54 MARCH 2014 • WORLD AQUACULTURE • WWW.WAS.ORG TABLE 3. Mean fatty acid methyl ester (FAME; % total) concentrations in the treatment diets. FAME (% total) Steelhead egg Commercial diet Experimental diet Experimental diet - red 14:00 3.3 7.4 6.0 6.2 16:00 15.0 23.1 22.6 21.7 18:00 4.9 4.7 4.7 4.8 Total SFA1 24.2 37 35.1 34.5 16:1(ω-7) 5.1 7.6 6.4 6.1 18:1(ω-9) 15.8 12.7 18.9 19.3 18:1(ω-7) 2.9 2.2 1.3 1.2 Total MUFA2 26.0 24.6 29.2 29.8 18:2(ω-6) 1.4 3.8 6.8 6.7 20:4(ω-6) 1.3 1.4 1.3 1.2 Total(ω-6)3 4.4 6.5 9.8 9.6 18:3(ω-3) 0 0.2 0.7 0.6 20:5(ω-3) 12.8 17.3 12.6 12.1 22:5(ω-3) 6.4 2.8 2.0 2.1 22:6(ω-3) 25.9 11.6 10.7 11.0 Total(ω-3)4 45.3 31.9 25.9 25.9 Total 18-C PUFA5 2.6 5,0 8.6 8.5 Total LC-PUFA6 47.2 33.4 27.1 27.2 EPA:ARA 9.8 12.2 9.9 10.5 DHA:EPA 2.0 0.7 0.8 0.9 ω-3:ω-6 10.2 4.9 2.7 2.7 1 Also includes 11:0, 12:0, 13:0, 15:0, 17:0, 20:0, 22:0, 23:0, and 24:0. 2 Also includes 14:1(ω-5), 20:1(ω-9), 22:1(ω-9), and 24:1(ω-9). 3 Also includes 18:3(ω-6), 20:2(ω-6), and 20:3 (ω-6). 4 Also includes 20:3(ω-3). 5Also includes 18:3(ω-6). 6Also includes 20:2(ω-6), 20:3(ω-6), 20:3(ω-3), and 20:2(ω-9). Growth of fish fed the commercial diet by hand or underwater was significantly greater than that of fish fed either experimental diet. Growth of fish was ranked commercial feed > steelhead eggs > both experimental diets. The feed efficiency of fish fed steelhead eggs was greater than that of fish fed the commercial diet through underwater feeding and either experimental diet. However, the feed efficiency of fish fed steelhead eggs was less than that of fish fed the commercial diet by hand. Nutrient Profiles of Steelhead Fish collected at stocking (n=20) and all remaining fish after 60 days in the study were sealed in plastic freezer bags and stored at −80 C until analysis. Proximate analysis and fatty acid profile of whole fish and diets was determined using standard methods (AOAC 2005). Diet did not affect carcass moisture, ash, protein, or lipid content. Lipid levels of steelhead were less at the end of the study compared to fish at stocking. Fatty acids were examined in this study because marinederived highly unsaturated fatty acids (HUFA) are important to young salmonids (Ashton et al. 1993). Although diet did not affect the total lipid content of steelhead, there were numerous differences in the carcass lipid profiles of fish among dietary treatments (Table 4). For example, the eicosapentaenoic acid (EPA, 20:5(ω-3)) concentration of fish fed the commercial diet was significantly greater than those of fish fed eggs or either experimental diet. Fish fed eggs had significantly greater EPA content than fish fed the experimental diet with and without red coloring. For development of an egg analog, commercially obtained fish oils have a HUFA content that varies substantially (Sargent et al. 1999). When comparing fatty acid profiles of feeds (Table 3), the EPA levels in the three commercial diets differ although the eggs and the experimental diet are similar. In contrast, the docosahexaenoic acid (DHA, 22:6 (ω-3)) content of eggs is more than twice as much as in the commercial diets. Interestingly, the arachidonic acid (ARA, 20:4 (ω-6)) is about the same in all of the feed items or diets. Although levels of some HUFAs were greatly different in diets, eggs, and fish fed those diets, the essential fatty acid requirements of fish were met. Research Needs For stream nutrient enhancement, the use of egg analogs should be further explored. Work on the formulation is needed to better match the egg fatty acid profile and to ensure other nutrient needs are met. The stability, physical properties and application method of egg analogs also deserve further study.
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