Medroxyprogesterone Acetate: RESULTS(8)

The last follicular wave before ovulation following MAP treatment contained ovulatory follicles in all ewes; of all follicles reaching >5 mm in diameter in this wave, 86% (12/14) ovulated (Table 2). The penultimate wave before ovulation contained ovulatory follicles in seven of eight ewes. In the penultimate follicular waves, 60% (9/15) of follicles >5 mm in size were ovulatory. None of the follicles that emerged before the penultimate wave ovulated. Ovulatory follicles in the penultimate wave emerged approximately 3 days earlier and had a significantly longer static phase (4.5 ± 0.9 vs. 1.7 ± 0.4 days; P < 0.05) compared with ovulatory follicles in the last follicular wave.

All but one treated ewe responded to PGF2a with a decline in circulating concentrations of progesterone within 24 h after injections. In one ewe, CL could be observed for 7 days after PGF2a until regression just before estrus after MAP treatment, and serum concentrations of progesterone declined to 0.50 ng/ml 24 h after treatment (Day 0), then rose to 1.23 ng/ml on Day 4, and finally declined to 0.10 ng/ml on Day 7 after PGF2a. In this same ewe, a breakthrough ovulation occurred on Day 4 after PGF2a and ovulations of follicles from the last two waves of the cycle were seen.