The effect of feeding on CO2 production and energy expenditure in ponies measured by indirect calorimetry and the 13C-bicarbonate technique

Abstract

Energy expenditure (EE) can be estimated based on respiratory gas exchange measurements, traditionally done in respiration chambers by indirect calorimetry (IC). However, the 13 C-bicarbonate technique ( 13 C-BT) might be an alternative minimal invasive method for estimation of CO 2 production and EE in the field. In this study, four Shetland ponies were used to explore the effect of feeding on CO 2 production and EE measured simultaneously by IC and 13 C-BT. The ponies were individually housed in respiration chambers and received either a single oral or intravenous (IV) bolus dose of 13 C-labelled sodium bicarbonate (NaH 13 CO 3 ). The ponies were fed haylage 3 h before ( T − 3 ), simultaneously with ( T 0 ) or 3 h after ( T + 3 ) administration of 13 C-bicarbonate. The CO 2 produced and O 2 consumed by the ponies were measured for 6 h with both administration routes of 13 C-bicarbonate at the three different feeding times. Feeding time affected the CO 2 production ( P < 0.001) and O 2 consumption ( P < 0.001), but not the respiratory quotient (RQ) measured by IC. The recovery factor (RF) of 13 C in breath CO 2 was affected by feeding time ( P < 0.01) and three different RF were used in the calculation of CO 2 production measured by 13 C-BT. An average RQ was used for the calculations of EE. There was no difference between IC and 13 C-BT for estimation of CO 2 production. An effect of feeding time ( P < 0.001) on the estimated EE was found, with higher EE when feed was offered ( T 0 and T + 3 ) compared with when no feed was available ( T − 3 ) during measurements. In conclusion, this study showed that feeding time affects the RF and measurements of CO 2 production and EE. This should be considered when the 13 C-BT is used in the field. IV administration of 13 C-bicarbonate is recommended in future studies with horses to avoid complex 13 C enrichment-time curves with maxima and shoulders as observed in several experiments with oral administration of 13 C-bicarbonate.Keywords: 13 C-bicarbonate, indirect calorimetry, energy expenditure, pony ImplicationsEnergy expenditure (EE) can be estimated based on measurements of respiratory gas exchange. This is traditionally done by indirect calorimetry in respiration chambers. However, the horse has to be confined to the chamber during measurements, which might affect its normal behaviour. Moreover, this technique requires expensive research facilities and skilled personnel. The minimal invasive stable isotope 13 C technique for measuring EE in the field was evaluated successfully in ponies. The present study developed this technique further and the results provide new information on how it can be used under field conditions.

Estimation of energy expenditure using the oral 13C‐bicarbonate technique in privately owned adult and senior dogs of three different body sizes

“…The isotope excretion time after NaH 13 CO 3 administration is relatively fast, minutes to hours, again depending on the size of the subject. The 13 CBT has been validated against IC in many different species of animals (mouse: Speakman & Thomson, 1997; goats: Junghans et al, 1997; bulls: Junghans et al, 2007; humans: Junghans et al, 2008; mink: Larsson & Tauson, 2012; ponies: Jensen et al, 2015; Jensen et al, 2015) including dogs (Larsson et al, 2014; Larsson et al, 2014). Previous studies in dogs and ponies have suggested that measurements with the 13 CBT can be performed in a minimally invasive way by using oral administration of the isotope and collection of breath samples for isotope ratio analyses (Jensen, Larsson, et al, 2015; Larsson et al, 2015; Larsson, Jensen, et al, 2014; Larsson, Vitger, et al, 2014).…”