Nutritional value of Ethyl Ester oils in fish diets: A review on their potential impact on growth and health

Summary

The Norwegian Pelagic sector plays a significant role in producing pelagic fish products for human consumption, including concentrated marine omega-3 fatty acids (FA) used in dietary supplements. To fully utilize fish sources, the sector must explore to use valuable side stream products as ingredients in aquaculture feeds, such as ethyl ester (EE) oils derived from production of concentrated omega-3 FA for dietary supplement. Despite annual production of approximately 10,000 tons of EE oils in Norway, there is limited knowledge about their suitability in aquafeeds. This knowledge gap may stem from the absence of EE in aquatic animals' natural diets, unlike in human dietary supplements. Moreover, varying FA compositions of EE oils used in different fish trials present challenges in drawing definitive conclusions about their effects. Fish metabolism differs from mammals in digesting dietary lipids, lacking the necessary lipase enzymes for monoacylglycerol production during TAG digestion. This may affect the efficiency of lipid transport and metabolism in salmonids, potentially influencing intestinal health and overall lipid metabolism. Furthermore, studies suggest lower digestibility of EE oils compared to free FA or TAG forms, indicating potential limitations in their re-esterification process in enterocytes. Concerns also arise regarding ethanol release during EE hydrolysis in the gut and its potential impact on intestinal health. Additionally, EE oils' susceptibility to oxidation suggests variations in stability in feeds depending on composition and antioxidant content. In SalmoE2, we aim to assess the safety and suitability of EE oils in salmonid diets, addressing the challenge of locally sourcing sustainable ingredients with low CO2 footprints. Understanding the effects of EE oils on salmon and trout performance, health, and fillet quality is crucial for both the pelagic industry and feed producers, optimizing the exploitation of side stream products while promoting sustainable marine product usage. Quantitative data on safety, optimal inclusion, and potential benefits of EE oil use in salmonid diets are essential.