Research Article
De Silva MPKSK, Senaarachch
Abstract
Effect of six diets having two lipid levels and three crude protein levels on growth and fillet composition of Genetically Improved Farmed Tilapia (GIFT) reared in cages was evaluated. Diets having Crude Protein levels (CP) 26%, 30% and 36% and Crude Fat levels (CF) (7% and 12%) were formulated. Experiment was set up according to 3 X 2 factorial designs. GIFT fingerlings (2.94 ± 1.47g) were stocked at a density of 75 fish /m-3 in net cages each having a water volume of 2 m3. Fish in quadruplicated treatments were fed with six diets for 150 days. Fish fed with 36% CP diets had significantly different (P≤0.05) values for all growth indices; Final Mean Weight, Specific Growth Rate, Feed Conversion Ratio and Net Yield while no such difference found between 26% CP and 30% CP diets for the same growth indices. Increasing fat level from 7% to 12% had no significant effect on growth performances in GIFT in any protein level diet. Diets having higher CF level (12%) had significantly affected (P≤0.05) the, CF content in fish fillets while no protein sparing seen in fish fillets. There was no marked difference in protein content in fish fillets of fish fed with 30% and 36% CP diets. Findings reveal that increased fat levels do not contribute for protein sparing of fish and the diet having 36% CP and 7% CF is suitable for the grow out phase and 36/12 for fattening phase of GIFT reared in cages.