Daily serum concentrations of FSH, estradiol, and progesterone for all ewes were aligned with the day of PGF2„ treatment for the treated ewes (Day 0), and analyzed for the period from Day —1 to Day 7. Daily concentrations of the hormones were also aligned with the day of ovulation after the MAP treatment period (Day 0) and analyzed for the period from Day — 3 to Day 5 in all ewes (the period when sponges were withdrawn in the treated ewes to 1 day after CL detection in all ewes studied). Main effects of group, day, and group-by-day interaction were determined by repeated measures ANOVA (SigmaStat 2.0).
The PC-PULSAR program was used to estimate LH/FSH pulse frequency, amplitude, and duration as well as mean and basal serum concentrations of LH and FSH obtained by frequent blood sampling. The basal serum level (‘‘smoothed series’’) was generated after the removal of short-term variations in hormone concentrations, including possible pulses. Standard deviation criteria (G and Baxter parameters) were used for pulse detection. These characteristics of FSH/LH secretion were then compared between the treatment and control groups by ANOVA (SigmaStat 2.0).
Additional analyses. Daily serum concentrations of FSH, estradiol, and progesterone in the six treated ewes that ovulated after PGF2„ injection and before the removal of progestogen sponges were aligned with the day of such ovulations in each ewe (Day 0) and analyzed for the period from Day —2 to Day 2 by one-way repeated measures ANOVA (SigmaStat 2.0).
Following MAP sponge removal in treated ewes, some ovulated follicles in three treated and three control sheep failed to form detectable CL (i.e., inadequate CL). In order to assess differences between the ewes with normal CL only (n = 8) and those that had both normal and inadequate CL (n = 6), hormonal data were compared between the two groups in question, after alignment with the day of ovulation, as described above for endocrine data.