The objective of this study was to investigate the interaction between feeding, exercise and
cortisol on metabolic strategies of common carp over a 168h post-implant period. Feeding provided readily available energy and clearly increased muscle and liver
protein and
glycogen stores. Swimming, feeding and
cortisol all induced aerobic metabolism by increasing oxygen consumption, and stimulated
protein metabolism as demonstrated by the increased
ammonia and
urea excretion and
ammonia quotient. Hypercortisol stimulated
ammonia self-detoxifying mechanisms by enhancing
ammonia and
urea excretion, especially during severe exercise. At high swimming level, higher branchial clearance rates in
cortisol treated fish succeeded in eliminating the elevation of endogenous
ammonia, resulting in reduced plasma Tamm levels compared to control and
sham implanted fish. Carp easily induced anaerobic metabolism, both during routine and active swimming, with elevated
lactate levels as a consequence. Both feeding and
cortisol treatment increased this dependence on anaerobic metabolism. Hypercortisol induced both glycogenesis and gluconeogenesis resulting in
hyperglycemia and muscle and
liver glycogen deposition, most likely as a protective mechanism for prolonged stress situations and primarily fuelled by
protein mobilization.