How to Assess Mare Pregnancy

Mares typically enter heat during the spring months due to increased daylight. Throughout the spring and summer, a mare typically goes into heat every 3 weeks. If you own a breeding mare or if your mare has been in contact with a stallion during her heat cycle, you may want to determine if she is pregnant. The gestation period for horses is 11 months, and mares do not begin to visibly show signs of pregnancy until the final 3 months. Here are steps to check mares for pregnancy.

Observe the mare's behavior around stallions. A mare suspected to be pregnant can be introduced to a stallion fourteen days after the last contact with the stallion to observe her response, which may indicate pregnancy. A pregnant mare is likely to reject the advances of the stallion and avoid presenting her rear end, behaviors typical during heat. It's worth noting that a mare not in heat may also reject the stallion's advances for other reasons.

Observe your breeding mare for signs of heat. Some mares exhibit behaviors such as raising their tails, opening and closing the lips of the vulva, and squatting to release urine or mucus during their heat cycles. If these behaviors are observed 21 days after potential impregnation, the mare is likely not pregnant.

Arrange for a veterinarian to perform a transrectal palpation. Between 16 to 19 days after the mare's contact with a stallion, a veterinarian can conduct a transrectal palpation. This involves the vet inserting their hand into the mare's rectum to assess the uterus for signs of pregnancy, including its size, shape, and any swellings on the ovaries.

Arrange for a veterinarian to perform an ultrasound examination. An ultrasound examination can detect pregnancy as early as 16 days after breeding. Between 55 to 70 days, the sex of the fetus may also be determined. Ultrasound utilizes sound waves to generate images of the uterus and can monitor the fetus's heartbeat, making it the most reliable method for confirming pregnancy.

Have a blood test conducted on your mare. A blood test can detect pregnancy hormones in a pregnant mare, providing an alternative to non-chemical methods. This is particularly useful if the mare is uncooperative for physical exams or if rectal examination is not feasible. Testing for pregnant mare serum gonadotropin (PMSG) between 40 to 100 days post-breeding can confirm pregnancy. Additionally, analyzing the level of oestrone sulphate 100 days after breeding can provide further confirmation.

Utilize a urine test for your breeding mare. Oestrone sulphate, an indicator of pregnancy, can be detected in the urine of pregnant mares. This test can be conducted by a veterinarian or using a home test kit. Follow these steps for the urine test: obtain a home pregnancy testing kit, collect your mare's urine 110 to 300 days post-breeding, cut a container in half to collect urine, and follow the test kit instructions for analysis, which typically takes 10 minutes.

Verify pregnancy test outcomes. While chemical tests may suggest pregnancy in mares, it's prudent to have a secondary test conducted by a veterinarian, regardless of the method used. This additional confirmation ensures that the fetus has not been lost and helps mitigate the risk of false positives due to improper test administration.