The last follicular wave detected before the PGF2c,/MAP treatment of treated ewes emerged, on the average. 1.9 ± 0.2 days before the day of PGF2c, injection (range. 1 to 3 days), in both treatment and control groups (P > 0.05). During the 6-day period in which treated ewes had MAP sponges in place, follicles from at least two waves were present in all ewes studied. The mean number of emerging follicular waves during MAP treatment in treated ewes did not differ (P > 0.05) from that observed during the same period in control ewes (1.7 ± 0.1/ewe; range. 1 to 2).
Following the removal of sponges, the mean ovulation rate was 3.1 ± 0.4 (range. 2 to 5) in treated ewes vs. 2.0 ± 0.3 (range. 1 to 3) in control ewes (P < 0.05; Table 2). The mean ovulation rate after treatment (3.1 ± 0.4) was also greater (P < 0.05) than the pretreatment ovulation rate (1.9 ± 0.3) for ewes given PGF2c, and MAP sponges. In control ewes, there was no significant difference (P> 0.05) in the mean ovulation rate at the beginning (1.4 ± 0.2) and end (2.0 ± 0.3) of the interovulatory interval studied. All but one ovulation were detected after the onset of estrus. A single treated ewe ovulated one follicle 24 h before estrus (left ovary) and then two follicles 24 h after the onset of estrus (both in right ovary); the ovulation prior to estrus did not result in formation of a CL.