A balanced dietary amino
acid profile improves amino acid retention in post-larval Senegalese sole (Solea
senegalensis)
C. Aragão, L.E.C. Conceição, D. Martins, I. Rønnestad,
E. Gomes, M.T. Dinis-2004
Aquaculture, 233(1-4): 293-304
Abstract:
The rearing of most marine fish larvae still relies
on live food. Dietary amino acid (AA) imbalances when using live food in the
larval rearing of flatfishes have been suggested. The aim of this study was
to test if dietary AA supplementation affects AA metabolism in Senegalese
sole (Solea senegalensis) post-larvae. This was done by tube-feeding Artemia-fed
sole with a dipeptide solution containing two potential limiting AA (leucine
and phenylalanine), in order to supplement the larval gut content and to
balance the dietary AA profile. Two experiments were done using different 14C-labelled
AA as tracers. The first used a 14C-protein hydrolysate to test
the effect of balancing the dietary AA profile on the overall AA metabolism.
The second experiment analysed the effect of balancing the dietary AA
profile on metabolism of three-selected AA: arginine, leucine and glutamate.
A set-up to determine the handling of 14C-labelled AA was used,
in order to quantify the absorption, catabolism and retention of the test
mixtures by the sole post-larvae. The first experiment demonstrated that,
when fish were fed the dipeptide supplement, AA catabolism decreased and AA
retention increased. This agrees with the hypothesis that balancing the
dietary AA profile increases AA retention in fish. In the second experiment,
arginine and glutamate catabolism were reduced by the dipeptide
supplementation. Leucine supplementation did not reduce leucine catabolism
but instead increased arginine and glutamate retention. This result supports
earlier studies that fish larvae are able to regulate their AA metabolism. A
balanced dietary AA profile increases the AA retention and may improve
growth and nitrogen utilisation.
(CCMAR, Universidade do Algarve, Campus de Gambelas,
8000-117, Faro, Portugal, e-mail: caragao@ualg.pt)