EFFECTS OF DIETARY PROTEIN LEVELS WITH OR WITHOUT SYNTHETIC AMINO ACIDS AND ENZYME SUPPLEMENTATION ON PERFORMANCE OF BROILER CHICKENS

This experiment was conducted to study the effect of using two levels of (recommended (R), R-2%) crude protein (CP) supplemented with or without the requirements of methionine and lysine (Met. and Ly.) and each with two levels (0.00 and 0.10%) of Avizyme 1500 in 2 x 2 x 2 factorial arrangement (giving eight dietary treatments) on growth performance of broiler chickens (Ross strain). Accordingly, a total numbers of 192 one-day old unsexed Ross broiler chickens were initially fed a control diet for five days. At six days of age, chicks were randomly allotted to the dietary treatments, birds were divided into eight treatments (24 birds each), each treatment contained three replicates of eight birds each. Results obtained could be summarized in the following: The main effects of level of CP had insignificant effect on live body weight (LBW), live body weight gain (LBWG), feed intake (FI), feed conversion (FC) and performance index (PI) during finisher (25 to 41) and overall experimental periods (6 to 41 days). Level of CP had significant effect on crude protein conversion (CPC) during the period from 6 to 41 days, chicks fed diet containing R had the worst CPC during same period. Chicks fed adequate amounts of amino acids (AA) supplement diets recorded significantly higher PI value during the period from 6 to 41 days, while, recorded significantly the worst values of FC and CPC during the same period. Level of AA had insignificant effect on LBW, LBWG and FI during overall experimental period. Neither enzyme addition nor interaction between level of CP, AA and enzyme addition had any significant effect on LBW, LBWG, FC, CPC and PI during the period from 6 to 41 days. No significant differences due to level of CP or AA on blood constituents, except, red blood cells count (RBCs) which was significantly affected. Chicks fed diet containing R-2% CP or diet containing inadequate amounts of AA had higher value of RBCs. No significant differences due to enzyme addition and interaction effect of dietary treatments on blood constituents, except, interaction effect on neutrophils% (segment) which was significantly affected. Neither level of CP and enzyme addition nor interaction between level of CP, AA and enzyme addition had any significant effect on slaughter parameters% and tibia weight and ash% at the end of the finishing period. Level of CP, AA and interaction between level of CP, AA and enzyme addition had insignificantly affected chemical composition of broiler meat. Chicks fed diet containing R-2% supplemented with the requirements of Met. and Ly. with 0.10% of Avizyme had the best economical and relative efficiency values during the period from 6 to 41 days of age, as compared with those fed the control diet and other treatments. It can be concluded that, CP can be reduced from the recommended level by 2% and supplement these diets with either Met. and Ly or Avizyme without affecting performance. Besides, using such diets reduces feed cost and N pollution.