Consumption vs. deposition
of essential fatty acids in gilthead sea bream (Sparus aurata) larvae
fed semi-purified diets
J.H. Robin, A. Peron-2004
Aquaculture, 238: 283-294
Abstract:
Semi-purified diets were used to feed gilthead sea
bream larvae as first food from mouth opening until day 17. Four diets were
formulated on the basis of a previous one used as control (D1). Three
experimental diets differed only by the lipids added. One diet contained n-3
highly unsaturated fatty acids (n-3 HUFA) plus arachidonic acid (D2), one
diet n-3 HUFA without arachidonic acid (D3) and one diet without n-3 and n-6
HUFA (D4). The three experimental diets contained 18:3n-6 in order to follow
the influence of dietary HUFAs on elongation-desaturation capacities. Larval
growth and survival were similar with diet D1 and D2. Lowest growth and
survival were observed for larvae fed the HUFA free diet D4. Larval survival
but not growth was significantly decreased by lack of arachidonic acid in
diet D3 compared to D2. Utilization of fatty acids by larvae was studied by
comparing the fatty acid quantities per larva in initial (before feeding)
and final samples. In larvae fed the HUFA-free diet D4, a significant
increase of 20:3n-6 showed that some elongation from 18:3n-6 occurred, while
quantities of arachidonic acid and n-3 fatty acids (except 18:3n-3)
decreased compared to initial larvae. A consumption of endogenous HUFAs was
evidenced despite effective incorporation of dietary fatty acids such as
18:2n-6, 18:1n-9 and 18:3n-3. Fatty acid profile of these larvae changed,
according to dietary fatty acid influence, by turnover rather than by a raw
incorporation of fatty acids. Larvae fed the n-3 HUFA diet depleted in
arachidonic acid (D3) had a total fatty acid content lower than those fed
with arachidonic acid (D2); compared to those fed D4, the elongation of
18:3n-6 to 20:3n-6 seemed to be repressed by dietary n-3 HUFA.
Consumption of long-chain unsaturated fatty acid is a
main conclusion of this study; a rate of loss around 1.1, 0.5 and 0.05 mg
day−1 g−1 mean dry body weight of larvae
for docosahexaenoic, eicosapentaenoic and arachidonic acid, respectively,
may be estimated in larvae fed the HUFA free diet D4. No desaturation
capacities of gilthead sea bream larvae were evidenced; however, some low
capacities might be masked by the consumption of HUFAs.
(Unité mixte Nutrition, Aquaculture, Génomique
INRA-IFREMER-Bordeaux I, Centre IFREMER de Brest, BP 70, 29280 Plouzané,
France, e-mail: jrobin@ifremer.fr)