Bacillus licheniformis and phytase combination in broiler chicken diets: Effects on growth performance, digestibility coefficients, gut microbiome activities, and bone quality

In the present study, B. licheniformis was added to broiler chicken diets alone or in combination with 6-phytase and the effects on growth performance, coefficients of ileal nutrient digestibility, morphometrical measurements of selected internal organs, gut microbial activity, and bone quality were determined. Four hundred 1-day-old female birds (Ross 308) were randomly allotted to 4 dietary treatments (10 replicate pens, 10 birds each). The trial was set up as follows: negative control (NC), basal diet without any feed additive; NC+Pro, basal diet with B. licheniformis (500 g/t of diet); NC+Phy, basal diet with 6-phytase (400 g/t of diet); and NC+Pro+Phy, basal diet in which both experimental factors were added at the same levels as above. The interaction between treatments was noted in each evaluated period regarding BWG and FI. In the entire experiment, an increased body weight gain (P < 0.001) was observed in the NC+Pro+Phy treatment compared to the other groups. The birds that received both feed additives combined were characterized by an increased feed intake (P < 0.001), contrary to NC+Pro and NC+Phy. Moreover, in terms of microenvironment modulations, interactions (P < 0.05) were observed in the jejunal and cecal digesta pH, short-chain fatty acid (SCFA) level, and microbial enzyme activities. However, the impacts of B. licheniformis and phytase on cecal SCFA concentrations and bacterial enzymes were mainly opposite. There were no interactions (P < 0.05) in terms of geometrical, mechanical, and structural selected tibia and femur indices. However, 6-phytase addition improved bone structure, stiffness, and elasticity. In conclusion, the interactions between 6-phytase and B. licheniformis positively affect growth performance via microbial activity changes; however, the supportive bone quality maintenance properties are only connected to 6-phytase supplementation.