Effect of the humidity level of ambient air (temperature 28°C) on the growth performance of growing-finishing pigs

An experiment was carried out on 144 cross-bred growing-finishing pigs to determine the effect of ambient air relative humidity levels on growth performance and on animal health. Three relative humidity levels were studied (45%, 60% and 75%) while the ambient temperature was maintained at 28 °C. Only one diet was used and it was available ad libitum.The atmospheric conditions were measured (temperature, hygrometry, air replacement flow rate, gas, dust, germs) as well as the evolution in sanitary conditions (the incidence of coughing and sneezing and the number of veterinary treatments).The lungs were examined at the slaughterhouse.Feed intake was significantly reduced by the increase in hygrometric level. The average decrease was 140g/day and growth rate was reduced by 7% when the relative humidity level increased from 45% to 75%. However the energy metabolism of the animals was unaffected and food conversion ratio remained constant whatever the hygrometric level.Air quality was significantly modified by a high hygrometric level increasing the number of dust particles, however, this had no effect on the health status of the animals.