Abstract
The effects of ration levels on growth, conversion efficiencies and body composition of fingerling Heteropneustes fossilis (6.8 +/- A 0.04 cm, 5.0 +/- A 0.02 g) were studied by feeding isonitrogenous (40% crude protein) and isocaloric (19.06 MJ kg(-1) gross energy) diets representing 1, 3, 5, 7 and 9% of the body weight (BW) day(-1) to triplicate groups of fish . Growth performance of the fish fed at the various ration levels was evaluated on the basis of live weight gain percentage (LWG%), feed conversion ratio (FCR), specific growth rate percentage (SGR%), protein retention efficiency (PRE%) and energy retention efficiency (ERE%) data. Maximum LWG% and SGR were obtained at a feeding rate of 7% BW day(-1), whereas best FCR (1.6), PRE% and ERE% were recorded at a feeding rate of 5% BW day(-1). Maximum body protein was also obtained for the group receiving the diet representing 5% of their body weight. However, a linear increase in fat content was noted with the increase in ration levels up to 7% BW day(-1). The SGR, FCR, PRE and ERE data were also analyzed using second-degree polynomial regression analysis to obtain more precise information on ration level, with the results showing that the optimal ration for these parameters was 6.8, 6.1, 5.9 and 6.2% BW day(-1), respectively. Based on the above second-degree polynomial regression analysis, the optimum ration level for better growth, conversion efficiencies and body composition of fingerling H. fossilis was found to be in the range of 5.9-6.8% of the BW day(-1), corresponding to 2.36-2.72 g protein and 88.20-101.66 MJ digestible energy kg(-1) diet day(-1).