عنوان مقاله [English]
In this study three digestible energy levels at constant protein level of 35% were utilized. Diets were made in semi purified that in all of them fish meal, casein and gelatin as the sources of protein and dextrin, starch and oil as the sources of energy were used. Each of experimental diets was fed to triplicate groups of 20 fish with an average individual weight of 81.5g in 3 2000/L, flow through fiberglass tanks that each of tanks divided exactly into three parts by polyethilen plastic net. During this experiment water temprature, dissolved oxygen, pH and EC were 15± 2’C, 6-8.5 mg/l, 7.5-8.8 and 25400pm Cm respectively. The diets were fed at a rate between 1.6-2% wet body weight per day, depended to water temperature, in three equal rations and adjusted two weekly for 84 days. Weight gain (WG%), average daily growth percent (ADG%), protein efficiency ratio (PER), apparent net protein utilization percent (ANPU%) or protein deposited percent (PD%), specific growth rate (SGR) were found to increase and food conversion rate (FCR) was found to decrease with an increasing energy levels from 370 to 430 Kcal/100g. The best growth performance was attained by fish fed a 35% protein and 430 Kcal/100g digestible energy (crude lipid 19.8%). Fat and moisture of carcass were affected by energy levels of test diets, while protein and ash of carcass were relatively constant in different treatments.