TECHNICAL NOTE: Comparison of Thermostatic and Humidistatic Controls of Ventilation in a Modified Open Front Swine Finishing Facility1

Four experiments were conducted to compare the CO2 and relative humidity levels in a modified open front swine finishing house under 2 types of ventilation controls - thermostat and humidistat. The first 3 experiments were conducted during the winter. In Exp. 1, a thermostat (set at 18.3°C) activated an automatic winch to open or close a ventilating curtain. In the other room, the automatic winch was controlled by a humidistat [set at 55% relative humidity (RH) with an over-riding thermostat setat 12°C]. Experiments 2 and 3 were conducted in the same manner except that in the humidistat-controlled room, the overriding thermostat was set at 14.4 to 15.5°C, and a heater was employed to maintain a temperature similar to that of the thermostat-controlled room. Experiment 4 was conducted with a lower humidistat setting and identical thermostat settings in each room to measure room effects. Carbon dioxide concentrations and RH were significantly lower (P < 0.05) in the humidistat-controlled room than in the thermostat-controlled room in Exp. 1, 2, and 3. No differences between rooms were observed for lung or snout scores in the 3 experiments (P > 0.05). As anticipated because of the identical settings in Exp. 4, CO2 concentration and RH were similar in both rooms, as were all measures of growth performance. These results indicate that a humidistat can be used to reduce RH and CO2 concentrations in a swine-finishing facility.