Diet supplement could turn back the clock on salmon health risks

A diet supplement already consumed by humans for its anti-ageing benefits could be used to help salmon digest feed and improve their natural disease resistance, with feed trials kicking off next month.

A team of aquaculture and veterinary experts are looking at the impact of adding spermidine – a compound found in vegetables, cereals and soybean products – into fish feed to support the breakdown of fatty acids and maintain optimal immune function in adult fish.

The project is being led by the University of Edinburgh’s Roslin Institute and recently received over £150,000 in funding from the UK Seafood Innovation Fund (SIF) with additional support from the Sustainable Aquaculture Innovation Centre (SAIC). Seafood producer Mowi and the University of Stirling’s Institute of Aquaculture are also partners in the research.

As the sector continues to move towards a spectrum of more sustainable plant-based feed ingredients, vegetable and algal oils are becoming increasingly common ingredients in farm-raised fish feeds. However, like humans, as fish age it becomes more difficult for them to break down their fat reserves into free fatty acids to be re-used, in a biological process known as lipophagy. Rather than the fat reserves being used for energy and muscle growth, they instead build up in the body and can block the immune system, making fish more susceptible to health issues.

Supplementing feeds with spermidine could ultimately maintain the sharpness of the salmon’s immune response and natural ability to fight virus-induced diseases such as cardiomyopathies, for which there is currently no vaccine available. The supplement, which is sold as an anti-ageing ingredient for people, will help to break down stored fats, giving the fish more energy and helping to maintain the balance between omega-3 and omega-6, which is important for anti-inflammatory processes. 

The potential impact spermidine has on humans has also been explored in numerous studies, including an ongoing clinical trial evaluating the effectiveness of the supplement in maintaining immune responses in elderly humans to the Covid-19 vaccination.

Kanchan Phadwal, research fellow at the University of Edinburgh’s Roslin Institute, said: “Just like humans, as fish get older and grow to their full size, their systems slow down and become weaker. Fatty acids are essential for nutrition and disease resistance but retrieval from their storage in fat tissue can be difficult, particularly when derived from plant-based oils and as fish age.

“The spermidine supplement we are planning to use will give fish a helping hand to extract the healthy fats, regulating the immune response and boosting health and wellbeing overall. It is already delivering great results for humans, and we anticipate it will have a similar impact for aquaculture.”

Heather Jones, CEO of SAIC, added: “As the sector seeks to minimise its environmental impact, sustainable feed ingredients are increasingly becoming the norm for aquaculture. But this must be balanced to ensure that we are delivering the best recipes for fish health and nutrition. This research is a great example of thinking differently, applying the ‘One Health’ approach whereby efforts are made to transfer knowledge about the health and wellbeing of one species – in this case, humans – to another, salmon.”    

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