Effects of Bacillus subtilis UBT-MO2 on growth performance, relative immune organ weight, gas concentration in excreta, and intestinal microbial shedding in broiler chickens

This study was conducted to investigate the effects of Bacillus subtilis UBT-MO2 on growth performance, relative immune organ weight, gas concentration in excreta, and intestinal microbial shedding in broiler chickens. A total of 480 1-d-old mixed sex broilers were randomly allotted to a 2×2 factorial arrangement of treatments with 2 levels of enramycin (0 or 5 ppm) and B. subtilis (0 or 105 cfu/kg) for 35 d. Each treatment had 6 replicate pens with 20 broilers in each pen. Diets were fed in 2 phases: starter phase (from d 0 to 21) and grower phase (from d 22 to 35). Overall, broilers fed diets supplemented with B. subtilis had 4.4% greater (P=0.01) body weight gain than those fed non-probiotic diets. The feed conversion ratio in broilers fed diets containing enramycin was decreased by 2.8% and 4.2% during d 0-21 (P=0.05) and throughout the experimental period (P=0.02), respectively, than those fed diets without antibiotic. Broilers fed B. subtilis diets had 30.9% greater (P=0.02) relative weight of thymus than those fed diets without probiotic. Dietary supplementation with B. subtilis resulted in 26.9% and 37.9% lower (P=0.03) NH3 and H2S concentrations, respectively, in excreta compared with no supplementation. However, no differences were observed in intestinal bacterial concentrations among treatments. In conclusion, dietary supplementation with 105 cfu/kg of B. subtilis could improve the growth performance of broiler chickens, and reduced NH3 and H2S emissions.