Submitted to: Aquaculture Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2010
Publication Date: 4/20/2011
Citation: Stone, D.A., Oliveira, A.C., Plante, S., Smiley, S., Bechtel, P.J., Hardy, R.W. 2011. Enhancing highly unsaturated omega-3 fatty acids in phase-fed rainbow trout (Oncorhynchus mykiss) using Alaskan fish oils. Aquaculture Nutrition. 17(2):e501-e510. Interpretive Summary: Results from this study indicated that the fatty acid (FA) composition of oils derived from Alaskan seafood by-products were nutritionally well suited for inclusion into feeds for rainbow trout and superior, in respects to long chained omega-3 FA levels, to menhaden oil. With respect to EPA and DHA levels and the ratio of omega-3 FA/omega-6 FA, the phased feeding strategy adopted in this study was successful and has the potential to reduce feed and fish production costs significantly. On an edible portion basis, it was possible to boost EPA and DHA levels and to improve the ratio of omega-3 FA/omega-6 FA in fillets of rainbow trout by replacing menhaden oil with the Alaskan fish oils over the eight week trials. In addition, all dietary treatments resulted in EPA and DHA levels that exceeded those reported for wild rainbow trout and fillets had healthful ratios of omega-3 FA/omega-6 FA. Coupled with the reported low levels of organic contaminants in the Alaska fish oils result in fillets with a reduced potential exposure to many harmful pollutants. These characteristics make Alaska fish oils suitable for incorporation into aquaculture finishing diets that may also contain substantial amounts of plant oils.
Technical Abstract: The objective of this research was to investigate differences in the kinetics of fatty acids (FA) deposition in fillets of market-sized (approximately 450g) rainbow trout (Oncorhynchus mykiss) fed diets containing commercial Alaskan fish oils versus menhaden oil. Comparisons were made with FA levels of fillets from wild trout, or commercially produced trout fed menhaden oil diets exclusively. Emphasis was placed on the fillet levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and the ratio of omega-3 to omega-6 FA. The sensory characteristics of trout fillets were also evaluated. In the first phase of the experiment rainbow trout (75g fish-1) were fed a commercial diet (45% crude protein, 20% crude lipid), using poultry fat as the primary lipid source, for eight weeks. In the second phase, trout (186g fish) were fed one of five experimental diets (39% digestible protein and 20% digestible lipid) for a further eight weeks. The experimental diets contained 15% of either menhaden oil, Alaskan pollock oil, pink salmon oil or rockfish oil. A diet containing 15% canola oil was also included for comparison. Oil type did not significantly effect the final fish weight (range of 391 – 411) specific growth rates (SGR, range, 1.26 – 1.34), feed conversion ratios (FCR, range, 1.22 – 1.13), skin-on fillet yields (range 50.9 to 54.3%), or skin-off fillet yields (range, 36.1 to 38.3%). After eight weeks of feeding it was possible to boost EPA and DHA levels and increase the ratio of omega-3 to omega-6 FA in fillets of rainbow trout by replacing menhaden oil with the Alaskan fish oils. In addition, all dietary treatments resulted in EPA and DHA levels that exceeded those reported for wild rainbow trout. This was achieved while still maintaining healthful ratios of omega-3 to omega-6 FA, and acceptable fillet sensory attributes. The phased feeding strategy adopted in this study was successful. The FA composition of oils derived from Alaskan seafood by-products were nutritionally well suited for inclusion into feeds for rainbow trout, and with respect to long chained omega-3 FA levels, superior to menhaden oil.