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Study reveals candidate genes to improve Atlantic salmon fatty acid composition through selective breeding

St. Andrews, New Brunswick, Canada – January 7, 2025

Most are familiar with the term ‘fatty acids’ from widespread media coverage and various recipe/health publications given their requirement for normal cellular development and other biological functions. There are three categories of naturally occurring fatty acids: saturated FAs (SFAs), monounsaturated FAs (MUFAs), and polyunsaturated FAs (PUFAs). Perhaps the most famous of the PUFAs is omega-3 – a member of the n-3 and n-6 fatty acids, which humans are unable to produce on our own and must acquire from our diet. These two groups of essential fatty acids provide opposing health benefits with n-3 enhancing anti-inflammatory properties important for wound healing and reducing the risk of certain diseases and cancers while the pro-inflammatory properties of n-6 are important to protect the body against certain pathogens, infections and injury.

Marine fish species, including Atlantic salmon, are well known to be major dietary sources of nutritional and digestible fatty acids. Surprisingly, there have been limited studies globally focused on fatty acid heritability and genomic structure in Atlantic salmon. These attributes have never been reported until now for North American-origin Atlantic salmon given its different number of chromosomes compared to its European-origin counterpart.

Researchers from Huntsman Marine recently published results from a study that quantified 35 fatty acids and searched for candidate genes associated with each of them from Atlantic salmon fillets sampled following commercial culture of the fish.

“Common Atlantic salmon marketing efforts focus on its high nutritional value, including as a source of essential fatty acids such as omega-3, and we wanted to determine whether any of these fatty acids were heritable and associated with specific genes to allow for more efficient selective breeding in the future,” explained Dr. Barbara Langille, Huntsman Marine Associate Research Scientist and lead author of the recent publication in the international peer-reviewed journal BMC Genomics.

Under the direction of Huntsman Marine, Atlantic salmon families were created in a partial factorial design using 56 females (dams) and 38 males (sires) as part of a commercial breeding program. All families were combined post-hatch then communally reared in a commercial hatchery before stocking approximately 11,500 fish into a single sea cage for commercial grow out until harvested. A fish fillet portion from a sub-set of 208 salmon representing 60 families were sampled and shipped to the Agriculture and Agri-Food Canada-Lacombe Research and Development Centre (Lacombe, Alberta) to quantify 35 fatty acids from each fillet and five calculated traits (SFA, MUFA, PUFA, n-3 and n-6).

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The total amount of fatty acids in an Atlantic salmon fillet had a wide range between 0.04 and 41.3 mg per gram of flesh. Three fatty acids were present in the largest quantities with palmitic acid (a SFA), oleic acid (a MUFA) and linoleic acid (a PUFA) combining to account for almost 70% of the total fatty acid content of the salmon fillets. In contrast, 19 other fatty acids were present in trace amounts and accounted for less than 0.5% of the total fatty acid content. Based on the study results, Atlantic salmon is a better source of PUFAs compared to other livestock animals and contains a more balanced contribution across all fatty acids compared to other fish species.

The wide range in specific fatty acid content was reflected in their moderate to high genomic heritability suggesting that selection for improved fatty acid content is possible for most all fatty acids within a breeding program. An important observation from the study was that bled weight and total fat both had a high positive correlation to fatty acid content. This is important since weight (growth) is often an important trait of interest within family-based breeding programs and selecting for growth should therefore also provide meaningful benefit to the fatty acid content of cultured Atlantic salmon.

The same genomic peak for three fatty acids was present on Chromosome 23 (including γ-linoleic acid, stearidonic acid and dihimo-γ-linolenic acid). Three genes – sin3b, acbd6 and fads2 – coincide with this chromosomal location and functionally involved in lipid metabolism. Five other fatty acids were associated with genetic markers on different chromosomes that have genes associated with fatty acids and adipose cells. Otherwise the vast majority of studied fatty acids had no clear association with any specific chromosomes or genes. These results suggest fatty acid composition in Atlantic salmon is generally a polygenic trait that may be controlled by many genes of small effect with a few major genes. The few genes identified in the publication are ideal candidates for future functional studies as it relates to fatty acid composition.

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“We are pleased with results from this study as they provide important baseline data related to fatty acid content in Atlantic salmon at a time when the industry continues to make considerable diet formulation improvements,” concluded Langille. “Atlantic salmon provides consumers with a highly nutritious source of essential fatty acids and now we also better understand how selective breeding may be used to increase these dietary benefits in the future.”

The research publication was co-authored by researchers at the Agriculture and Agri-Food Canada Lacombe Research and Development Centre (Lacombe, AB), Mowi Genetics AS (Bergen, Norway) and Tri-Gen Fish Improvement Ltd. (Lacombe, AB). The study was funded by the Atlantic Canada Opportunities Agency (ACOA) Atlantic Innovation Fund, New Brunswick Innovation Foundation (NBIF) Research Innovation Fund, Genome Canada & Genome Atlantic, and industry partners.

Research Publication: 

Langille, B.L., M. Juárez, N. Prieto, S. Boison, P. Sae Lim, B.D. Swift and A.F. Garber. 2024. Candidate genes associated with fatty acid compositions in north American Atlantic salmon (Salmo salar). BMC Genomics 25: 1208. https://doi.org/10.1186/s12864-024-11131-2

Image 1: Huntsman Marine research staff completing an Atlantic salmon harvest evaluation within a commercial processing plant.

Image 2: Atlantic salmon fillets assessed during a harvest evaluation within a commercial processing plant.
 

Story by Bud Adams, The Huntsman Marine Science Centre.  

For additional information or images relating to this article, please email huntsman@huntsmanmarine.ca. 

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