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

Published 2024

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.