Health & Wellness

What to Expect When Your Mare is Expecting

Dr. Cameron Etherington, DVM

Last year you had the idea to breed your mare. Maybe you were lucky and it only took one attempt; maybe it took two or three. Maybe this is your first time or maybe you’re a regular breeder. You got her bred, got her vaccinated, gave her extra feed, and waited 11 months. The time is almost here.

So now what? During the last two months of gestation, the fetus begins repositioning itself and moving into the birthing position: front feet and head first. These movements may be visible externally or may be misconstrued as mild gastrointestinal colic signs, but do not last very long. Once there, the fetus will typically stay in this position until it is born.

As your mare gets closer to “the big day,” you will notice signs of impending foaling. Mammary gland development begins around one month pre-foaling, but often begins slowly. The muscles and tendons around the perineum become looser to allow for stretching during parturition. Finally mammary gland secretions (not milk quite yet) typically begin a few days before the foal is born. You may see these dried “waxy” secretions hanging from the teats. Commercial foaling prediction tests are available once secretions appear.

Eventually you will notice your mare acting a little bit unusual. Some mares distance themselves from their pasture-mates while others may have a decreased appetite for a short while. Most mares will foal late at night or in the very early morning. The first stage of labor looks very similar to gas colic, but your mare will continue eating and drinking, urinating and defecating in between fetal movements and the initial contractions. The length of stage one is highly variable with some mares showing signs for several hours and others showing little to no signs. Stage one ends when the amnion ruptures and the amniotic fluid is released.

Stage two labor is the period of time from the mare’s “water breaking” to when the foal is expelled through the birth canal. This stage is the quickest, lasting less than 20-30 minutes, and the mare will usually lie down during the strong contractions that characterize this stage. Once the foal is born, both mare and foal will often lie still and rest for a short while. Foals should progress through a series of steps, following the “1-2-3-hour rule.” Newborn foals should stand within one hour, begin nursing by two hours, and the remaining portion of the placenta should be expelled by three hours, which ends the third and final stage of labor.

Due to the way the placenta forms in the horse, foals are born with a naïve immune system, meaning they have no natural defense against disease. The first milk a mare produces is called colostrum and contains a high volume of antibodies for her foal. These antibodies constitute the only immune system the foal will have for the first few months of its life, while the immune system develops and begins to produce its own. However, the foal can only absorb these antibodies for the first few hours of life, and loses 50% of its absorptive ability after approximately 12 hours. This process is called passive transfer of immunity.

Most foals come into this world and meet all their progress markers with no complications, but some need a little extra help. Failure to meet any of the above time “limits” by a few minutes should not be an immediate cause for concern, but foals that struggle to progress should be evaluated by a veterinarian on an emergency basis. Prematurity/dysmaturity, in utero infections, and neonatal maladjustment (dummy foal) syndrome can all contribute to foals struggling during the neonatal period. Many owners will attempt to step in and assist the foal to meet one or more of its markers by the suggested time, but foals should not require any help, no matter how small. Foals that receive assistance often appear to take longer to progress, though this may be just viewer perception.

We at McKinlay and Peters Equine Hospital recommend that all foals receive a new foal exam somewhere between 12 and 24 hours after birth. During this exam your veterinarian will evaluate the foal for congenital abnormalities and early signs of illness. Your foal should also receive an immunoglobulin G (IgG) test at this appointment to evaluate the amount of colostral antibodies absorbed. Failure, either complete or partial, of passive transfer can be treated with a transfusion of immunized plasma. This plasma contains the antibodies the foal failed to received from the mare’s colostrum and, since it goes directly into the bloodstream, there is no absorption necessary. Without these antibodies, as discussed above, the foal has no immune defense against the various pathogens it will encounter over the next few months.

Fortunately, while there are a lot of uncertainties with foaling out by yourself, Mother Nature has designed the process to be largely hands-off. So, sit back and try to enjoy the ride…despite the sleepless nights.

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