Breeders and veterinarians understand the risks and frustrations involved in trying to obtain that perfect, healthy foal. Sometimes there are added complications of a mare which has problems that might prevent or hinder her ability to produce a foal. With veterinary care and knowledge of the mare's problems, that dream foal can become a reality even from a problem mare. Attendees at the 2003 American Association of Equine Practitioners' convention learned more about the high-risk mare at a table topic moderated by Tom Riddle, DVM, of Rood and Riddle Equine Hospital in Lexington, Ky.; and Wendy Vaala, VMD, Dipl. ACVIM, of B.W. Furlong and Associates in Oldwick, N.J.

Riddle started with a discussion of non-reproductive problems in the mare that could affect her pregnancy, such as laminitis, an old performance injury, or hypothyroidism. For the laminitic mare or for one which has an old injury, pain management must be considered. Pain could affect her ability to conceive and maintain a pregnancy, said Riddle. He commented that there has been a previous concern about fertility of the mare with hypothyroidism; however, he said there has been no study confirming a relationship between low thyroid levels and low fertility.

The discussion turned to vulvar conformation. Riddle considers it a given that a proper Caslick's (an operation to improve the vulva seal) procedure should be done, especially if there are signs of infertility. "You should look for any indication that the vulva needs reconstruction," he advised.

He recommended that a veterinarian examine a mare with a speculum and by manual palpation in case there are significant tears in the reproductive tract.

Riddle said he considers an ultrasound examination of the uterus necessary for problem mares. If excess fluid is found on ultrasound, then Riddle prescribes oxytocin, cloprostenol, and uterine lavage to help the mare clear the fluid.

Vaala will use transabdominal scans on mares at 140 days of gestation. At that point in the pregnancy, the umbilical cord is more prominent, and it is easier to see more placental folding. She cautioned that sometimes placental folding can look like early placental separation when it is not.

Riddle said that he has never been too concerned over the discovery of endometrial cysts. He cited one study that found no relationship between endometrial cysts and fertility. It is typical for older mares to have cysts, he said, and these mares can be known for subfertility, which is probably why fertility issues have been connected with the appearance of endometrial cysts. Riddle said he will let the horse "live with the cysts," although he will identify cysts on a "map" to help differentiate between a vesicle and a cyst. To determine the difference when examining pregnancies at less than 17 days of gestation, he will try to move the object--if it doesn't move, it's a cyst. Riddle recommended removal of large cysts that could interfere with the movement of the vesicle or the ability of the cervix to close.

Riddle also recommended evaluating the ovaries and taking a uterine biopsy to evaluate inflammation. He prefers the use of cytology (cell examination via microscope) over cultures, and questions the validity of positive cultures if the cytology is negative.

In problem mares which have shown susceptibility to infection, Riddle likes to give systemic antibiotics starting at the beginning of estrus (heat) until seven days after the mare ovulates.

The discussion then turned to the dangers of endophyte-infected fescue and its effects on relaxin values. The hormone relaxin is produced by the fetoplacental unit to help prime and relax the mare's cervix in preparation for delivery. Endophyte-nfected fescue can lower relaxin levels through its effect on fetoplacental function. Vaala said that it is always recommended to remove a mare from an infected fescue pasture. In addition, domperidone can be given to affected mares to reverse many of the signs of fescue toxicity resulting in an increase in relaxin levels and improvement in fetoplacental function.

In instances where mares have problems bonding with their foals and are not producing enough milk, Vaala likes to administer a combination of estrogen, Regumate, and domperidone. She has found that within three to four days on this combination, that a mare will bond with her foal and begin producing more milk. She also said that this treatment might be useful to help a nurse mare bond to a new foal.

Mare Reproductive Loss Syndrome
Riddle discussed his experience with mare reproductive loss syndrome (MRLS). As early as 35-40 days of gestation, he was seeing cloudy allantoic and amniotic fluids on ultrasound. He said that not all of the mares with cloudy fluid aborted; however, he estimates that in the first year of MRLS 25-30% of these mares aborted before Day 80. By 80-90 days of gestation, he found that all mares had some echogenicity (some solid matter visible on ultrasound; fluid appears black), leading him to question if this was a normal physiologic process. A study done in Florida had similar findings, and also found that at 120 days the amniotic fluid was more echogenic than the allantoic fluid. During MRLS in 2001, Riddle was checking mares every five to seven days for fetal viability.

Riddle said that between 150 and 300 days of gestation, the measurement of total estrogens is a useful indicator of fetal viability. Levels of 1,000 pg/ml or greater indicate that the fetus is alive at that time. He said if movement of the fetus is not felt, it doesn't necessarily mean the foal is dead. Abdominal ultrasound is needed after 150 days to image the heartbeat, said Riddle.

The At-Risk Pregnancy
Riddle commented that progestins can also be measured several times and values compared to help monitor the pregnancy. If progestin levels are going down or if the values are greater than 50% of the previous value, then normal, acute, or chronic stress is indicated. Riddle said that measuring levels past 310 days of gestation is not helpful because progestins will normally rise at that time.

Clinical signs of a pregnancy in jeopardy include vulvar discharge or premature udder development. Mares which have undergone a severe medical problem or surgery are at increased risk for pregnancy loss.

If treatment of a pregnancy at risk is needed, Riddle will prescribe a double dose of Regumate, along with antibiotics and pentoxifylline, to increase circulation to the placenta. Vaala has had success with clenbuterol for cases of fetal compromise. She said that it keeps mares from foaling early. She will use this off-label treatment within the last four to six weeks of the pregnancy, evaluating the mare daily through transabdominal ultrasound.

The discussion turned toward treatment of mares with Cushing's disease with pergolide during pregnancy. Vaala said that it was necessary to stop treatment two to three weeks before foaling since pergolide can cause similar effects in the mare as infected fescue. Treatment with domperidone might be an option for these mares.

With advances in modern veterinary medicine happening all of the time, the practitioners agreed that management of high-risk mares is becoming easier, and the probability of a healthy foal is increasing.

About the Author

Sarah Evers Conrad

Sarah Evers Conrad has a bachelor’s of arts in journalism and equine science from Western Kentucky University. As a lifelong horse lover and equestrian, Conrad started her career at The Horse: Your Guide to Equine Health Care magazine. She has also worked for the United States Equestrian Federation as the managing editor of Equestrian magazine and director of e-communications and served as content manager/travel writer for a Caribbean travel agency. When she isn’t freelancing, Conrad spends her free time enjoying her family, reading, practicing photography, traveling, crocheting, and being around animals in her Lexington, Kentucky, home.

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