METABOLIZABLE ENERGY-INTAKE AND SUSTAINED ENERGY-EXPENDITURE OF ALASKAN SLED DOGS DURING HEAVY EXERTION IN THE COLD

Objective-To measure energy expenditures of Alaskan sled dogs at rest and during racing under frigid conditions, using the doubly labeled wa ter (DLW) technique. Animals-18 fit Alaskan sled dogs. Procedure-Energ y expenditure was measured in 9 dogs during a 490-km sled dog race by use of the DLW technique, whereby dogs were administered water enriche d with nonradioactive isotopes of hydrogen and oxygen. Energy intake w as determined by dietary analysis. Changes in background abundance of the isotopes H-2 and O-18 were monitored in 5 dogs that did not receiv e isotope-enriched water.Results-Dogs completed the 490-km race at an average speed of 7 km/h at ambient temperature of -35 to -10 C. Total energy expenditure, measured by the DLW technique, was 47,100 +/- 5,90 0 kJ/d (4,400 +/- 400 kJ.kg(-0.75)/d), and metabolizable energy intake was 44,600 kJ/d (4,100 kJ.kg(-0.75)/d) during the 70-hour race. Concl usions-The sustained metabolic rate for these sled dogs during racing was extraordinarily high for a large mammal. This study validated use of the DLW technique in dogs with exceptionally high energy expenditur e associated with prolonged exercise in the cold.