Partial recycling of ambient air in a piggery

Two ventilation systems were studied in two identical piggeries equipped with total slatted floors. Data were collected on pig growth performance and health status as well as on the quality of ambient air. Two trials were conducted. The first trial used a classical ventilation system compared to a recycling system, where the recycling fan was adjusted (the quantity of air recycled varied from 0 to 33m3/h/pig). In the second trial the classical system was compared to a recycling system but this time the ventilation rate was constant (air recycling varied from 0 to 68m3/h/pig).During the two trials the mean temperature (24°C), the CO2 level (0.25%) and the NH3 concentrations (19 ppm) were the same for all the systems used. There were no differences between treatments for health status and pig growth performance.However, dust concentrations for the classical and the recycling systems were different (2.36 mg/m3 vs 1.25 mg/m3, respectively ; p