Dietary amino acid l ‐histidine requirement of fingerling I ndian catfish, H eteropneustes fossilis (Bloch), estimated by growth and whole body protein and fat composition

Summary An eight‐week feeding trial was conducted to determine the dietary histidine requirement of Indian catfish, H eteropneustes fossilis (6.20 ± 1.25 cm, 4.65 ± 0.48 g) in 75‐L flow‐through circular troughs. Six isonitrogenous (40%) and isoenergetic (17.90 kJ g −1 ) amino acid test diets with graded levels of l ‐histidine (0.25 – 0.75%, dry diet), in gradation of 0.10% histidine were formulated. Fish were randomly stocked in triplicate groups and fed experimental diets at 4% BW per day at 08:00 and 18:00 h. Maximum live weight gain (288%), best FCR (1.40) and PER (1.78) were occurred at 0.55% dietary histidine level. For the live weight gain, FCR , PER and body protein deposition data were examined using quadratic regression analysis, the breakpoints indicating requirements for histidine at 0.58, 0.54, 0.53 and 0.54% of dry diet, respectively. Significantly (P  <  0.05) low moisture and higher whole body protein content were obtained in the 0.55% histidine diet, while body fat showed an increasing trend with the increase in dietary concentrations. Ash content remained insignificantly (P  >  0.05) low among all dietary groups, except in diet I and diet II. Based on the above results, the recommended diet for young H. fossilis should contain histidine at 0.54% of dry diet, corresponding to 1.35% of dietary protein for optimum growth and efficient feed utilization.