Validation of the oral ¹³C-bicarbonate tracer technique against indirect calorimetry for the estimation of energy expenditure in resting dogs

Abstract

To be able to provide guidelines for appropriate nutrition of dogs, a reliable and feasible method for investigations of their energy expenditure (EE) would be very valuable. The ¹³C-bicarbonate tracer technique (¹³C-BTT) has been used to assess EE in several species of animals (Junghans et al., 2007; Lachica and Aguilera, 2003) and in humans (Junghans et al., 2008). This stable isotope method is based on the ¹³C kinetics in breath CO₂ after administration of ¹³C labeled sodium bicarbonate (NaH¹³CO₃). After tracer administration, the ratio between the ¹³C and ¹²C in spot samples of expired air collected over a sufficient period of time can be used to estimate the CO₂ production rate (RCO₂) and thereafter the EE. By using oral administration of the tracer the method can be completely non-invasive, making it an appropriate method for studies in dogs. The aim of this study was to validate the oral ¹³C-BTT (o¹³C-BTT) against indirect calorimetry, the ‘gold standard’ for the estimation of EE. The hypothesis is that the o¹³C-BTT can be used as a minimal restrictive and non-invasive method to obtain reliable estimates of EE in dogs under near natural conditions.