Rate of carbon dioxide production and energy expenditure in fed and food-deprived adult dogs determined by indirect calorimetry and isotopic methods

Abstract

Objective - To evaluate energy expenditure (EE) in dogs by estimating rate Of CO2 production (rCO2). Animals - 15 Beagles. Procedure - Food was withheld for 24 hours, and all dogs received an IV infusion of 13C sodium bicarbonate for 8 hours. Breath samples were collected before infusion and at 30-minute intervals from 4 to 8 hours, and 13C enrichment in breath CO2 was measured, using gas chromatography-isotopic ratio mass spectrometry. Food was withheld from 6 dogs, and rCO2 and O2 consumption were measured, using a conventional indirect calorimeter. The CO2 production and O2 consumption were measured by use of indirect calorimetry in 6 other fed dogs that were injected with 2H2O and H218O. Blood samples were collected before tracer injection, 4 hours later, and on days 4, 7, and 11. Deuterium and 18O enrichments in plasma water were determined. Results - Mean rCO2 measured by indirect calorimetry was 516 ± 34 and 410 ± 16 μmol/kg0.75/min in 6 fed and 6 food-deprived dogs, respectively. The rCO2 calculated from 13C-bicarbonate dilution was 482 ± 30 μmol/kg0.75/min. Mean rCO2 determined by use of the double-labeled water method was 1,036 ± 46 mmol/kg0.75/d. Mean energy expenditure calculated from rCO2 determined by infusion of 13C bicarbonate, indirect calorimetry in fed and food-deprived dogs, and infusion of double-labeled water was 386 ± 39, 379 ± 25, 338 ± 14, and 552 ± 25 kJ/kg0.75/d, respectively. Conclusions and Clinical Relevance - Energy expenditure calculated by indirect calorimetry in unfed dogs can be considered representative of basal metabolic rate.