Gestation Length is Associated With Early-Life Limb Deformities in Thoroughbred Foals.
Authors: Mouncey Rebecca, Arango-Sabogal Juan Carlos, de Mestre Amanda M, Verheyen Kristien
Journal: Journal of equine veterinary science
Summary
# Gestation Length and Limb Deformities in Thoroughbred Foals Flexural and angular limb deformities represent a significant welfare concern in neonatal Thoroughbreds, yet their aetiological basis remains poorly defined; Mouncey and colleagues hypothesised that maternal and pregnancy-level factors influencing in-utero development might contribute substantially to their development. Prospective data on veterinary interventions for limb deformities within the first six months of life were collected across seven UK and Irish studs, with associated mare and pregnancy characteristics retrieved retrospectively from stud and veterinary records (275 pregnancies in 235 mares over two breeding seasons). One in five foals (57 of 272, 21%) required veterinary treatment for limb deformities, and notably, the odds of deformity decreased by 4% for each additional day of gestation length between 314 and 381 days—a finding that remained statistically significant even within the normal gestational range for Thoroughbreds. This association suggests that prolonged gestation, within physiological limits, may allow enhanced skeletal and soft-tissue maturation in utero, potentially reducing the predisposition to early-life deformities. Whilst the precise biological mechanisms warrant further investigation, these findings warrant consideration of gestation length as a measurable pregnancy indicator when counselling breeders regarding deformity risk, and may have implications for management decisions in mares carrying pregnancies at the shorter end of the normal range.
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Practical Takeaways
- •Monitoring gestation length in breeding mares may provide insight into foal limb deformity risk, though further research is needed to establish clinical thresholds
- •Foals from shorter gestations (even within normal range) may warrant closer early monitoring for signs of flexural or angular limb deformities requiring intervention
- •Maternal factors affecting gestation length should be investigated further as potential modifiable risk factors for preventing congenital limb deformities in Thoroughbreds
Key Findings
- •21% of 272 Thoroughbred foals (n=57) required veterinary intervention for limb deformities in the first six months of life
- •Odds of limb deformities decreased by 4% per day increase in gestation length between 314-381 days (OR 0.96, 95% CI 0.93-0.99, P=0.01)
- •Longer gestation length within the normal range for Thoroughbreds appears protective against early-life limb deformities
- •Maternal and pregnancy-level factors influencing in-utero growth and development may be important in the etiology of congenital limb deformities