Aspect | Details |
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Mare Gestation Period | 320 to 362 days; most mares foal between 330 and 345 days |
Common Foaling Signs |
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Milk pH Levels | Drop from around 7.6 to 6.6 in the days leading up to foaling; reliable indicator of foaling within 24 hours |
Key pH Testing Findings |
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Steps for Milk pH Testing |
|
Benefits of Milk pH Testing |
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Predicting Foaling in Horses: The Role of Milk pH Levels
Predicting the exact time of foaling in mares has always been a challenge for horse breeders and veterinarians. Traditional methods, such as observing physical signs and calculating gestation periods, often lack precision. However, recent studies have shown that monitoring the pH levels of a mare's milk can provide a reliable indicator of impending parturition. This blog explores the science behind this method and its practical applications.
Understanding Mare Gestation and Foaling Signs

Mare gestation typically ranges from 320 to 362 days, with most mares foaling between 330 and 345 days. This wide range makes it difficult to predict the exact foaling date based solely on gestation length. Common signs that a mare is nearing parturition include:
- Development of the mammary gland (2-6 weeks prior)
- Relaxation of the croup muscles (7-19 days prior)
- Teat distension with colostrum (4-6 days prior)
- Waxing or dripping from teats (2-4 days and 24-48 hours prior, respectively)
While these signs are helpful, they do not provide a precise timeline. This is where milk pH testing comes into play.
The Science Behind Milk pH Testing

Research by Korosue et al. (2013) and Canisso et al. (2013) has demonstrated that the pH level of a mare's milk decreases significantly as parturition approaches. In their studies, the pH of the milk dropped from around 7.6 to 6.6 in the days leading up to foaling. This drop in pH is a reliable indicator that foaling will occur within 24 hours.
Key Findings:
- pH Levels: The pH of the milk remains relatively stable until about four days before foaling, after which it begins to decrease significantly. On the day of parturition, the pH drops dramatically.
- Calcium Carbonate Levels: Alongside the pH drop, the calcium carbonate content in the milk increases from 100 µg/g to 500 µg/g as foaling approaches.
- Total Alkalinity: Unlike pH and calcium levels, the total alkalinity of the milk does not show significant changes and is not a reliable indicator of impending foaling.
Practical Application of Milk pH Testing

To implement milk pH testing, breeders can use pH meters or test strips to monitor the pH levels of the mare's milk daily. Here’s a step-by-step guide:
- Sample Collection: Collect 10-15 mL of milk from the mare's mammary gland daily, preferably between 12 and 3 PM.
- pH Measurement: Use a calibrated pH meter or test strips to measure the pH of the milk. Ensure the pH meter is calibrated daily with a buffer solution of pH 4.0 for accuracy.
- Monitoring Changes: Record the pH levels daily. A significant drop in pH (to around 6.6) indicates that foaling is likely to occur within the next 24 hours.
Benefits of Milk pH Testing

Using milk pH testing provides several benefits:
- Accuracy: Provides a more precise prediction of foaling compared to traditional methods.
- Preparation: Allows breeders to be better prepared to assist with foaling, ensuring the safety and health of both the mare and the foal.
- Cost-Effective: pH meters and test strips are relatively inexpensive and easy to use.
Conclusion

Monitoring the pH levels of a mare's milk is a scientifically backed method that offers a reliable way to predict foaling within a 24-hour window. This technique enhances the ability of breeders to prepare for and manage the foaling process effectively, ensuring better outcomes for both mares and foals. By incorporating milk pH testing into their routine, breeders can significantly improve their foaling management practices.
For more detailed information and to access the original research, you can refer to the study by Korosue et al. (2013) and the subsequent validation by Canisso et al. (2013).
By understanding and utilizing the changes in milk pH levels, horse breeders can take a significant step forward in the precise prediction of foaling, ensuring better care and management of their mares and foals.
Explore our range of supplements to support the health of your mares and foals during this crucial period.