Follicular persistence induced by adrenocorticotropic hormone administration in goats

The objective of the present study was to examine the effect of adrenocorticotropic hormone (ACTH) administration on the induction of persistent cystic follicle in the goat in order to establish a method to experimentally induce cystic follicle. Four cross-bred goats were intramuscularly administered ACTH at 0.78 and 6.25 µg/10 kg twice a day from Days 15 to 21 (Day 0 was defined as the day of last estrus). Follicular status in the ovary was monitored by ultrasound examination. The plasma concentrations of estradiol, progesterone and cortisol were measured. Treatment with ACTH at the 0.78 and 6.25 µg/10 kg levels caused persistent follicles (> 10 days delay from the expected ovulation date) in 50% of the goats in both treatment groups. In those animals, ovulation occurred 17 and 27 days and 11 and 12 days after the expected days in the 0.78 and 6.25 µg/10 kg groups, respectively. The maximum follicle diameters were 10 and 9 mm in the 0.78 and 6.25 µg/10 kg ACTH groups, respectively. In the control group, the estradiol concentration increased on Day 18 and remained at a high level for a few days. However, such an increase was not seen in both ACTH groups. The estradiol concentration increased gradually from Days 21 to 27 in the 6.25 µg/10 kg ACTH group. These results suggest the possibility that ACTH induces persistent follicles in goats, which may be related to the delay of the onset of estradiol secretion followed by its maintenance at a high concentration.