GnRH Treatment at CIDR Insertion Influences Ovarian Follicular Dynamics in Japanese Black Cows

Abstract

ABSTRACT. Ovarian follicular dynamics and estrous synchronization after Gonadotropin-releasing hormone (GnRH) treatment at Controlled Internal Drug Releasing device (CIDR) insertion were investigated in Japanese Black cows. CIDR was inserted for eight cows at 7 days after estrus. Cows were allocated to either Group A: 8-day CIDR insertion with GnRH treatment on d 0 (n=4, d 0=CIDR insertion) or Group B: 8-day CIDR insertion (n=4). Both groups were injected with prostaglandin F 2α (PGF 2α ) on d 7. Ultrasonography and blood sampling were performed twice daily. Intensive sampling was performed every 15 min for 8 hr to determine the pulsatile release of LH on d -1, d 5 and d 10. Three of four cows showed intermediate ovulation within 2 days after GnRH treatment during CIDR insertion in Group A, whereas no ovulation was found in Group B. Three of four cows in Group A and all four cows in Group B ovulated after CIDR removal. Plasma progesterone concentrations from d 3 to d 7 in three intermediate ovulatory cows in Group A (8.4 ± 1.6 ng/ml) was significantly higher than those in Group B (4.1 ± 1.2 ng/ml; 4 cows) during CIDR insertion (P<0.01). Interval to estrus and ovulation after CIDR removal was observed at 60.0 ± 12.0 hr and 76.0 ± 6.9 hr in three cows in Group A, and 75.0 ± 15.1 hr and 93.0 ± 20.5 hr in Group B, respectively. There was a significant increase in LH pulse frequency on d 10 compared on d -1 or d 5 in both groups (P<0.05), in addition those on d 10 in Group A tended to be higher than in Group B. As a result, GnRH treatment at CIDR insertion at 7 days after estrus induced intermediate ovulation with formation of corpus luteum (CL) and rather synchronized emergence of ovulatory follicle during CIDR insertion. These induced CL increased plasma progesterone concentrations and contributed to precise synchronization.

Efficacy of Intravaginal Progesterone Administration as an Additional Treatment on Two Types of Timed AI Protocols in a Commercial Herd of Holstein Heifers

“…By contrast, in heifers with CL on day 0, intermediate ovulation was limited (CIDR-treated group: 21.4%, No-CIDR-treated group: 39.1%). This result may due to that CIDR insertion with GnRH treatment induces intermediate ovulation of the existing dominant follicle [1] and forms new CL [2]. However, on the whole, CIDR insertion suppressed the intermediate ovulation during initial 7 days induced by GnRH treatment as compared to No-CIDR-treated group in the present study (CIDR-treated group: 33.3%, No-CIDRtreated group: 52.6%, P<0.05).…”

“…GnRH induced the intermediate ovulation even during the period of CIDR insertion. Ando, et al reported that the ovulation was not induced during CIDR insertion without GnRH treatment at CIDR in [2]. These results indicated that CIDR insertion with GnRH treatment on day 0 probably does not affect intermediate ovulation induced by GnRH in heifers without functional CL on day 0, however CIDR tends to suppress intermediate ovulation in heifers with functional CL on day 0 together with existent CL.…”

Effects of AI protocol and time interval from onset of estrus to AI on conception rate in Japanese Black cows

“…In this study, the time interval to ovulation confirmation after PRID removal was 72.0-72.1 h in 4/5 cows in the synchronized AI group (73.2 Ϯ 2.7 h). Ando et al (2005) reported that ovarian follicular dynamics and estrus synchronization occurred after GnRH treatment at CIDR insertion in Japanese Black cows. The time interval to ovulation after CIDR removal was 72 h in the group that showed ovulations both intermediately during CIDR insertion and after CIDR removal.…”

“…In this study, the time interval to ovulation confirmation after PRID removal was 72.0–72.1 h in 4/5 cows in the synchronized AI group (73.2 ± 2.7 h). Ando et al . (2005) reported that ovarian follicular dynamics and estrus synchronization occurred after GnRH treatment at CIDR insertion in Japanese Black cows.…”