Dynamic changes in plasma concentrations of gonadotropins, inhibin, estradiol-17 beta and progesterone in cows with ultrasound-guided follicular aspiration

To elucidate the effects of ultrasound-guided transvaginal follicular aspir ation, plasma concentrations of FSH, LH, inhibin, estradiol-17 beta and pro gesterone, and folliculogenesis were examined in Holstein cows. Four clinic ally healthy cows with regular estrous cycles were scanned by ultrasound pe r rectum once a week for 9 weeks before the commencement of follicular aspi ration. All visible follicles were divided into 3 categories based on their sizes (2 less than or equal to small < 5 mm; 5 <less than or equal to> med ium < 10 mm, large <greater than or equal to> 10 mm). The follicular aspira tion was started at random during the estrous cycle and conducted under epi dural anesthesia induced with 5 ml of 2% lidocaine once a week for 6 weeks. The average number of total visible follicles greater than or equal to 2 m m in diameter at 7 days after aspiration (21.7 +/- 7.4, n=24) was similar t o that before starting aspiration (26.7 +/- 10.5, n=36). Plasma inhibin and estradiol-17 beta declined and fell to a trough on 1.5 days and returned t o pre-aspiration values by 5 days after aspiration. Plasma concentrations o f FSH increased and reached peak levels between 1 and 1.5 days after aspira tions. Plasma concentrations of LH also increased and reached peak levels b etween 0.5 and 1.5 days after aspirations. Both plasma FSH and LH had retur ned to pre-aspiration levels by 5 days after aspirations. Plasma concentrat ions of progesterone did not change with the follicular aspiration. These r esults demonstrate that follicular aspiration decreases plasma concentratio ns of inhibin and estradiol-17 beta, which in turn leads to a rise in plasm a concentrations of FSH and LH. It is suggested that marked increases in pl asma concentrations of FSH and LH after the aspiration stimulate the develo pment and maturation of a new cohort of follicles within one week in cows.