Managerial and nutritional study on Nile tilapta fish

A factorial experiment (2x3) was carried out to investigate the effect of stocking density (10 and 20 fish/aquarium)and organic selenium supplementation (0.0, 0.35, 0.69 mg organic selenium/kg) on growth performance traits, feed efficiency, chemical body composition, water quality and blood parameters of Nile Tilapia (Oreochromis niloticus) fish, with average initial weight of (5±0.1 g). The experiment period lasted 12 weeks from May to August, 2006. Growth performance as live body weight, average body gain, weight gain percent and specific growth rate significantly (p<0.05) increased with selenium addition. The maximum growth performance and feed intake and the lowest feed conversion ratio were obtained when fish fed diet containing 0.69 mg organic selenium/Kg. Total lipids in fish body significantly (p<0.05) decreased with the increase of organic selenium level in fish diet, while crude protein and ash content significantly increased in low stocking density (10 fish/aquarium) and the interaction between 0.35 mg organic selenium supplementation and low density. 0.69 mg organic selenium supplementation decreased serum creatinine, uric acid and alanine aminotransferase (ALT) while aspartate aminotransferase (AST) not affected. Ammonia (NH4) and Total NH4 were significantly (P<0.05) decreased with decreasing stocking density or increasing organic selenium supplementation and their interaction, while the other water quality parameters insignificantly affected. These results indicate that organic selenium can be used successfully as a feed additive for Nile tilapia fish diet. These results show that 0.6 mg organic selenium supplementation realized increases in all economic parameters (total feed cost, return from body gain and economic margin) compared with the other tested diets.