How to Detect Early Pregnancy in Mares

Mares can become pregnant seven days after giving birth.

A mare's estrous cycle -- the time between the ovulation of one egg and the next -- runs about 21 days. Estrus, when the mare is sexually receptive, occupies approximately seven days of the cycle, but may last between two days and three weeks. "Teasing" your mare with a stallion to see how she reacts can help you pinpoint when her estrus cycle occurs and determine when she is ready to breed. Because pregnancy in your mare lasts 11 months, early detection of a viable embryo allows you to provide her with the proper nutrition and veterinary care that leads to a healthy, happy foal.

Instructions

1. Note the first and last day of breeding for your mare. Cover, or breed, your mare on the third day of her estrus cycle and every other day until the cycle ends -- usually seven days. Breeding at least three times during the cycle optimizes the chance of pregnancy.

2. "Tease" your mare with a stallion and observe her behavior. If she has returned to estrus -- meaning she is not pregnant -- she will stand calmly, squat and evert her vulva in a "winking" motion; she may raise her tail and urinate. Pregnant mares rebuff the stallion by squealing, kicking, laying back their ears and other agitated behaviors.

3. Allow your veterinarian to palpate the mare's uterus through her rectum. By day 16 to 17 of pregnancy, the uterus elongates and becomes firm and tubular. By the fourth week of pregnancy, the vet feels an embryo the approximate size of a small egg.

4. Permit the veterinarian to perform a rectal ultrasound examination on your mare after day 17 of the last breeding. The embryo implants on the uterine wall by this date and can be seen by the ultrasonic probe. If you choose to wait until day 23 or 24, the ultrasound will detect a fetal heartbeat.

5. Consent to have your mare blood-tested for equine chorionic gonadotropin -- eCG -- a hormone found only in pregnant mares.

Tips & Warnings

• When teasing your mare, keep a tall barrier between the stallion and the mare as a safety measure. If she has a newborn foal at her side, pull the foal away long enough for the stallion to smell the mare's vulva and get a reaction, then put the foal and mare back together.

• Ask your vet to pinpoint a fetal heartbeat with ultrasonography on the mare's side. Draw an "X" in permanent marker on that spot so that you can listen for the heartbeat using a stethoscope.

• If you choose to have your mare tested for eCG, note that the hormone remains elevated even after fetal death, according to veterinarians at Louisiana State University. This means that you may think your mare is pregnant even after she miscarries.

• For safety reasons, never ride a stallion up to a mare to tease her. You will be at risk of being bucked off or kicked and seriously injured.

References

• University of Minnesota Extension: Breeding Your Mare
• Louisiana State University Veterinary Medical School: Equine Pregnancy
• "Equine Reproductive Physiology, Breeding and Stud Management"; Mina C. G. Davies Morel; 2003

Resources

• PetPlace.com: Care of the Normal Pregnant Mare
• TheHorse.com: Preparing for Foaling