Serum Anti-Mullerian Hormone Levels and Estrous Monitoring of GnRH Agonist Deslorelin-Induced Estrus in Bitches: A Pilot Study

Simple Summary Deslorelin is a slow-release gonadotropin-releasing hormone (GnRH) agonist that has been successfully used to induce an estrous cycle in bitches. Little is known regarding the details of ovarian follicle development in estrous bitches induced by the deslorelin implant. Anti-Mullerian hormone (AMH), produced by granulosa cells in the ovary, is involved in the mechanism of follicle development. Nevertheless, information of AMH as a fertility marker in the bitch is scarce. The current study aimed to monitor estrous pattern and follicular development in deslorelin-induced estrous bitches. The changes in AMH concentrations and ovarian ultrasonography during the peri-ovulatory period were mainly investigated. Results showed that a slow-release deslorelin implant successfully induced estrus and ovulation in all bitches. The induction of estrus occurs shortly after deslorelin implantation. AMH concentrations varied greatly among bitches. No significant differences in AMH levels were observed between pre- and post-implantation. Concentrations of AMH and the pattern of AMH were different from natural estrus. Ovarian ultrasound revealed changes in follicular development over the observation period. It seemed that the fertile period of deslorelin-treated bitches was shorter than that of natural-occurring estrous bitches. In conclusion, our findings suggest that AMH is not suitable as a fertility marker to monitor ovarian response to deslorelin treatment for estrus induction in bitches. This study was performed to monitor estrous patterns and, more importantly, changes in anti-Mullerian hormone (AMH) concentrations during the peri-ovulatory period in deslorelin-induced estrous bitches. Healthy anestrous bitches (n = 4) were used. Estrus and ovulation were monitored after deslorelin implantation. Blood samples were collected for analysis of progesterone, estradiol-17ss and AMH concentrations before implantation (day 0) and on days 6, 8, 10, 12, 14, 16, 18, 20 and 22 after implantation. Six days following treatment, all bitches showed estrus signs. Ovulation took place between days 12 and 15. Circulating AMH concentrations varied among bitches from 0.12 to 3.08 ng/mL. However, no significant differences in AMH levels (mean +/- SD) were observed between day 0 and days following post-implantation (p > 0.05). There were no significant correlations between AMH and estradiol or AMH and progesterone (p > 0.05). Ultrasonographically, the number of clearly identifiable ovarian follicles was higher before ovulation and the area of ovaries increased after ovulation (p < 0.05). Except for AMH, changes in vaginal cytology, estradiol-17ss and progesterone levels observed in our study were similar to naturally occurring estrus. Large intra- and inter-individual variation in AMH were observed suggesting that AMH is currently not suitable as a canine fertility marker to monitor ovarian response to deslorelin treatment for estrus induction.