Replacing fish oil and astaxanthin by microalgal sources produced different metabolic responses in juvenile rainbow trout fed 2 types of practical diets.

Shanli Zhu, Mark Portman, Beth M Cleveland, Andrew D Magnuson, Kun Wu, Wendy Sealey, Xin Gen Lei

Journal of animal science 2021 Jan 01

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Dietary fish oil supplementation provides n-3 long-chained polyunsaturated fatty acids for supporting fish growth and metabolism and enriching fillet with eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; c22:6n-3). Two experiments were performed as a 3 × 2 factorial arrangement of dietary treatments for 16 wk to determine effects and mechanisms of replacing 0%, 50%, and 100% fish oil with DHA-rich microalgae in combination with synthetic vs. microalgal source of astaxanthin in plant protein meal (PM)- or fishmeal (FM)- based diets for juvenile rainbow trout (Oncorhynchus mykiss). Fish (22 ± 0.26 g) were stocked at 17/tank and 3 tanks/diet. The 100% fish oil replacement impaired (P < 0.0001) growth performance, dietary protein and energy utilization, body indices, and tissue accumulation of DHA and EPA in both diet series. The impairments were associated (P < 0.05) with upregulation of hepatic gene expression related to growth (ghr1and igf1) and biosynthesis of DHA and EPA (fads6 and evol5) that was more dramatic in the FM than PM diet-fed fish, and more pronounced on tissue EPA than DHA concentrations. The source of astaxanthin exerted interaction effects with the fish oil replacement on several measures including muscle total cholesterol concentrations. In conclusion, replacing fish oil by the DHA-rich microalgae produced more negative metabolic responses than the substitution of synthetic astaxanthin by the microalgal source in juvenile rainbow trout fed 2 types of practical diets. © The Author(s) 2020. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Citation

Shanli Zhu, Mark Portman, Beth M Cleveland, Andrew D Magnuson, Kun Wu, Wendy Sealey, Xin Gen Lei. Replacing fish oil and astaxanthin by microalgal sources produced different metabolic responses in juvenile rainbow trout fed 2 types of practical diets. Journal of animal science. 2021 Jan 01;99(1)