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Predicting Foaling in Mares: A Review of MethodsBy Kentucky Equine Research Staff · December 13, 2017

Mares keep their own schedules when it comes to foaling, but that doesn’t stop expectant owners from trying to predict when mares will deliver.

“Gestation length varies considerably among mares; some may routinely carry 325 days while others hold on to foals for a year or longer,” said Laura Petroski, B.V.M.S, a veterinarian at Kentucky Equine Research (KER). “This variance can be frustrating for mare owners and foal-watchers, especially to those who raise other species, like dogs, that have more well-defined gestation periods. Only under especially specific circumstances are mares induced into labor, so as maddening as it is to wait, there is nothing that can be done to hasten foaling.”

Owners, however, remain undaunted and in recent years have used mammary secretions in an attempt to foretell foaling. Researchers recently set out to determine if there is any truth in these tried methods of predicting foaling*.

Twenty-three Standardbred mares varying in age from 8 to 23 years old were observed daily for signs of foaling. Beginning on day 320 of pregnancy, mammary secretions were collected each day and evaluated using calcium titration, digital pH meter, pH test strips, water hardness test trips, and Brix refractometer (a measure of sugar). These methods were then compared with a birth-monitoring system.

Of the methods evaluated, calcium titration most reliably predicted foaling. According to the researchers, “calcium titration was significantly related to foaling with the highest proportion (94% and 95%) of mares showing readiness to foal on day -1 and day 0, respectively. Birth-monitoring resulted in 82% of mares foaling with an alarm, 18% without, and 19% false alarms.”

Commercial calcium titration kits are available for at-home use.

“Knowing exactly when a mare will foal may be important, but nourishing a mare properly to support a growing fetus and a newborn foal is essential. Be sure all pregnant mares have properly balanced diets replete with the nutrients necessary to produce strong, healthy foals,” said Petroski.

Do you have questions about feeding a mare in gestation? Contact the nutrition advisors at KER today.

*Diel de Amorim, M., M. Morrison, Y. Montanholi, D. Whitehead, M. Lopez, and C. Card. 2017. Comparison of foaling prediction methods in periparturient Standardbred mares. In: Proc. American Association of Equine Practitioners Convention 68:462.