Novel Omega-3 Sources in Feeds and Impacts on Salmon Health

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Dietary omega-3 fatty acids are key nutrients that have beneficial health effects playing a critical role in the immune system as well as contributing to the normal function of the heart and development of the brain. The human body is unable to produce omega-3, which is why it is important to eat these essential fats. Fish and seafood are unique sources of omega-3 in the human diet, but decline in traditional fisheries means that more than half of all fish consumed is now farmed. Until recently the only way to ensure high levels of omega-3 in farmed fish and seafood was to deliver these nutrients in feeds by using the marine ingredients, fishmeal and fish oil. However, paradoxically, they too are derived from marine fisheries that are at their sustainable limit making them finite and limited resources. The rapid expansion of fish farming in the last two decades has ony been possible with increasing dilution of the traditional marine ingredients with more economical alternatives, primarily plant meals and vegetable oils that lack the omega-3 fatty acids found in fish. Therefore, the development of these alternative feeds in Atlantic salmon (Salmo salar) farming has seen levels of omega-3 in farmed salmon halved in recent years. Dietary omega-3 are equally essential for the health of fish, just as they are for humans. Several negative issues related to farmed fish performance and health have paralleled the development of alternative, low marine feeds with reduced levels of the beneficial omega-3, including higher incidence and severity of inflammatory diseases. However, in addition, inflammation is a key component of the immune response to all pathogens, including parasitic, bacterial and viral infections and so the current low levels of omega-3 in feeds for farmed fish has had consequences for fish health and welfare. Thus, the dual impacts of reduced dietary omega-3 levels on fish health, and the nutritional quality of farmed fish products for human consumers has meant that fish farming, especially of salmon, has spearheaded efforts to both highlight and close the gap between supply and demand for the key omega-3 nutrients. Specifically, the Global Salmon Initiative announced a tender for commercial organisations to supply up to 200,000 tons annually of novel omega-3-rich oils. In addition, a consortium including The World Bank, announced the F3 (Fish Free Feed) Fish Oil Challenge to create a fish-free 'fish oil' substitute. Consequently, new sources of omega-3-rich oils from marine microalgae and genetically-modified oilseed crops have been developed and tested as feed ingredients for farmed fish, including salmon. While these studies have proved the effectiveness of these new oils in increasing omega-3 content of farmed fish, the impact on fish health has been neglected. This project will directly investigate the important health impacts of entirely novel omega-3 rich oils as feed ingredients for farmed Atlantic salmon. The studies will focus on determining not only impact of the new omega-3 sources on the response of salmon to specific disease and parasite challenges, but also on defining the biochemical and molecular mechanisms underpinning fish health, quantifying the potential of these new dietary oils for use in UK salmon farming. The proposal is timely and highly relevant and appropriate as it responds to current needs with cutting edge research to improve the quality and effectiveness of modern alternative feeds in fish farming, enhancing production and feed efficiency, while maintaining the health and improving the nutritional quality of farmed fish, delivering greater sustainability and food security.