Meta-analysis of the potential of dietary Bacillus spp. in improving growth performance traits in broiler chickens

Abstract

Bacillus probiotics have been shown to possess several advantages over conventional probiotics, including the capacity to withstand heat during feed manufacturing processes and to be stored for a long time without losing viability, as well as the ability to survive and function in the acidic environment of the chicken gut. However, there are inconsistent results on the effect of Bacillus on growth performance of broiler chickens. The objective of this meta-analysis was to assess the effect of dietary Bacillus supplementation on feed intake (FI), feed conversion efficiency (FCE), and average daily gain (ADG) in broiler chickens. PubMed, Google Scholar, and Scopus databases were searched for studies that fed diets with and without Bacillus to broilers. Pooled estimation revealed that Bacillus supplementation improved FCE (standardised mean difference [SMD] = −0.33, 95% confidence interval (CI) −0.39 to −0.28) and increased ADG (SMD = 0.37 g/bird/day, 95% CI 0.28–0.46). In contrast, feed intake (SMD) = 0.03 g/bird/day, 95% CI −0.03 to 0.09) was not significantly different from controls. Subanalysis revealed that broilers fed with Bacillus at 0.1–0.5 × 106 colony-forming unit (cfu)/g had higher ADG than controls. There is evidence of significant heterogeneity (inconsistency index [I 2] = 80–93%) among the studies included in the meta-analysis. Meta-regression showed that studied moderators (i.e., Bacillus spp., duration of supplementation, and broiler strain) explained most of the effect. In conclusion, our results suggest that Bacillus supplementation at 0.1–0.5 × 106 cfu/g improved FCE and ADG in broiler chickens. However, it is recommended that more research be conducted to determine the Bacillus supplementation dose that optimises growth performance indices in broiler chickens.