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Abstract The present study was carried out in Poultry Nutrition Farm, Poultry Production Department, Faculty of Agriculture, Ain Shams University, Shoubra El-kheima, Egypt. The objective was to evaluate the effect of supplementing different levels of threonine and tryptophan on growth performance, carcass traits and some plasma parameters of broiler chicks under Egyptian summer conditions. All farm work during the experimental period from August to September 2017. A total of 360, Ross 308, one-day-old broiler chicks were randomly allocated into 9 treatments with 8 replicates of 5 chicks each. Three levels of threonine (100, 150 or 200 %) and three levels of tryptophan (100, 150 or 200%) according to dietary requirements for Ross 308 chick’s guidebook were used in a factorial design arrangement to obtain nine experimental treatments. Two periodical diets (A corn-soybean basal diets) were used (starter phase 1-21 days of age and grower phase 22-35 days of age). Growth performance traits including live body weight (LBW), Body weight gain (BWG), feed consumption (FC) and feed conversion ratio (FCR) were recorded at the end of each week. Carcasses were manually eviscerated and weighed. Components of total protein, albumin, cholesterol, and triglycerides were analyzed by using commercial kits. The main results could be summarized as follows: 1- Chicks fed diet supplementing 200 % threonine had an improvement in live body weight and body weight gain with different levels of tryptophan compared to other treatments. 2- The highest LBW was recorded by chicks fed diet supplemented with 150 % of chicks’ requirements of both types’ amino acids and the lowest was recorded by chicks fed diet supplemented with 200% of the tryptophan requirement with 150% threonine (1593.91 vs 1504.75g).3- Birds fed diet supplemented with 150% tryptophan gave the highest daily body gain compared with other groups fed diets supplemented with tryptophan. (44.13 g/d). 4- Concerning relative weight of carcass and edible parts, there were significantly reduced with increasing threonine level in the broiler diets, but tryptophan amino acid had not any significant effect on the above-mentioned traits. 5- Percentages of giblets differed significantly related to tryptophan amino acids effect, where giblets weight percentage increases with increasing tryptophan, so the interaction between types and levels was affected. But threonine amino acid had not any significant effect on the percentage of giblets. 6- Liver weight percentage differed significantly related to tryptophan amino acids effect, where it increased with increasing tryptophan levels in broiler diets, but threonine amino acid and the interaction between types and levels were not affected on the percentage of liver. 7- The percentage of gizzard weight affected significantly decreased with increasing of both types of amino acids, but the interaction between types and levels was not affected. 8- Percentage of heart differed significantly related to tryptophan amino acids effect, where this percentage increased with increasing tryptophan, but threonine levels and the interaction between types and levels were not affected. 9- Spleen percentage reduced significantly with increasing threonine amino acid but adding tryptophan in the diets significantly increased this percentage, but the interaction between types and levels was not affected. Bursa percentage was affected significantly by threonine level in diets where chicks fed 100% recorded highest bursa percentage (0.17%), so the interaction was affected, but chicks fed diets with tryptophan had not affected. 10- There were no significant (P>0.05) differences of different types and levels of amino acid on percentages of breast, thigh, drumstick, wing, and nick. 11- Birds fed diets with 150% tryptophan were recorded higher percentages of breast, drumstick, and nick (32.19, 11.18, 5.38%, respectively) and birds received diets with 200% recorded higher thigh percentage (21.24%) and higher wing percentage (7.99%) in birds fed diets with tryptophan. 12- The differences between plasma concentration of total protein, globulin, and A/G ratio were significant due to both tryptophan and threonine supplementation of experimental diets. 13- Total cholesterol concentration increased significantly with the different levels of threonine, and interaction between them. Whereas, adding threonine has no effect on the concentrations of triglyceride. Tryptophan supplementation had no impact on the blood plasma concentrations of total cholesterol and triglyceride. In this study, it concluded that supplementation of threonine and tryptophan improves productive performance and health status of broiler chicks without imposing any toxicity as all blood components were in normal range. |