J Appl Ichthyol. 2018;34:929–936. wileyonlinelibrary.com/journal/jai | 929 © 2018 Blackwell Verlag GmbH Received: 23 July 2017 | Accepted: 25 November 2017 DOI: 10.1111/jai.13604 ORIGINAL ARTICLE Dietary niacin requirement of fingerling Channa punctatus (Bloch) S. Zehra | M. A. Khan Fish Nutrition Research Laboratory, Department of Zoology, Aligarh Muslim University, Aligarh, India Correspondence Mukhtar Ahmad 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: No. F.15-1/2014-15/PDFWM-2014-15-GE- UTT-28177 Summary A 16-week experiment was accomplished to determine the dietary niacin requirement of fingerling Channa punctatus (6.8 ± 0.92 cm; 4.65 ± 0.46 g) by feeding seven casein- gelatin based isonitrogenous (450 g/kg CP) and isoenergetic (18.39 kJ/g GE) diets with graded levels of niacin (0, 10, 20, 30, 40, 50 and 60 mg/kg diet) twice a day to apparent satiation to triplicate groups of fish. Significantly best absolute weight gain (AWG; 38.19 g/fish), feed conversion ratio (FCR; 1.42) and protein retention effi- ciency (PRE; 26.47%) were registered in fish fed 40 mg niacin/kg diet. Also, fish fed above diet exhibited maximum carcass protein. Hemoglobin (Hb), RBCs counts and hematocrit (Hct) were improved with the incremental levels of dietary niacin up to 40 mg/kg. However, liver niacin content showed the positive correlation up to 50 mg/ kg niacin and then leveled off. Fingerling C. punctatus fed niacin-free diet showed re- tarded growth, poor feed utilization, high mortality, difficult motion and skin haemor- rhage. Broken-line regression analysis of AWG, FCR and PRE indicated that fingerling C. punctatus require niacin in the range of 37.1–42.1, whereas that of liver niacin concentration indicated the niacin requirement at 52.3 mg/kg dry diet. 1 | INTRODUCTION A balanced diet is a prerequisite to maximize the growth and conver- sion efficiency in an intensive aquaculture system. Vitamins and min- erals are included in aquaculture feeds to promote optimal growth and health. Vitamins are involved in all the biological functions that allow the animals to use energy and protein for maintenance, growth, health, feed conversion and reproduction. If one or more vitamins are deficient, increase in the other nutrients will not overcome the deficiency and permit these functions to occur (Kamalzadeh, Ila, & Heydarnejad, 2009; Zehra & Khan, 2012a, 2012b). The traditionally defined water-soluble vitamins seem to be essential to all exam- ined farmed fish species so far (Waagbo, 2010). The basic roles and deficiency signs of the single vitamins are detailed in the liter- ature (Halver, 2002; NRC, 2011, Jiang et al., 2014; Xia et al., 2015; Li et al., 2016). Among these water-soluble vitamins, niacin is one of the most stable vitamins and exists in two forms, nicotinic acid and nicotinamide. Both forms are readily absorbed from the stom- ach and the small intestine. Dietary supplementation of niacin is essential for normal cell function and the development of farmed fish (Shafaeipour, Gorjipour, Kamayi, & Falahatkar, 2011). It is a vital part of the coenzymes needed to release energy from carbohydrate. Niacin is essential in the metabolism of carbohydrates, fats, and pro- teins (Halver, 2002) and, is an essential nutrient for optimal growth of aqua-species. The symptoms associated with niacin deficiency are well documented for many cultured fish species (Halver, 2002; NRC, 2011; Li et al., 2016). Consequently, supplementation of diets for intensively cultured fish with niacin is now commonplace (Jiang et al., 2014; Xia et al., 2015; Li et al., 2016). Several studies have been accomplished on niacin requirement of fish species including brook trout Salvelinus fontinalis, rainbow trout Salmo gairdneri, common carp Cyprinus carpio, channel catfish Ictalurus punctatus, Japanese amberjack Seriola quinqueradiata, hybrid tilapia Oreochromis niloticus x O. aureus, gilthead seabream Sparus aurata, African catfish Clarias gariepinus, stinging catfish Heteropneustes fos- silis, Pacific salmon Oncorhynchus kisutch (Halver, 2002; NRC, 2011), rohu Labeo rohita, mrigal Cirrhinus mrigala (Ahmed, 2011), Tilapia, Oreochromis niloticus (Jiang et al., 2014), grass carp Ctenopharyngodon