الفهرس 
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Abstract
Dissertation Abstract The experimental chicks (320 one day old Cobb broiler chicks) were randomly divided into 8 equal tetra replicate groups (10 chicks / replicate), the control group and 7 experimental groups. The 2nd group fed the ideal protein diets, while the other 6 diets were containing 2 low levels of CP (5 or 10% less than the recommended level of broiler Cobb 500) with supplementation of 110, 120 and 130% of commercial synthetic EAAs of the recommended level of Cobb 500. The experimental diets were formulated, according to Cobb vantress.com recommendation table for the nutrient specifications of broiler chicks, to contain 3035, and 3108 Kcal ME/Kg and 21.5, & 19% CP for starter, grower phases respectively. The chick groups (8) were fed the experiment diets, differing in level of protein and supplemented with commercial synthetic EAAs, each group was fed its respective starter and grower diets. Body weight of the chicks and consumed diets were weekly recorded and the feed conversion ratio was calculated. At the end of the experimental period, a digestibility trial was carried for 5 days to determine the digestion coefficients of nutrients. At the end of experiment (5 weeks of age), 8 chickens from each group slaughtered to evaluate carcass traits and serum metabolites parameters. The results of the study revealed that : Body weight and body weight gain of the broiler chickens fed low protein diets (5% and 10% less than the recommended levels) and supplemented with 120 and 130 %EAAs with 5% low CP and 110, 120 and 130% with 10% low CP were significantly lower than that of the broiler chickens fed the control diets (basal diets). Body weight and body weight gain of the broiler chickens fed low protein diets (5% and supplemented with 110% of the recommended level of digestible EAAs) or ideal protein diets (based upon digestible AA requirements) were not significantly different from that of the broiler chickens fed the control diets (basal diets). Feed consumption of the broiler chickens fed the low protein diets (5%) and supplemented with 120 and 130% of the recommended level was significantly decreased compared to that of the broiler chickens fed the control diets.Decreasing dietary CP by 10% with EAAs supplementation maintained feed consumption near to that of the broilers fed the control or ideal protein diets. Feed conversion ratios (FCR) of the broiler chickens fed diets containing low CP by 10% of the recommended level and supplemented with 110, 120% and 130% of the recommended levels of EAAs were higher than those of the other treatments. FCR of the broiler chickens fed diets containing low CP 5% of the recommended level and supplemented with 110 and 120% EAAs of the recommended levels and those fed ideal protein diets were not significantly different from those of the broiler chickens fed control diets containing recommended protein. There were not significant differences of Protein efficiency ratio (PER) of broiler chickens between experimental groups. There were not significance differences of apparent digestibility of dry matter, crude protein, and ether extract between experimental groups.