Improved embryo recovery through increased flushing media volume and the impact on unintended pregnancies in a single subject donor mare.
Authors: Sala-Ayala Laura, Cuervo-Arango Juan, Martinez-Bovi Rebeca
Journal: Journal of equine veterinary science
Summary
# Editorial Summary This case report examines a persistent clinical problem in embryo transfer programmes: a donor mare experiencing repeated unintended pregnancies despite apparently negative embryo flushing (EF) outcomes, suggesting embryos were being retained in the uterus. Over two years, researchers compared two flushing protocols on the same non-lactating Spanish purebred mare—six cycles using 1 litre of Ringer's Lactate versus five cycles using 2 litres—to determine whether increased medium volume could improve embryo recovery and eliminate retained pregnancies. Doubling the flushing medium volume from 1 L to 2 L dramatically improved embryo recovery rates from 25% to 85.7% (p < 0.05), whilst completely eliminating unintended pregnancies in the second group (0/7 cases versus 4/8 in the initial protocol). Double ovulation occurred in 36.3% of cycles overall and was comparable between groups, ruling this out as a confounding variable. The findings suggest that practitioners using standard flushing volumes may unknowingly be leaving embryos in the uterus, resulting in failed transfers and unexpected pregnancies that compromise breeding schedules and donor welfare; adjusting flush volume upwards warrants serious consideration in cases of unexplained low recovery rates or recurrent unplanned conceptions.
Read the full abstract on PubMed
Practical Takeaways
- •Consider increasing flushing media volume to 2 L when encountering consistently low embryo recovery rates or repeated unintended pregnancies in donor mares, as this may substantially improve outcomes
- •Double ovulation occurs frequently (36.3%) in this mare and appears unaffected by flushing volume; protocols should account for multiple embryos regardless of flushing technique
- •Omitting post-flushing PGF2α administration may contribute to unintended pregnancies—evaluate whether increased flushing volume alone or combined with hormonal protocols is appropriate for your practice
Key Findings
- •Increasing flushing media volume from 1 L to 2 L significantly improved embryo recovery rates from 25% to 85.7% (p < 0.05)
- •Double ovulation frequency was consistent between groups at 36.3% overall and did not differ significantly between 1 L (33.3%) and 2 L (40%) protocols
- •Unintended pregnancies were significantly reduced in the 2 L flushing group (0/7) compared to the 1 L group (4/8, p < 0.05)
- •A tendency toward 100% positive embryo flushing outcomes was observed with increased flushing volume (p = 0.06)