Project Year 2017
Farmed salmon need marine omega-3
A doctoral project shows that more than 1% marine omega-3 fatty acids in feed are essential to preserve the good health of farmed salmon.
Norwegian salmon farming has more than doubled over the past ten years, resulting in increased demand for feed ingredients.
Since the supply of fish meal and fish oil is limited, current salmon feed consists of roughly 70% plant proteins and plant oils. This has led to reduced levels of healthy, marine omega-3 fatty acids in the salmon’s tissue and organs.
EPA and DHA fatty acids
The demand for fish oil resources will increase further in the future, requiring new knowledge about salmon’s minimum requirements for essential omega-3 fatty acids.
In her doctoral project, Marta Bou Mira at Nofima studied the minimum levels of marine omega-3 fatty acids in feed required to ensure good health and growth in farmed salmon. She studied two fatty acids (EPA and DHA), whose main source today is fish oil. There is limited access to fish oil in the market, meaning it is preferable not to use more than necessary in aquaculture feed.
In the doctoral work, salmon were fed from 0 to 2% EPA and DHA in feed from the juvenile stage and up to a slaughter weight of 4 kg. Bou Mira’s work shows that in purely resource-economic terms, it is profitable with up to 1% marine omega-3 fatty acids in the feed, as this provides the highest own production of omega-3 in salmon. However, trials showed that 1% EPA and DHA in the feed (the level that was previously considered adequate) is too low for the salmon to maintain good health in the demanding environment in pens at sea.
The lowest levels of omega-3 fatty acids in the feed led to structural changes in the intestine and spine and a higher mortality rate after sea lice treatment.
The content of marine omega-3 in commercial feed is well above the levels that resulted in negative effects in these trials.
IN COOPERATION WITH:
The Research Council of Norway