Effects of Dietary Protein Levels on Growth, Body Composition and Jematological Responses of Round Batfish, ＂Platax orbicularis＂

The study was aimed to quantify the dietary optimum protein levels for juvenile round batfish, ＂Platax orbicularis＂. Experimental diets with five dietary protein levels (24, 30, 36, 42 and 48%) were each fed to triplicate groups of batfish (mean initial weight: 4.45 ± 0.10 g) in a recirculating rearing system maintained at 29 ± 1°C for 6 weeks. Weight gain and feed efficiency were highest (p ＜ 0.05) in fish fed diets with ≥42% protein, followed by fish fed the diet with 36% protein, then the fish fed the diet with 30% protein and lowest in fish fed the diet with 24% protein. Protein efficiency ratio and protein retention of the fish decreased with increasing the dietary protein level. Fish fed the diet with 24% protein showed lower red blood cell count and hematocrit values compared to other dietary treatments. When the broken-line model was employed, based on weight gain for estimating the dietary protein requirement, the optimum dietary protein level for maximum growth of juvenile round batfish is estimated to be 40%.