Equine Medical Center

Rectal palpation and ultrasound are performed daily or every other day during estrus to determine the optimal time for insemination. The day after insemination, rectal exams are repeated to confirm ovulation and evaluate uterine health. Presence of free intrauterine fluid > 24 h after insemination indicates the presence of endometritis. Mares with endometritis receive intrauterine treatments (uterine lavage, infusion with antibiotics) to ensure the uterine environment is optimal to support embryonic development. A pregnancy exam is performed 14 days after ovulation.

Hormones are administered as necessary to bring the mares into estrus (prostaglandin), induce ovulation (human chorionic gonadotropin or deslorelin) or help clear the uterus from free fluid (oxytocin). Semen quality (sperm count, motility and morphology) is evaluated with each artificial insemination.

Artificial insemination is performed with fresh semen when the mare and the stallion are held at the same location. Once the mare is ready for insemination, the stallion is collected at the farm or at the VHC. A complete semen evaluation is performed, and semen is deposited into the mare within 30 minutes of collection.

Artificial insemination with shipped cooled semen allows the mare to be maintained at home while being inseminated to stallions from other locations. Semen is diluted with an extender, maintained at 4°C to 6°C and transported throughout the country to be used within 12 to 36 h of collection. The stallion’s owner or manager is contacted by the Theriogenology Service during the mare’s initial visit to obtain information on semen collection and shipping schedule and requirements. Once the mare is ready for insemination, semen is ordered. Semen is shipped overnight via commercial carrier, or on the same day of collection counter-to-counter via commercial airline. The VHC receives semen shipped in both ways, including Saturday Delivery service from most commercial carriers. A complete semen evaluation is performed upon arrival of the semen before insemination.

Frozen semen is kept in liquid nitrogen at -196°C and can be used years after collection. This allows transportation of semen overseas and insemination of mares to stallions that are already dead. However, because freezing and thawing induce changes in the spermatozoa that decrease their half-life, frozen semen need to be deposited into the mare within 12 hours before to 6 hours after ovulation. Because of this, mares are either ultrasounded every 6 h and inseminated with a full dose of semen as soon as ovulation is detected, or they are timed-inseminated 24 and 40 h after administration of an ovulation-inducing agent with half a dose of semen each time. Frozen semen can be temporarily stored in the VHC’s liquid nitrogen tanks until insemination.

Equine Viral Arteritis is a contagious, primarily respiratory viral disease. It is of special concern because it can result in abortion in pregnant mares, illness and death in young foals, and establishment of the carrier state in stallions. EVA can be transmitted through respiratory and venereal routes. EVA can be spread during teasing, mating or insemination through contact with semen or reproductive tract secretions of acutely infected stallions and mares. In addition, chronically infected carrier stallions also shed the virus in their semen. The virus is resistant to cooling or freezing and transmission can occur after insemination with infected fresh, cooled or frozen semen. Because of its contagious nature, the VHC requests that semen shipped to our premises be accompanied by results of blood tests and proof of vaccination of the stallion. A seropositive result will not impede breeding the mare or accepting the semen into the VHC, but it will indicate the need for specific isolation protocols to prevent spreading the virus.

To obtain acceptable pregnancy rates after traditional artificial insemination, the minimum insemination doses are 500 x 106 motile spermatozoa for fresh or cooled semen, and 240 x 106 motile sperm for frozen semen. Low dose insemination allows for a drastic reduction in the number of spermatozoa required to achieve pregnancy. Insemination doses typically range from 1 to 25 x 106 motile spermatozoa in volumes from 0.2 to 1 mL. Low dose insemination makes more efficient use of frozen-thawed semen or of ejaculates of heavily booked stallions. Two non-surgical low-dose insemination techniques are available, hysteroscopic and deep horn insemination.

A reproductive or breeding soundness exam (BSE) is a series of diagnostic procedures performed on a mare to identify the cause of subfertility, elaborate a treatment plan and/or give a prognosis for future fertility. Routinely, a mare BSE includes a reproductive history, physical exam, rectal palpation and ultrasound, vaginoscopy, vaginal palpation, and endometrial culture, cytology and biopsy. In addition, uterine endoscopy, hormonal and cytogenetic tests, or exploratory laparoscopy or laparotomy may be required to identify the cause of subfertility. BSEs are performed in the fall or early spring to determine the cause of barrenness and initiate treatment before the breeding season starts, as part of a pre-purchase exam of any broodmare, after a pregnancy loss to identify its cause and any time a diagnosis for subfertility and prognosis for fertility are required.

There are many infectious and non-infectious causes of infertility in mares, including endometritis, ovarian tumors, ovulatory failure and embryonic death. A complete reproductive exam is performed initially to identify the cause of infertility. Based on the results of the exam, a treatment and/or management plan is elaborated. The Theriogenology Service offers intensive diagnostic, treatment and management plans to get your problem mare pregnant. In addition, the latest reproductive biotechnologies (embryo transfer, oocyte transfer) are available for the treatment of mare infertility.

Pregnancy diagnosis is an essential part of a breeding program and it is routinely performed by ultrasonography 12 to 16 days after ovulation. Early diagnosis allows us to identify mares that are not pregnant and breed them again before their next ovulation, and to detect mares carrying twins. Twins are a serious problem in horses and early detection before day 16 is essential to reduce these pregnancies to singleton pregnancies. Mares that lose their pregnancy later than 35 days after ovulation will generally not return to estrus that season because of the formation of endometrial cups. For this reason, pregnancy is re-evaluated 24 to 30 days after ovulation to confirm the presence of a heart beat in a normal looking embryo. Any abnormalities noted in the embryo may indicate the need to terminate that pregnancy before endometrial cups are formed so that the mare can be re-bred on the same season. Most pregnancy losses occur before day 60 of gestation, so pregnancies are reconfirmed again at 60 days. Ideally, a final confirmation of pregnancy is made at 120 days before vaccination, nutritional and management schedules specific for the pregnant mare are initiated.

Mares that are diagnosed with twins, placentitis, uterine torsion, colic and laminitis, among other diseases, are considered to have a high-risk pregnancy. Oxygen and nutrient supply to the fetus, as well as wastage removal by the placenta are usually impaired in these mares. This can result in pregnancy loss or birth of a compromised foal. The VHC offers an intensive pregnancy monitoring program and elaborates treatment plans tailored to your mare’s and foal’s specific needs. In addition, mares with high-risk pregnancies can be foaled at the VHC to ensure immediate neonatal support is available for the compromised foal.

The VHC foals out pregnant mares and provides routine neonatal care. Foaling services include 24-hour monitoring, milk calcium testing to predict impending foaling, Foal Alert® foaling monitoring system to detect onset of foaling, veterinarian present during foaling, umbilical cord care, antibody level measured in the foal’s blood, and mare and newborn post-partum examinations. Additional services include supplementation of colostrum or plasma, treatment of unexpected events such as dystocia or retained placenta and foal heat breeding.