Microparticulate diets as
first food for gilthead sea bream larva (Sparus aurata): study of
fatty acid incorporation
J.H.
Robin, B. Vincent-2003
Aquaculture, 225(1-4) : 463-474
Abstract:
Recent advances have led to the development of inert
diets for first-feeding marine fish larvae. The purpose of the present study
was to evaluate fatty acid (FA) incorporation into larva using
practical-type and semipurified diets as first food for larvae. Experimental
microparticulate diets were fed to gilthead sea bream larvae, right from the
mouth opening to day 21 post hatching. Five basal diets were compared, using
fish meal or casein as main protein sources, and fish protein concentrate or
casein hydrolysates and algae powder (Schizochytrium). Diets
contained soybean lecithin to provide polar lipids and this also provided a
high linoleic acid (18:2n-6) content. n-3 HUFA (1.5–1.7% DM) were mainly
in dietary neutral lipids, with a part in polar lipids in diets containing
fish meal or fish hydrolysates. Fatty acid incorporation was studied by
analysing FA content of larvae at the beginning and at the end of the trial.
A semipurified diet (casein+Schizochytrium
powder) led to the best mean survival rate of 25% at day 21. While length
increments were low, basal diets containing fish meal gave higher growth in
size than casein-based diets. Whole body total fatty acid content differed
between treatments and was higher in larvae fed casein-based diets than in
those fed fish meal-based diets. As a result, fatty acid profiles shown
showed various differences between treatments but not clearly related to
dietary fatty acids. No clear sign of desaturation nor elongation of fatty
acids was observed; the presence of 22:5n-6 (from Schizochytrium)
into some diets did not seem to induce retroconversion to 20:4n-6 by larva.
Fatty acid profiles incorporated into larvae were compared to those of diets
in order to display common tendencies: the incorporation of n-6 fatty acids
was higher than their relative proportion in the diets, even for 18:2n-6
despite high dietary supply; incorporation of 20:4n-6 was two- to fourfold
higher than the proportion in diets (irrespective of the level of 22:5n-6).
Among saturated FA, high stearate but low myristate incorporation was
observed. Taking into account the high level of n-3 HUFA in the larvae
before first feeding, n-3 long-chain PUFA were not selectively incorporated
into larvae during feeding, with a negative tendency for EPA, and variable
incorporation of DHA between treatments.
(Fish Nutrition Laboratory INRA-IFREMER, Centre de Brest de L'IFREMER, BP
70, 29280, Plouzané, France, e-mail : jrobin@ifremer.fr)