E706
 Reproductive Problems

anestrus | uterus infection (endometritis, metritis, and pyometra) | retained placenta | problems with the ovary

Introduction: A variety of situations can cause problems with the reproductive system in mares. The following section will address anestrus, reproductive tract infections (metritis, endometritis), retained placentas, and ovary problems.

Anestrus

Introduction: True anestrus means no ovarian activity at the expected time. Often a mare is suspected of being anestrus when she fails to show signs of estrus (heat). In many of these cases, the mare is actually cycling but just not manifesting any signs of estrus or not being detected in estrus. Keeping reproductive records on each animal's estrous dates, examination dates and findings, unusual events such as difficult foaling or retained placenta, and any treatments will help identify problem animals early and provide information that can help determine a possible cause. True anestrus can be caused by pregnancy, seasonal anestrus, pyometra (pus in the uterus), undernutrition, granulosa cell tumors, and genetic defects. Each of these causes of anestrus will be discussed below along with their treatment:

  1. Pregnancy - Any animal that is pregnant will not cycle and would be considered anestrus during the time of pregnancy.
  2. Seasonal Anestrus - Most mares in North America are seasonally anestrus, meaning that during the months where there is less light (usually the winter), they do not cycle. This period of anestrus can last from one to many months. In areas that receive more light throughout the year (the tropics, California, Australia, etc.) some mares may actually cycle year round. For details on how to help transition a mare from a non-cycling state to regular cyclic activity refer to page A714.
  3. Pyometra (infection or pus in the uterus) - It is important to identify the source of the infection and then utilize oxytocin, prostaglandin (PGF2a), antibiotics, or uterine lavage to help resolve the problem.
  4. Undernutrition - Severe undernutrition can affect the mare’s reproductive activity. The obvious solution is to improve the mare’s nutritional status and ensure that she is on a proper de-worming and vaccination schedule. Ideally, a mare’s body condition should not go below a 5 at the time of breeding.
  5. Granulosa Cell Tumors - This is a type of tumor that is found in tissues of the ovary. See page below for more details.
  6. Genetic Defects - Certain genetic defects such as gonadal dysgenesis can cause abnormalities in the reproductive organs. In the case of gonadal dysgenesis, the ovaries are small and firm. There is no treatment.



Uterus Infection (Endometritis, Metritis, and Pyometra)

Introduction: Endometritis (inflammation of the lining of the uterus), metritis (inflammation of the uterus), and pyometra (infection or pus in the uterus) are potential problems in mares. If not resolved, these problems will lead to estrus abnormalities, failure to conceive, and even death.

Causative Agents: Most problems in the uterus are caused by injury or infection that occur during or soon after the breeding or foaling process. Injury or contamination of the reproductive tract can be the result of a difficult birth where manipulations have been made and/or medications have been given in the uterus. Abortions can also cause or lead to problems with the uterus. Bacteria such as Taylorella equigenitalis, Streptococcus spp., E coli, Pseudomonas, and Klebsiella commonly infect the uterus. One of the most common causes of a uterus infection is a retained placenta.

Clinical Signs: In many cases, the infection may not be that obvious. The most common problem noticed is that the mare fails to conceive. Upon additional investigation, the mare may have fluid accumulating in the uterus, shortened interestrus intervals, and discharge out of the vagina. Many of the signs associated with this problem can only be detected with palpation and ultrasound. In very severe cases, the mare may act sick, not want to eat (anorexia), have a fever, and have an obvious, smelly vaginal discharge. In mares, laminitis is commonly a problem following a severe metritis infection.

Diagnosis: When compared to cattle, techniques such as cultures, cytology, and biopsies are performed more frequently in mares with these problems. Cultures are often taken of the uterine contents and lining. This should be done using a swab that is protected from contamination until it reaches the uterus. These cultures should be performed when the mare is in estrus. A culture and sensitivity can help determine what bacteria are causing the infection and what antibiotics can be used to treat the infection. Swabs of the uterus can also be taken and stained for cytology (viewing a sample using a microscope). Neutrophils, red blood cells (RBCs), and mononuclear cells are sometimes found with the cytology. The presence of neutrophils can indicate endometritis. The presence of mononuclear cells may indicate the presence of a more long term (chronic) infection. When RBCs are present, this can indicate a very recent (acute) infection or trauma to the uterus.

A biopsy is a common tool used in diagnosing endometritis in mares. It is performed by using a biopsy instrument that collects a tissue sample from the very inside surface of the uterus. This sample is examined for evidence of inflammation, fibrosis, and stage of the mare’s cycle. When inflammation is noted on a biopsy and a culture indicates bacterial infection, a diagnosis of endometritis caused by bacterial infection can be made.

