My Mare is Not Pregnant - What Now?

September 18, 2012

If you bred your mare last year and were unable to get her in foal, you are not alone. According to The Jockey Club, 44,184 mares were bred in North America in 2010 of these only 23,558 live foals were registered in 2011. A stallion with good semen quality, a mare with a healthy reproductive tract and properly timed inseminations are three critical elements that must align to maximize your chance of success. If you are looking to improve your odds for the 2013 breeding season, Dr. Holly Mason from Unionville Equine Associates outlines some things you might consider doing now to prepare for the upcoming season.

The Stallion

Semen arrangements being finalized in advance of needing to breed your mare will be greatly appreciated by your Veterinarian. You should consult your Veterinarian when selecting semen and review your breeding contract from the prior year if applicable. Many factors can influence whether you use the same stallion, fresh chilled or frozen semen. The most important of which are related to how your mare responded to her inseminations last year and on how many cycles she was bred. Your mare’s response to prior inseminations may dictate whether or not she will better tolerate fresh chilled semen, a different frozen semen protocol or additional therapies at the time of insemination. If your mare failed to conceive on multiple cycles or had embryonic vesicles that failed to develop, your Veterinarian may advise changing stallions to avoid possible genetic incompatibilities. If the stallion is known to have reduced fertility or does not freeze or ship well, some owners will send their mare to the stallion for breeding. Although this would negate the convenience and control of breeding on your farm with chilled or frozen semen, it is one way to gain access to a semen sample that has been minimally stressed by processing, transport or extreme temperature changes.

The Mare

Breeding records from the past year should be reviewed by your Veterinarian prior to the next insemination attempt. The breeding records can demonstrate patterns in a mare’s cycle and may indicate areas that need to be handled more aggressively next season.

A complete physical exam should not be overlooked as part of your mare’s breeding plans. Hormone abnormalities (such as Cushing’s disease) or inappropriate body condition are just two common disorders that, when addressed properly may improve fertility.

A breeding soundness evaluation is critical to start off the next season. This exam typically includes an evaluation of perineal conformation, rectal palpation, trans-rectal ultrasound, vaginal speculum exam and a manual vaginal exam. Gross abnormalities that may contribute to poor fertility as well as stage of cycle can typically be identified during this exam. Based on the exam findings and your mare’s history, your Veterinarian may choose to recommend further diagnostics or procedures to compliment the breeding soundness evaluation. Some diagnostics and exam findings are discussed below:

  • Uterine culture and cytology is routinely used to determine if there is infectious endometritis, a very common cause of poor fertility. Uterine culture and cytology are minimally invasive and ideally performed while the mare is in heat. There is a newer technique used to identify infectious endometritis called a low volume uterine lavage culture. When performed properly, this technique is more sensitive at detecting an infection. A mare that has failed to conceive despite negative results with a traditional uterine culture is a good candidate for this technique. In either case, when a pathogen grows from the culture, a sensitivity profile will determine the best course of antimicrobial therapy.
  • Uterine biopsy is a minimally invasive procedure that can yield a lot of useful information. The biopsy is graded to give you a percent chance of conception and carrying the foal to term. Additionally, it can provide important insight into ancillary therapies that may be employed around the time of breeding. As a result of studying uterine biopsies from sub-fertile mares, Veterinarians are becoming more aware of abnormalities involving mucous biofilms and inflammatory processes. Often these problems can be ameliorated using treatment protocols that involve intrauterine medications, uterine lavages, anti-inflammatories and oxytocin injections around the time of insemination. If permanent and severe changes are evident on the biopsy, you will get a realistic idea of whether your mare can conceive and support a pregnancy to full term. Some mares with poor biopsy grades are good candidates for embryo transfer. 
  • Cervical defects, although not very common, are another problem that the Veterinary community has become more aware of in recent years. The cervix is a dynamic component of the reproductive tract which must relax during heat and tightly constrict when not in heat or during pregnancy. Veterinarians are often asked to come to the farm when a mare is in heat. However, it is critical to evaluate the cervix while the mare is out of heat as well. Some cervical defects can only be appreciated when the cervix is tightly closed. Some cervical defects will require surgical repair. 
  • Uterine cysts are common in aged broodmares and can lead to problems with pregnancy recognition, embryo implantation and identification of twin pregnancies. Cyst removal is a simple procedure which can be accomplished with standing sedation using a few different techniques and can improve your odds of success next season.

Most of the above items can be addressed in the Fall if your mare is still cycling. Pursuing any type of reproductive surgery is naturally appropriate for the Fall or Winter as it leaves ample recovery time prior to the next breeding attempt. Communicate with your Veterinarian about your intentions for the next breeding season so that they may help you to schedule exams, diagnostics and treatments in a time effective manner.

Timed Insemination

Insemination of your mare will require keen Veterinary skills in order to be timed appropriately. The logistics of when to inseminate depend on a large number of factors which include monitoring daily, and sometimes hourly, changes in your mare’s reproductive tract via trans-rectal ultrasound and palpation, whether you are using fresh chilled or frozen semen, how many insemination doses you have and sperm and egg lifespan. If the logistics of timing are hampered by factors on the farm, consider shipping your mare into a Veterinary clinic that can provide full service reproductive work around the clock so that insemination timing can be optimized. You can facilitate the start of this process by giving your Veterinarian ample notice about when you think your mare will be coming into heat. If you are unable to tell from observation when she is cycling at home, regular Veterinary exams and or the use of hormonal therapy to control when she will come into heat will be useful.

As you can see, there are several components to consider regarding stallion selection, mare fertility and timing of inseminations. Quality teamwork between you and your Veterinarian will surely be a factor in your success. Good luck in the 2013 breeding season.


Holly M. Mason, MS, DVM is an Associate Veterinarian with Unionville Equine Associates, PC in Oxford, PA. As a seasonal component for the general practitioner, she and her colleagues enjoy the large reproductive caseload offered in Chester County, PA and the surrounding communities. You can learn more about Unionville Equine Associates, PC at