The only thing predictable about the pregnant mare is her unpredictability.
Mares are also sneaky. They often watch you suffer endless, sleepless nights in an attempt to attend the blessed event, and then go ahead and foal when you leave the barn for 10 minutes to get a cup of coffee.
Fortunately, 98% of mares can foal normally without assistance (miniature horses are the exception – they have a 15-20% incidence of complications). The 2% who get in to trouble need immediate assistance in order to prevent possible loss of the foal, the mare, or both. For this reason, all foalings should be attended.
Traditionally owners have used outward signs, such as udder development, ligamentous relaxation around the tailhead, color changes in udder secretions, and “waxing” of the teats as predictors of impending foaling. Maiden mares may show none of these signs, however, whereas some mares may show all of these signs for many days before foaling. Because outward signs can be unreliable, two test procedures have been developed to assist in the prediction process – measuring calcium levels in udder secretions and changes in rectal temperature.
The following steps can be easily followed to more accurately predict foaling time, although, to date, no test is 100% reliable:
1. At 320 days gestation, or when udder distention first becomes evident, monitor the calcium concentration of the mare’s udder secretions once a day with a commercial kit, such as Predict-A-Foal. Always do this in the evening.
2. Once a color change has occurred in 2 out of 4 zones on the calcium test strip, begin taking the mare’s rectal temperature in the late morning and in the late evening.
3. Start watching her around the clock when her evening temperature is equal to or less than her morning temperature, especially if her outward physical signs indicate that she is due, and 3 to 4 out of 4 calcium test strip zones show color change.
Oh, and keep your coffee maker in the barn, just in case!