Reproductive Glossary

Reproductive assessment to determine if the mare has defects that potentially may prevent her from conceiving, maintaining the pregnancy to term and safely deliver a foal.

The examination includes obtaining a medical history and reproductive history of the mare, a general physical examination, a reproductive examination including observation of the perineum and vulva, manual and visual examination of the vagina and cervix with a speculum, transrectal palpation and ultrasound examination and inspection of the mammary glands.

Consecutive palpations of the reproductive tract and scan (ultrasound) per rectum are required to determine when it is the best time for breeding or if there are any abnormalities of the internal reproductive tract.

A swab is passed aseptically through the cervix into the uterus to identify the presence of infection or inflammation. This will help to achieve a diagnosis of uterine infection and determine which antibiotics are needed to clear that infection.

Normally the vulva provides an effective barrier to protect the uterus from infection. Some mares do not have a good vulva conformation, making its seal to be incompetent. This condition will make the mare aspirate air or manure, leading to an uterine infection.

Caslick is a procedure that consists of stitching together the dorsal part of the vulva, improving the barrier reducing the chance of a bacterial infection.

This hormone is used to induce the mare’s ovulation.

This hormone is used to short cycling the mares, inducing oestrus (heat). A common side effect after administration of this hormone is sweating, which should resolve after a maximum of 30 minutes.

Good levels of progesterone are critical for mares to maintain a pregnancy. This hormone is produced by the corpus luteum, an ovarian structure that is formed after ovulation. Some mares have inadequate production of this hormone and need some supplementation to keep the pregnancy. In competition mares, progesterone can be used to suppress unwanted behaviours.

This hormone stimulates the contraction of the uterus and helps to evacuate fluid from the uterus.

When the mare is inseminated or covered naturally there is inflammation of the uterus, since the semen is seen as a foreign body. This inflammation will cause some accumulation of fluid in the uterus. Some susceptible mares have trouble evacuating it. For those mares, a uterine lavage will help remove this fluid.

After an endometrial swab is taken, the sample collected is cultured. If the mares are infected, with a bacteria or fungus they will require some treatment. Antibiotics or antifungal medicine can be infused into the mare’s uterus to fight the infection.

A screening swab of the clitoris to ensure transmissible venereal diseases are not present.

A contagious disease that is rarely life threatening to otherwise healthy adult horses, but it can cause abortion in pregnant mares, death in young foals and render breeding stallions permanent carriers of the virus.

Equine infectious anemia (EIA) or swamp fever is a viral disease. Once horses are infected with the EIA virus, they remain lifelong carriers and are a potential viral source. Most infected horses show no symptoms, but they remain infectious, endangering the health of other horses.

Contagious equine metritis is a sexually transmitted disease caused by the bacteria Taylorella equigenitalis. It is transmitted by live cover breeding, contaminated equipment, and in semen collected for artificial insemination. Mares may show no signs of infection or may exhibit mucopurulent vaginal discharge and infertility for one or more breeding cycles. Mares infected during pregnancy can produce carrier foals. Stallions do not typically exhibit signs of contamination but can be carriers and spread the bacteria.

When we are using frozen semen, we are using a very low volume of semen. Each storage straw has only 0.5ml of semen. This technique will allow to deposit the semen at the tip of the uterine horn (at the opening of the oviduct) on the side were the ovulation occurred, achieving satisfactory pregnancy rates with this low volume of semen.

The equine embryo is relatively big compared with other domestic species. For this reason, we can detect the pregnancy as soon as 14 days post-ovulation. At this time the vet will be able to tell if the mare will need or not help of progesterone to maintain the pregnancy.

A further scan at between 25-30 days of pregnancy is important to check if there is a developing healthy pregnancy, with a visible heartbeat.

A pregnancy scan at 45 days of 60 days is recommended, as after this stage pregnancy losses are rare.

Mares are not designed to carry more than one foal; they have no physical space and a placenta able to support two foetuses. Trying to carry twins to term can be life-threatening to the mare, so it is necessary to squeeze one of the twins around day 14-15 days post-ovulation.

The endometrial biopsy is the most frequent laboratory method used to evaluate infertility in the mare and to assess the mare’s prognosis for successfully carrying a foal to term.