Oestrous cycles and the breeding season of the Père David's deer hind ( Elaphurus davidianus )

Summary. Reproductive cycles were studied in a group of tame Père David's deer hinds. The non-pregnant hind is seasonally polyoestrous and, in animals studied over 2 years, the breeding season began in early August (2 August ± 3·3 days; s.e.m., N = 9) and ended in mid-December (18 December ± 5·7 days; N = 8) and early January (6 January ± 3·2 days; N = 11) in consecutive years. During the anoestrous period, plasma progesterone concentrations were low (0·2 ± 0·01 ng/ml) or non-detectable. There was a small, transient increase in progesterone values before the onset of the first cycle of the breeding season. In daily samples taken during an oestrous cycle in which hinds were mated by a marked vasectomized stag, progesterone concentrations remained low (<0·5 ng/ml) for a period of about 6 days around the time of oestrus, showed a significant increase above oestrous levels by Day 4 (Day 0 = day of oestrus) and then continued to increase for 18 ± 2·8 days to reach mean maximum luteal levels of 3·5 ± 0·6 ng/ml. The plasma progesterone profiles from a number of animals indicated that marking of the hinds by the vasectomized stag did not occur at each ovulation during the breeding season and therefore an estimate of the cycle length could not be determined by this method. In the following year, detection of oestrus in 5 hinds was based on behavioural observations made in the absence of the stag. A total of 19 oestrous cycles with a mean length of 19·5 ± 0·6 days was observed. However, on other occasions, the length of the luteal phase, as assessed by plasma progesterone concentrations, showed considerable variation. During the breeding season, experiments were conducted to investigate synchronization of oestrus with exogenous progestagens. Oestrus occurred 32–90 h after progestagen removal. The changes in plasma progesterone concentrations which followed oestrus were similar to those seen after natural oestrus.