Effect of supplementing exogenous protease in low protein poultry by-product meal based diets on growth performance and nutrient digestibility in broilers

A 3 × 2 × 2 experiment using 3 levels (0, 30 and 60 g/kg) of poultry by-product meal (PBM), two levels (180 and 190 g/kg) of crude protein (CP) and two levels of exogenous protease (with and without) was undertaken using factorial arrangement under completely randomized design. The birds (n = 1920) were randomly divided into 48 replicates with four replicates under each treatment (40 birds/replicate). Six isocaloric diets (ME 11.93 MJ/kg) were formulated with 2 CP (180 and 190 g/kg) levels. Each diet was supplemented with or without exogenous enzyme and fed to experimental birds from day 1-35. The dietary supplementation of exogenous protease increased feed intake (P < 0.001) and body weight gain (P < 0.001). The feed: gain was also improved by supplementation of protease during day 1-21 and day 1-35. However, feed intake and body weight gain (P < 0.001) decreased with decreasing level of CP during day 1-21 and day 1-35. Similarly increasing the level of PBM from 30 to 60 g/kg decreased feed intake and body weight gain (P < 0.001) during day 1-21. The feed: gain was also poor (P < 0.05) during this period. No effect of reducing CP level on AME, apparent digestibility co-efficient for nitrogen, and AMEn was noted. However, nitrogen retention (Nret) was decreased (P < 0.001) when CP level was decreased. Inclusion of PBM also had no effect on nutrient digestibility. A significant interaction (P < 0.05) of PBM and CP was noted on AME, Nret and AMEn. However, addition of enzyme improved all these parameters. In conclusion, CP level can be reduced to 190 g/kg with 30 g/kg PBM inclusion by supplementing exogenous protease.