الفهرس 
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Abstract
The present work was carried out to study the effect of different levels of protein and lysine in the starter, grower and finisher diets of broiler chickens and their effects on growth performance, carcass quality, serum metabolites. Effects on Haemagglutination inhibition titer against NDV and its histopathological changes of some immune organs were another objective of the study. The experimental chicks (315 one day old Cobb chicks) were divided into 7 equal triplicate groups (15 chicks) The experimental diets were formulated, according to the NRC recommendation Tables for the nutrient requirements of broiler chick, to contain 3200 Kcal ME / Kg with decreasing the protein levels by 5 and 10% lower than that of the recommendation with increasing the lysine level by 0.2 and 0.4% higher than that of the recommendation for the starter, grower and finisher diets. The 7 chick groups were fed the experiment diets differing in level of protein and supplemented with lysine, each group was fed on its respective starter, grower and finisher diets. All experimental chicks were subjected to vaccination program against Newcastle (NVD) & Avian Influnza and Gumboro diseases at proper time. Body weight of the chicks and consumed diets were weekly recorded and the feed conversion ratio was calculated. Blood samples were collected from the wing vein of broilers at 14, 21, 28 to separate sera for detection of antibodies titer against Newcastle disease vaccine and at 42 days of age to separate sera for analyzing total protein, albumin, total lipid, cholesterol, triglycerides and glucose. At the end of experiment, 5 chicks from each group were collected and slaughtered to evaluate the carcass quality and chemical composition data. The bursa, spleen and the upper three lobes of the thymus from the left side of the neck were dissected out from the same five birds of each group and cut and fixed in formalin for histopathological examination. The results revealed that body weight and body weight gain of the broiler chickens fed low protein diets either by 5 or 10% than that recommended without lysine supplementation were significantly lower than that of the broiler chickens fed the control diet. Body weight and body weight gain of the broiler chickens fed low protein diets either by 5 or 10% than that recommended with lysine supplementation by (0.2, 0.4 &0.4%) respectively above that recommended were not significantly differ from that of the broiler chickens fed the control diet. Feed consumption of the broiler chickens fed low protein diets either by 5 or 10% than that recommended without lysine supplementation were significantly increased compared to that of the broiler chickens fed the control diet. Lysine supplementation either by 0.2 or 0.4 % of diet increased the feed consumption compared to the control while decreased feed consumption compared to other group fed low crude protein diet. However, feed consumption of the broiler chickens fed low protein diets by 5% and 10% than that recommended with lysine supplementation by 0.2%, 0.4% and 0.4% respectively was lower than other groups and was not significantly different from the broiler chickens fed the control diet. Feed conversion ratios of the broiler chicks fed diets containing low crude protein by (5& 10%) less than that recommended were significantly increased compared to that of the broiler chickens fed normal recommended protein levels and FCR was improved with lysine supplementation. Feed conversion ratio of the broiler chicks fed low CP diets (5% lower than that recommended and supplemented by lysine by 0.4% of diet was not significantly differ from the broiler chickens fed normal recommended protein and lysine levels. Decreasing dietary protein by either 5 or 10 % than recommended dietary protein level has significantly increased abdominal fat and decreased breast meat yield percentages and thigh yield % in the carcass. Lysine supplementation has significantly decreased abdominal fat and increased breast meat yield % and thigh yield%. Feeding the broiler chicks low protein diets less than that recommended without lysine supplementation has significantly decreased the serum total protein, albumin, globulin, while increased serum total lipids, cholesterol, triglycerides and lipoproteins compared to that of broiler chicken fed the basal diet. Generally, it could be concluded that the dietary protein level could be decreased by 5% or 10% of the level recommended by NRC with lysine supplementation by 0.2& 0.4% respectively above that recommended without any adverse effects on Body weight, body weight gain, feed conversion ratio, carcass quality, composition, serum metabolites and immune response.