University of wisconsin-madison

Signs of Parturition - Milk Calcium

One of the best predictors of impending parturition is the milk calcium level. Calcium levels increase within the last 24 - 48 hours before parturition. The calcium level can be measured using several different commercial kits. These kits are based on water hardness tests. When the pre-milk calcium level first increases above 200 parts per million (ppm), 98% of mares will foal within 72 hours. When the level is less than 200 ppm in the evening, it is unlikely the mare will foal before morning. If the milk calcium is over 300, our experience is the mare will foal within a short time. A rapidly increasing milk calcium between samples taken within a day is also an indicator of impending parturition likely to occur that night.

The image below is the results of using the Foalwatch test kit for a single mare over 10 days. Each of the tubes represents a results on single day. Earliest samples before foaling are on the left with foaling occuring 5 AM of the day following the last sample on the right. In this kit, a change from an orange or pink to blue is when the level of calcium is determined. The calcium level is in ppm and read from the scale on each tube. Levels (ppm) are from left to right, <50, <50, <50, 50, 65, 90, 125, 130, 160, and 250.

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