Interactive effect of exogenous protease enzyme and dietary crude protein levels on growth and digestibility indices in broiler chickens during the starter phase.

This study was conducted to study the effect of protease as well as three dietary crude protein levels on growth and nutrient digestibility in broilers. The broiler chickens (n = 540) were assigned to six dietary treatments with six replicates. Three dietary crude protein (CP) levels (17, 19, and 21%) along with two levels of protease (0 and 30,000 IU/kg) were investigated in 3 × 2 factorial arrangement during the starter phase. Body weight was higher (P < 0.05) in group fed with CP-21; however, feed intake was significantly (P < 0.05) lower in CP-19 and CP-21. Resultantly, FCR was significantly (P < 0.05) improved in birds fed with CP-21. Similarly, body weight, feed intake, and FCR were significantly (P < 0.05) improved in enzyme-treated birds compared to the untreated birds. For practical purpose, birds fed CP-19 with protease enzyme resulted in improved FCR compared to birds fed with CP-21. The results revealed that CP and apparent metabolizable energy (AME) were significantly (P < 0.05) higher in birds fed with CP-21 along with supplementation of enzyme while abdominal fat was significantly (P < 0.05) lower in the same group compared to birds fed with CP-17. These results indicated that a diet having 21% CP supplemented with 30,000 IU/kg protease enzyme was superior in improving the performance and digestibility of nutrients in broiler during the starter phase.