Treatment: The treatment for mares with uterus infections can involve many different steps depending on the type and severity of the infection. Because of this, no specific treatment can be recommended to fit every mare. Following are common procedures that can be used:

  1. Prevent the infection: This can involve performing a Caslick (see page A245), discontinuing breeding, and/or performing any necessary surgery to correct physical defects to the reproductive tract. Natural breeding will always cause contamination in the reproductive tract. Because of this, some mares should be artificially inseminated, or bred by natural service less frequently (breeding only once during each estrous cycle).
     
  2. Uterine lavage or flushing: Many practitioners will lavage the uterus with warm sterile buffered saline (pH ~ 7.0). This can help remove any contamination. The procedure is usually done every 24-48 hours while the mare is in estrus. During each flushing episode, the uterus is flushed until the fluid that returns remains clear. The whole process is repeated until the mare’s uterus returns to normal. Some breeders recommend that a one time flushing take place as soon as 4-6 hours after breeding. Studies show that this does not reduce pregnancy rates.

    Some veterinarians recommend that the uterus be lavaged or infused with some type of antiseptic solution. There are many different combinations of solutions that have been used. One of the most common is diluted povidone-iodine, mixed 20 parts saline to 1 part of 1% iodine solution (or even weaker dilutions). Avoid strong iodine and chlorhexidine solutions. Chlorhexidine is very irritating to the equine endometrium and some mares are sensitive to even dilute iodine. Other solutions infused into the uterus include penicillin, ampicillin, amikacin, and gentamicin. Anti-fungal and anti-yeast medications such as clotrimazole, amphotericin B, and nystatin are also sometimes used. It is important to note that ALL antiseptic solutions infused into the uterus will cause some degree of irritation and inflammation to the lining of the uterus. This will delay healing and will often increase the days open. Because of this reason, many owners/breeders choose not to administer products into the uterus if it is at all possible.
     
  3. Another treatment for mares that have a uterus infection is the administration of prostaglandin (PGF2a) at 5-10 mg, IM or oxytocin at 20 IU, IV.
     
  4. For many mares, and particularly those that are sick and have signs of toxemia (fever, not eating, weakness), it is important to administer systemic antibiotics. Injections of gentamicin, penicillin, or amikacin are often given. Severely sick animals should also receive fluids and anti-inflammatory agents (flunixin meglumine, phenylbutazone) when necessary.

Prevention:
  1. Sanitation: Keep things clean during examinations, insemination procedures, and birthing. Do not use natural service if there is any indication of infection of the reproductive tract in either the mare or stallion. When the time comes for foaling, use clean stalls, paddocks or pastures in good weather, or sanitize and re-bed stalls after each foaling. Long-stem bedding is better than sawdust. If problems are widespread, rest birthing sites for 1-2 months and foal in a new, clean site. Keep other animals out of maternity areas.

    Ensure any instruments needed to assist the birthing process are sterilized, as well as the arms and hands of anyone assisting with the birth. A non-irritating lubricant used on one's arms will also help prevent injury to the reproductive tract. Wash the female's vulva and surrounding area with a mild disinfectant. Be gentle, working with the contractions of the mare. Make sure the position of the foal is normal before it is pulled. Call a veterinarian if problems arise that cannot be resolved. (See page A247 for help on handling a dystocia.)
     
  2. Diet and Conditioning: Prevent under and over-conditioning during pre-breeding and gestation. The ideal body condition score for a breeding mare is around a 5.
     
  3. Examinations and Treatment: Have a pre-breeding exam performed on all mares before the breeding season, ideally, after the mare has started to cycle. After the mare foals, watch for signs of infection (this may mean utilizing an ultrasound). Avoid routine medication of the mare and particularly the uterus unless a mare is known to be infected. Follow recommendations for retained placenta if that is considered the source of any metritis (see the following information).

 

Retained Placenta (Retained Fetal Membranes - RFM)

Causative Agents: A mare is said to have a retained placenta if she fails to expel the placenta within 3 hours of foaling. There are many things that can cause a mare to retain a placenta. They are often associated with mares that give birth prematurely (abortions), have an excessively large foal, or must have a cesarean section. Abortions, still births, dystocia, and metritis are also common problems that can lead to a retained placenta. There is also a positive relationship between the age of the mare and chances of developing a retained placenta. For example, mares over the age of 14 are more at risk of developing this problem.

Low selenium and calcium have been highly associated with RFM in cattle and there is evidence that there may also be an association in mares. There are also studies that indicate that fescue can cause problems. Tall fescue can be a very safe, inexpensive source of forage for horses. However, it can become infested with a fungus that can cause many problems primarily related to foaling. Lastly, poor nutrition might be a cause if the mare becomes physically exhausted after foaling and the uterus fails to receive enough energy to function.

