Ovarian follicular cysts are a major reproductive failure in lactating dairy cows, prolonging the calving-to-conception interval and resulting in great economic loss. Treatment with GnRH is currently the most common therapy used for ovarian follicular cysts in dairy cows, but definitive results remain inconclusive. Recently, the Ovsynch protocol has been introduced as a therapeutic strategy for ovarian cysts in dairy cows (Bartolome et al. 2000 Theriogenology 53, 815–825). The objective of the present study was to evaluate the therapeutic effect of a CIDR-based timed AI (TAI) protocol on ovarian follicular cysts in lactating Holstein cows. Lactating Holstein cows with ovarian follicular cysts were randomly assigned to two treatments: (1) insertion of a CIDR intravaginal progesterone device (CIDR^™, InterAg, Hamilton, New Zealand) with an injection of 100 μg GnRH (Conceral^®, Dongbang Co., Seoul, Korea) on Day 0, an injection of PGF_2α (Lutalyse^®, Pharmacia & Upjohn, Puurs, Belgium) and removal of the device on Day 7, an injection of GnRH on Day 9, and TAI 16 h after the GnRH injection (CIDR+GnRH-PGF_2α-GnRH group, n = 30); and (2) an injection of 100 μg GnRH on Day 0, and AI at estrus (AIE) within 2 months after treatment with GnRH (GnRH group, n = 72). Day 0 was the day of initiation of the experiment. Pregnancy diagnosis was determined at 60 days after AI using both ultrasonography and rectal palpation. Pregnancy rates between groups were compared by chi-square analysis. Treatment-to-conception interval for cows that conceived by 150 days post-treatment was compared by Student's t-test. The pregnancy rate after TAI following the CIDR+GnRH-PGF_2α-GnRH protocol (46.7%) was higher (P < 0.05) than that after AIE following GnRH injection (25.0%). The treatment-to-conception interval (mean ± SEM) was shorter (P < 0.01) in the CIDR+GnRH-PGF_2α-GnRH group (46 ± 12 days) than in the GnRH group (88 ± 10 days), representing 21.9% more cows being pregnant by 150 days after treatment. These results indicate that the CIDR-based TAI protocol can be used as an efficient therapeutic tool for ovarian follicular cysts in lactating dairy cows. Follicular dynamics and endocrine changes during the CIDR+GnRH-PGF_2α-GnRH protocol is being determined to clarify the beneficial outcome in this study.

This work was supported by a Chungbuk National University Grant in 2004.