Lipostatic regulation of feed intake in Atlantic salmon Salmo salar L. defending adiposity at the expense of growth?

Abstract

Production of Atlantic salmon Salmo salar L. utilizes feeds with high fat concentrations to give low feed:gain. However, increased dietary fat content inevitably leads to increased body fat deposition, and salmon with very high fat concentrations in the muscle (fillet) are regarded as being of inferior quality. Adiposity is thought to participate in the regulation of feed intake by means of negative feedback control. Thus, elevated adiposity is predicted to result in lower feed consumption, and thereby possibly impair growth. We tested the hypothesis that high body fat content in salmon would lead to reduced feed intake and growth. Salmon (740 g) were preconditioned with high- or low-fat feed (38.8 and 27.8% dietary fat content) for 10 weeks to establish differences in body fat storage (build-up phase). Thereafter, fat and lean fish (19.4% and 16.7% body fat content) were fed the high- and low-fat feeds for an additional 7 weeks (Phase Two). During Phase Two, the fat fish consumed 30% less feed than lean fish, which resulted in corresponding differences in growth. The differences in adiposity seen at the end of the build-up phase were still evident at trial end. Groups of fish, which were preconditioned with the same feed during the build-up phase, had similar feed consumption and growth to each other during Phase Two, indicating that body fat was playing an important role in the regulation of feed intake.