Computational Fluid Dynamics Analysis of Alternative Ventilation Schemes in Cage-Free Poultry Housing

Simple Summary Uncertainty regarding "cage-free" housing guidelines have left egg producers unsure about how to transition to cage-free housing. A primary driving force behind cage-free housing is the perceived animal welfare concerns for caged birds. Therefore, it is of great importance to perform a systematic investigation on specific cage-free facility types with an emphasis on bird comfort assessment. Thus, the goal of this study was to investigate alternative ventilation schemes of a cage-free house to provide practical designs for a comfortable interior environment at the hen level. By modeling four different ventilation schemes in a one-eighth section of a typical floor-raised layer house-indoor temperature, air speed, and static pressure were compared and analyzed quantitatively. Distribution contours and quantitative analysis of airflow, temperature, and pressure suggested that indoor conditions could be maintained at a suitable range uniformly, especially at the hen level. In addition, the ventilation rates of the hen house within four ventilation schemes fell at the higher end of the desired ventilation range, indicating that the barn could be expected to maintain good air quality during cold weather. This study demonstrated that computational fluid dynamics modeling was a powerful tool that facilitated researchers to address animal welfare issues in animal housing designs. This work investigated alternative ventilation schemes to help define a proper ventilation system design in cage-free hen houses with the goal of assuring bird welfare through comfortable conditions. Computational fluid dynamics (CFD) modeling was employed to simulate indoor and outdoor airflows to quantify the effectiveness of ventilation systems in maintaining suitable and uniform living conditions at the hen level. Four three-dimensional CFD models were developed based on a full-scale floor-raised layer house, corresponding to ventilation schemes of the standard top-wall inlet, sidewall exhaust, and three alternatives: mid-wall inlet, ceiling exhaust; mid-wall inlet, ridge exhaust; and mid-wall inlet, attic exhaust with potential for pre-treatment of exhaust air. In a sophisticated and powerful achievement of the analysis, 2365 birds were individually modeled with simplified bird-shapes to represent a realistic number, body heat, and airflow obstruction of hens housed. The simulated ventilation rate for the layer house models was 1.9-2.0 m(3)/s (4100 ft(3)/min) in the desired range for cold weather (0 degrees C). Simulation results and subsequent analyses demonstrated that these alternative models had the capacity to create satisfactory comfortable temperature and air velocity at the hen level. A full-scale CFD model with individual hen models presented robustness in evaluating bird welfare conditions.