Schematic representation of the experimental designs used in the present study. In experiment 1, injections of GnRH (200 ng; IV) were given every hour for 96 h starting on Day 7 after ovulation (Day 0). In experiment 2, progesterone implants were inserted subcutaneously 4 days after ovulation and remained in place for 10 days. Control animals received saline or empty implants in experiment 1 and 2, respectively. Daily transrectal ovarian ultrasonography and blood sampling was performed on all ewes starting from the day when the ewe was marked with a vasectomized crayon-harnessed ram (estrus) until ovulation at the end of cycle. Blood samples were also taken every 12 minutes for 6 h (intensive bleeds) on Day 7, Day 9 and Day 11 after ovulation in experiment 1 and on Day 3, Day 10 and Day 16 in experiment 2, to characterize the pulsed secretion of LH and or FSH.