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How to Predict Foaling

How to Predict Foaling
By Heather Smith Thomas
Your mare was bred on June 1 of last year. Equine gestation is about 340 days (roughly 11 months), so her expected due date is coming up in a few months, around May 6. That 340-day figure is just an average, however, meaning it’s perfectly normal for a mare to foal as many as three weeks earlier or later than expected.
You’d like to be present at the birth in case there’s a problem, but that’s quite a window and you’ve got a lot going on this spring. Hovering over the expectant dam in the barn 24/7 is impractical and, quite frankly, could make her nervous and delay the process. Like many breeders, you’d like to be able to predict when exactly she might foal.
Good news: There are signs and tools to help. Here two reproduction-focused vets offer their expertise and suggest ways to take away some of the mystery, so you can be there for the big event.
Physical Changes
In late gestation (from Day 250 onward) mares experience several observable physical changes. Ahmed Tibary, DVM, PhD, Dipl. ACT, professor of theriogenology in Washington State University’s Department of Veterinary Clinical Sciences, in Pullman, advises breeders to examine the mare periodically to monitor how her body is changing to be ready for parturition (birth).
“Mares are quite variable in their signs of preparation for foaling, depending on whether they are older broodmares that have had several foals or maiden mares,” he says. “Premonitory signs based primarily on morphological (structural) changes can be quite subtle in some mares, difficult to discern, and are not precise. They tell you that the mare is getting ready, but they don’t narrow down the time of foaling to an actual day.”
There are, however, things you can monitor to make sure the mare is progressing normally in preparation for foaling.
“The classic physical change is mammary development, or a significant increase in udder size,” says Robyn Ellerbrock, DVM, Dipl. ACT, a PhD candidate at the University of Illinois Urbana-Champaign’s College of Veterinary Medicine. This can begin two to three weeks before foaling—further out than this can signal problems such as placentitis (inflammation of the placenta). As the mare gets closer to parturition (usually in the last two to three days of pregnancy) she’ll begin accumulating dried secretions on the tips of her teats, a process known as waxing.
“It is important to realize that we are talking about probability, rather than a definite time frame, when we see a mare waxing,” says Tibary. “About 90% of mares will foal within 24 to 48 hours, but some mares wax longer. A mare might wax very briefly or for several days. Last year we had a mare at the hospital that waxed for about a week. That might be due to being in the hospital where there is a lot more going on; if the mare doesn’t find a quiet time she may delay foaling.”
Other signs include relaxation and elongation of the vulva, as well as softening of the pelvic ligaments around the tailhead. “Sometimes you can also see an actual change in the shape of her abdomen as the foal is repositioning and preparing to enter the birth canal,” Ellerbrock says.
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