Reason for performing study: An understanding of the normal events of foaling, causes of dystocia and clinical outcomes is important for equine practitioners.
Objectives: The goals of the present study were to: 1) evaluate factors that influence gestation length; 2) report duration of Stage II labour; 3) determine the frequency of dystocia and premature placental separation; and 4) determine the relationship between problems at foaling and foal survival.
Materials and methods: Foaling records of 1047 mare births were evaluated.
Results: The average gestation length was 341 ± 0.3 days, with no effect of mare age or breed observed. Mares carrying male fetuses had a longer gestation (P≤0.001) than mares carrying female fetuses. A majority (52.8%) of mares foaled at night between 2000 h and 0200 h when the facility was quiet. Dystocia occurred in 10.1% of all births and the incidence rate was higher in Thoroughbred mares than in Quarter Horse mares. The most common cause of dystocia was abnormalities of fetal posture. A delay in foal delivery beyond 40 min of Stage II of labour was associated with a significant increase in foal mortality. In addition, an increase in foal morbidity and mortality was noted when the interval from birth to standing or birth to nursing was prolonged.
Conclusion: Early detection and rapid appropriate intervention are critical to foal survival in an equine dystocia.
Potential relevance: Equine veterinarians should counsel horse owners that early recognition of a foaling problem and rapid, appropriate intervention are critical to the survival of a foal.