Nutritional control of lipid deposition in rainbow trout : effect of rearing temperature

Abstract

In the light of bibliographic and personal data, this paper is aimed at summarising the knowledge of the dietary regulation of mechanisms involved in fat deposition in the rainbow trout. Dietary lipid levels affect quantitative body lipid deposition in the rainbow trout, but the mechanisms are similar whatever the dietary treatment. Perivisceral adipose tissue is the main lipid storage site in this species. Carbohydrate rich diets lead to an increase in body lipids which seems to be more related to a lipid sparing effect by carbohydrates than to de novo lipid synthesis. In fact, the ability of the rainbow trout to synthesise lipids from glucose is low. The regulation of lipogenic enzyme activity is less efficient in fish than in higher vertebrates. Variations in dietary lipid levels higher than 10% are needed to induce significant changes in enzyme activities. A cumulative effect of dietary lipids and carbohydrates on hepatic lipogenesis is also observed. Rearing temperature interacts with dietary factors on the mechanisms involved in body lipid deposition: in the rainbow trout, lipid transport becomes faster at low temperatures whereas the lipid synthesis capacity is lower at 8° than at 18°C.