Vers une amélioration de l'efficacité alimentaire chez le poisson : nouveaux critères et voie de sélection

Improving feed use efficiency (FE) is one of the major steps needed for the development of sustainable fish farming. However, to date, no selection program has started. This can be explained by the difficulty to measure individual FE in fishes reared in groups. The use of indirect, easy to measure criteria linked with FE would be highly valuable in order to start a breeding program. The aim of the present work is to set the foundations of a future strategy for improving fish FE based on such indirect criteria. The resistance to feed deprivation (FD) et the compensatory growth (CG) were selected as potential indirect criteria. Indeed, these traits supposedly reflect the maintenance requirements et metabolism rate of individuals. The originality of the present study is the complementarity of the two model species used: rainbow trout clones are genetic replicates of the same individual, which makes the determination of individual FE easier, et sea bass families display a large genetic variability which allows accurate estimation of genetic parameters. In our clone population, we demonstrated significant genetic variability for FE as well as a genetic correlation between FE et a composite trait integrating both FD et CG. In sea bass, the relevance of FD et CG as indirect criteria was validated: i) a trait integrating RD et CG being significantly correlated with FE in this species as well ii) FD et CG being heritable iii) FD et CG being stable through time. An optimised protocol for improving fish FE is proposed based on results from this work.