Aquaculture Nutrition. 2017;1–8. wileyonlinelibrary.com/journal/anu | 1 © 2017 John Wiley & Sons Ltd Received: 28 July 2016 | Accepted: 31 January 2017 DOI: 10.1111/anu.12555 ORIGINAL ARTICLE Dietary riboflavin requirement of fingerling Channa punctatus (Bloch) based on growth, conversion efficiencies, protein retention, liver riboflavin storage, RNA/DNA ratio and carcass composition Seemab Zehra | M.A. Khan Fish Nutrition Research Laboratory, Department of Zoology, Aligarh Muslim University, Aligarh, India Correspondence Mukhtar A. Khan, Fish Nutrition Research Laboratory, Department of Zoology, Aligarh Muslim University, Aligarh, India. Email: khanmukhtar@yahoo.com Funding information UGC Women PDF, Grant/Award Number: F.15-1/2014-15/PDFWM-2014-15-GE- UTT-28177 Abstract A 16-week experiment was conducted to determine the dietary riboflavin require- ment of the fingerling Channa punctatus (6.7 ± 0.85 cm; 4.75 ± 0.72 g) by a feeding casein–gelatin-based (450 g/kg crude protein; 18.39 kJ/g gross energy) purified diet containing graded levels of riboflavin (0, 2, 4, 6, 8, 10 and 12 mg/kg diet) to triplicate groups of fish near to satiation at 09:30 and 16:30 hr. Absolute weight gain (AWG), protein efficiency ratio (PER), specific growth rate (SGR, % per day), protein retention efficiency (PRE%) and RNA/DNA ratio were positively affected by increasing concen- trations of dietary riboflavin to 6 mg riboflavin per kg diet. Feed conversion ratio (FCR) decreased up to 6 mg riboflavin per kg diet but did not decrease further with higher riboflavin supplementation. Hepatic thiobarbituric acid-reactive substance (TBARS) concentration also supported the pattern of FCR, whereas superoxide dismutase and catalase activities increased with increasing concentrations of dietary riboflavin from 0 to 6 mg/kg. Liver riboflavin concentrations increased with increasing levels of ribo- flavin up to 8 mg/kg diet. Broken-line regression analysis of AWG, PRE and liver ribo- flavin concentrations of fingerling C. punctatus with dietary riboflavin level indicated optimum growth and liver riboflavin saturation at 5.7, 6.1 and 7.7 mg riboflavin per kg diet, respectively. KEYWORDS Channa punctatus, fingerling, growth, requirement, riboflavin, thiobarbituric acid-reactive substance 1 | INTRODUCTION One of the important cultivable indigenous finfishes which deserves immediate attention for commercial-scale seed production and farm- ing is the snakehead, Channa punctatus. Provision of nutritionally complete feeds is a bottleneck in the intensive culture of this fish. For intensive culture of this species, quality feeds with all the essential nutrients such as vitamins must be developed. Vitamins are not syn- thesized in the body and hence must be supplied by the diet (NRC 2011). Their supplementation in fish diets has been used widely to im- prove fish production in aquaculture. Vitamins improve the immunity system, meat quality, survival, growth, resistance against diseases and stressors, fecundity, and reproductive efficiency (Racotta et al., 2004; Sharifzadeh, Khara, & Ghobadi, 2015). Unlike other groups of nutri- ents, vitamins are not chemically similar to each other. Each vitamin has a specific chemical structure and a specific function in the living system. Most of the vitamins act as coenzymes in the body and a well- balanced diet requires all the necessary vitamins in sufficient quantity (Halver, 2002). Riboflavin is a water-soluble vitamin that functions primarily as a component of two flavin coenzymes such as flavin mononucleotide and flavin adenine dinucleotide. These coenzymes are essential components