191 TIMING OF OVULATION IN THE GONADOTROPHIN-STIMULATED SOUTHERN HAIRY-NOSED WOMBAT, LASIORHINUS LATIFRONS

Abstract

The southern hairy-nosed wombat (SHW), Lasiorhinus latifrons, is a model species in which to develop assisted breeding techniques for the endangered northern hairy-nosed wombat, Lasiorhinus krefftii. We recently showed that anoestrus SHW respond to eutherian gonadotrophins by production of multiple ovarian follicles, but ovulation had not occurred at the time of examination 24 h post-LH (Druery GV et al. 2003 Theriogenology 59, 391 abst). This study investigated the timing of ovulation in six anoestrus captive adult female SHW (n = 3 per group) after ovarian superstimulation using porcine FSH (200 mg total, Folltropin-V, Bioniche, Belleville, Ontario, Canada) administered s.c. at 12-h intervals over 7 days. Ovulation was triggered by a single s.c. dose of porcine LH (25 mg Lutropin-V, Bioniche) 12 h after the final FSH injection. Superstimulatory response was determined by laparoscopy immediately after the final FSH injection on Day 7 prior to LH. Group 1 was re-examined at 33, 36, and 39 h post-LH, and Group 2 at 42, 45, and 48 h post-LH, for evidence of ovulations using laparoscopy and transabdominal ultrasonography. Laparoscopy on Day 7 revealed an ovarian follicular response in all six females, which coincided with the highest levels of estradiol. The reproductive tract also responded to the treatment (swollen fimbriae and enlarged, highly vascular uteri). Multiple follicles (range 16–31) up to 11 mm in diameter were observed in five females. One female had ovulated, as determined by the presence of corpora lutea. Transabdominal ultrasonographic imaging was unable to confirm the number of follicles in stimulated ovaries. Ovulation had commenced by 36 h post-LH, with the majority occurring 39–45 h post-LH. Ovulation was recorded as having occurred if a dark red, highly vascular crater on the surface of the newly formed corpus hemorrhagicum was observed. Increased circulating levels of progesterone were confirmed 9 days after the last laparoscopies. These results have important implications for the development of assisted reproductive technologies in the SHW: (1) transabdominal ultrasound imaging is ineffective for determining ovarian activity; (2) laparoscopy is a well-tolerated, repeatable minor surgical procedure that can be used for intrauterine AI in this species in which nonsurgical AI is unlikely to succeed (Paris DBBP et al. 2003 Theriogenology 59, 401 abst); and (3) knowledge of the timing of ovulation will enable insemination of spermatozoa into the uterus prior to ovulation. Financial support was provided by Dr. M. Jacobson, and hormones were supplied by Bioniche.