From 4–14 days after birth, foals often develop a mild, self-limiting diarrhea. During this time, the dam is usually undergoing her first estrous cycle, hence the name “foal heat diarrhea.” However, diarrhea can also occur at this time in orphan foals; therefore, hormonal activity in the mare is unlikely to be involved in the pathogenesis. Although the cause is unknown, it may be associated with alterations in the foal's intestinal microbial flora or alteration in diet as the foal begins to eat small amounts of hay and grain. Coprophagy may also have a role.

The foal remains active and alert and has a normal appetite. Vital signs remain normal. Feces are semiformed to watery and not malodorous. Monitoring is important to ensure the foal's condition does not deteriorate. Specific treatment is usually not necessary, but application of a protectant to the skin around the perineum helps prevent scalding of the buttocks.

Last full review/revision March 2012 by Allison J. Stewart, BVSC (Hons), MS, DACVIM-LA, DACVECC; John E. Madigan, DVM, MS