Wallowing in mud or water is a fundamental thermoregulatory behavior in pigs. Denial of wallowing opportunities has significant welfare implications that are increasingly recognized in welfare frameworks.
Wallowing is so fundamental to pig thermoregulation and skin care that its denial constitutes a welfare deficit whenever temperatures are high enough to trigger the behavior. Indoor pigs in conventional systems have no opportunity to perform this strongly motivated natural behavior. Outdoor pigs without mud wallow access seek any available water source and show behavioral frustration. Providing wallow facilities to outdoor pigs in summer dramatically reduces heat stress indicators. As climate change increases summer temperatures, wallow provision becomes an increasingly important welfare obligation for outdoor pig keepers.