2019
Balancing Dietary Lipid and Cholesterol to Increase Fillet Omega-3 Deposition in Rainbow Trout Fed a Soy-Based Diet
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Contributor/Checkoff:
Soy Aquaculture Alliance
Category:
Export/Trade
Keywords:
Aquaculture
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Brian Small, University of Idaho
Co-Principal Investigators:
Ron Hardy, University of Idaho
Jeongwhui Hong, University of Idaho
Ken Overturf, University of Idaho
+2 More
Project Code:
44206
Contributing Organization (Checkoff):
Soy Aquaculture Alliance
$78,806
Institution Funded:
University of Idaho
$78,806
Brief Project Summary:

Aquaculture is often touted as a solution to ensuring enough fish protein for a rapidly increasing global population (FAO, 2014). A great deal of research in the aquaculture field now emphasizes the need to make fish farming more sustainable (FAO, 2014). A large effort in this regard is to develop feeds that reduce our reliance on capture fisheries for fish meal and fish oil. Success in this regard has brought with it a complication for human health, which is lower omega-3 (n-3) fatty acids (FA) in fish feeds leading to lower n-3 FA in the consumable flesh of the fish produced (Sprague et al., 2016). Omega-3 fatty acids, particularly EPA (20:5n-3) and DHA (22:6n-3) have been identified as...

Unique Keywords:
#aquaculture, #omega-3, #rainbow trout
Information And Results
Final Project Results

Updated February 19, 2021:
Results of the present study showed that:
1) a plant-based diet without added cholesterol resulted in reduction in growth and hypocholesterolemic effect in plasma in juvenile rainbow trout;
2) Furthermore, fish fed 100% of linseed oil with cholesterol supplementation had significantly higher weight gain and feed intake compared with other plant-based diets;
3) Cholesterol supplementation numerically increased EPA and DHA levels in fish fillet when linseed oil was provided above 50 %;
4) Growth performance on an all-plant diet high in soy protein (35%) can be achieved by supplementing with cholesterol and using a plant oil high in a-linolenic acid (ALA, 18:3n-3).

View uploaded report PDF file

We hypothesized that soybean farmers could increase the value of U.S. soybean oil by establishing soybean oil as a preferred lipid ingredient to replace fish oil in global aquaculture feeds while lowering costs and improving profits for the aquaculture industry. This hypothesis was based on our primary objective to blend soybean oil with linseed oil and supplemental cholesterol to maintain fish growth and increase de novo production of the omega-3 fatty acids (n-3 FA) EPA and DHA in trout muscle, since EPA and DHA have been identified as beneficial nutrients in human nutrition, and farmed seafood must meet consumer needs and expectations. To accomplish this, we attempted to use soy oil for it’s low phytosterol properties in combination with linseed oil for it’s n3-FA content, with and without cholesterol to improve utilization. Upon conclusion of the study, our results did not support our hypothesis. Fish fed all-plant based diets containing any amount of soy oil had reduced growth performance.

Only fish fed the all-plant diet with 100% linseed oil plus supplemental cholesterol grew as well as the fishmeal/fish oil positive control group. With regard to fillet EPA and DHA content, no improvements were seen with soybean oil. Dietary cholesterol supplementation improved plasma cholesterol levels and numerically increased EPA and DHA levels in fillets when linseed oil was provided above 50 %. Gene expression results support the fatty acid analysis, indicating no significant enhancement by soybean oil or cholesterol. Although, our hypothesis failed and soybean oil was found to be less accepted by the fish, resulting in lower growth and feed intake. We were successful in developing a high soy-protein diet (35%) with all-plant ingredients using linseed oil and supplemental cholesterol that resulted in equal fish performance to fish fed a fishmeal/fish oil control diet. More research is needed to identify a cost-effective EPA/DHA source to meet consumer needs and expectations for n-3 FA in trout fillets.

In conclusion, results of the present study showed that: 1) a plant-based diet without added cholesterol resulted in reduction in growth and hypocholesterolemic effect in plasma in juvenile rainbow trout; 2) Furthermore, fish fed 100% of linseed oil with cholesterol supplementation had significantly higher weight gain and feed intake compared with other plant-based diets; 3) Cholesterol supplementation numerically increased EPA and DHA levels in fish fillet when linseed oil was provided above 50 %; 4) Growth performance on an all-plant diet high in soy protein (35%) can be achieved by supplementing with cholesterol and using a plant oil high in a-linolenic acid (ALA, 18:3n-3)

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.