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Inflammation and/or infection of the endometrium is the leading cause of subfertility in the horse, with persistent breeding-induced endometritis (PBIE) effecting approximately 10-15% of broodmares [1].  The deposition of spermatozoa, seminal plasma, and/or bacteria into the reproductive tract causes an inflammatory response, leading to an activation of the immune system.  This involves an activation of signaling molecules (cytokines), recruitment of immune cells (neutrophils), and eventual release of prostaglandin F2 alpha (PGF_2a) from the inflamed endometrium, all of which lead to the eventual expulsion of excess fluid and contaminants [2-10].

The establishment and loss of twins, often results in a mare that is barren for a year and the associated economic loss.  The incidence of twin births has been documented as occurring in 1-2% of the equine population with twinning accounting for 6-30% of abortions in the mare. When twins are present, gestation proceeds normally until the conceptuses begin to compete for uterine space or placenta.  With or without mummification, death of one fetus leads to abortion, usually between 5 and 9 months of gestation. Lactation commonly occurs after one foal dies and causes premature mammary gland development.  Surviving foals are usually weaker, more susceptible to infection, and slower to develop than singletons. Fortunately, with the use of ultrasound and an increased understanding of the mechanisms involved in twinning, better approaches to twin reduction have been developed.

Now that your mare is safely checked in foal, the next step in the journey begins. It is time to plan ahead for the care and management of your pregnant mare and for welcoming the arrival of your foal. A major first step is, where will your mare foal out? If she is to foal out at home it is assumed you have a suitable foaling stall, a pasture with shelter and safe fencing to house the mare and her foal. Research and start to compile your foaling kit, emergency plans and contacts, secure a source of colostrum and research options for nurse mares. Of course, we all hope for a normal, successful delivery, but we have to be prepared for worst case scenarios. If the unexpected happens at such an emotional time, having a plan in place will alleviate stress and save time when tough decisions must be made. If your mare will foal out at another facility, plan on moving her 20-30 days prior to foaling so she can build up immunity to her new local environment.

Early detection of pregnancy in mares is strongly demanded by owners in order to maximize breeding efficiency and economic investment. The most reliable and earliest available tool for conceptus detection is ultrasonography. Other diagnostics include palpation per rectum and hormonal blood tests (i.e. estrone sulfate in serum or urine; equine chorionic gonadotropin in serum) as these methods are useful when examination by ultrasound (per rectum or transabdominally) is not possible or feasible.

Early demise due to illness or injury can shorten a mare’s reproductive career. Additionally, subfertility can also have a negative impact on a mare’s ability to produce a foal. There have been a multitude of advances in the past 20 years that have allowed for the preservation of genetics in mares. Techniques such as transvaginal ultrasound-guided oocyte aspiration (TVA) and intracytoplasmic sperm injection (ICSI) have allowed us to produce embryos in vitro, circumvent subfertility in mares, and preserve genetics from mares that have died.

To evaluate a mare's potential for reproductive success or failure, veterinarians often perform a "breeding soundness examination" (BSE). As the breeding season approaches, many owners may opt for a pre-breeding BSE to identify and address any potential reproductive issues prior to breeding. This examination is invaluable for estimating the likelihood of a mare successfully conceiving, carrying a pregnancy to term, and delivering a healthy foal. Pre-breeding examinations are usually performed early in the breeding season when the mare has just begun to cycle or, at the very least, is not in anestrus. Furthermore, the BSE provides veterinarians and owners with important information to determine whether a particular mare should carry a foal herself or whether she might better serve as an embryo or oocyte donor, as well as what breeding strategies are most appropriate for the individual mare.

In the equine breeding industry, many different assisted reproduction techniques (ARTs) are widely used to aid the management of equine reproduction. ARTs provide options to owners looking to obtain embryos from genetically valuable mares and/or stallions for whom conventional breeding management strategies are insufficient. This article provides a concise summary of several common ARTs, as well as information regarding innovative techniques just entering clinical use.

When considering common causes of infertility in the mare, the oviduct is one of the last places an equine reproductive specialist looks. Uterine infections, poor conformation and stallion subfertility are much more likely causes for a mare’s failure to produce a pregnancy. That being said, there are rare cases where oviduct pathology is suspected, and in the past few years there have been advances for oviductal treatment that are cost effective, safe and have restored fertility in some patients. This summary will highlight some unique features of the mare oviduct, discuss when to suspect oviductal pathology or dysfunction, and review some of the current treatments available.

Beta-hemolytic Streptococcus equi subsp. zooepidemicus (BHS) is the most frequently isolated pathogen in the uterus of mares. However, in a large fraction (>50%) of subfertile mares there is no obvious reason identified. We recently demonstrated that BHS have the ability to reside deep in endometrium and may also gain intracellular access. The ability to escape and hide from the immune system allows BHS to cause long lasting, hardly detectable infections. In addition to this, we have shown that BHS are able to enter a dormant state where the bacteria can slow down their metabolism. Most antibiotics inhibit bacterial growth by disrupting the microbial metabolism which makes the dormant bacteria highly tolerant to antibiotics.

Breeding season is just around the corner and most breeders dread the frustration of subfertility in certain broodmares. A thorough breeding history is key to diagnosing the cause of subfertility. Questions that address previous breeding management, stallion selection, and general wellness are important when performing a breeding soundness evaluation. Diagnostics such as trans-rectal palpation and ultrasound examination of the reproductive tract, vaginal speculum examination, digital cervical palpation, endometrial cytology and culture, endometrial biopsy, and hysteroscopic examination are useful in determining the cause of subfertility. Typically, a cause of subfertility can be determined utilizing the diagnostics mentioned above, but there may be some cases in which diagnostic test results are negative and yet a mare is still subfertile. So what’s next?