Influence of dietary polar lipids' quantity and quality on ingestion and assimilation of labelled fatty acids by larval gilthead seabream

Dietary supplementation of phospholipids seems to be extremely important to promote growth and survival in fish larvae. Several studies also suggest t he importance of n-3 highly unsaturated fatty acids (HUFA) rich phospholipi ds to further enhance larval performance. In the present study, four differ ent diets were formulated in order to compare the effect of total dietary p olar lipid contents, of soya bean lecithin supplementation and of feeding n -3 HUFA in the form of neutral or polar lipids on ingestion and incorporati on of labelled fatty acids in gilthead seabream larvae. These diets were pr epared including radiolabelled fatty acids from palmitoyl phosphatidylcholi ne, glycerol trioleate, free oleic acid (FOA) and free eicosapentaenoic aci d (FEPA) and were fed to 25 day-old larvae. The results of these experiment s showed that the elevation of the dietary polar lipid levels significantly improved microdiet ingestion, regardless of the origins of the polar lipid s. This effect caused an improved incorporation of phosphatidylcholine fatt y acids to the larval polar and total lipids (TL) as the dietary polar lipi ds increased. Nevertheless, a better incorporation of fatty acids from diet ary polar lipids in comparison with that of fatty acids from dietary trigly cerides into larval lipids was found in gilthead seabream, whereas a better utilization of dietary triglycerides fatty acids than dietary free fatty a cids could also be observed. Besides, the presence of n-3 HUFA rich neutral lipids (NL) significanlty increased the absorption efficiency of labelled oleic acid from dietary triglycerides, but the presence of n-3 HUFA rich po lar lipids, particularly improved the incorporation of FEPA. This fatty aci d was preferentially incorporated into larval polar lipids in comparison wi th FOA.