The effect of different dietary protein and lipid levels on growth performance in Caspian Kutum (Rutilus frisii kutum, Kamensky, 1901)

A feeding trial with three protein levels (30, 35 and 40%) and three lipid levels (10, 12 and 14%) was conducted to evaluate the optimum protein and lipid ratio of Caspian Kutum (Rutilus frisii kutum). Six hundred and seventy five fish (1.15±0.01g mean ±SD) were randomly distributed in 27 aquaria (45L) and were fed four times daily for 8 weeks. Results showed that interaction between protein and lipid did not significantly affect the growth parameters. Weight increased with increasing dietary protein level up to 35%, and then decreased significantly. Specific growth rate (SGR) and average daily growth (ADG) of fish fed the diets containing 35 and 40% protein increased with increasing lipid level, but protein efficiency ratio (PER) of fish decreased with increasing dietary protein level. Fish fed the diet containing 40% protein and 10% lipid showed the lower protein productive value (PPV). Lipid efficiency ratio (LER) of fish fed the diets containing 30 and 35% protein decreased significantly with increasing lipid level (p< 0.05). Lipid production value (LPV) of fish fed the 35% protein and 10% lipid was higher than those of other treatments. Results regarding to the analysis of body compositions showed that dietary protein levels made no significant differences among treatments, but the increase of lipid level in diets led to fish body lipid increase and the highest amount of lipid were observed in fingerlings fed 35% protein and 14% lipid. Survival was 100% in all treatment. In conclusion, it appears that Caspian Kutum juveniles could adapt to 14% dietary lipid without negative effects on growth and the diet containing 35% protein with 14% lipid would be suitable for optimum growth of Caspian