Effect of dietary lipid and protein levels with different protein to energy ratios on growth performance, feed utilization and body composition of R utilus frisii kutum (Kamenskii, 1901) fingerlings

A 3 × 5 factorial design including three lipid levels (100, 130 and 180 g kg −1 diet, based on dry matter) and five dietary protein levels (370, 420, 470, 520 and 570 g kg −1 diet, based on dry matter) was conducted to investigate the optimum dietary lipid and protein requirements for R utilus frisii kutum fingerlings. Triplicate groups of 80 kutum (500 ± 60 mg initial weight) were stocked in 250‐l tanks and fed to apparent satiation thrice daily for 8 weeks. The results showed that the growth performance and feed utilization were significantly ( P  < 0.05) affected by dietary protein and lipid levels. Weight gain, specific growth rate and feed conversion ratio of kutum improved significantly with increasing protein level from 370 to 470 g protein kg −1 diet, but there was a significant decrease in growth parameters with increasing protein level from 470 to 570 g protein kg −1 diet. Also, the higher values of weight gain, specific growth rate and better feed conversion ratio were observed for fish fed diets containing 130 g kg −1 lipid diet. The results of this study showed that diet containing 420 g kg −1 protein and 130 g kg −1 lipid with a P:E ratio of 19.22 mg protein kJ −1 of gross energy is optimal for kutum fingerlings.