Effects of dietary protein and lipid levels on growth performance, feed utilization and carcass biochemical composition in Sobaity juvenile, Sparidentex hasta

In this study, the effects of different dietary protein and lipid levels including three dietary protein levels (35, 40 and 45%) and two dietary lipid levels (7 and 14%) were investigated on growth indices and hepatosomatic and viscera somatic index of Sobaity seabream juvenile (Sparidentex hasta) in triplicates. Fish with the mean initial weight 36.55±0.28 g were randomly introduced in eighteen 300 l polyethylene tanks and fed dietary treatments three times daily to satiation for a 56- day period. According to the results, weight gain and specific growth rate were significantly affected by different levelsof dietary protein (P<0.05). But varying levels of dietary protein and lipid had not any significant effects on condition factor, intraperitoneal fat percentage and feed intake (P>0.05). At the 14% dietary lipid level, hepatosomatic and viscera somatic index, protein efficiency ratio and carcass lipid content increased significantly(P<0.05). However, the food conversion ratio significantly decreased. With increasing the dietary lipid level, protein retention decreased and energy retention increased significantly. The highest nitrogen retention efficiency was observed at 40% protein level. Dietary protein and lipid levels significantly affected carcass protein and lipid contents (P<0.05), but had not any significant effect on moisture and ash contents (P>0.05). It was concluded that Sobaity seabream juveniles are able to utilize protein in 14% dietary lipid. Therefore, with increasing dietary lipid level to 14%, dietary protein level can be reduced to 40% in Sobaity seabream juveniles (S. hasta).