Influence of different sources and levels of dietary protein and lipid on the growth, feed efficiency, muscle composition and fatty acid profile of Snakehead Channa striatus (Bloch, 1793) fingerling

Nine isoenergetic (18.5 kJ g-1) diets were formulated, in a 3 x 3 factorial design, by varying three levels of dietary protein (350, 400 and 450 g kg-1) at each of three levels of dietary lipid (65, 90 and 115 g kg-1) accordingly. Each diet was hand fed two times daily for 8 weeks to triplicate homogenous groups of eight fish (average weight 3.34 +/- 0.02 g) per tank connected to a recirculation system. Results showed that the feed efficiency and growth performance significantly (P < 0.05) increased with increasing protein level at the two lower lipid levels (65 and 90 g kg-1), respectively, as indicated by indices such as %weight gain, specific growth rate, protein efficiency ratio, feed conversion ratio and feed intake, but did not at the highest lipid level (115 g kg-1). The muscle polyunsaturated fatty acids (PUFA) content declined with increasing dietary protein level at the lipid levels producing the highest growth, suggesting that the utilization of PUFA influences growth. Whereas the muscle monounsaturated fatty acids level was generally lower than the dietary levels in all the treatments tested, indicating preferential catabolism for energy, the muscle saturated fatty acids level was comparatively higher than in the diets, indicating selective deposition. Docosa hexaenoic acid (22:6n3, DHA), which was very low in the diet and in the initial fish, was higher in the muscle of some of the treatments, indicating the ability of Channa striatus to desaturate and elongate short-chain PUFA to long-chain HUFA, due to the availability of dietary 18:3n3 and 20:5n3 (the precursors for DHA biosynthesis). It could be concluded, based on the results of this trial, that a diet formulated to contain 65 g kg-1 lipid and 450 g kg-1 protein, with a gross energy of 18.5 kJ g-1 and a dietary n3/n6 PUFA ratio of about 0.1, is sufficient to promote good feed efficiency and growth performance in C. striatus fingerling.