Some cooling of hogs can be accomplished with air alone. There must be a temperature difference between the air and the pig's body core of about 10 degrees F or greater. That is, if the air temperature is above about 92 degrees there will be no cooling no matter how fast the air moves. Pigs in crates can be zone cooled, using one air duct per animal, aimed at the head. One study of snout cooling on farrowing sows showed an increased feed consumption of five percent and a five percent increase in piglet average daily weight gain, compared to the uncooled control group.
Water is one of the most effective ways to cool hogs.
The simplest is to wet the skin of the pig and let air movement evaporate the water. Use circulation fans or tunnel ventilation where necessary. Use sprinklers, not fogger nozzles, because fog droplets will raise the relative humidity excessively. However, the evaporative cooling may be more expensive to build than drip or sprinkling, and not be any more effective. A two-summer Oklahoma study of farrowing sows showed there was no significant difference between cooling the sow with drippers and cooling the entire room with an evaporator pad.