Effect of Bacillus licheniformis on Growth, Bone Mineralization, and Intestinal Microbiota in Broilers Fed Cowpea Diets

This study investigates the effects of the Bacillus licheniformis (BL) ATCC 21424 strain, as a potential bacterial probiotic in broiler diets based on soybean meal (SBM) or cowpea seeds (CWP), on growth performance (GP), bone mineralization, and intestinal/fecal microbiota status (0 to 42 d age). A 2 × 2 factorial arrangement was employed in a completely randomized design, with four dietary treatments: SBM and CWP diets with or without BL supplementation (1.0 × 1011 CFU spores g−1 feed). A total of 480 one-day-old mixed-sex Ross 308 broiler chickens were randomly assigned to the treatments, with 6 pens of 20 chicks each. The results showed that broilers fed with CWP diets showed comparable body weight gain (BWG), feed intake (FI), and feed conversion rate to those fed the SBM diet (p > 0.05). The inclusion of BL improved BWG during the grower and finisher periods (p = 0.01) and overall study (p < 0.001), resulting in a numerical increase in FI (p = 0.054). In addition, BL in birds’ diets reduced abdominal fat (p = 0.032) and influenced cecum weight (p = 0.040). Additionally, BL improved tibia iron (Fe) and phosphorus (P) bone mineralization and reduced the calcium–phosphorus (Ca:P) ratio (p = 0.0001). Microbial analysis revealed that BL inclusion decreased Coliforms counts in the CWP diet (p = 0.073), reduced E. coli in the ileum (p ≤ 0.05), and lowered Clostridium spp. and Enterococcus spp. in the cecum broilers on SBM diets (p ≤ 0.05). The presence of Staphylococcus spp. in broiler feces was also reduced in both SBM and CWP groups (p < 0.05). In conclusion, the addition of BL to broiler diets enhanced growth performance and bone mineralization and positively influenced gut and excreta bacterial populations in both SBM and CWP diets.