Development of Corpora Lutea and Plasma Progesterone Levels Associated with the Onset of the Breeding Season in White-tailed Deer (Odocoileus virginianus)

Histology of ovaries of mature white-tailed deer (Odocoileus virginianus) collected at 1 month intervals from August through October and at 1 week intervals in November 1976 revealed multiple luteal cycles and a sharp reduction in atresia of large follicles (diameter >3 mm) during the onset of the breeding season at Plum Brook Station, OH. Active corpora lutea were first observed in ovaries of does collected on 6 November; these were small (76 ± 15, X̄ ± SEM) and associated with relatively low levels of circulating progesterone (0.61 ± 0.24 ng/ml plasma). Plasma progesterone levels were correlated (r = 0.79, P<0.05) with the total volume of active luteal tissue/doe and both increased throughout November, reaching maximum values of 4.2 ± 0.68 ng/ml and 347± 32 mm3, respectively. Both active and regressing corpora lutea were found in 79% of the ovaries of does collected on 20 November, just 2 weeks after the first corpora lutea of the season were observed. Apparently, the first ovulation produced only transient corpora lutea and was followed by a second ovulation in less than 15 days. These observations suggest that formation of small, short-lived corpora lutea was involved in the transition from seasonal anestrus to productive estrous cycles.