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 (PGF2a) 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.
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.
Post-partum colic is a major issue and scientists are still not completely
sure what occurs in a broodmare’s gastrointestinal (GI) tract that makes
them at a greater risk for colic after giving birth. There have been recent
studies characterizing the mare’s gut microbiome during and after pregnancy
as well as immediately before an episode of colic in order to get a better
idea of any changes occurring in their GI tract. Understanding changes in
their microbiome may give us clues on how to better manage broodmares after
parturition.
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?
Thank you to Dr. Pat McCue from the Equine Reproduction Laboratory for last
month’s article, Progesterone Therapy for Pregnant Mares – Part 1, in which
he reviewed the formulations and use of progesterone therapy in mares. Dr.
McCue did a yeoman’s task in outlining the formulations and principles of
therapy available to veterinarians for the suppression of estrus, pregnancy
support, and treating cases of suspected or diagnosed placentitis. However,
the maintenance of pregnancy is by far the most common area in which we
receive questions about supplementing mares with exogenous (therapeutic)
forms of progesterone.
By far, the most discussed topic is supplementation of progesterone to pregnant mares to help them maintain a pregnancy. Many times, the questions stem from the necessity of such therapy, duration, and efficacy of supplementation. Sometimes, even with the best therapy, we fail to reach a good outcome, but the following discussion about the forms of supplementing progesterone is well worth a quick read for any breeder.
Endocrine diagnostics certainly have a place in the routine management of mares and stallions as well as in diagnosis of problems and diseases. However, there are likely more applications for measuring hormones in mares than stallions. Dr. Ed Squires will discuss the hormones tested in mares in this article and will then cover the testing of stallion hormones in a subsequent article.
It has been almost 20 years since I started an assisted reproduction program at Colorado state University. The purpose of that program was to develop techniques to preserve equine genetics. It is beyond the scope of this article to discuss all the goals of that program but I would like to focus on production of foals from old mares and stallions via in vitro technology (aka test tube horse). 
A common question asked by many breeders is whether the volume of semen deposited into the mare affects fertility. When a mare and a stallion mate naturally the entire ejaculate is deposited into the mare. This volume is usually 50 ml or more and includes several billion sperm. However, when breeding mares using artificial insemination, good fertility can be achieved with as little as 1/2 ml of semen. I have been telling breeders for years that the volume of the ejaculate is not important as long as the stallion is producing good sperm numbers. For example, a stallion can produce 8 billion sperm with 80 ml of semen at a concentration of 100 million sperm/ml or 20 ml of semen at a concentration of 400 million sperm/ml. Volume of the ejaculate and concentration are inversely related (i.e. if volume goes up then concentration goes down). 
Oxytocin is one of the most utilized hormones in broodmare practice. With so many possible clinical applications, a review of the use of oxytocin in the mare highlights the benefits of oxytocin, as well as necessary precautions with its use. Oxytocin is a nine-amino acid neuropeptide that is produced in the hypothalamus and released by hypothalamic neurons that terminate in the posterior pituitary. It is released in a natural pulsatile manner and exerts its effects by coupling with oxytocin receptors on various tissues such as the endometrium, myometrium, heart, kidney, pancreas, and fat tissue. There are also local effects of oxytocin and receptor binding, notably in the utero-placental tissues that help to increase the effect and intensity of pituitary derived oxytocin pulses. Clinically, oxytocin is available as a sterile injection, 20 IU (international units) per milliter. It can be administered intravenously or intramuscularly. 
Horse breeders are always interested in the well being of their broodmares as well as the well being of the fetus they are carrying. Advances in reproductive techniques have made it possible to gain insight into how the fetus is progressing as well as the ability to determine its gender. Knowing whether a mare is carrying a colt or a filly can help owners make important decisions concerning their herds and the industry in general. For example, fetal sex determination is used on a regular basis among thoroughbred breeders prior to stock auctions. In this article, we discuss the sorting of equine sperm for sex as well as fetal sex determination via transrectal and transabdominal ultrasound.
Once young colts and fillies reach the age of puberty their behavior may become an issue in the show ring or on the race track. Castrating a colt which you intend to use for breeding purposes may not be an option and mares are not typically permanently sterilized. Their sexual behavior may also cause problems with housing, trail riding, etc. In this article, Dr. Ed Squires discusses some of the common ways stallion and mare owners suppress the behavior of their horses.
Mares can develop problems during pregnancy or be at high risk of losing the pregnancy for a variety of reasons. These include age (old mares frequently have endometriosis in which the uterus is unable to properly supply the fetus with appropriate blood supply and nutrients), physical conditions (placental and fetal fluid abnormalities; body wall tears; chronic debilitating conditions such as laminitis and Cushing’s disease), and acute disease or injury (placentitis, uterine torsion, surgical colic, colitis, acute laminitis, or fractures). When a mare becomes stressed or debilitated, inflammatory chemicals and prostaglandins increase and induce abnormal uterine contractions and potential pregnancy loss. Reproductive problems that arise during gestation, however, when detected and diagnosed early, can still result in the survival of the mare and usually the foal. The abnormalities most commonly seen during the middle to late stages of pregnancy will be discussed in this article.
