When crop producers wished for summer heat to push corn and soybean crops along, they didn’t have our current weather as their goal. For grain farmers in the upper Midwest, there is enough moisture from all of the June rains that there are no indications of moisture stress even as we have temperatures in southern Minnesota approaching 100F yesterday and today with dew points close to 80F.

While corn and soybean plants may need heat units to attain maturity, these heat units are really hard on our pigs. This week I was with 2 different production groups that used little if any wetting of pigs in hot weather for heat relief. Their response to my questions was that at one time they felt they had respiratory or other health challenges as a result of ‘wetting’ pigs for heat relief so they felt they were better off not wetting pigs. In the past few months I’ve heard this comment from several producers.

When air temperatures are in the 90’s, if we don’t figure out how to add water to the skin of pigs for evaporative cooling, they suffer terribly from heat and may even have an increased death loss. Data published in 2005 showed that on partially slatted floors, feed intake for 132 lb pigs decreased when air temperatures hit 77F, which is considerably lower than the 90+F temperatures this week.

Skin temperature of a growing pig is approximately 95F. When air temperature is near 95F or even above 95F, there is no possibility of the pig loosing metabolic heat by a difference in air temperature. Blowing 95F air across the surface of a 95F pig results in no heat transfer unless we allow the pig to wet the skin surface and loose heat by evaporation.

The basics of wetting pigs for summer cooling are:
• Wet the pig and then let it dry. The pig looses heat by drying, not during the wetting process
• Use big droplets to wet pigs. A fine mist cools the air above the pigs and increases humidity. A fine mist also ‘drifts’ in the wind and is more apt to wet feeders and the grass on the north side of curtain barns.
• The target is to wet no more than 60% of the pen area so pigs that may not be feeling good can avoid getting wet and you can avoid water in the feeders.
• For curtain barns, set the cooling to begin at 18F above set point. For tunnel barns, because I know there will be a very effective draft, set it at 20F above set point.
• Many now install a time clock on the solenoid for the cooling system with it set to shut the system off from midnight to 8 am or 2 am to 10 am, a long enough period of time for the flooring and facility to completely dry out.