Meclofenamic acid extends donor-recipient asynchrony in equine embryo transfer

Abstract

Summary Reasons for performing study: A level of synchrony between embryo and uterine environment is essential for the establishment of pregnancy when performing embryo transfer. The ability to extend the acceptable degree of asynchrony would allow more efficient use of recipient mares. Objectives: To establish if administration of the prostaglandin synthetase inhibitor, meclofenamic acid, to asynchronous recipient mares could widen the acceptable window of asynchrony for embryo transfer. Hypothesis: The prostaglandin synthetase inhibitory action of meclofenamic acid may act to suppress luteolysis and thereby allow for a greater degree of asynchrony between donor and recipient mares. Methods: A total of 72 Grade 1 horse embryos were transferred nonsurgically into the uteri of recipient mares that had ovulated 2 (n = 20), 3 (n = 20), 4 (n = 16) or 5 (n = 16) days before the donor. Half of the mares in each group were treated orally with 1 g meclofenamic acid, beginning on Day 9 after ovulation and continuing for 7 days after embryo transfer. Results: Comparison of recipient:donor asynchrony between treated and untreated mares was: +2 days, 9/10 pregnancies vs. 8/10 (P = 1.00); by +3 days, 8/10 vs. 2/10 (P = 0.025); by +4 days, 5/8 vs. 1/8 (P = 0.121); and by +5 days 3/8 vs. 0/8 (P = 0.20). In 10/11 meclofenamic acid‐treated and 23/25 untreated recipient mares that failed to become pregnant, luteolysis occurred at the normal time (14–19 days) after ovulation. Conclusion: Treatment with meclofenamic acid supported the establishment of pregnancy in recipient mares that ovulated before the donors. However, meclofenamic acid appeared to provide this support in a manner other than by suppression of luteolysis. Potential relevance: Pregnancy rates can be increased in recipient mares that ovulate 3 days before the donor by administration of meclofenamic acid.

The effects of an advanced uterine environment on embryonic survival in the mare

“…Indeed, Stout et al [4] and others have proposed that maternal recognition of pregnancy in the mare must occur before Day 10 after ovulation in order to prevent the upregulation of oxytocin receptors and initiation of the luteolytic cascade. However, a recent experiment that included the successful transfer of Day 10 embryos to Day 12 recipient mares [5] suggested that luteolysis is either stoppable once initiated or does not begin until after Day 12. On the other hand, transfer of Day 7, instead of Day 10, embryos to Day 12 recipients did not prevent luteolysis [3].…”

“…Transfer to recipients that have ovulated Ն2 days ahead of the donor invariably lowers pregnancy rates and increases early embryonic loss [2]. Although treatment of recipient mares with the prostaglandin synthetase inhibitor meclofenamic acid has been shown to improve the rate of establishment of pregnancy in mares that ovulate 2 or 3 days ahead of the donor, a high incidence of early embryonic death was still evident in treated recipients that ovulated 4 or 5 days before the donor [3].…”

Equine embryo transfer: review of developing potential

“…In an attempt to widen the window of acceptable synchrony, Wilsher et al (2006) treated recipient mares that ovulated more than 1 day before the donor with meclofenamic acid beginning on Day 9 after ovulation; high pregnancy rates were achieved in recipients ovulating 2 and 3 days before the donor, although it is not clear how the effect was mediated. Pregnancies established after more extreme donor-recipient asynchrony (+4 or 5 days) were almost invariably lost later in gestation.…”

Practical Experience with the Treatment of Recipient Mares with a Non‐Steroidal Anti‐Inflammatory Drug in an Equine Embryo Transfer Programme

“…Treatment with meclofenamic acid, one of the NSAID, has been reported previously to improve pregnancy rate in embryo recipient horse mares. The authors suggested that this treatment overcomes ovulatory asynchrony between recipient and donor mares (Wilsher et al. 2006), a finding not confirmed by studies from our group (Koblischke et al.…”