Effect of protease on growth performance and carcass traits of broilers fed diets with different crude protein levels

The study investigated effect of protease (Cibenza DP100, Novus International Inc.) on growth performance and carcass traits of broilers as affected by dietary crude protein level.

There were 6 treatments in a 3 × 2 factorial arrangement with 3 levels of crude protein (LO, ME, HI) and 2 levels of protease (0 or 300 units/g). Diets were corn SBM based with starter diets (0–19 d) in crumbled form, and grower (19–35 d) and finisher (35–42 d) diets in pellet form. The 3 crude protein levels were 20.5, 22.5, 24.5% for starter, 18.5, 20.5, 22.5% for grower, and 16.5, 18.5, 20.5% for finisher diets. Each diet was fed to 8 replicate pens of 18 male broilers. Body weight, feed intake, FCR, and mortality were determined at d 19,35, and 42. On d 43, carcass parameters – dressing percentage, breast yield and fat pad weight, were obtained. Data were analyzed as 3 × 2 factorial design and statements of significance were based on P­value ≤0.05. On each weigh day, body weight increased as dietary protein level increased from LO to ME and from ME to HI. On d 19 and 35, feed conversion ratio was the best for HI protein diets, the worst for LO protein diets, and intermediate for ME protein diets. On d 42, birds fed ME or HI protein diets had better FCR than those fed LO diets, but there was no difference between ME and HI protein diets. 

Protease increased body weight significantly on d 35 (P = 0.049) and numerically on d 42 (P = 0.060). On d 35 and 42, protease significantly improved FCR for birds fed diets containing LO or HI protein. Dressing percentage was higher for birds fed HI protein diets in comparison to ME or LO protein diets with no difference between ME and LO protein diets. Fat pad weight was reduced with each increase of dietary protein level. Carcass traits were not significantly affected by protease supplementation. In summary, for broilers fed corn SBM based diets, protease had the potential to increase body weight and to improve FCR when dietary protein level was not optimal without compromising processing parameters.

Key Words: broiler, protease, crude protein