The n-3 highly unsaturated fatty acids requirements of gilthead seabream (Sparus aurata L.) larvae when using an appropriate DHA/EPA ratio in the diet

Three day-old Sparus aurata larvae were fed rotifers (Brachionus plicatilis ) previously enriched with four lipid emulsions containing different percen tages (10-30%) of n - 3 highly unsaturated fatty acids (HUFA) but a fixed d ocosahexaenoic (DHA; 22:6n - 3) to eicosapentaenoic acid (EPA; 20:5n - 3) r atio of about 2/1. The n - 3 HUFA content of the enriched rotifers varied f rom 0.9 to 3.0% on a dry weight basis (DWB). In addition, the four groups o f rotifers displayed a constant DHA/EPA ratio of around 1.4/1. After 7 days of feeding, no significant differences in larval growth were observed amon g the treatments. One week later, larval total length was significantly imp roved by the elevation of the n - 3 HUFA level in the diet from 0.9 to 1.5% DWB, with further increment not exerting any apparent effect on larval dev elopment. There was some loss of total lipids in the larvae during the firs t week of feeding which particularly affected the levels of n - 3 HUFA in t he polar lipid fraction. These losses were clearly restored from day 7 to 1 4 of feeding. At the end of the experimental period, larvae fed rotifers co ntributing less n - 3 HUFA, contained lower levels of total and polar lipid s, as well as lower levels of n - 3 HUFA in the polar lipids. In conclusion , under our experimental conditions, the minimum requirement for n - 3 HUFA of 17 day-old S. aurata larvae appears to be met by 1.5% in rotifers DWB, almost four times less than the value previously reported by our group when using rotifers with DNA/EPA ratios 2-3 limes less favourable to DHA than t o EPA. (C) 1998 Elsevier Science B.V. All rights reserved.