Fatty acid composition in Arctic char (Salvelinus alpinus) fed with red yeast biomass : a comparison between large and small specimens

Abstract: Oleaginous yeast has shown to be a promising alternative to replace vegetable oils in fish feed. A problem in aquaculture is that different growth rates can be observed among farm-raised fish, supressing the productions full potential. When different growth rates are observed, it can be questioned if the fish assimilate the feed to the same extent. Therefore, the aim of this study was to analyse the lipid content, fatty acid composition and lipid groups of large and small specimens of Arctic char (Salvelinus alpinus), fed with either control feed or feed containing biomass of the oleaginous yeast species Rhodotorula toruloides, to examine the fish welfare, performance and intake of feed in fish of different size. Lipid extraction followed by gas chromatography was used to analyse the fat content and fatty acid composition in 16 fish. Furthermore, thin layer chromatography was performed to analyse lipids groups. No significant differences in lipid content, fatty acid composition or lipid groups could be observed between large and small specimens fed either control of yeast feed. However, small fish tend to have higher levels of polyunsaturated fatty acids. The result of this trial indicates that there is no difference is feed assimilation between large and small specimens of Arctic char (S. alpinus).