Effect of dietary lipid levels on growth, intestinal enzyme activity, and expression of genes involved in long chain polyunsaturated fatty acid synthesis in scale carp, Cyprinus carpio var. communis fingerlings

Abstract

Lipids play a significant role in growth and various metabolic activities in fish, inclusion of appropriate level of lipid is therefore essential in aquaculture. A 70-day feeding trial was conducted to evaluate the effect of dietary lipids levels on growth performance, hemato-biochemical parameters, serum parameters, intestinal enzyme activity, and expression of genes involved in long chain polyunsaturated fatty acids in scale carp fingerlings. Cyprinus carpio var. communis fingerlings (1.57 ± 0.02 g/fish) were fed isonitrogenous diets (428 g/kg crude protein) containing varying lipid levels (20, 40, 60, 80,100 and 120 g/kg). Fish were fed twice daily to triplicate group of 20 fish per tank at 09:00 and 16:00 hours at the rate of 4% body weight/day. The results show that growth parameters including live weight gain (LWG%), protein efficiency ratio (PER), specific growth rate (SGR%), feed conversion ratio (FCR) and proximate composition vary significantly (P < 0.05) with different dietary lipid levels. While, no significant (P > 0.05) differences in body ash content were observed among the treatments. Hematological and serum parameters also showed significant variation among the treatment. Higher enzymatic activity, with the exception of amylase, was observed at 60.0 g/kg lipid diet. Fatty acid desaturase 2 (FADS2) and elongase of very long chain fatty acids (ELOVL5) mRNA showed higher relative expression at 60.0 and 80.0 g/kg lipid fed diets, respectively. Based on the findings of quadratic regression analysis the optimal dietary requirement of linseed oil as a lipid source for maximum growth in scale carp fingerlings was established at 68.0 g/kg in presence of 20.0 g/kg of cod liver oil of dry diet.