Effect of dietary protein and energy levels on growth of juvenile orange-spotted grouper‎, Epinephelus coioides‎

In order to evaluate the protein and energy requirement of orange-spotted grouper، Epinephelus coioides fingerlings، nine semi-purified experimental diets containing 3 levels of crude protein (40%، 50% and 60%) and 3 levels of diegestible energy (DE، 14، 16 and 18 KJgr-1)، in a flow-throught system (2 Litmin-1) at 24.32 1.11 C were tested. For 8-weeks، Triplicate groups of 20 fish (16.79 .4 gr) were each stocked in 300 L circular polyethylene tanks and were fed the experimental diets to approximate satiation، twice daily. Results showed that the survival rate، hepatosomatic index (HSI) and condition factor (CF) were independent of the dietary treatments، but final weight، weight gain، specific growth rate(SGR)، feed efficiency (FE)، feed conversion ratio (FCR)، protein efficiency ratio (PER) and daily feed intake (DFI) were significantly affected by protein and digestible energy levels. Diet 5 (50%CP and 16 KJ/gr DE) was the preferred diet and resulted in the best growth performance، feed and protein efficiency and nutrient utilization among the examined diets. DFI was the lowest for diet with the highest protein (60%) and energy (18 KJgr-1). Apparent net protein utilization (ANPU) varied insignificantly (P0.05) between the treatments. viscerosomatic index(VSI) increased significantly with increasing dietary energy concentrations. Body lipid، ash and moisture contents were affected by dietary protein and energy levels (P0.05). Body lipid content increased with increasing dietary energy levels، but carcass ash and moisture decreased with increasing dietary energy levels. Body protein content was not affected by dietary energy level، but significantly increased with the increase of protein from 40 to 50% at same energy levels. The study revealed that fingerlings of orange-spotted grouper، E. coioides performed best a diet containing 50% crude protein، 16 KJgr-1 diegestible energy and a P/DE ratio، 31.25 mgkJ-1. Key words: Epinephelus coioides، protein، energy، growth، feed utilization، body composition