Higher omega-3 in rainbow trout boosts fillet content, Nofima reports

NORWAY – New research from Nofima, a leading fisheries and aquaculture research institute, indicates that feeding rainbow trout higher levels of omega-3 increases the fatty acid content in their fillets but does not improve fish health, survival, or production performance.

The study highlights key differences between salmon and trout, showing that insights from salmon research cannot always be applied directly to other salmonid species. 

“Much of what we know about salmonids comes from salmon, but these species are not identical,” explains Marta Bou, a scientist at Nofima. “It is essential to generate species-specific knowledge for rainbow trout.”

Omega-3 fatty acids, particularly EPA and DHA, are vital nutrients for salmonids. 

While studies in salmon have demonstrated that elevated levels of these marine fatty acids can enhance robustness, growth, and fillet quality, the effects in rainbow trout under commercial sea-cage farming conditions have been less clear. 

To investigate this, Nofima partnered in research on Cargill’s licence-operated facilities run by Hofseth Aqua, examining how omega-3 affects cellular mechanisms and fillet composition.

Sea-cage feeding trials

The research involved full-scale sea-cage trials at three sites along Norway’s west coast, conducted at different times of the year. 

Rainbow trout were fed either standard or elevated omega-3 levels, and scientists monitored growth, welfare, survival, and fillet quality. 

Complementary indoor trials at Nofima’s Sunndalsøra research station compared rainbow trout and Atlantic salmon, focusing on differences in omega-3 uptake and metabolism.

The findings revealed that rainbow trout accumulate more omega-3 in their fillets than salmon when fed identical diets. 

However, unlike salmon, increasing omega-3 intake in trout did not translate to better health, survival rates, or growth performance. 

“Extra omega-3 did not provide additional production benefits for rainbow trout under these conditions,” Bou says.

Omega-3 levels meet consumer needs

The study measured fillet EPA and DHA content, showing that trout on standard feed contained around 20 mg per gram, while those on elevated omega-3 diets had approximately 26 mg per gram. 

By comparison, salmon on the same high omega-3 diet had just over 16 mg per gram. 

According to the European Food Safety Authority (EFSA), an average adult requires 250 mg of EPA and DHA daily.

“Eating 125 grams of rainbow trout fillet produced with standard feed fulfils an adult’s daily requirement,” Bou notes. “Although high omega-3 feed raises the fillet content further, it doesn’t necessarily justify the extra resource use.”

Cargill emphasises the importance of targeted rainbow trout research. 

“While salmon and trout share many traits, the knowledge transfer between species has limits,” says Terje Utne, head of field trials at Cargill. “This project highlights why investing in rainbow trout-specific studies is critical.”

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