High-yield induced ovulation in the adult marsupial fat-tailed dunnart (Sminthopsis crassicaudata)

Assisted reproductive technologies play a crucial role in marsupial conservation, but developing protocols to harvest large numbers of oocytes remains a key challenge. In this study, we aimed to develop a high-yield induced-ovulation protocol to collect a higher number of MII oocytes from adult, cycling, female dunnarts. We first synchronized the female dunnart reproductive cycles using luteinizing hormone-releasing hormone (LHRH). The reproductive cycles were monitored by examining cytology of vaginal lavage samples. After administering four LHRH injections given at three-day intervals, 88.9% (n = 36) of the adult female dunnarts responded to the treatment, with their estrous cycles synchronized at the diestrous stage. We then induced ovarian follicle development through two PMSG injections over 6 days, followed by hCG administration to trigger ovulation. By combining estrous cycle synchronization with PMSG stimulation, we achieved 77.8% (n = 36) ovulation success and obtained an average of 20.1 ± 9.1 (n = 28) MII oocytes per adult dunnart. These data demonstrated that estrous cycle synchronization followed by the PMSG-hCG treatment yields consistent, highly efficient induced-ovulation in adult dunnarts. This approach of combining estrus synchronization and follicle stimulation to produce sufficient MII oocytes for ART purposes could be applied to other valuable marsupial species to support conservation efforts.