Fat content in turbot feed: influence on feed intake, growth and body composition

The influences of dietary fat concentration on growth and energy deposition were studied in two replicated groups of turbot, Scophthalmus maximus (L.) . Individually tagged turbot (202.3 g) held at 15.6 degreesC were offered d ry pellets in excess. These contained either high-fat (25.4%) or low-fat (1 6.6%) concentration and identical protein (43.2%). After 3 months, feed tre atments were crossed in two replicates, and the remaining fish were offered a mix of feeds for a further 2 months. Fish were sacrificed for analysis o f body composition at the start of the experiment, at the time of feed trea tment changes and when the experiment was terminated. There were no signifi cant differences in energy intake, specific growth rate or weight between t reatments at any time during the experiment. At the time of the feed treatm ent change fish offered high-fat feed had a significantly higher relative b ody fat (8.2 vs. 6.3% w/w) and lower body water (71.2 vs. 73%), but there w ere no differences in protein or ash content. By the end of the experiment, differences in body composition had diminished. The results indicate that fat content in the turbot may be manipulated by changing the dietary fat co ntent, apparently without major influences on weight gain.