Supplemental Microalgal DHA and Astaxanthin Affect Astaxanthin Metabolism and Redox Status of Juvenile Rainbow Trout

Authors: WU, KUN - Cornell University; PORTMAN, MARK - Us Fish And Wildlife Service; SEALEY, WENDY - Us Fish And Wildlife Service; Cleveland, Beth; LEI, XIN GEN - Cornell University

Submitted to: Antioxidants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2020
Publication Date: 12/27/2020
Citation: Wu, K., Portman, M., Sealey, W., Cleveland, B.M., Lei, X. 2020. Supplemental microalgal DHA and astaxanthin affect astaxanthin metabolism and redox status of juvenile rainbow trout. Antioxidants. 10(1):16. https://doi.org/10.3390/antiox10010016.
DOI: https://doi.org/10.3390/antiox10010016

Interpretive Summary: Expansion of the aquaculture industry will require utilization of sustainable feed ingredients to replace those of marine origin. Algal-based feed ingredients show potential to fit this need, particularly since they can be engineered to benefit fish health. This study investigated how the antioxidant status of rainbow trout is affected by replacement of fish oil and synthetic astaxanthin (AST) with a more sustainable high-omega-3 algal meal and algal AST. Results indicated that algal meal inhibited tissue AST enrichment and reduced the antioxidant defense system of the fish, although without consequence on markers of oxidative stress. In addition, algal AST showed higher degradation rates which reduced tissue AST enrichment but did not affect antioxidant status. These findings suggest that algal AST is not as effective at pigmenting fillets as synthetic AST. Furthermore, replacement of fish oil with algal meal may reduce the antioxidant defense system, indicating that further refinement of algal-based ingredients is needed prior to their use in aquafeeds.

Technical Abstract: Algae-based oil and astaxanthin (AST) are now increasingly recognized as substitute for traditional fish oil/synthetic AST, which contribute to solving the issues of finite fish oil supply and chemical AST safety. This study focused on AST enrichment and redox status affected by supplemental microalgal DHA and AST in rainbow trout. A total of 612 juvenile rainbow trout were randomly assigned to 36 tanks (three tanks per treatment, 17 fish per tank) for sixteen-week feeding trials. The diets containing two protein sources (fishmeal or plant meal), two AST sources (synthetic astaxanthin or algae-based astaxanthin), and three levels of fish oil substitution with algal oil (0%, 50% or 100%). In the present study, high level of algae DHA replacement generally inhibited AST enrichment, independent of AST source, and down-regulated the activity and expression of several antioxidant proteins. Despite that algae AST showed lower deposition efficiency than synthetic AST, likely due to increased metabolism of AA, data supported that dietary AST source was not a significant regulator of the antioxidant defense system. However, a higher concentration of AST could improve antioxidant capacity by enhancing antioxidant activities and the expression of antioxidant genes.