Processing of canola meal for incorporation in trout and salmon diets

Canola meals (two commercial meals and one low-heat meal) were processed to reduce fiber content, then washed with selected solvents to reduce the content of antinutritional substances and further concentrate protein. The meals, fiber-reduced meals, and washed meals were used to provide 40% of total protein (26–38% of feed) in the diets of 6-g rainbow trout for 3 weeks or 25% of total protein (21–31% of feed) in the diets of 23-g chinook salmon for 11 weeks. Air-desolventized (low-heat) canola meal, as compared to commercial meal, provided no protein quality advantage in trout feeds. Fiber reduction processing of commercial meal increased meal protein content by 11–16% and reduced crude fiber by 23–50%, but did not have any effect on the quality of protein for trout or salmon. Solvent-washing of fiber-reduced meal improved fish response to canola meal, probably due to reduced glucosinolate content, but possibly also due to reduced sinapine content and alterations in protein availability. Protein concentration was increased by 25–40% by washing, and glucosinolate concentration was reduced by 40–90%.