Metabolic response to feeding rates in common carp, Cyprinus carpio

Common carp weighing about 46 g were fed on a commercial diet for 30 days at various daily feeding rates of 2.28 (satiation), 2.07, 1.85, 1.64, 1.16, 0.72 and 0% (starvation), and the hepatopancreatic enzyme activities and body composition were determined. The concentrations of serum triglyceride and cholesterol as well as body fat and glycogen contents decreased as the feeding rate decreased, while serum glucose and free amino acid concentrations scarcely changed. The serum free fatty acid concentration in the starved fish was higher than those in the fed fish. The activities of hepatopancreatic glucosephosphate isomerase, pyruvate kinase, glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, NADP-isocitrate dehydrogenase, and -malate dehydrogenase significantly decreased with decreasing feeding rates, and there were strong positive correlations between enzyme activities and feeding rates. On the other hand, glucose-6-phosphatase and alanine aminotransferase activities remained relatively constant. These results suggest that feed restriction stimulated fatty acid and glycogen mobilization, maintained gluconeogenesis and amino acid degradation, and depressed glycolysis and lipogenesis in the hepatopancreas. (C) 1997 Elsevier Science B.V.