Clinical Signs/Diagnosis: A mare may take up to 3-6 hours to dispel the placenta. If the placenta is still attached after 3 hours, there may be a problem and the placenta is usually considered retained. A mare that has retained the placenta will often have some of the placenta hanging out of the vagina. This can vary in length from a few inches to a few feet. In some cases, there may not be any of the retained placenta that can be viewed from the outside. In these instances, all of the retained part of the placenta is still contained within the uterus and vagina. When infection is present, mares with a retained placenta will sometimes have a fever, act sick, not want to eat, and experience colic-like symptoms. As the placenta decomposes and infection sets in, a very foul odor can be noticed, and a dark, blood-tinged fluid may come out the vagina.

After a mare has given birth, and what is thought to be the entire placenta has been passed, the placenta should be filled with water from a hose. All areas of the placenta should be expanded, looking for any spots where part of the placenta may be missing. These areas could still be in the mare and may result in a uterine infection.

Treatment: In all cases, it is important to never try and pull the placenta out of the mare. Pulling or forcing a retained placenta from the uterus will only cause injury to the mare, delay healing, result in potential bleeding, and increase the chances for severe infections.

The preferred treatment for retained placentas in mares is the administration of oxytocin (5-20 IU every 15-30 minutes IV or 20-40 IU every 30-60 minutes IM) when the problem is diagnosed. In addition to the oxytocin, additional treatments include antibiotics (ampicillin, gentamicin, penicillin, trimethoprim-sulfas), anti-inflammatory medications (flunixin meglumine, phenylbutazone), and tetanus antitoxin or toxoid (anti-toxin for mares not vaccinated previously and toxoid for mares that have been vaccinated).

Prevention: To help prevent this problem, minimize stressful conditions during the pre-foaling period and at foaling time. Prevent diseases and problems such as dystocia and abortions. Vaccinate all animals for potential reproductive diseases. Evaluate all rations to make sure mares receive proper nutrition. Give supplements if rations are deficient in calcium, phosphorus, magnesium, selenium, and vitamins A and E.



Problems with the Ovary

Introduction: The two common problems found in the equine ovary that can cause one ovary to be larger than the other are described below:

  1. Ovarian hematoma: An ovarian hematoma occurs when an excessive amount of blood fills a follicle that fails to ovulate (hemorrhagic anovulatory follicles) or fills a follicle after ovulation. It usually does not cause any abnormal signs in the mare and is most often diagnosed during an ultrasound exam. The problem usually resolves on its own over a period of weeks to months. Surgical removal of the ovary is not recommended.
     
  2. Ovarian tumors: The most common ovarian tumor in the mare is the granulosa cell tumor (GCT). These tumors are almost always found on only one ovary. They are slow growing and are considered benign. When these tumors are present, one ovary is usually small, while the other ovary with the tumor will be extremely large (as large as a grapefruit and larger). Mares that develop granulosa cell tumors will often display one of three types of behavior: 1) stallion-like behavior, 2) prolonged anestrus, or 3) persistent or intermittent estrus behavior (nymphomania). Mares that exhibit stallion-like behavior may actually develop a crested neck.

    Most tumors are found on rectal palpation or through an ultrasound exam. Blood tests can also be done to help confirm the diagnosis. For example, inhibin and testosterone are often elevated in mares with a GCT, while progesterone levels are often decreased. Inhibin is elevated (>0.7 ng/mL) in the vast majority of the mares with a GCT, and testosterone levels may be elevated (>50 - 100 pg/mL) if a significant portion of the tumor is composed of theca cells (i.e., a granulosa-theca cell tumor or GTCT). Because normal ovarian function does not occur, progesterone concentrations in mares with a GCT are almost always below 1 ng/mL. Surgery is the treatment for GCT tumors in most mares. Once removed, most mares may return to having normal estrous cycles within 2-16 months.

    Other tumors that can be found in a mare’s ovary include teratomas, cystadenomas, and dysgerminomas. Teratomas and dysgerminomas are tumors that come from the germ cells that are part of ovarian development. Both tumors are rare and are most often found on only one ovary. They do not cause changes to normal estrous cycle activities. Teratomas often contain small bits of bone, hair, muscle, teeth, and other tissues. Teratomas are benign tumors, while dysgerminomas are malignant. Cystadenomas are benign tumors that are more common than teratomas or dysgerminomas. They are found on only one ovary and do not cause changes to the mare’s normal reproductive cycle or the opposite ovary. All three types of tumors should be removed with surgery. Mare’s with dysgerminomas that have spread are considered to have a poor prognosis.