Comparative Evaluation of Bioengineered High DHA Canola (NS‐B50027‐4) Meal and Conventional Canola Meal in Diets for Rainbow Trout Juveniles on Growth Performance, Feed Utilization, Body Composition, and Blood Chemistry

Identifying novel plant‐based protein ingredients, including coproducts of bioengineered oilseeds, is important for sustainable trout farming. In the current study, effects of a bioengineered oilseed ingredient, a high docosahexaenoic acid (DHA) canola (NS‐B50027‐4) meal, have been evaluated in relation to conventional canola meal in rainbow trout diets. For this purpose, three experimental feeds for rainbow trout were produced by adding 20% of the DHA canola meal and control canola meals with other basal ingredients for the first two diet groups, diet‐1 and diet‐2, respectively, and a mixture of 10% DHA canola and 10% control canola meals were added with similar basal ingredients for producing the third experimental diet (diet‐3). Diets were fed to ~42 g sized rainbow trout at the start for a period of 64 days. Following the feeding trial, the growth performance indices (final weight, percentage weight gain, and specific growth rate) were not significantly different among treatments. However, feed intake of fish fed diet‐3 was significantly lower ( p   < 0.05) than that of fish fed the other treatments. Diet‐3 fed fish also had higher lipid retention when compared to diet‐2, with diet‐1 having an intermediate value. Among the measured blood biochemical parameters, only the alanine amino transferase (alanine transaminase [ALT]) value was significantly influenced, with fish fed diet‐1 having a significantly lower ( p   < 0.05) value compared to other treatments, suggesting a modulation of hepatic metabolism. Whole‐body proximate composition was not significantly influenced by dietary treatments. Whole‐body α‐linolenic acid content was significantly lower ( p   < 0.05) in fish fed the conventional canola meal diet (diet‐2), reflecting the lower α‐linolenic acid content of that diet. Although DHA canola meal contains relatively higher DHA, whole‐body DHA content of fish fed the DHA canola meal was not significantly influenced, likely because the meal has a low residual lipid content and fish oil (FO) supplied more than 97% of dietary DHA in all diets. In summary, no significant differences in growth or feed conversion were detected between fish fed 20% DHA canola meal and those fed 20% conventional canola meal. While fish fed diet‐1 had lower plasma ALT, liver histopathology should be evaluated in a future study to better characterize the impact on liver health. This study supports the incorporation of the DHA canola meal, a coproduct of high DHA omega‐3 canola (NS‐B50027‐4) oil production, into rainbow trout diets as a nutritional ingredient.