Time of ovulation in the brushtail possum (Trichosurus vulpecula) following PMSG/LH induced ovulation

This study aimed to determine the timing of ovulation in response to a new induced ovulation regime for the monovulatory brushtail possum (Trichosurus vulpecula). Ovarian stimulation was achieved by a single subcutaneous injection of 15 IU pregnant mare serum gonadotrophin (PMSG). This treatment resulted in promotion of a large number (9–16) of Graafian follicles >2mm diameter on the ovaries. Seventy‐two hours later a single intramuscular injection of 4 mg porcine luteinizing hormone (LH) was administered to induce ovulation. Groups of possums were killed 24 hr post‐LH injection and subsequent groups were killed at 6‐hr periods up to 48 hr later. Ovulation occurred from 30 hr to 42 hr post‐LH. The ovulatory success increased from 3% at 30 hr post‐LH to 83% at 48 hr post‐LH. Oocytes were recovered primarily from the oviducts at 36 hr post‐LH. Thereafter oocytes were recovered increasingly from the uteri and by 48 hr post‐LH, were only found there. The implications of these observations for artificial breeding in possums are discussed. J. Exp. Zool. 283:608–611, 1999. © 1999 Wiley‐Liss, Inc.