When is my mare going to foal?

The first post in a series about foaling out your mare.

Foaling season is upon us and mare owners everywhere are left guessing as to when their mares are going to foal.  Watching your mare can be frustrating and confusing, but knowing some basics and being prepared can go along way to help bring a healthy foal into the world, or to help save a sick one.  This spring we will have a series of posts about foaling – what to watch for when your mare is close to foaling, how to be prepared, what to do once the foal is on the ground, and when to breed back your mare.  This first post in the series covers information on the signs that your mare is close to foaling.

Many mares are bred naturally on pasture leaving a large window of time for when they might foal, but even owners with exact breeding and ovulation dates can’t accurately predict a foaling date.  This is largely due to the mare’s varied gestational length.  The average gestational length for horses is 340 days and we use this to calculate due dates, but mares can have normal foals anywhere from about 325 days gestation to over 365 days gestation.  Most mares will have their own “typical” gestational length, but even this can vary with the time of year they are due (e.g. early spring vs. late summer), and it isn’t helpful with maiden mares.  So what are some signs to monitor in your expectant mare?

Knowing your mare is very important.  This can help you monitor for behaviour changes that could signal impending parturition, as many mares seem more excitable than usual.  It can also help to signal if something is wrong with the pregnancy, for example if a mare with a good appetite suddenly is not interested in feed this could signal an infection such as placentitis.  For mares that have had foals in the past, knowing their previous gestational lengths and how they acted around foaling is very useful.  Often a mare will follow a similar pattern each year, with a similar gestational length.

Photo: Valerie Hinz

Photo: Valerie Hinz

There are also many useful signs that indicate foaling is near.  Mares will “bag up” before foaling which is indicative of the beginning stages of milk production.  Their udders start to enlarge and will sometimes begin to drip milk (this can also be indicative of a problem with the pregnancy if it begins before the mare is “due” and is an important reason to call a veterinarian).  Bagging up can occur anywhere from around 6 weeks prior to foaling to just days before foaling, but it is a good time to begin watching the mare.  They will also form a wax-like substance on the ends of their teats, called “waxing up”, within a few days of when they will foal. 

When a mare begins to produce pre-foaling milk in her udder and it can be milked out from the teats, this can be used to further narrow down her foaling date.  Commonly, milk calcium is measured to help determine the foaling date.  In more recent years, pH of the pre-foaling milk has proved more useful, and easier to do, in predicting foaling.  Once there is fluid in the udder that can be milked out, its pH can be tested with normal pH strips (such as the ones you would use to monitor pools or hot tubs).  The pH will decrease as the mare becomes closer to foaling.  Once it drops to around 6.4, the mare should foal within 48 hours.  Of course not all mares follow the rules and some will foal sooner or later than the books say they should.

Within a few days of foaling the muscles around the mare’s tailhead and vulva will begin to relax as well – another tell-tail sign that a foal is coming soon.

Mare owners also find monitoring tools such as video monitoring and Foal Alert systems useful.  If your mare is in a stall overnight, video monitoring allows you to monitor your mare from the comfort of your house, meaning you can watch for signs of early labor before rushing to the barn.  Foal Alert systems are small devices that are sewn across the mare’s vulva.  When the foal begins to arrive, the device breaks and alerts you to the foaling.  Unfortunately Foal Alerts can produce false alarms by breaking apart when the foal isn’t actually coming, and mares can easily rub them out if they find the devices irritating.

Now that you know the signs to monitor, what do you need in your foaling kit to welcome a new foal into the world?  Stay tuned for the next post to find out more.