Resumption of ovarian activity following removal of a 4.7 mg deslorelin implant in queens

Deslorelin implants are widely used in felines. Due to their prolonged duration cat breeders frequently request early implant removal. The interval between deslorelin implant removal and resumption of ovarian function in queens is unknown. The aim of this study was to evaluate the interval between the removal of a deslorelin implant and the resumption of ovarian activity in adult queens. Twenty-three queens were treated with a 4.7 mg deslorelin implant placed in the periumbilical area. In the 16 queens completing the study implants were surgically removed at 3, 6 or 9 months (n = 6, 4 and 6 queens, respectively). Queens received a GnRH stimulation test as part of their pre-treatment general and reproductive health check. Following implantation treatment, all queens in inter-oestrus-anoestrus at the time of treatment came in oestrus within 2-5 days. Starting 7-14 days following implant removal queens were checked every 1-2 weeks with reproductive ultrasonography, a vaginal smear and blood collection. The interval to resumption of ovarian function ranged from 3 to 7 weeks irrespective of treatment length and age of the queen but was longer when the implant was removed at decreasing photoperiod (p < .05). In conclusion, at least 3 weeks post-removal are needed during increasing photoperiod to achieve follicular development and oestrogen production sufficient to support oestrous behaviour in queens following removal of a 4.7 mg deslorelin implant, while this time may increase up to 7 weeks during decreasing photoperiod. Further studies are needed to assess the interval between removal of a deslorelin implant and occurrence of ovulation as well as fertility at the first oestrus after a deslorelin treatment.