Study of Bacillus subtilis on growth performance, nutrition metabolism and intestinal microflora of 1 to 42 d broiler chickens.

To study the influence of different levels of Bacillus subtilis on growth performance, nutrition metabolism and intestinal microflora of 1 to 42 d Arbor Acres (AA) broilers, a total of 800 one-day-old healthy broilers were randomly divided into 5 groups with 4 replicates per group and 40 broilers per replicate. Broilers were fed a basic diet (group 1) which acted as the control group, and 4 other groups (2 to 5) were fed the basal diet with B. subtilis added at concentrations of 100, 150, 200 and 250 mg/kg, respectively for 42 days. The results showed as follow: the average daily gain (ADG) of group 4 was significantly higher than ( P  < 0.05) that of group 1, and the average daily feed intake (ADFI) of group 5 was the highest but the differences between groups were not significant ( P  > 0.05). The feed to gain ratio (F/G) of all the experimental groups was lower than that of the control and the difference was significant in group 4 ( P  < 0.05). In addition, supplementation of B. subtilis increased the apparent metabolism of crude protein ( P  > 0.05), crude fat ( P  > 0.05), dry matter ( P  > 0.05) and organic matter ( P  < 0.05). B. subtilis decreased the Escherichia coli and Salmonella populations in the cecum. This shows that adding B. subtilis to the broiler diet can improve the growth performance, increase feed efficiency, regulate serum index and reduce harmful bacteria in the intestinal tract. Based on our study, it could be recommended that addition of B. subtilis at 200 mg/kg could improve the growth performance of broilers.