Dietary indispensable amino acids profile affects protein utilization and growth of Senegalese sole larvae
In diet formulation for fish, it is critical to assure that all the indispensable amino acids (IAA) are available in the right quantities and ratios. This will allow minimizing dietary AA imbalances that will result in unavoidable AA losses for energy dissipation rather than for protein synthesis and growth. The supplementation with crystalline amino acids (CAA) is a possible solution to correct the dietary amino acid (AA) profile that has shown positive results for larvae of some fish species. This study tested the effect of supplementing a practical microdiet with encapsulated CAA as to balance the dietary IAA profile and to improve the capacity of Senegalese sole larvae to utilize AA and maximize growth potential. Larvae were reared at 19 °C under a co-feeding regime from mouth opening. Two microdiets were formulated and processed as to have as much as possible the same ingredients and proximate composition. The control diet (CTRL) formulation was based on commonly used protein sources. A balanced diet (BAL) was formulated as to meet the ideal IAA profile defined for Senegalese sole: the dietary AA profile was corrected by replacing 4 % of encapsulated protein hydrolysate by CAA. The in vivo method of controlled tube-feeding was used to assess the effect on the larvae capacity to utilize protein, during key developmental stages. Growth was monitored until 51 DAH. The supplementation of microdiets with CAA in order to balance the dietary AA had a positive short-term effect on the Senegalese sole larvae capacity to retain protein. However, that did not translate into increased growth. On the contrary, larvae fed a more imbalanced (CTRL group) diet attained a better performance. Further studies are needed to ascertain whether this was due to an effect on the voluntary feed intake as a compensatory response to the dietary IAA imbalance in the CTRL diet or due to the higher content of tryptophan in the BAL diet.
KeywordsIndispensable amino acids Balanced diet Metabolism Growth Fish larvae
This work was funded by Project EPISOLE (FCT) [PTDC/MAR/110547/2009] from FCT (Portugal). P. Canada and N. Richard were supported by FCT (Portugal) Grants SFRH/BD/82149/2011, and SFRH/BPD/65578/2009, respectively. Sofia Engrola was supported by investigator grant IF/00482/2014/CP1217/CT0005 funded by the European Social Fund, the Operational Programme Human Potential and the Foundation for Science and Technology of Portugal (FCT). The authors acknowledge the collaboration of André Santos (SPAROS Lda), the Aquagroup team, Sara Ferreira in particular (CCMar), Cláudia Figueiredo-Silva and the Evonik Industries AG (Essen, Germany).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Experiments were performed by trained scientists and following the European Directive 2010/63/EU of European Parliament and of the Council of European Union on the protection of animals used for scientific purposes.
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