A note on the effects of L-carnitine on the energy metabolism of individually reared carp, Cyprinus carpio L.

Twelve carp, Cyprinus carpio L., were grown from 30 to 120 g live mass on four diets, control (405 g kg⁻¹ crude protein, 20.6 MJ kg⁻¹ gross energy) and control + 200, 400 or 600 mg kg⁻¹ L -carnitine. The diets were designated as CONT, C200, C400 and C600, respectively. Each diet was randomly assigned three fish kept in individual open-circuit respirometers. Fish that ate diets C400 and C600 grew faster than the controls, expended less energy and retained more energy per unit of food energy intake. Average energetic efficiency, expressed as energy retained per unit of energy expended, was 30% higher in the C400 group than in the controls. However, owing to the small number of fish in each group and the large variations in all these parameters, especially within the control group, none of these differences reached statistical significance at the P = 0.1 level.