Administration of Bacillus cultures as Direct-Fed Microorganisms improves growth performance and reduces mortality of broilers raised under performance-reducing stress challenge

Summary The use of Direct-Fed Microorganisms (DFM) is an important alternative to antibiotic growth promoters (AGP) for improving growth and managing disease in poultry production. We investigated the administration of two multi-strain Bacillus cultures administered as DFM on growth performance and mortality of broiler chickens reared under performance-reducing stress challenge. The first experiment evaluated the dose response of the growth of broiler chickens to the administration to three increasing concentrations of direct-fed Bacillus culture A (DFM A). Administration of the low dose of DFM A improved starter, grower, and cumulative FCR of broiler chickens as compared to an untreated control with no further benefit being observed at higher doses. The second experiment compared the administration of the low dose of DFM A with a second multi-strain direct-fed Bacillus culture (DFM B) administered at a dose demonstrated previously to improve growth at a level similar to an AGP. The overall elevated level of mortality observed in this experiment was reduced by DFM A administration when compared to an untreated control over the grower phase and cumulatively. Additionally, when compared to an untreated control, DFM A administration reduced starter FCR, while DFM B administration reduced grower FCR. Overall, the results of our study suggest administration of multi-strain Bacillus spp. cultures of as DFM may be used as a potentially important alternative to AGP for improving growth and managing disease in poultry production.