Energy cost of physical activities in growing broilers

1. The time-energy budget method estimates the energy used for physical activity (PA) by integrating behaviour PA patterns with energy cost for specific PAs. Nevertheless, information about individual energy cost by type of PA are not available and so this study estimated the energy cost of PA for growing broilers. 2. An indirect calorimetry system for single birds was constructed to measure the variation in the rate of O₂ consumption (V˙O₂, L/min) and rate of CO₂ production (V˙CO₂, L/min) produced by these PAs. 3. A total of five birds were used in a replicated trial where their body weight (BW) ranged from 1.5 to 2.5 kg to measure the increase in heat production (HP) above resting levels as a result of PA. The procedure in the chamber was divided into five steps: (1) initial baselining, (2) resting metabolic rate, (3) PA such as feeding, drinking and other standing activities, (4) removal of gas exchange produced in step 3, and (5) final baselining. The PA was recorded using a video camera fixed at the chamber’s top (and outside). 4. The area under V˙CO₂ and V˙O₂ curves was used to calculate the CO₂ production (vCO₂, L) and O₂ consumption (vO₂, L). Then, the HP (cal/kg^−0.75) was calculated according to the Brouwer equation. Two observers analysed the video records to estimate the time spent for each PA (seconds and frequency). 5. To calculate the energetic coefficients, the HP was regressed with the function of time spent to perform each PA allowing to estimate the energy cost for eating, drinking and stand activities, which were 0.607, 0.352 and 0.938 cal/kg^−0.75/s, respectively.

1. 时间-能量预算法通过将体力活动（Physical Activity, PA）的行为模式与特定体力活动的能量消耗相结合，来估算体力活动所消耗的能量。然而，目前尚无按体力活动类型划分的个体能量消耗数据，因此本研究针对生长肉鸡的体力活动能量消耗进行了估算。
2. 本研究搭建了一套针对单只肉鸡的间接测热系统，用于测量这些体力活动所引发的氧气消耗速率（V̇O₂，单位：升/分钟）与二氧化碳生成速率（V̇CO₂，单位：升/分钟）的变化情况。
3. 本研究共选用5只肉鸡开展重复试验，试验个体的体重（Body Weight, BW）介于1.5~2.5 kg之间，旨在测量体力活动导致的产热量（Heat Production, HP）相较于静息水平的增量。代谢舱内的试验流程分为五个步骤：(1) 初始基线校准；(2) 静息代谢率测定；(3) 体力活动阶段，包括采食、饮水及其他站立活动；(4) 清除步骤3中产生的气体交换产物；(5) 最终基线校准。试验过程中，通过固定在代谢舱顶部（及外部）的摄像机记录体力活动情况。
4. 通过计算V̇CO₂与V̇O₂曲线下的面积，可得到二氧化碳生成量（vCO₂，单位：升）与氧气消耗量（vO₂，单位：升）。随后，根据Brouwer公式计算产热量（单位：卡路里·千克^-0.75）。由两名观察员分析录像记录，以估算每种体力活动的持续时长（单位：秒）及发生频率。
5. 为计算能量系数，本研究将产热量与每种体力活动的持续时长进行回归分析，由此估算出采食、饮水及站立活动的能量消耗分别为0.607、0.352及0.938 卡路里·千克^-0.75/秒。