A pattern of ovarian follicular development and change in the concentration of FSH in 8-mo-old prepubertal cattle similar to those detected in the present study has been previously reported, with the concentration of FSH elevated 1 day before the increase in the number of subordinate follicles (a 4 mm). In postpubertal cattle, the concentration of FSH starts to increase 2-4 days before the emergence of waves of ovarian follicular development, and peaks 1 or 2 days before the emergence of those waves. The number of follicles a 5 mm and the concentration of FSH increased between 8 and 3 mo prepuberty. Because increases in concentration of FSH precede the increase in number of follicles at initiation of a new wave of ovarian follicular development in prepubertal and postpubertal cattle, it is possible that greater concentrations of FSH as puberty approached may have induced development of greater numbers of follicles a 5 mm. proventil inhaler
The selection phase of the largest follicle was between Days 1 and 4 after follicle aspiration, with the number of follicles a 5 mm increasing rapidly during this time period. More rapid growth occurred, however, after aspiration of the largest follicle at 1 than at 8 mo prepuberty. Although the regression phase of the largest follicle in the present study was not apparent in terms of a decline in diameter of the largest follicle, the increase in follicles a 5 mm between Days 7 or 8 and 9 after follicle aspiration indicates that the large ovarian follicle was beginning to lose dominance and a new wave of ovarian follicular development was being initiated. The number of subordinate follicles increases around the time of initiation of atresia of dominant follicles in 8-mo-old prepubertal and postpubertal cattle.