Effet du taux et de la nature des lipides alimentaires sur les mécanismes intervenant dans la constitution des dépôts lipidiques (transport, captage, synthèse) chez la truite arc-en-ciel et le bar

Replacement of dietary fish oil by a blend of vegetable oils for more than a year does not affect growth, hepatic lipogenesis and tissue lipid uptake in rainbow trout and European seabass. However, this replacement decreases plasma cholesterol level in both species and LDL amount in rainbow trout. Such replacement does not affect muscle lipid content of fish but modifies fatty acid composition of fish flesh which reflects in most part that of dietary lipid source. Increasing dietary lipid level inhibits hepatic lipogenesis but does not modify tissue lipid uptake in seabass and in two trout lines selected for muscle lipid level. In seabass, dietary lipid level had a lower impact on growth and lipid metabolism than rearing temperature. In this species, increasing temperature enhances hepatic lipogenesis, increases plasma VLDL and LDL amount and depletes surface component proportions (phospholipids and proteins) in these two lipoprotein classes. Both rainbow trout lines cannot be differentiated by endogeneous synthesis of lipid or by tissue lipid uptake ability.