Asher G W, Smith J F
Ruakura Animal Research Station, Ministry of Agriculture and Fisheries, Hamilton, New Zealand.
J Reprod Fertil. 1987 Sep;81(1):113-8. doi: 10.1530/jrf.0.0810113.
Twenty non-lactating fallow does were each treated with an intravaginal progesterone device (CIDR) for 14 days followed by an i.m. injection of 500 i.u. PMSG, 3-4 weeks before the expected start of the natural rut. An additional 7 does received no treatments and were used as controls. Induced oestrus was observed for 19 (95%) of the treated does, the onset occurring between 48 and 76 h after CIDR removal/PMSG administration. Laparoscopic examination 12 days after CIDR removal revealed ovulation rates ranging from 1 to 4 in treated does. Non-ovulating luteinized follicles were also a feature of PMSG treatment and there was a significant inverse relationship between ovulation rate and numbers of luteinized follicles. Only 3 (14.3%) of the treated does conceived at or near the induced oestrus, the remainder returning to oestrus 21-27 days later. Mid-cycle progesterone concentrations were positively related to ovulation rate. All control does showed evidence of a recent single ovulation at laparoscopy, although first oestrus did not occur until 7-15 days later, indicating the occurrence of silent ovulations before the natural breeding season.
