fa Biology & physiology Biology & physiology The study was conducted with a completely randomized design consisting of four treatments in triplicates. Experimental diets were formulated to contain four different lipid levels (8, 10, 12 and 14%) at constant protein level (46.8%) and different gross energy of 4314, 4417, 4519 and 4622kcal/kg, respectively. Kutum fry (average weight, 203&plusmn;4mg) were randomly assigned and distributed at a density of 2 fish/l into twelve 80 liter fiberglass tanks equipped with a tap-freshwater system and water temperature of 22-24^oC. Fish were fed the experimental diets thrice a day at 10% of body weight for 81 days. Statistical analysis indicated that fish fed the lowest lipid level of 8% showed significant differences (p<0.05) with other treatments. Fish growth, survival, protein and energy retention showed a marked decrease with an increase of dietary lipid level. Crude lipid of carcass composition increased, but ash and moisture decreased with an increase of lipid levels. Rutilus frisii kutum, Dietary lipid, Nutritional performance, Feed conversion ratio 13 24 http://jifro.ir/browse.php?a_code=A-10-61-7&slc_lang=fa&sid=1 D.T. Haghighi davoudir@yahoo.com 100319475328460024085 100319475328460024085 Yes C.R. Saad 100319475328460024086 100319475328460024086 No H. Hosseinzadeh Sahafi 100319475328460024087 100319475328460024087 No D. Mansouri 100319475328460024088 100319475328460024088 No