If you think your job is stressful, consider the job of a broodmare–in most performance horse circles she’s expected to have one foal per year for six out of seven years to be considered successful. This belief stirs up the perennial question, should you breed on the foal heat?

"There is only a period of approximately one month after foaling to establish pregnancy if the mare is to foal at the same time the following year, which is often desired," explained Tom Stout, VetMB, PhD, of Utrecht University’s Department of Equine Sciences, in The Netherlands at the recent American Association of Equine Practitioners’ Convention, held Dec. 1-5 in Anaheim, Calif.

Although mares come into heat within five to 12 days of foaling, and many can conceive, they might not be ready to maintain a pregnancy. The uterus might not be fully finished undergoing normal involution (returning to its regular size and shape) by the time the foal heat comes, making it uninhabitable by a fetus, or the mare could develop inflammation of the uterine lining called post-breeding endometritis.

"The major dilemma for breeders is whether to breed on the foal heat or to wait until the second heat when there is a better chance of pregnancy maintenance," noted Stout. "The catch is that not all mares will cycle normally following the foal heat."

Specific factors to consider when making this decision include:

  • Time of year the mare foals Mares that foal early in the year might be more at risk of not resuming normal estrous cycles after the foal heat (due to the decreased amount of light in the Nor