Effect of fish oil substitutes in white fish (Coregonidae) food on growth, physiological indicators and fatty-acid lipid composition

Abstract

The results of a study on the replacement of fish oil in the feed for two-year-old whitefish with other sources of lipids have been carried out. When replacing a fifth of the fish oil (4 out of 20%) with flaxseed oil, there was no significant difference in growth, fish survival, physiological parameters, and fatty acid composition of lipids. In the following experiments, fish oil was changed to linseed, soybean, rapeseed and camelina oils. When replacing 5, 7, 10 and 15 of 20% of fish oil with flaxseed oil, the content of omega-3 acids in fish muscles increased from 9 to 27%, including the sum of long-chain acids – docosahexaenoic (DHA) and eicosapentaenoic (EPA) – from 2.4 to 23.5%, which demonstrates the ability of whitefish to transform maternal alpha-linolenic acid, which is rich in linseed oil, into long-chain polyunsaturated acids. At the same time, the amount of monounsaturated oleic acid decreased from 41.4 to 21.7%. An improvement in the fatty acid composition of feed when vegetable oils were introduced instead of fish oil indicates its low quality, as indicated by high mortality, a decrease in vitamin C, and a deterioration in the fatty acid composition of lipids in fish that received food with the highest amount of fish oil. Based on the consideration of all indicators, the best results were obtained when replacing half of the fish oil with linseed oil (10% out of 20%). At the same time, the quality of fish products was preserved. The amount of DHA and EPA in 100 g of farmed fish muscle was 0.89 g, which satisfies the daily human need for these important omega-3 acids for health. When replacing fish oil with camelina, soybean and rapeseed oils, the results were slightly worse.