Climatic factors affecting gestational length in mares under subtropical climate.
Authors: Moraes Bruna S S, Curcio Bruna R, Müller Vitória, Bruhn Fabio R P, Santos Isadora P O D, Danielski Júlio N S, Nogueira Carlos E W
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Researchers analysed 470 gestations from 202 Criollo mares on a southern-hemisphere breeding farm to establish how subtropical climatic conditions influence gestation length, finding a mean gestational period of 337±0.4 days (range 311–363 days). Parity significantly affected duration, with primiparous mares carrying pregnancies approximately 6 days longer than multiparous counterparts (340 versus 334–336 days), though foal sex had no bearing on length; notably, individual stallions also demonstrated measurable effects on gestational length. Environmental exposure during pregnancy proved consequential—mares experiencing autumn and winter periods with reduced daily sunshine hours showed statistically significant prolongation of gestation, whilst daily sunshine hours, precipitation and temperature-humidity index all displayed negative correlations with gestation length. These findings suggest that subtropical breeding programmes warrant careful attention to seasonal stressors and photoperiod exposure, particularly for young primiparous mares who already display longer gestations and may therefore benefit from enhanced welfare monitoring and adjusted management protocols during pregnancies spanning months with lower light exposure or higher thermal stress indices.
Read the full abstract on PubMed
Practical Takeaways
- •Breeding farm managers should expect longer gestations in first-time Criollo mares (~3 days longer) and account for this when predicting foaling dates
- •Seasonal and climatic factors significantly influence pregnancy duration; mares bred for autumn–winter gestation will have extended pregnancies, requiring adjusted management timelines and monitoring
- •Parity and mare age are more reliable predictors of gestational length than foal sex; consider mare history when calculating expected foaling dates
Key Findings
- •Mean gestational length in Criollo mares was 337±0.4 days (range 311–363 days)
- •Young-primiparous mares had significantly longer gestations (340±0.9 days) compared to young-multiparous (336±0.7 days) and mature-multiparous (334±0.7 days) mares (P<0.001)
- •Daily sunshine hours, precipitation, and temperature-humidity index showed negative correlation with gestational length
- •Mares gestating during autumn and winter with reduced daily sunshine hours experienced increased gestational length (P<0.05)
- •Foal gender had no effect on gestational length; stallion had a significant effect