Comparisons between ewes with normal and inadequate CL after the final ovulation of the study period. After the ovulation following MAP treatment of treated ewes, eight ewes formed as many CL as ovulated follicles (ewes with normal CL), but six ewes had fewer CL than ovulations (three treated and three control ewes; ewes with inadequate CL). The mean ovulation rate was 2.1 ± 0.3 and 3.2 ± 0.4, for ewes with normal and inadequate CL, respectively (P < 0.05). The mean number of detected luteal structures per ewe was 2.1 ± 0.3 and 1.7 ± 0.2 (P > 0.05) for ewes with normal and inadequate CL, respectively. The time from ovulation to detection of CL averaged 3.1 ± 0.2 days for both groups of ewes in question (P > 0.05).
When data were normalized to the day of ovulation, mean serum concentrations of estradiol were significantly higher in ewes with normal CL on Day 1 (4.2 ± 0.4 vs. 2.5 ± 0.4 pg/ml) and Day 2 (4.6 ± 0.3 vs. 2.8 ± 0.4 pg/ml), and daily serum concentrations of progesterone were higher (P < 0.05) on Day 3 (1.03 ± 0.20 vs. 0.50 ± 0.14 ng/ml) and Day 4 (1.60 ± 0.28 vs. 0.81 ± 0.18 ng/ml) after ovulation (ewes with normal CL vs. ewes with inadequate CL, respectively).
Seven ovulations were detected in five of eight ewes between 1 and 6 days after the injection of PGF2a and insertion of MAP sponges (Table 1). Six of 19 follicles (32%) that were >5 mm in diameter on the day of PGF2a injection ovulated during treatment with MAP. In addition, one ewe had a follicle that emerged on Day 3 and ovulated on Day 6 after PGF2a.