Abstract
Effects of varying protein-to-energy (P/E) ratios on growth performance, nutrient retention, body composition, and digestive enzyme activities of Singhi, Heteropneustes fossilis (7.90 +/- 0.40 g; 9.40 +/- 0.20 cm) were evaluated. Six experimental diets (350Low, 350High, 400Low, 400High, 450Low, and 450High) in a 3 X 2 factorial design were formulated to contain three protein levels (350, 400, and 450 g/kg crude protein) and two energy levels (4.07 and 4.54 kcal/g gross energy [GE]) to provide six different dietary P/E ratios (86.1, 77, 98.3, 88, 110.6, and 99 mg protein/kcal GE). The diets were hand-fed to triplicate groups of fish for 84 d to apparent satiation at two feeding frequencies. Live weight gain, feed conversion ratio, protein retention efficiency, energy retention efficiency, somatic indices, and digestive enzyme activities were maximized by the groups fed on 400 g/kg protein with 4.07 kcal/g GE in diet 400Low with a P/E ratio of 98.3 mg/kcal energy. The results indicate that 400 g/kg of dietary protein and 4.07 kcal/g of dietary GE with a P/E ratio of 98.3 mg protein/kcal energy is optimum for achieving efficient growth, feed conversion, and nutrient retention in H. fossilis.