Efficacy of Bacillus subtilis administered as a direct-fed microorganism in comparison to an antibiotic growth promoter and in diets with low and high DDGS inclusion levels in broiler chickens

SUMMARY Direct-Fed Microorganisms (DFM) are potentially important alternatives to antibiotic growth promoters (AGP). We investigated the administration of Bacillus subtilis administration as a DFM in broiler chickens. Comparison of DFM and AGP administration determined the DFM improved BW, BWG, ADFI, and carcass yield with compared to broilers fed an untreated diet and to those administered an AGP. Evaluation of DFM administration in broilers fed low and high distiller's dried grains with solubles (DDGS) diets determined starter and cumulative FCR of broiler fed a high DDGS diet was greater than those fed a low DDGS diet, while DFM administration improved FCR during the starter phase, days 0–28, and days 0–42 as compared to the untreated diet. Additionally, a DDGS × DFM interaction was observed on days 0–28 FCR. Although they were not significant, differences in FCR between untreated and DFM-treated broilers tended to be greater with high DDGS diets than with low DDGS diets. Overall, our results suggest that administration of B. subtilis as a DFM may potentially be used as an alternative to AGP and FCR improvements may be greater when broilers are fed high-DDGS diets compared to broilers fed low-DGGS diets.