Evaluation of graded levels of soy oil as a fish oil replacement in high soy protein feeds for juvenile red drum, Sciaenops ocellatus

Authors: WATSON, AARON - South Carolina Department Of Natural Resources; NAPOLITANO, MICHAEL - South Carolina Department Of Natural Resources; SCHOCK, TRACEY - National Institute Of Standards & Technology (NIST); BOWDEN, JOHN - National Institute Of Standards & Technology (NIST); Frost, Jason; YOST, JUSTIN - South Carolina Department Of Natural Resources; DENSON, MICHAEL - South Carolina Department Of Natural Resources

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2020
Publication Date: 6/26/2020
Citation: Watson, A., Napolitano, M., Schock, T., Bowden, J., Frost, J.B., Yost, J., Denson, M. 2020. Evaluation of graded levels of soy oil as a fish oil replacement in high soy protein feeds for juvenile red drum, Sciaenops ocellatus. Aquaculture. 529. Article 735627. https://doi.org/10.1016/j.aquaculture.2020.735627.
DOI: https://doi.org/10.1016/j.aquaculture.2020.735627

Interpretive Summary: As the world population increasingly relies on aquaculture for sources of healthy protein, the aquaculture industry is transitioning away from costly feed ingredients with finite production, such as fishmeal and fish oil. Looking to replace fishmeal and fish oil with sustainable products, soybeans have been proven to be a viable candidate for both for several reasons including high protein and oil levels that can be utilized by fish. Red drum, Scianepos ocellatus, is a hardy marine species that has potential to become a prime species for aquaculture. This study was to evaluate the use of soy oil as a dietary fish oil replacement in diets that contained three different primary protein sources, fishmeal, soybean meal, or soy protein concentrate. Growth performance and dietary utilization parameters were evaluated in the fish along with tissue fatty acid ratios and the expression of lipid related processing genes. Better growth was observed in the fish that received diet fish the soy bean meal primary protein diet containing 50% fish oil replacement. All the other diets performed similar to the fishmeal control diet. Overall, the six soy protein, fishmeal-free formulations performed equivalently or better than the fishmeal references with up to 50% of fish oil replaced by soybean oil.

Technical Abstract: A 9-week feeding trial was conducted with juvenile red drum, Sciaenops ocellatus, to evaluate the use of soy oil as a fish oil replacement. Three primary protein sources (fishmeal - FM, soybean meal - SBM, and soy protein concentrate - SPC) were utilized with 100% fish oil (FM, SBM, SPC), 75% fish oil (SBM, SPC), or 50% fish oil (FM, SBM, SPC) as the lipid source. Traditional growth and performance metrics (specific growth rate, feed consumption, feed conversion ratio) were tracked and tissue samples (liver, muscle, plasma, adipose, and brain)were collected for gas chromatography-based fatty acid profiling. Ten lipid metabolism related genes were analyzed for potential expression differences between dietary treatments in liver and muscle tissues and whole body and fillet tissues were sampled for proximate composition analyses. Forty- four fatty acids were measured by gas chromatography-flame ionization detector and evaluated with principle component analysis and ANOVA to understand the dietary influence on lipid metabolism and health. Significant differences in growth rate were observed with the SBM 50% fish oil diet outperforming the FM 100% fish oil reference diet. All other soy protein-based diets performed statistically equivalent to both FM reference diets (100% and 50% fish oil) in regard to growth, however all soy protein-based formulations had significantly lower feed conversion ratios than the fishmeal-based references. Gene expression differences were not significant in most cases, however often trended similarly as the observed performance. Fatty acid profiles differed as a function of oil source, with no apparent influence by protein source, with C18:2n-6 being-the primary differentiator. Overall, the six soy protein, fishmeal-free formulations performed equivalently or better than the fishmeal references with up to 50% of fish oil replaced by soybean oil.