Talk with any experienced foaling manager, and he or she will have a favorite method of knowing when a mare is about to foal. But you’ll also hear stories of mares that fooled them, and of the time they stepped into the office to grab a cup of coffee and came back to find a newborn foal.
Normal gestation ranges from 320 to 365 days, and normal signs of imminent foaling, such as bagging up, “waxing” teats, and relaxed pelvic ligaments, can mean foaling is anywhere from hours to days away.
So a simple, inexpensive, noninvasive test would be a welcome addition to a horseman’s bag of tricks. Robyn E. Ellerbrock, DVM, Dipl. ACT, presented information at the 2016 American Association of Equine Practitioners convention indicating that a simple pH test strip might be just the ticket. She said she’s used this method in practice at the University of Illinois College of Veterinary Medicine, in Urbana, the past three years with good results.
She said to “milk” the mare of a few drops of secretion into a Dixie cup, and use a test strip or pH meter to get a reading on it. (Taking a sample does not affect the colostrum.) Most commercial water hardness strips are not sensitive enough. You need a range from 5.5 to 8.0, in increments of 0.1 or 0.2 units.
Here’s how it works. When a mare nears foaling, her udder enlarges as pre-foaling secretions increase. Normal pre-foaling secretions have a pH of 8.0 to 8.5. That decreases as the mare gets close to foaling, eventually dropping to a pH of 6.5 or lower at the time of foaling.
When pH is 6.4 there’s a 97% chance the mare will foal in 72 hours, Ellerbrock said.
Her research led her to observe three patterns:
- Pattern 1 is seen in maiden or young broodmares, which tend to have mammary gland development happen suddenly, 24 to 48 hours prior to foaling. The next day, pH drops from 7.5 to 6.8 (roughly), then they foal that night. Mares that drop pH rapidly in 24 hours are close to foaling.
- Pattern 2 is seen with older maidens or broodmares that have had more than one foal. Their mammary glands develop several days before foaling. It can take seven to 10 days for the pH to drop from 7.5 to 6.5, and mares will not foal until the pH drops to 6.4 or below. A higher percentage of immature foals or postpartum complications can be seen among mares following this pattern.
- Pattern 3 is uncommon, with mares foaling with high, alkaline pH levels (7.5 to 8), but otherwise without problems and with normal foals.
If you see a drop in pH to 6.5 or lower, but the mare doesn’t foal, there might be something else going on that warrants a veterinary examination. Ellerbrock said other tests of sodium, calcium, and potassium have been tried, but they require an expensive meter or test kit.
Perhaps an inexpensive test can help a weary foaling manager get extra sleep? It’s worth a try.