Effect of Replacement of fish oil by vegetable oils ( rice bran oil, linseed oil and Soybean oil) on fatty acid profiles of muscle, serum lipids and health parameters of rainbow trout (Oncorhynchus mykiss)

The aim of the present study was to determine the impact of replacing the fish oil by alternative lipid sources in diets for rainbow trout (Oncorhynchus mykiss) on fatty acid profiles of muscle, serum lipids and health parameters. Five isonitrogenous and isoenergetic semipurified diets were formulated containing pure fish oil (FO) as diet1 that compared to four diets: 100% rice bran oil (RBO, as diet2), 100% linseed oil (LO, as diet3), 100% Soybean oil (SO, as diet 4) and a 1:1:1:1 rice bran, linseed, soybeen and fish oil mixture (MX, as diet 5). For this, 450 fish with an initial weight of 90 ± 1g (distributed in 15 tanks) fed for 15 weeks. Fillet fatty acid composition reflected dietary fatty acid composition. The highest and lowest levels of n-3 PUFA concentrations were recorded in fish fed the LO and the RBO diets respectively. Also, the highest and lowest levels of n-6 PUFA concentrations were recorded in fish fed the SO and the FO diets respectively.The highest n-3/n-6 ratios (an indicator of food healthy),amounts 0.91 and 0.89, were in fish fed the diet3 and diet1 respectively. The difference in cholesterol and Triglycerides content of the diets seems to be too low and there were statistically significant differences in the IT and IA of muscle from diets with different lipids (p<0.05). Whereas in respect to nutritional point of view and food safety, they were in acceptable range. Providing of cheap lipid sources in fish food production, in accordance with food healthy and safety, is possible by an appropriate combination of vegetable and fish oils