ABSTRACT

The oral ¹³C-bicarbonate technique (o¹³CBT) can be used for short-term measurements of CO₂ production (RCO₂) and energy expenditure (EEx). The method relies on appropriate estimates for the respiratory quotient (RQ) and recovery factor (RF) of ¹³C. Four Retriever dogs were included in four experiments to validate the o¹³CBT against indirect calorimetry (IC), and determine RQ and RF; Expt. 1: feeding different protein:fat:carbohydrate ratios [in % of metabolisable energy]: 25:33:42 in a maintenance (Mnt.) diet; 38:26:36 in a high-protein high-fibre (H_Fibre) diet and 27:56:17 in a high-fat (H_Fat) diet, simultaneously with start of measurements (T₀); Expt. 2: the Mnt. diet at T₀ or 4 h postprandial (T₄); Expt. 3: T₄ at different ambient temperatures, 22°C and 15°C; Expt. 4: T₄ after 1 h physical activity. The RCO₂ and EEx were determined from the respiration chamber measurements made simultaneously with IC and the o¹³CBT (o¹³CBT_online), and in Expts. 1 and 2, also on two consecutive days using o¹³CBT with collection of breath into breath bags (o¹³CBT_breathbags). The RQ values obtained at T₀ reflected dietary compositions, with the highest least square mean (LSM) of 0.954 for the Mnt. diet, 0.905 for the H_Fibre and 0.877 for the H_Fat diet (p < 0.05). An increased interval between meal and measurement period decreased RQ significantly (p < 0.05) in Expt. 2, LSM being 0.954 at T₀ and 0.909 at T₄. Ambient temperature (Expt. 3) and physical activity (Expt. 4) did not influence postprandial RQ. The RF values were not significantly affected by diet (Expt. 1). Measurements starting at T₀ (Expt. 2) resulted in higher (p < 0.05) RF values than at T₄ (LSM = 0.971 and 0.836, respectively). The ambient temperatures (Expt. 3) did not influence postprandial RF. However, when dogs were physically active prior to measurements (Expt. 4), RF values (LSM = 1.019) were higher (p < 0.05) than when resting only (LSM = 0.836). Calculations based on RQ and RF determined in each experiment resulted in RCO₂ and EEx values which were not different regardless of method used, except for Expt. 1 where EEx-values [kJ · kg BW^–0.75 · d^–1] were higher (p < 0.05) when measured with o¹³CBT_breathbags (460) than by IC (421) and o¹³CBT_online (420). Provided accurate RQ and RF values, the o¹³CBT_breathbags can be used as an independent and minimally invasive research tool to determine EEx in dogs under carefully standardised conditions.

摘要

口服¹³ C-碳酸氢盐技术 (o ^{13 CBT) 可用于 CO} ₂产生 ( R CO ₂ ) 和能量消耗 (EEx)的短期测量。该方法依赖于对¹³ C 的呼吸商 (RQ) 和恢复因子 (RF) 的适当估计。四个实验中包括四只猎犬，以验证 o ¹³ CBT 与间接量热法 (IC) 的对比，并确定 RQ 和 RF；过期。1：在维持（Mnt.）饮食中饲喂不同的蛋白质：脂肪：碳水化合物比例[以可代谢能量的百分比]：25:33:42；38:26:36 高蛋白高纤维 (H _Fiber ) 饮食和 27:56:17 高脂肪 (H _Fat) 饮食，同时开始测量 (T ₀ )；过期。2：Mnt。餐后T _{0或 4 小时 (T 4} )饮食；过期。3：不同环境温度下的T ₄，22°C和15°C；过期。4 ： 1 小时体力活动后的T _{4 。}R CO _{2和 EEx 是从与 IC 和 o} ¹³ CBT（o ¹³ CBT _online）以及在Expts中同时进行的呼吸室测量中确定的。1和2，也连续两天使用 o ¹³将呼吸收集到呼吸袋中的 CBT（o ^{13 个}CBT呼吸_袋）。_{在 T 0}获得的 RQ 值反映了膳食成分，Mnt 的最高最小二乘均值 (LSM) 为 0.954。_H纤维饮食为 0.905， H_脂肪饮食为 0.877 （ p < 0.05）。进餐和测量期间之间的间隔增加显着降低了Expt中的 RQ ( p < 0.05) 。如图2所示，LSM 在 T _{0时为 0.954，在 T 4}时为 0.909 。环境温度（Expt. 3）和体力活动（Expt. 4) 不影响餐后 RQ。RF 值不受饮食的显着影响（实验 1）。从 T ₀ ( Expt. 2 ) 开始的测量导致比 T _{4时更高的 (} p < 0.05) RF 值（LSM = 0.971 和 0.836，分别）。环境温度（实验3）不影响餐后射频。然而，当狗在测量前进行身体活动时（实验 4），RF 值（LSM = 1.019）高于仅休息时（LSM = 0.836）（p < 0.05）。基于在每个实验中确定的 RQ 和 RF 计算得出R CO ₂和 EEx 值无论使用何种方法都没有差异，除了Expt。1其中，当使用 o ^{13 个}CBT_呼吸袋(460) 测量时，EEx 值 [kJ · kg BW ^–0.75 · d ^–1 ] 高于使用 IC (421) 和 o ¹³ CBT_在线(420)测量时 ( p < 0.05 )。^{o 13} CBT_呼吸袋提供准确的 RQ 和 RF 值，可用作独立的微创研究工具，在仔细标准化的条件下确定狗的 EEx。