Necessity of
dietary lecithin and eicosapentaenoic acid for growth, survival, stress
resistance and lipoprotein formation in gilthead sea bream Sparus aurata
J. Liu, M.J. Caballero, M. Izquierdo, T.
El-Sayed Ali, C.M. Hernández-Cruz, A. Valencia, H. Fernández-Palacios-2002
Fisheries
Science, 68(6):
1165-1172
Abstract:
The substitution of dietary
docosahexaenoic acid (DHA) with eicosapentaenoic acid (EPA) reduces larval
growth in gilthead sea bream. However, the value of EPA when dietary DHA is
able to meet the requirements of the larvae has not been sufficiently
studied. Dietary phosphoacylglyceride levels also affect fish growth and it
has been suggested that they enhance lipid transport in developing larvae.
The present experiment was carried out to further study the effect of
dietary lecithin and eicosapentaenoic acid on growth, survival, stress
resistance, larval fatty acid composition and lipid transport, when DHA is
present in the microdiets of gilthead sea bream. Eighteen thousand gilthead
sea bream larvae of 4.99 ± 0.53 mm total length were fed
three microdiets tested by triplicate: a control diet [2% soybean lecithin
(SBL) and 2.89% EPA], a low EPA diet (2% SBL and 1.63% EPA) and a no SBL
diet (0% SBL and 2.71% EPA). Handling, temperature and salinity tests
determined larval resistance to stress. The results show that when dietary
DHA levels are high, but dietary arachidonic acid (ARA) levels are about
0.2%, EPA is necessary to improve larval growth, and survival. Larval EPA
content, but not DHA or ARA, was affected by dietary EPA levels. Increased
dietary EPA improved larval stress resistance to handling and temperature
tests, which could be related to its possible role as a regulator of
cortisol production, whereas it did not affect stress resistance after
salinity shock. Larvae fed the no SBL diet showed a lower lipid content
characterized by a low proportion of saturated and monounsaturated fatty
acids, together with a significant reduction in the appearance of
lipoprotein particles in the lamina propria and in the size of such
particles, denoting a critical reduction in dietary lipid transport and
utilization, and lower larval growth and survival rates.
(Institute of Oceanology Academia Sinica, Quingdao
266071, People's Republic of China, e-mail of M. Izquierdo: marisoli@iccm.rcanaria.es)