A predictive model for reproductive performance following abortion in Thoroughbred mares.
Authors: Schulman M L, Kass P H, Becker A, Van der Merwe B
Journal: The Veterinary record
Summary
# Editorial Summary Following pregnancy losses in Thoroughbred mares, the long-term reproductive consequences remain poorly understood despite the significant economic impact of conditions such as EHV-1 abortion epidemics. Schulman and colleagues conducted a prospective cohort study across two South African breeding farms affected by EHV-1 outbreaks, developing predictive models to identify which factors—including early embryonic death (EED), abortion aetiology, mare age and breeding timing—most strongly influenced subsequent breeding efficiency, conception rates and foaling outcomes. Early embryonic death emerged as the strongest predictor of poor reproductive performance across all measured outcomes, whereas later-term abortion (including EHV-1) extended the timeframe needed to re-establish pregnancy and delayed breeding into later seasons, though it did not ultimately prevent conception or live foal production; advancing age consistently reduced breeding efficiency and pregnancy success. Practitioners should counsel owners that mares recovering from EED warrant more cautious long-term expectations than those experiencing later abortions, whilst recognising that strategic early-season breeding of barren mares showed improved conception prospects—a finding that may guide targeted management of problem breeders during the initial breeding window.
Read the full abstract on PubMed
Practical Takeaways
- •Early embryonic death has more severe long-term consequences for reproductive performance than later abortion, warranting investigation and prevention strategies
- •Mares with previous abortion history require more breeding attempts but ultimately can still achieve pregnancy and foaling outcomes comparable to non-aborted mares
- •Consider prioritizing breeding of older mares and those with reproductive challenges earlier in the breeding season to maximize conception rates
Key Findings
- •Early embryonic death predicted all reproductive outcomes studied (breeding efficiency, month of last breeding, subsequent pregnancy and live foal rates)
- •Abortion predicted increased breeding effort and delayed month of breeding to establish pregnancy, but did not significantly affect becoming pregnant or foaling rates
- •Increasing mare age predicted decreased reproductive efficiency and reduced pregnancy and foaling probabilities
- •Breeding in the first month of the season was associated with improved probability of pregnancy in barren mares