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Pregnant Mare

Question: Last spring I bred my favorite riding mare and am starting to get worried as she gets closer to foaling.  I’ve never had a pregnant mare before and I don’t want to do anything wrong! Do you have any suggestions for what I can do to prepare and a sort of timeline for what should happen as she starts to foal?

Answer: First off, congratulations on your upcoming addition and I hope everything goes smoothly. That said a good first step to being prepared is to have your veterinarians phone number handy in case problems arise.  Depending on the breeding date of your mare, you should expect a foal around 11 months later though gestation can range anywhere from 320-360 days.  While it’s important to take proper care of your mare throughout her pregnancy, the last 4-6 weeks prior to her estimated foaling date are integral.  At this time you should move her to the place where you are planning to foal her out so that her immune system has time to respond to the new antigens (germs) in the area.  This allows her to form antibodies to these germs which will be passed to the foal in her colostrum (the initial antibody rich milk that the mare produces).  It is also important to vaccinate you mare with all her yearly shots during this time period so she can pass those antibodies to her foal as well.  Lastly, she should be administered a dewormer with either an Ivermectin/Praziquantel combination (Equimax, Zimectrin Gold) or a Moxidectin/Praziquantel combo (Quest plus) at least a month prior to foaling.

As far as a timeline goes, you should expect your mare’s udder to start getting bigger anywhere from 4-6 weeks out from foaling. It’s also not uncommon for a mare to develop ventral midline edema which appears as large plaque of swelling along the bottom of her abdomen when she’s within a few weeks of giving birth so don’t be concerned if you see it.  A few days prior to foaling, the muscles in mare’s hind end will relax.  This is most easily noticed by focusing on her tailhead which becomes much more prominent with this relaxation.  Anywhere from 4-6 days prior to parturition (birth) the teats themselves will become engorged with milk and lastly a process called “waxing” will occur where a yellowish secretion (colostrum) builds up and drips from the udder when your mare is within a day or two of foaling.  If you’re looking for a more scientific way of predicting your mare’s due date, calcium levels in her milk are a good indicator and can predict foaling within 1-2 days.  There are several stall side products that can be used and will come with instructions on use and how to interpret the results.  Generally, a large spike in the calcium level of the secretions indicates imminent foaling.

The act of foaling itself is divided into three stages. Stage one lasts anywhere from 30 minutes to 2 hours during which time your mare may appear restless, anxious, or even colicky as uterine contractions move the foal into the proper position.  During this stage it is best to leave your horse alone as they tend to prefer to give birth in solitude and frequent interventions may delay the process.  Stage two begins when your mare’s “water breaks” which occurs as the foal moves into the birth canal.  This is when time is of the essence as stage 2 ends with a fully delivered foal and should only last from 15-30 minutes.  If you notice that your mare has entered this stage but does not appear to be making progress after 20 minutes, she may be experiencing a dystocia (difficult birth) and you should seek veterinary assistance immediately as both mare and foal can come to harm if this stage is prolonged.  A foal is usually delivered head first with its back facing up and front legs extended under its chin (much like a nose dive).  If at any point in the delivery you notice a configuration other than two front feet with soles pointing down followed by a nose, the foal is abnormally positioned and you should call your veterinarian for assistance.  Another emergency that can occur during this stage is called a “red bag delivery”.  This condition is caused by a premature placental separation and results in the foal to losing its oxygen supply.  It’s diagnosed by the presence of a velvety red membrane over the foal as it begins to pass through the vulva.  If you notice this, immediately cut open the membrane to allow the foal access to oxygen.  After you’ve done this call you veterinarian immediately as many foals born with a “red bag delivery” struggle in their first hours of life and require intensive care.  Once the foal is on the ground, stage three begins and consists of the mare passing her placenta.  This stage usually last from 1-2 hours and happens without apparent effort or straining on the part of the mare.  A placenta is considered retained after 3 hours and can cause serious problems for your mare such as infection or laminitis if not remedied quickly so this is another situation requiring timely veterinarian intervention.

Tune into next month’s ask the vet article for a continuation on what to expect and watch for in the first 24 hours of your new foals life.