Effect of dietary lipid content on circadian rhythm of feeding activity in European sea bass.

In fish, dietary digestible energy (DE) content is a major factor controlling feed intake. It was therefore of interest to determine how circadian rhythm of feeding activity is influenced by the dietary DE levels. To that end, groups of European sea bass were fed on demand by means of self feeders, under light-dark and constant light conditions, with a fixed or an unlimited amount of feed with variable lipid contents. Daily total feed intake, but not the feeding rhythm, was adjusted in relation to the DE content of the diet regardless of the lighting conditions. We conclude that a satiation mechanism was likely responsible for the regulation of feed intake in relation to the dietary fat content but was not acting in itself on the mechanisms that drive the free-running rhythms of feeding activity. These results are giving additional evidence that a true endogenous clock is driving feeding activity rhythms in fish.