Induction of Ovulation in Pere David’s Deer Hinds at Two Stages of Seasonal Anestrus

Pere David’s deer hinds were treated with gonadotrophin-releasing hormone (GnRH) administered either intermittently by IV injections (2 μg GnRH at 2-h intervals) for 4 days or as a continuous subcutaneous infusion (1 μg/h) for 14 days for 14 days after progestagen pretreatment early (February to March) or late (May to June) in the period of seasonal anestrus. Both treatments at both stages of anestrus induced ovulation indicated by an increase in progesterone concentration exceeding 0.5 ng/ml for at least 7 days accompanied by behavioral estrus and an luteinizing hormone (LH) surge. Treatment was significantly more effective in inducing ovulation in late (9/12 animals) than early (3/13 animals) anestrus (P<0.01), and the onset of estrus behavior and LH surge were significantly earlier in late than early anestrus (P<0.05). These results indicate that there is a period of deeper anestrus following the end of the breeding season.