الفهرس 
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Abstract
One hundred and eighty Nile tilapia fingerlings Oreochromis niloticus with an average initial body weight of about21.44 g (± 0.31) divided into four treatment groups and stocked into 12 glass aquaria (70 L each)with three replicates(n=15),were stocked with density of fifteen fish per aquariums. To one control diet without supplement and three control diets with feed additives Spirulina (0.2%, 0.4%, and 0.6%). Used to evaluate the growth performance and feed utilization of Nile Tilapia fingerlings (Oreochromis niloticus). The results obtained from the first experiment could be summarized as follows: Diet2 had a significant (P<0.05) effect on body weight of Nile tilapia (Oreochromis niloticus) all over the experimental period. Diet2 had a significant (P ≤ 0.05) effect on weight gain throughout the whole experimental period. Feed intake was significantly increased in fish fed on diet2 when compared with the control diet or other supplemented diet during the third month of the experimental diets. Feed conversion ratio indicates that the lower level of supplementation S. platensis in the fingerlings Nile Tilapia diet, the smaller the obtained FCR value. During the experimental period from 1st to 3rd the experimental treatments indicated significant improvement in survival %. Diet2 had significantly the highest protein intake and Protein efficiency ratio at third month and whole the experimental period. Diet2 had significantly (P ≤ 0.05) the highest values of weight gain (%) during the 1st, 2nd, 3rd and whole the experimental period. Diet2 had the highest specific growth rate (p ≤ 0.05) followed by D3 and D4 when compared with the control group (D1) at 3rd month and all over the experimental periods. Condition factor (K- value) gradually improved (P ≤ 0.05) with advantage in age and fingerlings seem to be best in Diet2 group at 3rd month of the experimental treatments and the whole periods of treatments. A significant (p<0.0001) increase in the lysozyme activity was in Diet4 compared with control group and other fish groups at the 45 and 90 day. A significant (p<0.0001) increase in the Serum total protein was Diet3 group compared with control group and other fish groups at the 45day.While, Serum total protein was Diet4 fish group significantly higher than those control group or other fish groups at the 90day. The serum globulin value of Diet3 group was significantly (p<0.0001) higher compared to other fish group at the 45day. On the other side, the serum globulin value of Diet4 was significantly (p<0.0001) higher compared to control group and other fish groups at the 90day. Fingerlings Nile Tilapia fed on control diet had the lowest protein content however; other supplemented fish with S. platensis meal appeared to improve protein content. Total bacterial count on tryptic soya broth ranged between 1.91x 105 and 3.75 x 105cfu/ml as the percentage of S. platensis meal increased the total microbial count markedly decreased. The total number of anaerobic bacteria was less than those of total microbial count and coliform group but they have the same trend of decreasing the number as the amount of S. platensis meal increased. The total number of anaerobic bacteria was ranged between0.91x 105 and 1.21 x 105cfu/ml. Fermentation of lactobacilli was significantly increase in Diet2 and Diet3 where total Lactobacillus acidophilus range from (1.91, 1.70x 105cfu/ml) for Diet3 and Diet2, respectively and total Lactobacillus cellobiosus range from (2.0, 1.79 x 105cfu/ml) for Diet3 and Diet2, respectively.