Dietary protein and lipid concentrations affect the growth, nutritional indices, and whole-body composition of long-whisker catfish, Mystus gulio, fry

Abstract

Nine semi-purified diets with three different levels of protein (350, 400, and 450 g/kg diet) and lipid (80, 120 and 160 g/kg diet) were fed ad libitum to Mystus gulio fry (0.16 g) in triplicate groups (20 fish/replicate) for 90 days. Flow-through fiber-reinforced tanks (50 L; water flow rate of 0.5 L/min) were used for rearing the fish. Result of the experiment showed that the dietary protein, lipid, and their interactions affect significantly (P < 0.05) the weight gain, specific growth rate (SGR), protein efficiency ratio (PER), protein productive value (PPV), energy productive value (EPV), and feed conversion ratio (FCR). Among all the dietary treatment groups, the fish fed diet containing 400 g protein and 120 g lipid/kg resulted in significantly higher (P < 0.05) weight gain (4.62 g), SGR (3.77%/day), PER (1.52), PPV (23.39%), and EPV (64.74%) and lower FCR (1.64). The whole-body protein (15.28%) and lipid (5.33%) contents were significantly higher (P < 0.05) in fish fed diets containing 400 g protein and 120 g lipid/kg diet and 350 g protein and 160 g lipid/kg diet, respectively. Second-order polynomial regression analysis indicates that the optimum protein and lipid requirements of M. gulio fry are 409–411 g protein/kg diet and 122–126 g lipid/kg diet, respectively.