Growth performance, feed utilisation and fatty acid deposition in Atlantic salmon, Salmo salar L., fed graded levels of high-lipid/high-EPA Yarrowia lipolytica biomass

Abstract Salmon aquaculture is currently reliant on fish oil as the major source of the very long chain (VLc) n − 3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). This report details the first study of an alternative source of EPA from the yeast Yarrowia lipolytica in feed for fish. Atlantic salmon was fed three dietary levels, 10% (Y10), 20% (Y20) and 30% (Y30) of a heat killed dried yeast biomass containing 6% EPA and 20% oil by weight for 95 days. The yeast biomass was replacing fish meal, rapeseed oil and wheat meal in the diets. The increase in fish weight from 180 to 400 g on the diets containing yeast, was comparable to groups fed control diets with either rapeseed oil (RO) or a mix of rapeseed and fish oil. The apparent digestibility coefficient for energy, protein and lipids, including n − 3 fatty acids, decreased with increased inclusion of yeast biomass. Feed conversion ratio was higher, and energy retention lower, in the Y30 group than in the others. Protein retention was the lowest in the Y30 and FO groups followed by Y20. Fillet fatty acid composition reflected the higher ratio of EPA to DHA in the feeds added yeast. However, lower whole body retention of EPA, and higher retention of DPA (docosapentaenoic acid) and DHA, compared to average fatty acid retention, suggest that there had been some conversion of the EPA provided by the yeast into DPA (docosapentaenoic acid) and DHA in fish.