Medroxyprogesterone Acetate: RESULTS(1)
Follicular dynamics and ovulations. Individual follicle profiles (follicles that grew from 3 to >5 mm in diameter) are shown for two different animals for each group in order to illustrate the pattern of follicular wave development and the number and time of emergence of ovulatory follicles during the study period (Fig. 1).
Within 2 to 5 days of the injection of PGF2a and insertion of progestogen sponges (Day 0), 6 of 7 treated ewes ovulated, giving a total of 11 ovulations (Table 1). Inspection of growth profiles for individual antral follicles revealed that ovulation occurred in 50% (8/16) of all follicles >5 mm in diameter detected on the day of PGF2a injection in the treatment group. In addition, in one treated ewe, two follicles emerged on Day 2 and ovulated on Day 5, and in one other ewe, a follicle that emerged on Day 1 ovulated on Day 4 after PGF2a. No ewes were marked by rams and none of the follicles that ovulated after PGF2c, and before the withdrawal of sponges formed a CL. ventolin inhalers
In the six ewes that ovulated 2 to 5 days after PGF2c, treatment, there were no significant changes (P > 0.05) in serum concentrations of FSH in daily blood samples, from 2 days before to 2 days after ovulation, but mean serum concentrations of estradiol declined from 4.1 ± 0.2 pg/ml on Day -1 before ovulation to 1.5 ± 0.5 pg/ml on the day of ovulation (P < 0.001). and subsequently increased (P < 0.05) to 3.4 ± 0.7 pg/ml on Day 2 after ovulation.
TABLE 1. Percentage of ewes ovulating (treated ewes), mean ovulation rates and characteristics of ovarian antral follicles.
* Calculated for ovulating ewes only.
+ Based on daily (experiment 1) or twice daily (experiments 2 and 3) transrectal ovarian ultrasonography (i.e., mean follicular diameter before ovulation was determined at 24 h [experiment 1] or 12 h [experiments 2 and 3] before ovulation detection, respectively); nd, not determined.
* Ovulations were detected at the estrus prior to sponging (pretreatment) or after progestogen treatment (posttreatment).
ab Within experiments, means with different superscripts differ (P < 0.05) between the ovulations occurring before and after MAP treatment of treated ewes (Student f-test); AB between treated and control ewes for the ovulation following MAP sponge withdrawal in treated ewes (Student f-test); and Х’У between treated and control ewes (v2-test).