The main objectives of the project are to reduce ammonia-N losses through optimising amino acid balance and to elucidate the mechanisms explaining inter-specific variations in nitrogen excretion and utilization in four different species of teleosts (trout, sea bass, sea bream and turbot).
While some data on freshwater continental species is available, the potential of N utilisation, the routes and rates of N excretion of marine species have not received as much attention as they deserve. To benefit from the relative advance of our knowledge on continental freshwater species, the three marine finfish species will be compared to rainbow trout. The importance of amino acid balance on the reduction of N (ammonia and urea) excretion and optimisation of N utilisation will be studied. Specific attention will be paid to arginine, an essential amino acid in fish having multiple metabolic roles.
Therefore the proposal will consist of undertaking specific nutritional trails with the four different finfish species in order to
1) determine maintenance and growth requirement of protein and arginine,
2) study the effects of dietary arginine supply in plant protein-rich diets and
3) evaluate the effects of dietary supply of nucleic acids.
The studies with complementary approaches will be conducted in a comparative manner, using the same protocols and diets for
a) quantifying amino acid needs for maintenance and growth,
b) monitoring ammonia and urea excretions,
c) determining the activities of key enzymes of overall amino acid oxidation as well as urea synthesis and
d) measuring protein accretion and degradation
The data obtained will enable the optimisation of dietary formulation leading to improved protein yield in the different fish species. This inter-disciplinary comparative approach will form the basis to work out a general model on protein utilisation and N excretion by fish, which will be of use to estimate the potentialities of other new candidate species, or those grown under different culture conditions.
Funding SchemeCSC - Cost-sharing contracts