Dietary indispensable amino acids profile affects protein utilization and growth of Senegalese sole larvae

Abstract

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.

Dietary protein complexity modulates growth, protein utilisation and the expression of protein digestion-related genes in Senegalese sole larvae

“…In Senegalese sole, the larvae capacity to retain 6.8 kDa polypeptides increased throughout development (Canada et al, 2016;Engrola et al, 2013;Richard et al, 2015), which suggests that young sole juveniles AA anabolic and physiological needs may be better adapted to larger peptides rather than younger larval stages. The present results suggest that from a certain point of Senegalese sole development, the prehydrolysis of dietary protein is no longer beneficial and microdiets should include mostly intact protein.…”

Daily feeding and protein metabolism rhythms in Senegalese sole post-larvae

“…Several studies have determined the fate of ingested protein in fish larvae ( Rønnestad et al, 2001 ; Morais et al, 2004a ; Conceição et al, 2007a ; Engrola et al, 2009a , 2010 ; Richard et al, 2015 ; Canada et al, 2016 preprint ; Rocha et al, 2016 ). Nonetheless, quantifying feed intake based on a single meal, particularly after a pre-conditioning period under starvation conditions, may not give representative results, given that at this time the appetite may be at its maximum.…”