الفهرس 
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Abstract
This growth study aimed to demonstrate how the dietary supplementation of indispensable (IAA) and dispensable amino acids (DAA) could help in reduction of dietary intact protein (IP) content in channel catfish (Ictalurus punctatus) diets and their effect on the growth responses, feed utilization efficiency, whole body composition and other health indicators. Experiment (1): Nine isolipidic (8% lipid) experimental diets were designed, to contain graded IP levels (32, 30, 28, 26 and 24%) supplemented with IAA. Then different levels of DAA (2, 4, 6 and 8%) were added to 24%IP diet. Experimental diets were fed to juvenile channel catfish over 9 weeks growth period.Juvenile channel catfish (10.56 ± 0.1g) were randomly allocated into 9 groups, four replicates per each using 36 aquaria (15 fish per aquarium). Daily feed (on oven -dry basis) was calculated according to the wet weight of fish which weighed biweekly, according to % of the mean body weight to avoid over feeding while maintaining a level approaching satiation (3.5-6%) which decreased as fish grow.At the end of experiment, fish were group weighed and individually counted. Growth and feed utilization parameters ; final mean weight, weight gain, TGC, feed intake, FCR & protein and amino acids retention efficiency were computed. In addition, four fish were randomly chosen per tank for approximate chemical analysis of whole body. Another four fish were selected for whole blood, serum and further histopathological investigation. Experiment (2): Nine iso-lipidic (8% lipid) experimental diets were formulated, whereas the dietary IP was decreased from 30 to 24%.Then, the amino acids profile was balanced by using CAA supplementation at graded levels 100, 120 and 140% compared to channel catfish IAA requirement stated in NRC 2011 with and without adding of DAA. Besides, three different levels of IP 24, 27 and 30% supplemented with IAA up to 120% NRC requirements were also tested.Juvenile channel catfish (23.68 ± 0.16g) were randomly allocated into 9 groups, three replicates per each using 27 aquaria (15 fish per aquarium).Daily feed (on oven -dry basis) was calculated according to the wet weight of fish which weighed biweekly, according to % of the mean body weight to avoid over feeding while maintaining a level approaching satiation (4-3%) which decreased as fish grew.Collectively, it can be concluded that commercially available essential amino acids (lysine and histidine) could be used as a dietary supplement to reduce the dietary intact protein level in juvenile channel catfish (Ictalurus punctatus) practical diets from 32 to 26 %, with balancing the lysine and histidine level at the recommended level by NRC (2011). Additionally, the feed incidence cost decreased from 28.98 to 25.45 with decreasing the dietary intact protein from 32 to 26%, which consequently will help in the reduction of the production cost. But, lowering the dietary intact protein to 24% adversely limited the fish growth when IAA level maintained at the recommended level by NRC (2011). Dietary intact protein level could be lowered from 30 to 24%, with balancing the IAA level at 140% of the NRC (2011) requirements, with maintaining optimal fish growth and decreasing the feed incidence cost from 22.10 to 19.87 respectively. Supplementation of 2-6% DAA (glycine and glutamic acid) to 24% IP diet in which IAA level resorted to 100 % NRC (2011) requirement, showed numerical improvement in fish growth compared to fish fed 24% IP diet without DAA supplementation. While, supplementation of DAA (glycine and glutamic acid) to 24% IP diet in which IAA level resorted to 120% NRC (2011) requirement, did not show a substantial impact in improving fish growth compared to fish fed 24%IP diet with IAA 120% NRC (2011) without DAA. Also, the supplementation of DAA (glycine and glutamic acid) to 24% IP diet improved some blood parameters and immune response.