title: 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 13C-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.
authors.affiliation: 1Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences,University of Copenhagen,DK-1870 Frederiksberg C,Denmark.
authors.forename: R B
authors.initials: RB
authors.lastname: Jensen
authors.affiliation: 1Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences,University of Copenhagen,DK-1870 Frederiksberg C,Denmark.
authors.forename: T D
authors.initials: TD
authors.lastname: Kyrstein
authors.affiliation: 2Leibniz Institute for Farm Animal Biology,Institute of Nutritional Physiology 'Oskar Kellner',D-18196 Dummerstorf,Germany.
authors.forename: P
authors.initials: P
authors.lastname: Junghans
authors.affiliation: 1Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences,University of Copenhagen,DK-1870 Frederiksberg C,Denmark.
authors.forename: A H
authors.initials: AH
authors.lastname: Tauson
mesh_terms: D000818:Animals; D001639:Bicarbonates / Q000008:administration & dosage* / Q000032:analysis; D002153:Calorimetry, Indirect / Q000662:veterinary; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000008:administration & dosage / Q000032:analysis; D004734:Energy Metabolism; D006736:Horses / Q000502:physiology*; D008297:Male; D012119:Respiration
chemical_list: D001639:Bicarbonates; D002247:Carbon Isotopes; D002245:Carbon Dioxide
keywords: 13C-bicarbonate; energy expenditure; indirect calorimetry; pony