The effect of a reduction in animal housing density during the growing-fattening period on air quality and growth performance

Two trials were performed using 168 growing-fattening pigs in order to determine the effect of air renewal rate and housing density on growth performance and health status. Two air renewal rates (minimum and optimum) and two housing densities (0.70 and 0.93 m2/pig) were tested using a factorial 2 x 2 model. The minimum flow rate (DO) started at 8 m3/h/pig at 27 kg and was increased up to 19 m3/h/pig at 110 kg live weight. The optimum flow rate increased from 15 to 50 m3/h/pig over the same weight range. Temperature and humidity remained constant at 24°C and 65 %.Air quality (gas, dust and germs) were measured. Health status was noted during the growing-fattening period and at slaughter (pneumonia). Behaviour was also studied.The treatment DO decreased the concentrations of gas, dust and germs. Housing density had little effect on air quality, except for the concentration of ammonia which was increased for 0.93 m2/pig compared to 0.70 m2/pig. Health status was not affected by treatment. Treatment DM reduced growth rate by 6 % and average feed intake by 120 g/d.A decrease in housing density improved pig performance mainly for the DO treatment.The air renewal rate DM caused the pigs to go to the feeder more frequently. Once at the feeder they spent less time and consumed less per visit.