Canola oil substitution doesn't affect growth but alters fillet quality of triploid rainbow trout

A 12-week feeding trial was conducted to evaluate the impacts of high levels of canola oil (CO) substitution for fish oil (FO) on the growth and fillet quality of triploid rainbow trout. Three isonitrogenous (46% crude protein) and isolipidic (24% crude lipids) diets were prepared. The control diet containing supplemental FO with 18.6% level was compared with the diets, in which 75% (CO75) and 100% (CO100) FO was replaced by CO, respec-tively. Each diet was fed to quadruplicate groups of 100 fish (initial average weight of 208 g) in freshwater cages. Results showed that CO substitution did not significantly affect survival, weight gain rate and feed conversion ratio (P > 0.05), while affected fillet organoleptic properties and nutritional value based on the multivariate statistical analysis of 124 quality indicators. Generally, high levels of CO substitution significantly increased fillet redness (a*, C*ab), relative fillet length and fillet thickness value, fillet springiness and chewiness values, fillet collagen content and crosslink level, fillet odor-active compounds concentrations, fillet inosine-5 '-mono-phosphate (IMP), glutamic acid, histidine, sum of bitter taste compounds and sum of sour taste compounds contents, and fillet lipid and total fatty acids contents (P < 0.05). However, total substitution of FO by CO could result in high fillet fragility and low n-3 long-chain polyunsaturated fatty acids (LC-PUFA) content. In total, CO substitution did not affect growth, and could increase fillet appearance, texture, umami quality and lipid nutritional value of triploid rainbow trout, while total CO substitution was not recommended.