The use of the 
Older mares have a knack for being the sweetest and gentlest mares on the farm. We see them year after year, either carrying their own foals or returning to donate embryos if their reproductive status requires. Oftentimes, these mares are considered “special” patients, requiring a unique combination of diet, exercise, and metabolic support to maintain their physical and reproductive health. We often see older performance mares that are being bred for the first time following a long and successful show career. Reproductive problems such as cervical adhesions and uterine infection can be common in older mares which affect their ability to carry a foal or donate an embryo. 
Knowing when to stop riding your pregnant broodmare can be a debatable topic. This article will review recommended time points yet, like an individual person, each broodmare has independent feelings and each pregnancy can be different for a particular broodmare. There are noticeable signs your broodmare may be showing you she is uncomfortable or physically unable to do certain movements you ask of her when riding. It is always recommended that you consult your veterinarian when deciding the best plan of action regarding riding your broodmare and how strenuous the activity should be.
When one thinks of a broodmare they may think she is retired from the show ring and living out her days, pregnant in a pasture. However, with the implementation of embryo transfer (ET) in the horse breeding industry it is possible for a mare to produce several offspring in a given breeding season while continuing in competition. We recently published an article about 
There have been many changes in how we produce foals from our broodmares in the past few decades: cooled semen, frozen semen, embryo transfer, frozen embryos, etc. One procedure that has gained popularity is deep horn insemination. This refers to placing the semen deep in the uterine horn, close to the opening of the oviduct (uterotubal junction, UTJ) on the side of ovulation instead of depositing it in the uterine body. This is typically done using a flexible pipette that can be guided to the tip of the horn with the other hand in the rectum. The end of the pipette and the tip of the uterine horn can both be felt using this method. 
It has long been a goal for equine breeders to produce foals born as early in the year as possible. Foals born early in the year have a distinct economic advantage for breeders. However, Mother Nature, has a different plan.
Colic is usually a word that brings to mind fussy sick newborn children, sleepless nights, and sleep-deprived parents, unless you are a horse owner. Many horse owners live in fear of finding their horses in an episode of colic. Fortunately, many bouts of gastro-intestinal pain are mild, easily treated, or easily managed on the farm or with a visit from your veterinary professional. More serious episodes could be much more in depth, require extended medical therapy and possibly abdominal surgery. No episode of colic should be taken lightly and often times, intervention by your veterinary team can help prevent escalation of the pain and disease in the horse. In cases of serious colic, swift intervention can positively affect the outcome of prolonged hospitalization or surgical repair. 
Owning an animal, be it a household pet, horses, or livestock can be wonderfully rewarding. There are times, however, when the responsibility of animal ownership requires the consultation of a veterinarian to ensure the health and well being of your animals or livestock. Most of these appointments will be for routine care, whereas other visits may require specialized services, like lameness diagnosis, surgery or reproductive management. Many horse owners use different veterinarians or vet clinics depending upon the services they require. However, those in more isolated or rural areas may be limited to a general practice veterinarian who routinely works with all species, being neither an equine or reproduction specialist. A breeder can still be equally successful in both situations, so long as they are prepared and have done their research to find the best veterinarian available to suit their needs.
The horse is a seasonal breeder meaning that natural mating occurs during certain times of the year to ensure that the timing of birth is optimal for survival with regard to ambient temperature, food and water availability, and even changes in the predation behaviors of other species. Seasonal breeders are controlled by the length of daylight, i.e. the photoperiod, and can be divided into long day breeders, e.g. the horse, that start cycling when the days get longer (spring) and short day breeders, e.g. deer and some breeds of small ruminants, that start cycling when the days get shorter (fall). The length of photoperiod can be manipulated in order to hasten the onset of the breeding season. This is a popular management technique used in many breeds, so foals can be born as close to the standardized January 1st birth date as possible. It is also common with show or halter horses, with the goal being to maximize maturity for age determined competition.
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.
Breeding your mare is a big decision and the prospect can seem quite overwhelming - there is so much to research, organize and plan for as well as many different people to coordinate with. To make this process as stress free as possible, for everyone involved, it pays to be organized. The planning process will be a lot more enjoyable and exciting when you have everything lined up and are not surprised or caught off guard by any unexpected fees, decisions or situations. In this article, we have some suggestions for how you can be more organized for breeding season by considering what needs to be done before the season begins, when it's time to breed, before your mare foals, and once your new foal hits the ground.
