Temporal relationship between the onset of oestrus, the preovulatory LH surge and ovulation in farmed fallow deer, Dama dama

Abstract

A study was conducted to determine the timing of ovulation relative to the onset of oestrus and the preovulatory LH surge in fallow deer. Mature fallow does were randomly allocated to two treatments (N = 10 per treatment) designed to synchronize oestrus on or about 17 May. Does assigned to Group 1 (prostaglandin-induced oestrus) each initially received single intravaginal CIDR [Controlled Internal Drug Release] devices for 13 days followed by an i.m. injection of 750 mg cloprostenol on Day 12 (15 May) of the subsequent luteal cycle. Does assigned to Group 2 (progesterone-induced oestrus) each received CIDR devices for 13 days, with withdrawal occurring on 15 May. All does were run with crayon-harnessed bucks (10:1 ratio) from the start of synchronization (18:00 h 15 May). Ten does (5 per group) were blood sampled via indwelling jugular cannulae every 2 h for 72 h from cloprostenol injection or CIDR device withdrawal and the plasma was analysed for concentrations of progesterone and LH by radioimmunoassay. Does within each treatment were randomly allocated to an ovarian examination time of 12, 16, 20 or 24 h after the onset of oestrus. Laparoscopy was repeated at 12-h intervals until ovulation was recorded. The ovaries of does failing to exhibit oestrus were examined 72 and 86 h after cloprostenol injection or CIDR device withdrawal. A total of 17 does were observed to exhibit oestrus at a mean (± s.e.m.) interval from treatment of 44.6 ± 3.6 h for Group 1 (N = 9) and 34.1 ± 2.5 h for Group 2 (N = 8). The incidence of ovulation from 34 laparoscopic examinations was 0% for intervals <20 h, 50% at 24 h and 100% for intervals >28 h. There was no difference between animals in Groups 1 and 2. The onset of the preovulatory LH surge (n = 8 observations) occurred at the onset of oestrus, with maximum LH surge concentrations (30 ng/ml) occurring 6 h later. Of 3 does not exhibiting oestrus, 2 (Group 2) possessed active corpora lutea at CIDR device withdrawal and 1 (Group 1) possessed a large unruptured follicle 72 and 86 h after cloprostenol injection. The data indicate that ovulation in fallow deer occurs ~24 h after the onset of oestrus and ~18 h after the peak of the preovulatory LH surge.