Ovarian Follicular Development
Nine prepubertal female cattle (Angus, n = 5; Saler, n = 2; Braler, n = 2; 9 mo of age at the initiation of the experiment; 258 ± 25 kg) were used in the study. Age at puberty for each female was determined retrospectively on the basis of the time when luteal function was initially detected (concentrations of progesterone > 1 ng/ml of blood plasma). buy birth control online
To synchronize the stages of ovarian follicular development among females (day after follicular aspiration), ovarian follicles > 4 mm in diameter were aspirated via the transvaginal approach at 9 mo of age, a second time at 11 mo of age, and monthly thereafter at approximately the same time each month until puberty (day prepuberty). Ovarian follicular development was evaluated by ultrasonography on the day subsequent to follicular aspiration (Day 1) and every day thereafter for 9 days (Day 0 = day of follicular aspiration). Ovarian follicles were classified as < 5 mm, > 5 mm, or largest follicles depending on diameter. The largest follicle in each case was retrospectively identified as the follicle with the greatest diameter after follicular aspiration.