Story & Photos by Robyn Scherer, M.Agr. | Kiowa, Colo.

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April 8, 2013
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What to expect when your mare is expecting

All around the state, new animals are being born, breathing new life into the countryside. One of those animals giving birth is the horse, with April and May being the perfect time for foals to be born.

Anticipating the birth of a foal is one of the most exciting, and stressful times for a horse owner. Knowing what to expect when a mare is expecting can help an owner to feel more comfortable, and give the best care to the mare that is possible.

Mares can achieve a pregnancy through one of three ways: natural service, artificial insemination or embryo transfer. Pregnancy through embryo transfer occurs when the embryo of another mare is placed in the uterus of the recipient mare. The duration of pregnancy lasts on average 340 days, but can range 20 days shorter or longer, depending on the mare.

“An approximate foaling date may be calculated by subtracting 25 days from the day the mare was bred or ovulation was detected. Obviously, calculation of the potential foaling date is much more accurate when an actual breeding or ovulation date is known as compared to if the mare was pasture bred,” said Dr. Patrick McCue, Professor, Department of Clinical Sciences at Colorado State University, in a document titled “Care of the Expectant Mare.”

He added, “The length of pregnancy is usually five to 10 days longer for mares due to foal in the late winter or early spring than for mares that foal out in the late spring or summer. Mares will often (but not always) carry a foal for a similar time period during each pregnancy.”

Pregnant mares can be kept in groups, but should be separated from horses that leave the farm on a regular basis, to reduce the incidence of disease transmission. They should be kept in pens large enough to allow the mare to exercise as well.

“Exercise should be encouraged during early to mid-pregnancy. Mares in late pregnancy will generally obtain sufficient exercise from grazing in a pasture or walking in a paddock. Stress should be avoided as much as possible,” said Dr. McCue.

Mares should be taken care of more carefully, with routine care. “Routine dental care and foot care should be provided as needed. We generally recommend that annual dental examinations and procedures be performed after the mare foals and before she is re-bred to avoid the stress of the procedure(s) and avoid sedation while pregnant,” he explained.

Mares should not be moved in late pregnancy unless absolutely necessary. If they are moved to a foaling area that is different than where they are currently residing, they should be moved at least a week or two before the foaling date.

Dr. McCue stated, “This will allow her to become acclimated to her new environment and to begin to develop immunity or antibodies against the local pathogenic organisms. These antibodies will be passed on to the newborn foal through her colostrum.”

Mares should also receive vaccinations, to keep them healthy and produce antibodies. “Vaccination during pregnancy will also provide the neonate with immune protection via passive transfer of maternal antibodies in colostrum. Vaccination to prevent rhinopneumonitis or equine herpesvirus (EHV-1) abortion should be performed at five, seven and nine months of pregnancy. On farms with a history of EHV-1 abortions, it may be recommended that the vaccination series against EHV-1 be initiated at the third month of pregnancy,” he said.

He continued, “Pregnant mares should be vaccinated four to six weeks prior to their due date against tetanus, eastern and western equine encephalomyelitis (EEE and WEE) influenza, and West Nile Virus (WNV). This will provide immunologic protection to the mare as well as increase the amount of antibodies available for uptake by the mammary gland. These antibodies will be passed to the newborn foal in the colostrum.”

Routine deworming should also be performed. “Anthelmintics (dewormers) should be administered to pregnant mares on a routine basis, with the specific agent and frequency based on the exposure level, parasite load and farm management practices. Most commercially available dewormers are safe for use in pregnant mares. However, it is recommended that the product label be examined before administering dewormers or any other product to a pregnant mare. Routine deworming of the pregnant mare throughout gestation will decrease the exposure of the newborn foal to parasites. We recommend that you deworm your mare approximately one month prior to her anticipated due date,” Dr. McCue stated.

As the mare nears her due date, an owner should begin to look for the signs of impending parturition. In general, the mare’s belly will drop significantly two to three weeks prior to her foaling, and is easier seen in older mares.

Her tail ligaments at the top of tail will begin relaxing one to three weeks before foaling, preparing the mare for foaling.

The mammary gland will begin to develop as early as six weeks before delivery, and will be more pronounced the closer she gets to term. The teats will engorge seven to 10 days before foaling, and waxing, which is colostrum seeping from the teat, will occur two to three days before she foals.

Mares will generally foal at night or in the early morning, when they feel they have the most protection from predators. However, mares can foal at all hours of the day. A mare that is in labor will have a thick, mucous-like discharge, and will be getting up and down frequently.

Stage one of labor is when the water breaks. Shortly after this the mares moves to stage two, in which the rupture of the chorioallantoic membrane occurs. The mare will begin straining, and the amnion will appear. Once this is seen, the mare will usually foal within the hour.

The foal should present itself front feet first, with its head tucked between the two front legs. The most difficult part of the foal for the mare to pass will be its shoulders, and after that has passed, the foal should slide out easily.

If an owner is present for the birth, he or she can help to clean the mucous off the nose and mouth of the foal. However, the mare should be allowed to clean off the foal, as this is essential to their bonding.

If the amnion is present and the mare has not foaled within an hour, a veterinarian should be called as there may be a problem.

After the foal is delivered the mare moves to stage three. This is when uterine involution occurs, and the placenta is expelled. On average, it takes about an hour and a half. If the placenta has not been passed within three hours after birth, it may be retained and help should be sought.

The umbilical cord of the foal should be treated with chlorhexadine or betadine, to help the cord dry and prevent bacteria from entering through the umbilical cord.

Mares that have had several successful deliveries rarely have problems, and catching a mare foaling can be challenging. Many times, an owner will find the mare has foaled overnight, and will be greeted in the morning with a beautiful baby.

Maiden mares should be watched more carefully, as they don’t always know what to do and may not take care of the foal. Usually with a little time they figure it out, but it sometimes requires intervention. In all cases, if an owner is unsure what to do, he or she should call his veterinarian.

Foaling a mare can be a fun, exciting time for an owner. With a little preparation and a little patience, foaling can be a success. ❖


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The Fence Post Updated Oct 16, 2013 03:02PM Published Apr 15, 2013 11:17AM Copyright 2013 The Fence Post. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.