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

Abstract

Three day-old Sparus aurata larvae were fed rotifers (Brachionus plicatilis) previously enriched with four lipid emulsions containing different percentages (10–30%) of n−3 highly unsaturated fatty acids (HUFA) but a fixed docosahexaenoic (DHA; 22:6n−3) to eicosapentaenoic acid (EPA; 20:5n−3) ratio of about 2/1. The n−3 HUFA content of the enriched rotifers varied from 0.9 to 3.0% on a dry weight basis (DWB). In addition, the four groups of 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 among the treatments. One week later, larval total length was significantly improved 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 development. There was some loss of total lipids in the larvae during the first week of feeding which particularly affected the levels of n−3 HUFA in the polar lipid fraction. These losses were clearly restored from day 7 to 14 of feeding. At the end of the experimental period, larvae fed rotifers contributing less n−3 HUFA, contained lower levels of total and polar lipids, 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 DHA/EPA ratios 2–3 times less favourable to DHA than to EPA.