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Federal Research Center 
"Krasnoyarsk Science Center of the Siberian
Branch of the Russian Academy of Sciences"

 Федеральный исследовательский центр «Красноярский научный центр Сибирского отделения Российской академии наук»

Federal Research Center 
"Krasnoyarsk Science Center of the Siberian
Branch of the Russian Academy of Sciences"

Farm-raised trout turned out to be more useful than wild species

9 June 2022 г.

Искусственно выращенная форель оказалась полезнее дикой
Scientists found differences in the composition and content of fatty acids in different rainbow trout strains. At the same time, fish from the farm turned out to be richer in fatty acids than wild trout. One of the trout strains from the farm was able to regulate its fatty acid composition regardless of its content in the feed, which makes it possible to selectively breed trout with higher nutritional value. The results of the study are published in the journal Aquaculture.

Long-chain polyunsaturated fatty acids (PUFAs) of the omega-3 family, such as eicosapentaenoic (EPA) and docosahexaenoic (DHA), are important for human health, in particular, for the prevention of cardiovascular diseases. Currently, humanity is deficient in omega-3 PUFAs. The main dietary source of polyunsaturated fatty acids for humans is fish, such as trout. However, the content of polyunsaturated fatty acids in salmon aquaculture has recently been declining due to the replacement of deficient fish oil in feed with vegetable oils. One of the ways to increase the nutritional value of fish is selective breeding and raising fish strains in aquaculture which are able to synthesize polyunsaturated fatty acids despite vegetable oils in the diet.

A team of scientists from Krasnoyarsk and Moscow, including researchers of the Krasnoyarsk Science Center SB RAS, found differences in the composition and content of fatty acids in different strains of the rainbow trout Oncorhynchus mykiss. Aquaculture-raised fish species were found to be richer in fatty acids than their wild counterparts. And the Steelhead breed, among other things, is able to regulate its fatty acid composition, providing the possibility of selective breeding of trout with a higher nutritional value for humans.

The scientists compared the composition and content of fatty acids in the fillets of seven farm-raised rainbow trout strains and one wild trout caught in the western part of the Kamchatka Peninsula. They considered fish of different strains, having both similar diet and different one.

The analysis confirmed that the content of fatty acids in fish depends on what the fish was eating and what additives, in particular, vegetable or animal oils were present in the diet. For example, the Adler and Adler Amber breeds raised on vegetable oil diet had lower levels of EPA and DHA. The scientists also found that not only the composition of the diet, but also genetics can affect the composition of fatty acids. For example, Steelhead rainbow trout can retain high levels of eicosapentaenoic and docosahexaenoic acids despite the diet composition.

In addition, the researchers determined that fatty acid composition could be a "marker" to distinguish between wild and farm-raised rainbow trout. All farm-raised fish had higher levels of EPA and DHA than wild fish. The researchers also found less oleic acid in wild fish compared to that in farm-raised ones. They attribute this to the fact that on the farm, trout are limited in swimming and spend less oleic acid for energy, retaining and accumulating it.

“The content of eicosapentaenoic and docosahexaenoic acids is the main indicator of the nutritional value of fish for humans. In addition to lipids, fish products are a valuable source of other nutrients such as amino acids. However, fish provides only about 6% of all animal and vegetable protein consumed by humans, while fish-derived eicosapentaenoic and docosahexaenoic acids account for over 97% of these essential nutrients in the human diet. Genetic factors contribute significantly to the fatty acid composition of trout. Also, contrary to a popular belief in the higher nutritional value of wild fish, in our study wild rainbow trout had significantly lower EPA and DHA content, and thus lower nutritional value than farm-raised trout. Among farmed fish, Steelhead trout had the highest content of EPA and DHA in biomass and the ability to regulate the composition of fatty acids, regardless of their amount in their diet. Thus, we can consider this breed more suitable for raising on feed with a high content of vegetable oils and recommend selective breeding of this line of rainbow trout with a high content of EPA and DHA,” said the Principal Investigator, Corresponding Member of the Russian Academy of Sciences, Doctor of Biology Mikhail Gladyshev, Head of the Laboratory of Experimental Hydroecology of the Institute of Biophysics SB RAS, Head of the Department of Terrestrial and Aquatic Ecosystems of the Siberian Federal University.

The work was supported by the Krasnoyarsk Regional Science Foundation (No. 2021020207159).




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