Effect of Cycled Feeding by Diets Including Vegetable and Fish Oil on Growth Performances and Fatty Acid Profiles of Rainbow Trout (Oncorhynchus mykiss Walbaum, 1792)

The aim of this study was to evaluate the effects of alternate cycled feeding regime with diets including different oil sources on fatty acid profiles and growth performances of rainbow trout. Seven trials were implemented; fish oil trial [FO; continuously fed by diet with fish oil (FO)], canola oil trial [CO; continuously fed by diet with canola oil (CO)], safflower oil trial (SFO; continuously fed by diet with safflower oil (SFO)], mixture oil trial (CSFO; continuously fed by diet containing both %50 CO and %50 SFO), alternate cycled feeding trial [(FO/CO; fish fed by diet with CO for 2 weeks and FO for the following 2 weeks), (FO/SFO; fish fed by diet with SFO for 2 weeks and FO for following 2 weeks) and (FO/CSFO; fish fed by diet with CSFO for 2 weeks and FO for following 2 weeks)] for 12 weeks. Significantly higher SGR and the best FCR were detected in the CSFO and FO/CSFO feeding groups, respectively, compared to the FO group (p>0.05). The lowest HSI and VSI were in the CO group (p>0.05). The highest crude protein, lipid and ash contents were determined in the FO/SFO group (p>0.05). Experimental diets containing vegetable oil (CO and SFO) and vegetable oil blend (CSFO) had significantly higher concentrations of n-6 fatty acids, predominantly in the form of linoleic (LA, 18:2n-6c) and oleic acid (OA, 18:1n-9c), while n-3 fatty acids were present in significantly higher concentrations in the FO group. The fatty acid composition of rainbow trout fillet reflected the dietary lipid source. Fillet of fish fed by the FO diet had highest eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) amount. The n-3 PUFA accumulation (mainly EPA and DHA) was generally decreased in the fillets of the CO, SFO, CSFO groups compared to the FO group. The proportions of n-3 PUFA in the fillets of the FO/CO, FO/SFO and FO/CSFO groups throughout the experimental period were significantly higher than in the CO, SFO, CSFO groups, confirming the major effect of the fish oil intake at the cycled feeding stages of the experiment. This study shows that cycled feeding regimes by diets including vegtable and FO may be used in rainbow trout culture.