Air exchanges and indoor carbon dioxide concentration in Australian pig buildings: effect of housing and management factors

There has been a growing interest in improving air quality within livestock buildings. However, the influence of housing and management factors on air exchange rates and indoor gas concentrations is not well understood. The aim of this study was to determine the effects of housing and management factors on the concentrations of carbon dioxide (CO2) and air exchange rates in 160 representative Australian pig buildings. CO2 concentrations were measured, air changes per hour (ACH) were estimated using a CO2 balance method, and structural and management parameters were recorded. The mean CO2 concentration measured was 858 ppm and a mean air exchange rate of 22.8 ACH was estimated. The analysis showed that CO2 concentrations were affected by the type of building, season, control of the wall and ridge vents, ceiling height, size of the wall vents and height of the ridge vents. Weaner buildings had the highest CO2 concentrations while deep-bedding shelters had the lowest. Winter CO2 concentrations were higher in all buildings compared to summer. Buildings with automated ridge ventilation control had the lowest CO2 concentrations. The wall ventilation inlet height was negatively correlated with CO2 concentration. Air exchange rates were primarily affected by the type of ventilation, inlet height, stocking density, and building width and height. In conclusion, the equable Australian climate has allowed the construction of cheaper pig buildings, which provide an adequate environment for pig production, although these buildings may not always provide an optimal environment for pig production