Summer Heat has Arrived

Summer heat arrived this weekend in the upper Midwest. Relatively high dew point temperatures (67F dew point at 8:30 am as I write this) mean pigs are having trouble dissipating heat. I continue to walk wean-finish and grow-finish sites that have either no water system installed or incorrectly installed or programmed mister systems.

In general I set controllers to turn on cooling water lines at 18F above set point (assumes 62F or lower set point in late finishing) in curtain sided barns and 20F in tunnel barns. Many producers still wait until temperatures are above 85F before providing water for heat relief. This is too late to begin assisting the growing pig with cooling as evidence suggests feed intake is reduced at temperatures above 77F for 136 lb pigs on partial slats.

Too many equipment installers and producers still use ‘mister’ type nozzles for cooling. This nozzle results in evaporative cooling of the air above the pig and doesn’t effectively wet the skin of the pig. Cool air above the pig means heat loss has to occur due to the difference in temperature between the skin temperature (95F) and the air temperature. This type of cooling is not as effective as when the pig evaporates the water from the skin surface.

In addition, fine mists tend to ‘drift’ with any type of wind current. Producers can be hesitant to use these systems on windy days in curtain barns since the ‘drift’ results in wet feed in feeders. Pens on the north side of a facility tend to gain little benefit when the ‘drift’ ends up watering the grass on the north side of the barn rather than wetting pigs in pens.

Thus, sprinklers that result in large water drops are recommended. When sized correctly you should only need to wet about 50-60% of the pen area. This will keep the water out of the feeder and allow those pigs that don’t want to be wet a place to stay dry.

The ON time in the controller should only be long enough to wet the skin of the pigs in the pen farthest from the water line’s point of entry to unit. If the complaint is excess water filling a pit due to long ON times, consider replumbing the line with the entry point in the middle of the room.

Pigs do not cool during the ON period. When the water hits the skin of the pig they vaso-constrict in response the abrupt temperature drop so heat transfer is minimal. The pigs cool when they evaporate the water. Generally, with well wetted pigs the OFF time in the controller should be 15-20 minutes to allow for effective evaporation.

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