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Preparing yourself and your mare for breeding
Caity Cosentino, DVM
Deciding to breed your mare is a big decision. Whether this is your first time having a horse bred, or you’ve had mares bred before, there are a number of things to consider prior to having your mare covered by a stallion or artificially inseminated. Like any worthwhile endeavor, having a mare carry a pregnancy is not without its risks. Mares who become pregnant have the possibility of losing the pregnancy or even losing their own lives giving birth to the foal. Making sure your mare is a good candidate to carry a foal full term is an important first step in the breeding process.
Thorough reproductive examination by a veterinarian should be performed prior to when you want the mare bred. It is easiest to perform the exam when a mare is in heat, but the exam can be performed at any time. This examination will include multiple parts:
- A physical examination to determine the mare is overall healthy, listening to heart and lungs, making sure she has good dentition and is free of genetic abnormalities that could be passed on.
- External exam of vulvar lips and perineal conformation.
- Internal exam of vaginal vault and cervix with speculum to make sure the cervix seals properly, no adhesions or scarring, no urine pooling.
- Culture and cytology of the uterus to make sure there is no infection or inflammation present.
- Rectal palpation of the uterus and ovaries followed by ultrasound to evaluate the structures for potential problems, abnormalities and to map any uterine cysts.
- Making sure the mare has a normal and regular heat cycle is also important.
If there are any concerns or abnormalities on the exam the mare may require additional treatments or testing, such as uterine lavage and antibiotics, caslicks procedure after conception, or uterine biopsy. If there is a significant concern, the mare may be considered unfit to be bred or at a higher risk for complications after being bred. Depending on the abnormality on exam, she may have a more difficult time conceiving and carrying the pregnancy to full term.
Once the mare has been thoroughly examined and clears all the tests, the breeding plan can be discussed. Mares can be bred in several different ways including live cover, insemination with fresh, cooled or frozen semen, or have more complicated procedures done such as embryo transfer. The type of breeding that is chosen often depends on location of the mare and stallion as well as breed of horse involved. No matter what type of breeding is chosen, following the mares natural heat cycle is important for timing of insemination. Mares usually have ultrasounds performed to have ovarian follicles measured to insure the timing of breeding is correct. Different hormones can be used to help the mare ovulate once her follicle reaches a certain size.
Subsequent ultrasounds and pregnancy checks will need to be performed at different intervals to check for conception, viability of embryo, possible twins and health of the fetus. Depending on the history and age of the mare, the mare may be put on progesterone to help maintain the pregnancy. Progesterone levels may be checked early on to make sure the mares corpus luteum is producing sufficient levels. Mares will need to be vaccinated and dewormed at specific intervals to make sure mom and baby stay healthy. Monitoring the mare is also critical around foaling time to make sure if she needs help delivering the baby this assistance can be provided in a timely manner. The foal should also be closely monitored after being born to make sure it can stand and nurse on its own. Its antibody levels should be checked 12-24 hours after nursing.
Choosing to breed a mare not only comes with risks for the mare and the fetus, but also comes with a great deal of expense if all the recommend steps are followed. Having a discussion with your veterinarian before hand can help you decide if breeding is right for you and your mare.
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