Medroxyprogesterone Acetate: RESULTS(7)

RESULTS(7)

The mean day of emergence of the follicles that ovulated during sponging was -3.9 ± 1.5 days before PGF2a (range, from 8 days before to 3 days after PGF2a injection). No ewes were marked by rams and none of the follicles that ovulated during the treatment with MAP formed a CL; however, CH were detected after ovulations occurred (Fig. 3, A-D) for —4 days (Table 1). For comparison, a CL detected with ultrasonography 48 h after ovulation posttreatment is shown in Figure 3E. In the five ewes that ovulated 1 to 6 days after PGF2a, there were no changes (p > 0.05) in serum concentrations of FSH or LH in blood samples taken every 4 h, from 48 h before to 12 h after ovulations (Fig. 4), and serum concentrations of LH remained basal (time effect, P > 0.05) from 1 day before to 1 day after treatment with MAP sponges.

The mean number of emerging follicular waves during MAP treatment was 1.7 ± 0.2 per ewe (range, 1 to 2), and the last wave before sponging emerged 1.9 ± 0.3 days before treatment (range, 1 to 3 days). After the sponges were withdrawn, the mean ovulation rate was 2.8 ± 0.4 (range, 2 to 5). The mean ovulation rate after treatment was greater (p < 0.05) than the pretreatment ovulation rate (1.9 ± 0.1; Table 2). All but one ewe were well marked by rams; one ewe was not marked. In four ewes, a total of nine ovulations were observed before estrus, and five ovulations were detected after the onset of behavioral estrus; in the remaining four ewes all ovulations occurred after estrus. However, in all but one ewe, ovulations occurred within a 48-h period, between 2 and 5 days after sponge withdrawal. A single ewe ovulated on Days 2, 3, 4 (before estrus), and again on Day 6 after MAP treatment (after the onset of estrus).
Fig3Effects of a 6-Day Treatment-6
FIG. 3. Photographic reproductions of ultrasonograms of ovaries (left panels) with accompanying diagrams depicting the outlines of the ovary and intraovarian structures (right diagrams). Images obtained using an Aloka SSD-900 echo camera equipped with a 7.5-MHz transducer (experiment 2) were recorded on S-VHS, digitized, and then converted into gray scale bit-map images in order to delineate ovaries, antral follicles, CH, and CL. For illustrative purposes, ovarian stroma is shown in light gray, follicles in black, and CH/CL in dark gray. Sequential ultrasonograms (A-D) show an ovary recorded in a treated ewe at 0, 12, 24, and 48 h relative to ovulation, which was detected on Day 1 after PGF2a injection and insertion of a MAP sponge, and E depicts an ovary of a ewe 48 h after ovulation that was detected 3 days after the removal of MAP sponges. All ewes underwent transrectal ultrasonography of ovaries every 12 h, from 1 day before PGF2a/MAP treatment until 1 day after sponge withdrawal, and then daily for 8 days. Each scale bar represents 10 mm. Note the difference in the size and echogenicity (brightness) between demising CH (D) that did not form a CL, and a growing (full lifespan) CL (E) at 48 h postovulation.

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