Histomorphometric traits, microbiota, nutrient digestibility, growth performance, carcass traits and meat quality parameters of chickens fed diets supplemented with different levels of Bacillus protease

The effects of dietary Bacillus protease on broiler performance were examined. Three hundred ‘Cobb 500’ day-old broilers were randomly assigned to five dietary groups with five replicates of 12 birds each. Treatments include: PROT0; without protease addition (0 g/kg; control), PROT10, PROT15, PROT20 and PROT25 diets supplemented with Bacillus protease at the level of 1, 1.5, 2 and 2.5 g/kg, respectively. Birds fed PROT25 had the highest (p < 0.05) villi height and villi height to crypt depth ratio, as well as crypt depth at the duodenum, jejunum, and ileum of intestine. At starter and finisher phases, BWG was the highest (p < 0.05), whereas FI and FCR had their lowest values in PROT25 group (p < 0.05). PROT25 broilers had the best (p < 0.05) energy efficiency ratio. Crude protein, dry matter, and crude fibre digestibility were improved (p < 0.05) with increased inclusion levels of Bacillus protease. Lactobacillus and Bifidobacteria count increased (p < 0.05) as the inclusion levels of Bacillus protease increased in both ileum and caecum, while E. coli population decreased. Chickens fed with the PROT25 diets had the highest (p < 0.05) values for carcass, thigh, breast and drumstick weight. Cooking loss decreased (p < 0.05) as the inclusion levels of Bacillus protease increased, while water holding capacity increased (p < 0.05). Highest Bacillus protease (2.5 g/kg) inclusion improved digestibility, gut integrity, and health status with a better FCR, body weight gain, and retail cut yields.