Estrus Detection in Mares

Mares are seasonal polyestrous breeders meaning they have several cycles during specific times of the year.  Usually the cycle period is from March through September. During this period, the open and lactating mare undergoes a series of cycles, (approximately 22 days in length).  Estrus, or heat, is three to seven days in length and is the time when a mare is receptive to the stallion. The estrus portion of the cycle must be accurately determined because it is the period during which the mare must be bred in order to conceive. Ovulation (release of the egg for fertilization) usually occurs 24 to 48 hours before the end of estrus.  Conception rates are highest when the mare is bred 36 hours before and up to ovulation. Teasing is a way to determine if a mare is in heat by her response to the stallion.  The teasing process is necessary because mares do not predictably show signs of heat, either alone or with a group of mares, as other livestock do.  Here is a short video on Estrus Behavior in Mares from eXHorses.

Here are some publications from the University of Tennessee on Heat Detection and Teasing Systems for Mares and Oklahoma State University on Reproductive Management of the Mare.