Live preys commonly used in fish larval rearing seem to be imbalanced in
terms of amino acids. Manipulation of their amino acid composition is
difficult, but the use of microencapsulated diets allows this manipulation.
This study analysed the effect of amino acid supplementation, in order to
compensate for dietary amino acid imbalances, on growth and survival of
gilthead seabream (Sparus aurata) larvae. Larvae were reared until 32 days after
hatching, in a closed recirculating water system (19 °C), using only
live food (rotifers and Artemia). Thereafter, larvae were fed Artemia or one of the
experimental microencapsulated diets: supplemented with indispensable amino
acids (IAAsup diet), or supplemented with dispensable amino acids (DAAsup
diet). Experiment lasted for 10 days. Dietary supplementation with indispensable amino acids resulted in A/E ratios [(each indispensable amino acid) ×
(total indispensable amino acids)−1 × 1000] more similar to the ones of
larval seabream and in higher IAA:DAA ratios than in the DAAsup diet. Survival
was similar in larvae fed the IAAsup diet (75%) or Artemia (87%), but was significantly lower in larvae fed the DAAsup diet (52%). Larvae from all
treatments more than doubled their average dry weight during the
experimental period. Final dry weight was similar in larvae fed both
microcapsules, but these were lighter than larvae fed with Artemia. Relative growth rate (RGR) and total biomass production tended to be higher in larvae fed
the IAAsup (RGR = 9% day−1) than the DAAsup diet (RGR = 7.5%
day−1) and only in this last treatment these parameters were
significantly lower than in larvae fed with Artemia. Therefore, dietary
supplementation with indispensable amino acids resulted in a more balanced
dietary amino acid profile, which significantly increased survival. Further
studies introducing microdiets earlier in the development seem necessary in
order to optimise growth.