Evaluation of lipid sources in diets fed to bull trout,Salvelinus confluentus

Abstract

To aid in development of nutritionally complete diets, a 12-week experiment was conducted to identify appropriate sources of dietary lipid for bull trout. The basal diet was top-coated with marine fish oil (MFO) (pollock liver oil), canola oil (CO), linseed oil (LO) or a mixture of canola and linseed oils (CLO) to produce four treatments. Each diet was fed to triplicate groups of fish initially averaging 1.6 g per fish. Weight gain, feed efficiency, survival and carcass proximate composition were not significantly different among fish fed the dietary treatments. However, whole-body fatty acid percentages varied significantly among fish fed the four diets. Whole bodies of fish fed diets with vegetable oil (VO) contained significantly higher 18:2n-6, 18:3n-3 and total n-6 polyunsaturated fatty acid percentages and significantly lower 20:5n-3, 22:6n-3 and total saturated fatty acid percentages compared with fish fed the MFO diet. Whole-body fatty acid percentages also varied among fish fed VO diets. Despite similar 18:2n-6 and 20:4n-6 percentages in the VO diets, fish fed diet CO contained significantly lower 18:2n-6 proportions and significantly higher 20:4n-6 proportions compared with fish fed other VO diets. Results of this study suggest dietary fish oil is not required for short-term rearing of bull trout.