Factors affecting live foal rates of Thoroughbred mares that undergo manual twin elimination.
Authors: Schnobrich M R, Riddle W T, Stromberg A J, LeBlanc M M
Journal: Equine veterinary journal
Summary
# Editorial Summary: Twin Elimination and Live Foal Rates in Thoroughbreds Manual reduction of twin pregnancies in mares detected at 13–17 days post-ovulation is routine practice, yet considerable variation exists in pregnancy outcomes following the procedure. Schnobrich and colleagues investigated whether specific factors—including vesicle proximity, mare age, reproductive history, parity, breeding month, and progesterone concentration—influenced live foal rates following twin elimination in Thoroughbred mares. Vesicle location emerged as significant, with adjacent twin vesicles yielding substantially lower live foal rates compared to nonadjacent configurations; surprisingly, mare age, parity, and plasma progesterone levels did not meaningfully predict outcome. These findings suggest that embryo position within the uterus at the time of reduction may be a critical determinant of pregnancy viability, potentially reflecting differential placental development capacity or mechanical stress during manual elimination. For practitioners performing twin reductions, this work highlights the prognostic value of ultrasound assessment of vesicle positioning and implies that mares presenting with closely positioned twins warrant heightened monitoring and potentially different counselling regarding expected live foal rates.
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Practical Takeaways
- •Understanding factors affecting live foal rates after twin elimination helps veterinarians counsel breeders on expected outcomes and manage expectations for twin pregnancies
- •Consideration of mare-specific variables (age, parity, progesterone levels) may inform decision-making and post-procedure management protocols
- •Vesicle location and timing of elimination relative to these factors may be important for optimizing success rates in breeding programs
Key Findings
- •Manual twin elimination is a common procedure in Thoroughbred mares diagnosed with twin vesicles at 13-17 days post-ovulation
- •Study investigates whether vesicle location (adjacent vs. nonadjacent), mare age, reproductive status, parity, breeding month, and plasma progesterone concentration influence live foal rates following the procedure