Deslorelin acetate (Ovuplant) therapy in cycling mares: effect of implant removal on FSH secretion and ovarian function.
Authors: Farquhar V J, McCue P M, Carnevale E M, Nett T M, Squires E L
Journal: Equine veterinary journal
Summary
# Editorial Summary Deslorelin acetate implants (Ovuplant) reliably induce ovulation in mares but create a problematic side effect: suppressed follicle-stimulating hormone (FSH) secretion in the subsequent cycle, resulting in delayed follicular development and extended interovulatory intervals. To determine whether early implant removal could mitigate this effect, researchers compared spontaneous ovulation, ovulation induced by deslorelin with implant retention, and ovulation induced by deslorelin with implant removal after 2 days across 24 mares. Mares retaining the implant showed significantly reduced FSH concentrations by Day 10 postovulation, markedly smaller follicles on Day 14 (19.0 mm versus 30.5–36.6 mm in comparison groups), and substantially prolonged interovulatory intervals of 25.8 days compared to 18.5–19.4 days in mares with removed implants or spontaneous ovulation. Early implant removal completely prevented the gonadotrophin suppression and cycle lengthening, indicating that the deslorelin depot effect—rather than the ovulatory event itself—drives these reproductive disruptions. For practitioners managing breeding programmes, this finding strongly supports removing the implant once ovulation is confirmed ultrasonographically, ensuring return to normal cycle length and fertility without compromising the reliability of the initial ovulation induction.
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Practical Takeaways
- •Remove deslorelin implants within 2 days after ovulation is confirmed to prevent suppression of FSH and reduced follicular growth in the next cycle
- •Leaving deslorelin implants in place extends interovulatory intervals by approximately 6-7 days, which may complicate breeding scheduling
- •Early implant removal allows normal gonadotrophin secretion and follicular development, maintaining regular cycling patterns
Key Findings
- •Deslorelin implant removal 2 days after ovulation induction prevented the decrease in FSH secretion observed when implants were left in place (FSH not different between control and early removal groups on Day 10)
- •Mares with implants removed early had follicular diameter of 30.5 ± 2.0 mm on Day 14, compared to only 19.0 ± 2.1 mm in mares with implants retained (P < 0.05)
- •Interovulatory interval was 19.4 ± 0.3 days with early implant removal versus 25.8 ± 2.9 days with implant retention (P < 0.05)
- •Early deslorelin implant removal eliminates the prolonged interovulatory interval and FSH suppression associated with continued implant presence