Simple Foaling Predictors

Foaling watch is always stressful, even for old pros. Closed-circuit TVs and electronic monitors are great, but they have drawbacks, too, including the price. However, you can zero in on impending birth without breaking the bank.

Timing your mare’s foaling date takes a combination of science and plain, old horse sense. Foals due in the warmer months tend to be born closer to their due dates. Those due during colder months tend to ?”wait?’? longer.

A Cornell University study in the late 1980s recorded rectal temperatures of mares close to foaling at 7 a.m., 3 p.m., 11 p.m. and for 24 hours after foaling. Horses normally show a variation in their temperature over the day, with the lowest reading in early morning and a rise late in the day. On the day prior to foaling, however, this pattern was lost and the late-day temperature rise didn’t occur. Mares that foaled between 3 and 11 p.m., a peak foaling time, showed a drop in temperature prior to foaling. Most mares foaling at other times of the day also showed at least the loss of the normal late-day temperature rise the day prior to foaling, plus varying degrees of further drop compared to morning temps.

Milk Calcium
In January 2000, we compared electronic foaling monitors against commercial milk-testing kits for predicting foaling. While the monitors are a godsend, they’re also expensive. We found milk-testing kits a more economical option, recommending Predict-A-Foal (805-434-0321) as the best choice there.

The way a milk-test kit works is simple: When the milk’s calcium level is low, the odds of the mare foaling are slim. However, changes can occur rapidly so it’s always best to do your checks last thing at night. High calcium readings, especially if they’re a dramatic change from the last reading and/or if the color change to highest calcium reading is rapid, mean there is a good chance foaling is near.

An inexpensive alternative for early screening is to get the water-hardness test strip Sofchek, which costs about $10 for 50 strips (see sidebar).

Dr. William B. Ley, an equine-reproduction specialist, recommends that once the reading on the Sofchek strips reaches 120 ppm of calcium you should switch to a commercial kit to get more precise readings. However, other breeding specialists report having used the Sofchek system alone and suggest that, once a reading exceeds 250 ppm on Sofchek, 95% of mares will foal within 12 hours.

Physical Changes
• Udder: Mares that have foaled before can begin to show udder enlargement, “bagging up,” as early as a month before foaling. This isn’t quite as obvious in maiden mares, but some degree of swelling should be seen in the week or two before foaling. The veins along the abdominal wall that drain the udder will also become enlarged. The teats will elongate and fill four to seven days prior to foaling.

• Foal position: As foaling approaches, the foal will move from a position low in the abdomen up toward the birth canal. You’ll notice that when viewed from the front the mare doesn’t appear to be bulging out to the sides as prominently as she was. When viewed from the side, the mare looks more tucked up through the belly. This repositioning of the foal usually begins within a few days of foaling.

• Muscle and ligament: The hormonal changes that occur as the mare is preparing to foal cause the muscles and ligaments in the hindquarters/pelvic area to soften and relax. When viewed from behind, the mare’s tail base will appear more prominent as the muscles on either side become loose and may even appear caved in. This is more difficult to appreciate on fat mares or maiden mares, while mares that have had several foals may show this change prominently. Relaxation may be evident anywhere from a few days before foaling, to a month or more.

• Vulva: Within one to three days of foaling, the mare’s vulva will elongate. You may also see some grayish or slightly blood-tinged material on the vulva, which is the mucus plug, a collection of thick mucus that seals off the cervix during pregnancy and is lost close to foaling.

• Edema: Many mares develop significant edema along the lower belly in late pregnancy, as far forward as between the front legs. Hind-leg edema may also occur. This is caused by the weight of the uterus restricting blood return through the veins. The edema itself isn’t of any use in predicting foaling, but if you see a significant lessening it probably means the foal is moving into the birth position.

• Behavior: It’s difficult to predict impending foaling from a mare’s behavior unless you know her well. Some become hypervigilant, jumpy and more active close to foaling, others will be withdrawn and apparently preoccupied with what is going on in their bodies.

Waxing is the appearance of a coating — dried secrections from the udder — over the end of the teats that looks like wax. Waxing usually means foaling is quite near, however, it can begin anywhere from two days to two weeks before actual foaling.

Milk Characteristics
Experienced foal watchers can do a good job predicting foaling with nothing more than a good look at the mare’s udder. Secretions may be obtained from the udder beginning as early as four to six weeks prior to actual foaling. They will vary in color from yellowish to a cloudy gray. If the fluid is placed onto a black background, you’re supposed to be able to see the black through the secretions/milk until the mare is within 24 hours of foaling. At that time, the milk becomes significantly more opaque, like true milk, and you won’t be able to see the black through it.

The Calendar
The calendar is the least-reliable way to predict foaling. Normal pregnancy duration can be anywhere from 320 to 370 days, which is nearly a two-month difference. Foaling-predictor charts usually use a 340- or 345-day estimated gestation length as an average for giving you a due date, but few mares actually foal on that date.

Mares bred to foal in late winter or very early spring may carry their foals longer than those foaling in the warmer months, and colts are usually carried slightly longer than fillies. Mares that have had several foals will usually have pregnancies of similar lengths, so a mare’s foaling history is a more accurate predictor than a calendar chart.

Bottom Line
Our experience drove home the point that no foaling prediction system is 100% accurate. However, we find physical changes, milk appearance, milk-calcium levels, and temperature monitoring useful tools for letting you know when your mare needs close watching. We’d save the pricey predictors for the pros.

Also With This Article
Click here to view ”Sofchek Tests Milk Calcium.”
Click here to view ”Foal Watch: Our Trial.”