Freshwater, landlocked Grand Lake strain of Atlantic salmon (Salmo salar L.) as a potential genetic source of long chain polyunsaturated fatty acids synthesis

Authors: COLOMBO, STEFANIE - Dalhousie University; EMAM, MOHAMED - Memorial University Of Newfounland; Peterson, Brian; HALL, JENNIFER - Memorial University Of Newfounland; Burr, Gary; ZHANG, ZEYU - Dalhousie University; RISE, MATTHEW - Dalhousie University

Submitted to: Frontiers in Marine Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/2021
Publication Date: 7/7/2021
Citation: Colombo, S., Emam, M., Peterson, B.C., Hall, J., Burr, G.S., Zhang, Z., Rise, M. 2021. Freshwater, landlocked Grand Lake strain of Atlantic salmon (Salmo salar L.) as a potential genetic source of long chain polyunsaturated fatty acids synthesis. Frontiers in Marine Science. https://www.frontiersin.org/articles/10.3389/fmars.2021.641824/full.
DOI: https://doi.org/10.3389/fmars.2021.641824/full

Interpretive Summary: Selection efforts focused on adaptation to plant-based diets, particularly the ability to synthesize polyunsaturated fatty acids (PUFA), are now emerging in aquaculture. Landlocked salmon (Grand Lake population; GL) may differ from the commercial Saint John River (SJR) strain in terms of PUFA metabolism. The objective of this study was to determine if GL salmon can contribute toward broodstock selection for enhanced PUFA synthesis. Two diets containing either fish oil (FO) or plant-based oil (FO-free) were fed to the SJR and GL strains (~58 g/fish) for 16 weeks. Growth, liver, and muscle fatty acid (FA) content, and transcript expression of lipid metabolism and inflammation-related genes were evaluated. GL salmon fed the FO diet showed reduced growth compared to SJR salmon (fed either diet); however, GL salmon fed the FO-free diet, growth was not significantly different compared to any group. In liver, SJR salmon fed the FO-free diet had higher levels of n-6 PUFAs (21.9%) compared to GL fed the same diet (15.9%); while GL salmon fed the FO-free diet had higher levels of monounsaturated FAs (48.9%) compared with SJR salmon fed the same diet (35.7%). 20:5n-3 and 22:6n-3 were the same in GL and SJR salmon liver and muscle, respectively, fed the FO-free diet. Transcripts related to de novo FA synthesis, acac and acly, were higher in liver of GL salmon fed the FO-free diet compared to all treatments, while fasb was higher in GL salmon fed the FO-free diet compared to both strains fed the FO diet. These results suggest there is a genetic basis behind the potential for GL salmon to utilize plant-based diets more efficiently than SJR salmon, with regards to FA metabolism.

Technical Abstract: Selection efforts focused on adaptation to plant-based diets, particularly the ability to synthesize polyunsaturated fatty acids (PUFA), are now emerging in aquaculture. Landlocked salmon (Grand Lake population; GL) may differ from the commercial Saint John River (SJR) strain in terms of PUFA metabolism. The objective of this study was to determine if GL salmon can contribute toward broodstock selection for enhanced PUFA synthesis. Two diets containing either fish oil (FO) or plant-based oil (FO-free) were fed to the SJR and GL strains (~58 g/fish) for 16 weeks. Growth, liver, and muscle fatty acid (FA) content, and transcript expression of lipid metabolism and inflammation-related genes were evaluated. GL salmon fed the FO diet showed reduced growth compared to SJR salmon (fed either diet); however, GL salmon fed the FO-free diet, growth was not significantly different compared to any group. In liver, SJR salmon fed the FO-free diet had higher levels of n-6 PUFAs (21.9%) compared to GL fed the same diet (15.9%); while GL salmon fed the FO-free diet had higher levels of monounsaturated FAs (48.9%) compared with SJR salmon fed the same diet (35.7%). 20:5n-3 and 22:6n-3 were the same in GL and SJR salmon liver and muscle, respectively, fed the FO-free diet. Transcripts related to de novo FA synthesis, acac and acly, were higher in liver of GL salmon fed the FO-free diet compared to all treatments, while fasb was higher in GL salmon fed the FO-free diet compared to both strains fed the FO diet. Transcripts related to FA transport in liver, cd36c and fabp3b, were higher in GL salmon fed the FO-free diet compared to GL salmon fed the FO diet and SJR salmon fed either diet. Inflammation-related transcripts, lect2a and pgds, were higher in GL salmon compared to SJR salmon, fed FO-free diets. In muscle, FA desaturase encoding transcripts, fadsd5 and fadsd6b were higher in GL fed the FO-free diet compared with both strains fed the FO diet. These results suggest there is a genetic basis behind the potential for GL salmon to utilize plant-based diets more efficiently than SJR salmon, with regards to FA metabolism.