Dietary protein requirement for fingerling Channa punctatus (Bloch), based on growth, feed conversion, protein retention and biochemical composition

An 8-week feeding trial was conducted in a flow-through system (1-1.5 L min(-1)) at 27 degrees C to determine dietary protein requirement for Channa punctatus fingerlings (4.58 +/- 0.29 g) by feeding six isocaloric diets (18.39 kJ g(-1), gross energy). Diets containing graded levels of protein (300, 350, 400, 450, 500 and 550 g kg(-1)) were fed to triplicate groups of fish to apparent satiation at 09: 00 and 16: 00 h. Maximum absolute weight gain (AWG; 8.11 g fish(-1)), specific growth rate (SGR; 1.82%) and best feed conversion ratio (FCR; 1.48) were recorded in fish fed diet containing 450 g kg(-1) protein, whereas protein efficiency ratio (PER; 1.52), protein retention efficiency (PRE; 25%), energy retention efficiency (ERE; 78%) and RNA/DNA ratio (3.01) were maximum for the group fed dietary protein at 400 g kg(-1). Second-degree polynomial regression analysis of AWG, SGR and FCR data against varying levels of dietary protein yielded optimum dietary protein requirement of fingerling between 462.24 and 476.72 g kg(-1), whereas the regression analysis of PER, PRE, ERE and RNA/DNA ratio data showed a lower protein requirement of 438.28-444.43 g kg(-1) of the diet. Considering the PER, PRE, ERE and RNA/DNA ratio as more reliable indicators, this protein requirement is recommended for developing quality protein commercial feeds for C. punctatus fingerlings.