POSSIBLE EFFECTS OF FEEDING FISH THE DRIED-TREATED SEWAGE SLUDGE: I-CONCERNING GROWTH PERFORMANCE, FEED UTILIZATION AND CHEMICAL COMPOSITION

Abstract

A field study was conducted to investigate the effects of feeding fish [in a polyculture system consists of four freshwater species, namely Nile tilapia (T), silver carp (Sc), common carp (Cc), and African catfish (Cf)] the sewage (S) sludge comparing with a commercial diet for fish as a control (C) for 102days. From the obtained results, the use of sewage sludge in fish feeding led to lower growth performance. Silver carp reflected better growth performance than Nile tilapia, common carp and catfish, respectively, particularly with feeding the sewage sludge. The best feed utilization was showed by silver carp and Nile tilapia, the worst values with catfish. Nile tilapia fed the sewage sludge showed the best FCR and PER. The best chemical composition of the whole fish body was found with feeding the commercial diet (control). Catfish body contained the highest ash, CP and EC and the lowest EE among all tested fish species. Control tilapia had the lowest ash and EE contents, while highest CP and EC content was found with catfish fed the sewage sludge. Silver carp muscles contained higher DM and CP and lower ash, EE and EC contents among all fish species. The best ash, EE, and CP was determined in silver carp fed the control diet. Nile tilapia showed the highest values for condition factor, dressing and fillet percentages among the tested fish species, the lowest condition factor and dressing with catfish, and the lowest fillet with common carp. Therefore, it is not recommended to use sewage sludge in fish feeding, although its use in cultured fish feeding is wide spreading in Kafr El-Sheikh governorate.