Animal digestive health is key to obtain optimal performance. Antibiotic growth promoters (AGPs) have long been shown to be very effective to develop and stabilize a healthy gastro-intestinal tract. Other types of additives are being increasingly documented for their effects on gut health and animal performance. Bacillus-based direct-fed microbials (DFMs) are of particular interest due to their ability to modify gut microbiota, act as a probiotic, and their ability to remain viable after pelleting.
The objective of the present experiment was to investigate the effect of Bacillus strain DSM 29784 on the performance of broilers compared to or in combination with bacitracin methylene disalicylate (BMD). A total of 2400 day-old male broiler chickens, Cobb 500, were randomly allocated according to a factorial design with four treatments (12 replicates of 50 birds) and reared until 35 days in floor pens. The experimental treatmentswere: T1, negative control (basal diet, corn-based); T2, T1 + BMD at 55 ppm; T3, T1 + Bacillus strain DSM 29870 at 5.108 CFU/kg of feed; T4, T1 + Bacillus strain DSM 29870 + BMD (5.108 CFU/kg of feed and 55 ppm, respectively). Feed intake (FI) and body weight gain (BWG) were measured at 21 and 35 days and feed conversion ratio (FCR) calculated.
Results, presented in Table 1, showed that at 21 days, the three treatments (groups T2, T3 and T4) significantly improved BWG and FCR (P < 0.05). There was also a numerical improvement when T4 was compared to T2 and T3. At d35, all treatments increased BWG, significantly (P < 0.05) for T3 and T4 with an improvement of 7.7% and 6.8%, respectively. T2 and T3 improved significantly (P < 0.001) the FCR by 3.3% and 3.7%, respectively. For T4, there was also a significant (P < 0.001) FCR improvement of 4.1%, with a numerical (P > 0.05) increase compared to T2 and T3.
These results showed that Bacillus subtilis strain DSM 29784 improves broiler performance, and the level of improvement is similar to that obtained with BMD. There were no antagonistic interaction between the two products and a trend for performance increase was obtained with the combination. In conclusion, Bacillus subtilis strain DSM 29784 can be added to non-medicated as well as medicated diets to improve broiler chicken performance.