Effect of Nutritional Enrichment Method on Fatty Acid Contents of Rotifer Brachionus plicatilis

Nutritional enrichment for rotifer is necessary for the stable production in larviculture. Although manufacturers recommend feeding amount for enrichment diets, the effects of these recommended amounts on nutritional enrichment of rotifer are unknown. We assessed the effects of normal and overdose amount of enrichment diets on nutritional enrichment of rotifer using batch and continuous culture methods. Rotifer populations in two culture systems were enriched using four enrichment conditions, matched two diet levels, and two enrichment durations: 0.25 g/L for 8 h (normal enrichment) 0.25 g/L for 24 h (longer enrichment), 0.75 g/L for 8 h (overdose enrichment), and 0.75 g/L for 24 h (overdose + longer enrichment). When the batch-cultured rotifer populations were enriched, longer and overdose enrichments could not make the fatty acid contents differ from the normal one. Overdose enrichment was most effective of all enrichment conditions when continuous-cultured rotifer populations were used. In both culture methods, the docosahexaenoic acid (DHA) content under overdose + longer enrichment conditions was two to three times as high as normal enrichment conditions and it resulted in two- to threefold increase in DHA/eicosapentaenoic acid ratio by overdose + longer enrichment. Accordingly, it is possible to alter the fatty acid composition of rotifer by changing the enrichment method.