«We need more omega-3 sources in salmon feed,» says scientist Katerina Kousoulaki, who researched heterotrophic microalgae as a feed ingredient (photo: Terje Aamodt/Nofima).

Project Year 2014

Microalgae as salmon food?

Nofima scientists have concluded that microalgae meal could replace fish oil as feed for young salmon.

The aquaculture industry needs to access large volumes of new omega-3 sources for use in salmon feed. Fish oil is an ideal source of omega-3, but if salmon is to remain a rich source of omega-3 itself, it will not be possible to produce more farmed salmon with fish oil as the main source of omega-3.

«We need more sources of omega-3, and at the moment we have few other real alternatives to heterotrophic microalgae for high production. The algal flour we have tested has nutrients that salmon need. We have succeeded in liberating and keeping these important nutrients during the process of making feed, which means that it will be possible to use this ingredient in salmon feed,» says Scientist Katerina Kousoulaki.

Heterotrophic algae are single-celled algae that grow in oxygen and a carbon source (such as by-products of plants). Stable, sterile biomass can be produced from heterotrophic algae in great quantities. With today’s technology, this can be produced much more efficiently than phototrophic microalgae, which grow needing light, minerals and CO2.

Kousoulaki of Nofima and colleagues from the Feed Technology Centre in Bergen have tested microalgae meal to see how it affects the salmon’s health, performance and nutrition. Microalgae meal from Alltech, one of the world’s largest animal health and nutrition companies, is very rich in the healthy marine omega-3 fatty acid DHA, which represents more than a quarter of the fat in the microalgae.

Feed with and without microalgae was used in the trials. The microalgae feed was given to young salmon from about 200 grams for twelve weeks in the sea. The content of long-chain marine omega-3 fatty acids in the fillet was higher for salmon that had received algal meal in their feed than for salmon that had been fed with fish oil as the only source of these fatty acids. The feed containing algae produced salmon fillets of equal quality to fish oil. The fillets were equally firm in their structure, had the same amount of fluid loss and just as small gaps between the muscle fibres.

The conclusion is that the microalgae meal is a very good source of omega-3 for young salmon and it can replace fish oil in feed.


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