The oral (13)C-bicarbonate technique for estimation of energy expenditure in dogs: validation against indirect calorimetry.

To get more knowledge about the energy requirements of dogs and to formulate appropriate feeding guidelines, it is essential to determine their energy expenditure (EE) in a reliable and feasible way. In this study, the non-invasive oral stable isotope (13)C-bicarbonate technique (o(13)CBT) was validated against indirect calorimetry (IC) for the determination of CO2-production and EE in dogs. Eleven privately owned dogs were simultaneously measured with IC and the o(13)CBT after being fasted overnight. All dogs were measured twice on two separate days. For calculation, measurements were divided into two groups depending on dogs' behaviour during the measurement. Dogs of Group 1 (n = 17) were resting calmly in the chamber and dogs of Group 2 (n = 5) were more active. Mean heart rate was significantly higher in Group 2 (102 beats per minute [bpm]) than in Group 1 (77 bpm) (p < 0.001). Within groups, the CO2-production and EE [kJ d(-1) kg BW(-0.75)] estimated by the o(13)CBT or IC did not differ significantly (Group 1: [Formula: see text] = 368; EEIC = 363; Group 2: [Formula: see text] = 701; EEIC = 718). However, the estimated (13)C recovery factor (RF) for the estimation of CO2-production was significantly different between Groups 1 and 2 (0.72 and 0.94, respectively, p < 0.001). The respiratory quotient (RQ), which is needed for the estimation of EE, did not differ between groups. This study shows that the non-invasive o(13)CBT can be used for accurate estimation of the CO2-production rate and EE in resting dogs. A value of 0.77 can be applied as an estimate of the RQ in fasted dogs and 0.72 as an appropriate estimate for RF when dogs are resting calmly during the measurements.