Foaling Tendencies and Dystocia Rates in New Zealand
Foal size (and, indirectly, sex) appear to contribute to dystocia, especially among mares in New Zealand. | Photo: iStock
Dystocia (difficulty during birthing) in pregnant mares is most commonly attributed to an abnormal foal position in the womb. But researchers have recently learned that the foal’s size (and, indirectly, sex) also appear to contribute to dystocia, especially among mares in New Zealand.

The average gestation length for pregnant mares in New Zealand is seven to eight days longer than mares in the Northern Hemisphere. And the team believes this could mean larger, heavier foals and an increased risk of difficulty during birthing.

“Colts appear to be at a significantly higher risk of neonatal death compared to fillies,” said Cristina Rosales, BVSc (Hons), MVS, MANZCVS (Equine Medicine), MRCVS, a resident at the University of Melbourne’s Equine Centre, in Victoria, Australia. “This could be related to colts being typically heavier than fillies at birth.”

Rosales and colleagues recently performed a study to evaluate periparturient (around the time of birth) characteristics of mares and foals in New Zealand

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