Effects of dietary protein and lipid levels on growth, body composition and flesh quality of juvenile topmouth culter,Culter alburnusBasilewsky

Abstract

Nine experimental diets at three protein (35%, 40% and 45% crude protein) and lipid (5%, 8% and 11% crude lipid) levels with variable digestible protein to digestible energy (DP/DE) ratios ranged from 21.9 to 27.8 g protein MJ−1 were fed to topmouth culter (Culter alburnus Basilewsky) fingerlings (initial weight 6.5 ± 0.9 g) in triplicated groups (30 fish per replicated) for a period of 10 week to assess the optimum dietary DP/DE ratio and the protein sparing effect by utilizing dietary lipid. 27 cages of 1.5 m3 capacity placed in a lake located in Wuhan were used for rearing the fish. At the end of the experiment, maximum weight gain and thermal-unit growth coefficient was found in fish fed diet D4 with 45% protein, 8% lipid and P/E ratio of 26.2 g protein MJ−1, but without a significant difference compared to fish fed diet D5 with 40% protein, 8% lipid and DP/DE ratio of 25.3 g protein MJ−1. The best flesh quality evaluated by muscle collagen content was found in fish fed D5. High fat accumulation with increasing dietary lipid levels was observed in whole body but not in muscle tissue. Hence, it may be concluded that the optimum formulation for maximum growth and quality of topmouth culter is a diet containing 40% protein and 8% lipid with a resultant DP/DE ratio of 25.3 g protein MJ−1. In addition, the protein sparing effect by inclusion lipid was observed but limited.