Response to the ration levels on growth, body composition, energy, and protein maintenance requirement of the Indian catfish (Heteropneustes fossilis—Bloch 1974) Imtiaz Ahmed Received: 19 September 2009 / Accepted: 3 March 2010 / Published online: 30 March 2010 Ó Springer Science+Business Media B.V. 2010 Abstract An 8-week growth study was conducted to determine the effect of ration level, energy, and protein maintenance requirement of catfish, Hete- ropneustes fossilis–Bloch, fingerling (7.90 ± 0.55 cm; 3.10 ± 0.28 g) by feeding casein–gelatin-based purified diet (40% CP; 3.61 kcal g-1 GE) at six ration levels 1–6% of BW/day, at 0800 and 1700 h, in triplicate, with 20 fish per trough fitted with water flow-through system of volume 55 L. Maximum live weight gain, best feed conversion ratio (FCR), best specific growth rate (SGR), and highest protein efficiency ratio (PER) were evident for ration levels of 4–5% body weight. However, second-degree polynomial regression analysis for weight gain, FCR, PER, protein, and energy retention data indi- cated that the break-points occurred at 5.08, 4.18, 4.05, 4.16, and 4.17% BW/day, respectively. Signif- icantly (P \ 0.05) higher body protein content was recorded at 4 and 5% rations. While a linear increase in body fat content with inverse relationship in moisture content was evident with increasing rations. Ash content remained insignificantly (P [ 0.05) low at higher rations. Protein and energy retention values also produced significant (P \ 0.05) differences. Based on the results obtained, it is recommended that feeding in the range of 4 to 4.5% BW/day, corre- sponding to 1.60–1.80 g protein and 14.46–16.27 kcal energy g100 g -1 of the diet/day is optimum for the growth and efficient feed utilization of H. fossilis, while 2–3% ration levels (0.80–1.20 g protein and 7.23–10.84 kcal energy) suggest that these amounts approximate to the maintenance requirement of this fish. Keywords Heteropneustes fossilis  Nutrition  Feeding  Gross energy requirement Introduction Importance of fish as a source of high quality, balanced, and easily digestible protein as well as several other nutrients is well understood. Fish provides most of the gross and essential protein, fat, minerals, vitamins, and essential amino acids. It is excellent for growth and development of human body and prevents several nutritional deficiency diseases. Fish also have a good source of n - 3 PUFA that are considered to be important in human nutrition due to their therapeutic role in reducing certain cardiovascu- lar disorders (Lands 1986; Stickney and Hardy 1989; Sargent et al. 1989). Project supported by the Department of Science and Technology, Govt of India, New Delhi, India (Project No. SR/FT/L-57). I. Ahmed (&) DST-Sponsored Fish Nutrition Research Laboratory, Department of Zoology, University of Kashmir, Hazratbal, Srinagar, India e-mail: imtiazamu1@yahoo.com 123 Fish Physiol Biochem (2010) 36:1133–1143 DOI 10.1007/s10695-010-9391-x