Instructions
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.
"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.
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.
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.
Consent to have your mare blood-tested for equine chorionic gonadotropin -- eCG -- a hormone found only in pregnant mares.
How to Detect Early Pregnancy in Mares
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.