Fat requirement of hybrid Asp (Leuciscus aspius ♀) × Caspian Kutum (Rutilus frisii ♂); effect on growth and biochemical indices

This study aimed to determine the fat requirement and effect of dietary fat levels on growth and body composition indices of hybrid Asp (Leuciscus aspius ♀) × Caspian Kutum (Rutilus frisii ♂). For this purpose, 252 fish with an average weight of 29.3 ± 5.8 g were introduced in a completely randomized design with six treatments each with triplicate groups. After two weeks of adaptation, fish were fed by 6 isonitrogenic diets (40% crude protein) with different fat levels including 7, 10, 13, 16, 19 and 22%, 3 times daily according to satiation for 56 days. Some growth indices including final weight, body weight  increase, specific growth  rate, condition factor, feed conversion ratio, protein efficiency ratio, hepatosomatic index and visceral index were considered for this study. The results showed significant differences in various levels of dietary fat in feed conversion ratio and protein efficiency ratio (P<0.05). There was no significant difference on body composition, total protein, total lipid, cholesterol and triglyceride (P>0.05). From the results of the present study, it can be suggest that increasing dietary fat levels up to 16% for better growth performance of this fish.