Length of estrous cycle and gestation in the Arabian oryx (Oryx leucoryx) and the importance of the male presence for induction of postpartum estrus.

The reproduction of the Arabian oryx (Oryx leucoryx) has been studied in a breeding center in Taif (Saudi Arabia). In the first experiment, three groups of females were assigned to groups immediately after calving. In group 1, from the day of calving the females had visual and olfactory but not physical contact with a male. The calves were removed on the day of birth and each female was placed with a male on Day 45. In group 2, females and their calves were placed individually with a male the day after calving. In group 3, females and their calves were kept with neither visual nor olfactory contact with a male and then placed with a male on Day 90. The estrous cycle was deduced from assays of plasma progesterone up to Day 120 after calving. All females exhibited a postpartum estrus a few days after parturition but the occurrence of the estrus was significantly delayed in females of group 3. The length of the estrous cycle was 23.7 +/- 1.3 days and the gestation length was 255.2 +/- 1.5 days. In the second experiment, a group of adult females was formed in 1987 and the intervals between calving recorded over a period of 5 years. The mean interval between calving was 285 +/- 2 days (n = 99 gestations). However, 66.6% of these intervals averaged 276 days whereas 19.2% had averaged 294 and 13% averaged 321 days.