Improvement of the nutritional value of rotifers by varying the type and concentration of oil and the enrichment period

Abstract

Several enrichment conditions (type and concentration of oil in culture medium and time of enrichment) were tested in order to study their influence on rotifer (Brachionus plicatilis) lipid and fatty acid composition as well as on its population profile. Rotifers pre-fed on baker's yeast (Saccharomyces cerevisiae) were enriched with lipid emulsions containing triacylglycerols (TAG) or methyl ester (ME) mixtures at three different concentrations. Rotifers were sampled after 0 (yeast-fed rotifer), 3, 6, 12 and 24h enrichment. At every concentration and time assayed, the highest lipid levels were obtained when using TAG. In spite of the differences existing in saturated and monounsaturated fatty acid composition between the enrichment emulsions, rotifers tended to maintain the level of these fatty acids independently of the enrichment period and oil concentration. Increasing the enrichment period rather than the amount of oil present in the medium was found to be more efficient in increasing the n − 3 highly unsaturated fatty acids (n − 3 HUFA) level in rotifers. Rotifers reflected a better incorporation of eicosapentaenoic acid (EPA, 20:5n − 3) than of docosahexaenoic acid (DHA, 22:6n − 3), regardless of the ratio between both fatty acids in the emulsions. The use of ME as an enrichment source produced greater mortality in egg-carrying females than when using TAG.