ratio ( FCR  = 1·696) than did the group fed B. licheniformis CH 22 ( ADG  = 57·10 and FCR  = 1·792), the group fed B. subtilis HU 58 ( ADG  = 51·90 and FCR  = 1·868), BioPlus group ( ADG  = 59·32 and FCR  = 1·807) and the control group ( ADG  = 56·02 and FCR  = 1·880). In conclusion, CH 16 spores significantly increased ADG by 9·17% and reduced FCR by 9·79% in broilers. The result supports the use of B. subtilis CH 16 of chicken intestinal origin as a feed supplement that promote weight gain in broilers. Significance and Impact of the Study This study reports screening of Bacillus strains isolated from chicken gastrointestinal tracts for development of a feed supplement that promote weight gain in broilers. Of the seven Bacillus isolates with high sporulation efficiency (≥90%), Bacillus subtilis CH 16 strain showed the best growth and biofilm formation at body temperature of broilers (42°C). In large‐scale trials in broilers ( n  ≥   1150 per group), CH 16 spores induced a 9·17% increase in daily weight gain ( ADG ) and a 9·79% reduction in FCR while the commercial BioPlus ® YC induced only a 5·89% increase in ADG and a 3·88% reduction in FCR .