Comparing seven alternative oils as partial fish oil replacers in practical diets for rainbow trout over the entire production cycle

Due to economical and environmental concerns, the substitution of dietary fish oil is increasingly implemented by global aquafeed manufacturers. Over the last two decades, a variety of alternative oils have been tested in several cultured species at various levels of inclusion. However, direct comparisons between the most commonly used oils over the course of a production cycle and at commercially relevant inclusion levels are scarce, making it difficult for industry to ascertain the specific advantage of one oil over another. In this study, seven alternative oils, all of terrestrial origin, were tested at an inclusion level of 75% of the total added lipid source (with the remaining 25% provided by fish oil) in practical -commercial like- diets for rainbow trout (Oncorhynchus mykiss) over an entire production cycle. An eighth treatment, consisting of a 100% fish oil based diet (FO), was also included as the control diet. All oils used were in crude form and included canola/rapeseed (CO), Monola (MO, a high oleic acid canola cultivar), sunflower (SFO), high oleic acid sunflower (HSFO), palm olein (PO), soybean (SBO) and poultry by-products (PBO) oils. Tests diets were formulated and manufactured to be iso-proteic (40%) and iso-lipdic (20%), varying only in the source of the added dietary lipid. The feeding trial was initiated with ~5 g juvenile rainbow trout and was conducted until fish reached a commercial size (~400 g) 27 weeks later. All growth performance and feed utilization parameters, fish biometry, tissue proximate and fatty acid composition (fillet, liver and whole-body), in vivo fatty acid metabolism and overall final eating quality attributes, including fillet coloration, astaxanthin content, flavor volatile compounds and sensorial/organoleptic characteristic were evaluated. The major results of this study will be presented and discussed towards providing the industry with a comprehensive overview of the advantages and limitations of each the tested oils. This presentation will also highlight new research directions for future scientific investigation for the ultimate development of more effective and sustainable aquafeed.