Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Animal Production

In order to develop Economic and eco-friendly feeds for Nile tilapia and African catfish three experiments were conducted. Experiment 1, five isocaloric, isonitrogenous practical diets contain 30% crude protein and 7% crude lipid were formulated. Diets utilized were; control (C), 50% replacement soy meal (GMS50), 100% replacement soy meal (GMS100), 50% replacement fish meal (GMF50)and 100% replacement fish meal (GMF100) as the predominant protein source. The fish were stocked into 15 plastic tanks of 50 L capacity with 15fish of uniform size (6.5 g) each. At the end of the trial, fish were euthanized individually. The best productive values in terms of final body weight (FBW) were recorded for Nile tilapia fed the control and GMS50 treatments which were clearly superior to the other experimental diets. Fish fed the GMF100 diet recorded the lowest final body weight (P{u2264}0.05). Fish fed GMF100was significantly reduced FI (19.55 g) (P{u2264}0.05)compared to other treatments .The best FCR values were observed for fish fed the control and GMS50 diets (1.72 and 1.91 respectively), while the worst values (P{u2264}0.05) were recorded for the GMF50 (2.84) and GMF100 (3.64) diets. Concerning the influence of diets on the proximate composition of whole-body fish appeared decreasing EE% with increase guar % in diets. Experiment 2, two isocaloric, isonitrogenous practical diets contain 35% crude protein and 15% crude lipid were formulated. The production diet utilized soy oil (SBO) as the predominant lipid source, whereas the finishing diet contained fish oil (FO), to generate two distinct dietary FA profiles

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