CO2 Balance and Estimation of Ventilation Rates in Animal Studies

The CO 2 emissions were measured in environmental rooms in 15 animal operation studies, including studies of dairy cow, steer, swine, turkey, laying hen and broiler. The objectives of this paper are to summarize CO 2 emission data in these 15 studies;, to investigate the possible diet effect; and to evaluate the performance of the CO 2 balance approach to estimate ventilation rate (VR) of animal houses. Lower CO 2 emissions were observed from steers fed diets containing 60% DDGs as compared to that from steers fed the control diets (0% DDGs). Significant differences in CO2 emissions were observed among different studies for each species of broiler, laying hen, swine, and steer, which could be the result of different management practices, different stages of production, or different weather conditions. In 10 out of the 15 studies, the measured CO2 emissions were significantly larger than the estimated CO2 productions, which could represent the corresponding amount of CO2 generation that was not accounted in the metabolic CO 2 production as well as uncertainties in measurements of CO2 emissions. The overall R2 was 0.97 when treating each of the 15 studies as one data point. The relative differences between measured and estimated VR were in the range of 6.3% to 20.5%. Uncertainties in estimated VR in dairy cow studies were relatively large because the relatively large variations in measured CO2 emissions in these studies were not well represented by the relatively constant estimated CO2 production values.