Energy cost of physical activities in growing broilers.

The time-energy budget method estimates the energy used for physical activity (PA) based on recorded daily patterns and indirect calorimetry. 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.An indirect calorimetry system for single birds was constructed to measure the variation in the rate of O 2 consumption ( V ˙ O 2 , L/min) and rate of CO 2 production ( V ˙ CO 2 , L/min) produced by these PAs.A total of five birds were used in a replicated trialwhere 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).The area under V ˙ CO 2 and V ˙ O 2 curves was used to calculate the CO 2 production (vCO 2 , L) and O 2 consumption (vO 2 , 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).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.