Use of protease enzyme in diets with different levels of protein and amino acids on performance, carcass characteristics, nutrient digestibility and some blood parameters concentrations in broiler chicks

A total of 240 male Ross 308 broiler chicks were allocated in completely randomized design, including six experimental diets with 4 replicates and 10 chicks per replicate. Experimentaldiets include 1- a control diet based on corn and soybean meal, recommended according to the guide of Ross strain (308) 2- a control diet with the addition of protease enzyme with recommended levels (0/02 %) 3- low protein diet (five percent reduction) 4- Diet with low levels of protein and essential amino acids (five percent reduction) 5- Diet with low levels of protein (experimental diet three) with the addition of protease enzyme with recommended levels (0/02 %) 6- Diet with low levels of protein and essential amino acids with the addition of protease enzyme with recommended levels (0/02 %).The highest amount of feed consumption in the starter  period and the highest feed conversion ratio  in the growth period, as well as the highest percentage of abdominal fat, were related to the diet with low levels of protein and amino acids. Protease enzyme increased the body weight and decreased the feed conversion ratio during the growth period in diets with low levels of protein and amino acids (P<0.05).The use of protease enzyme in diets with low protein levels improved the digestibility of dry matter and organic matter, and the highest percentage of thigh and spleen and blood HDL concentration was related to the diet with low protein levels with the addition of protease enzyme (P<0.05). Based on the results, use of protease enzyme in diets with low levels of protein and amino acid improved the performance of broiler chickens.