This study was designed to determine the maximum replacing levels of Fish Meal protein (FM) by a mixture of oil seeds mealprotein (OSM) in five ration for Nile tilapia and Grey mullet. The OSM consisted of cottonseed, sunflower, canola and linseed meals. FM in the basal diet was replaced by OSM in the ration at replacing levels of (control) 0, 25, 50, 75 and 100%. A total number of 60 fingerlings; 40 of Oreochromis niloticus monosex and 20Mugil cephalus per hapa (3*8*1 m-2.5/m 3 ) were randomly distributed into five treatments, each in two replicates. After 6 months of feeding, replacement of 50% of FM by OSM for Nile tilapia and 25% for grey mullet did not significantly affected Feed Conversion Ratio (FCR) and Protein Efficiency Ratio (PER), Crude Protein (CP) and Ether Extract (EE), while the highest replacing levels (75 or 100%) significantly (P<0.05) reduced these parameters. Growth parameters were relatively parallel to those of FCR and PER whereas, replacement up to 50% exhibited Body Weight (BW), Body Length (BL), Weight Gain (WG) and Specific Growth Rate (SGR) not differing significantly (P<0.05) from the fish fed control diet. Compared to control, increasing OSM in the ration significantly reduced Hemoglobin, Hematocrit and the activity of Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST). The incorporation of OSM in ration did not significantly affect whole-body Dry Matter (DM) and Crude Protein (CP).Based on results obtained in this study and on the economical evaluation, it could be concluded that, replacement of FM by OSM up to 50% in tilapia ration but 25% in mullet ration reduced feed costs/kg diet.

This study was conducted over 12 weeks' period in order to studythelysine requirements ofgrowing mono-sex Nile tilapia (Oreochromisniloticus). There were nine treatments (cont. T1 without lysine, T2=0.1 lysine, T3= 0.2lysine, T4=0.3 lysine, T5=0.4 lysine, T6=0.5 lysine, T7=0.6 lysine, T8=0.7 lysine, and T9=0.8 lysine). Each treatment consisting of three replicates. Initial body weight of fish was 10 g,stocking rate was10fish/aquariumand daily feeding rate was3% of fish live body weight. Fish were fed a balanced diet of 20% protein. The results indicated that the best fish production, chemical composition, and physiological status were obtained byT6 and T7 (level of the added lysine 0.5 and 0.6% of the diet, i.e. 1.74& 1.84 of the diet as total content of lysine).

This experiment was carried out to determine the effect of adding 0, 0.25, 0.50, 0.75, and 1% of dry thyme (Thymus vulgaris) and sage (Salvia officinalis) leaves to the ration of Nile tilapia (Oreochromis niloticus) on growth performance, feed and nutrient utilization, whole body composition, hematogram, protein profile and the activity of serum enzymes. Fingerlings of 15g average weight were stocked in 27 glass aquaria (105x32x40cm) at a rate of 15 fish in each. Fish in each aquarium were handly fed on the experimental pelleted feeds twice daily, six days a week at a rate of 3% of body weight daily for a period of 105 days. The results showed that, nutrient utilization, growth performance, hematogram, protein profile and activity of serum enzymes were improved with adding the thyme at level of 0.25 and 0.5% and sage at 0.5% and 0.75%. Also, fish fed rations containing 0.25,0.5, 0.75. and1% thyme or 0.75, and 1% sage had significantly (P<0.05) lower body fat, ash and energy contents but significantly (P<0.05) higher dry matter and body protein content.There were no significant mortalities among fish groups during the experimental period. Therefore, the levels of 0.25 or 0.5% thyme and 0.25, 0.5 or 0.75% sage are recommended as growth promoters for Nile tilapia due to their favorable effects on growth performance and health status.

This study aimed to evaluate replacing fish meal with graded levels of silage made from fish by-products to feed monosex males of Nile tilapia (Oreochromis niloticus). Three diets were formulated in which fish meal was replaced by fish silage (0,25,50,75, and 100%). Diets were fed to experimental groups of tilapia for 120 days. The highest total weight gain TWG (49.93 g) was recorded for fish fed the control diet (SFB0) followed by those fed the diet SFB25% (44.01g/fish), SFB50% (43.08g/fish), SFB75% (38.65g/fish) and SFB100% (36.38g/fish), respectively and the differences in weight gain among the different fingerling groups were significant (P>0.05). Moreover, the same observation was noticed for specific growth rate SGR. In addition to that, the average feed intake and feed conversion ratio and protein efficiency ratio of Nile tilapia were significantly (P<0.05) affected by the incorporation of fermented fish meal as a substitute of fish meal. The carcass composition parameters of body composition was significantly altered while no significant differences were found among all studied groups concerning the moisture content.Replacing up to 75% of FM by SFB neither affected growth performance nor health state of tilapia but, economically decreased costs of production. Even though replacing up to (100%) was economically favored and gave good growth performance but it was a source of parastic infestation adversely affecting the health condition of tilapia and was cosmopolitan rendering fish esthetically unaccepted for human consumption.