Human chorionic gonadotrophin does not induce ovulation in the tammar wallaby

Abstract

We investigated whether human chorionic gonadotrophin (hCG), rather than porcine luteinising hormone (pLH), could induce ovulation in the tammar wallaby (Notamacropus eugenii) after priming with pregnant mare serum gonadotrophin (PMSG). pLH is effective, but is more expensive and supply is problematic. On Day 0 pouch young were removed (RPY) and 5mgkg−1 of bromocriptine mesylate was administered to all non-pregnant wallabies (n=12) to reactivate an oestrous cycle. On Day 20 RPY each female received 20IU PMSG i.m. and three days later (Day 23 RPY), the Single-Dose group (n=6) received 500IU of hCG suspended in oil at 0900 hours, and the Multi-Dose group (n=6) received 500IU of hCG at 0900, 1230 and 1630 hours. From Day 25 to Day 28 RPY copulatory plugs were observed in the Single-Dose (n=4 of 6; Day 25.3 to 28.3 RPY) and Multi-Dose (n=5 of 6; Day 25 to 28 RPY) groups. Autopsy on Day 31 RPY revealed that all females had reactivated, and despite all having large preovulatory follicles (4–6mm) in both ovaries, no ovulations or embryos were observed. We conclude that hCG is not an effective source of exogenous LH for the induction of ovulation in the tammar wallaby.