Road Transport of Late-Pregnant Mares Advances the Onset of Foaling.
Authors: Nagel Christina, Melchert Maria, Aurich Jörg, Aurich Christine
Journal: Journal of equine veterinary science
Summary
# Road Transport and Foaling Timing in Late-Pregnant Mares The initiation of parturition in horses involves complex hormonal signalling, and elevated maternal cortisol is recognised as a key trigger for labour onset. This study investigated whether transport stress—known to substantially elevate cortisol—could accelerate the timing of foaling in late-pregnant mares, testing the hypothesis that stress-induced endocrine changes might shorten the critical window between prepartum signs and actual delivery. Twelve pregnant mares underwent a single three-hour road transport between day 325 and 330 of gestation, whilst four controls remained stabled; researchers measured blood and saliva cortisol concentrations, precolostrum pH changes, and foetomaternal cardiac parameters throughout the peripartum period. Transport successfully elevated maternal salivary cortisol from 3.3 to 8.4 ng/mL, and remarkably reduced the interval from detectable precolostrum pH changes (≤6.5) to parturition from 134 hours in controls to just 40 hours in transported mares—a clinically meaningful compression of the preparation phase. Importantly, neither foetal health indicators nor postpartum foal outcomes differed between groups, suggesting that transport-induced stress accelerated the timing of labour initiation without compromising neonatal maturity or vigour. For equine professionals managing high-risk pregnancies or mares displaying prolonged prepartum signs, these findings highlight the potential risks of unnecessary transport in late pregnancy, whilst also suggesting that controlled stress exposure might theoretically facilitate delivery in cases of pathologically delayed parturition—though clinical application would require careful consideration of individual circumstances.
Read the full abstract on PubMed
Practical Takeaways
- •Avoid transporting mares during late pregnancy (after day 325 of gestation) unless necessary, as transport stress may precipitate premature foaling
- •If transport of late-pregnant mares is unavoidable, monitor closely for signs of impending parturition and ensure foaling facilities are available at destination
- •Transport-induced stress appears to accelerate the final stages of parturition without compromising foal health or vigor, but premature foaling remains undesirable
Key Findings
- •Road transport for 3 hours increased maternal cortisol concentration from 3.3 to 8.4 ng/mL in late-pregnant mares (P < 0.001)
- •Time from precolostrum pH decrease to parturition was significantly shorter in transported mares (40 ± 10 hours) versus controls (134 ± 49 hours, P < 0.01)
- •Transport did not affect fetal heart rate, heart rate variability, foaling duration, or foal postnatal outcomes
- •Gestation length was similar between groups (337 ± 2 days stressed vs 336 ± 2 days control), suggesting transport advanced parturition onset rather than overall gestation