Improved method of superovulation in monovulatory brushtail possums (Trichosurus vulpecula) using pregnant mares' serum gonadotrophin-luteinizing hormone.

A new superovulation regimen for the monovulatory brushtail possum (Trichosurus vulpecula) has been devised. It reduces the number of hormone treatments required and elicits a better rate of ovulation than the established pregnant mares' serum gonadotrophin (PMSG)-GnRH method. Ovarian stimulation was achieved by a single intramuscular injection of 15 iu PMSG. This treatment resulted in the recruitment and development of a large number (9-12) of Graafian follicles on the ovaries. Induction of ovulation was achieved by a single intramuscular injection of 2-10 mg pig LH or multiple intramuscular injections of GnRH, (4 x 50 micrograms, 90 min apart) given 72 h after PMSG treatment. Superovulation occurred in all animals (n = 48) examined 48 h after treatment irrespective of dose of LH or type of ovulatory stimulus used. The highest ovulatory success (83%), the maximum number of ovulation sites (9.5 +/- 2.8) and the highest number of oocytes recovered (9.0 +/- 2.5) were achieved after treatment with PMSG and 4 mg LH. These results were significantly greater than the ovulatory success (43%), numbers of ovulation sites (3.9 +/- 1.1) and number of oocytes recovered (2.1 +/- 0.9) after PMSG-GnRH treatment (P < 0.05). This simpler and more effective superovulation protocol should assist with more effective manipulation of possum reproduction in captivity.