Interovulatory intervals in mares receiving deslorelin implants in Ireland (2009 to 2010).
Authors: Henderson I S F, Brama P, Osborne M, Beltman M E
Journal: The Veterinary record
Summary
Deslorelin acetate implants offer a reliable method for inducing ovulation in mares, but their effects on subsequent cycle length remained unclear in European populations when this study was conducted. Irish and UK researchers retrospectively analysed 88 oestrous cycles in Thoroughbred broodmares to compare interovulatory intervals following three different protocols: implant left in situ, implant removed post-ovulation, or human chorionic gonadotrophin (hCG) administration. Mares retaining the deslorelin implant experienced statistically significantly prolonged interovulatory intervals compared with those having the implant removed or receiving hCG (P=0.02), though the delays were considerably less pronounced than those reported in earlier North American studies. Where logistically feasible, removing the implant after ovulation is advisable to minimise disruption to breeding schedules and cycle predictability. The findings provide reassurance that even if implant removal is not possible, the subsequent delay to next ovulation is unlikely to be problematic for practitioners planning mare breeding programmes in the UK and Ireland.
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Practical Takeaways
- •If using deslorelin implants for ovulation induction in Thoroughbred mares, plan to remove the implant post-ovulation when possible to minimise cycle disruption and maintain normal breeding schedules
- •Be aware that interovulatory interval prolongation after deslorelin treatment may be less severe in UK/Irish populations than reported in USA literature, allowing for more predictable breeding management
- •Consider deslorelin implants as a practical ovulation induction option without excessive concern about long-term cycle disruption if removal is not feasible
Key Findings
- •Deslorelin implants not removed significantly prolonged interovulatory intervals compared to implants removed post-ovulation (P=0.02)
- •Delay in subsequent ovulations was less marked in Ireland/UK mares than previously reported in USA studies, suggesting geographical variation
- •Implant removal when possible is advisable to minimise disruption to oestrous cycle length
- •Mares treated with deslorelin implants do not necessarily experience prolonged return to oestrus if implant is not removed, contrary to some previous concerns