In this stuyd, the effect of the dominant follicle aspiration for the superovulatory response in HanWoo was investigated. The criterion for the presence or absence of a dominant follicle based on their morphological examination. The dominant follicle was aspirated 48hr before the onset of superovulation treatment by 6.5MHz convex probe connected with a carrier and superovulation induced by FSH (Super-Ov Tyrer, Texas, U.S.A) adminstered twic a day s.c. over 4 day in a decreasing regimen. From 13 HanWoo scanned daily to determine the presence and growth of the dominant follicle, its an average diameter of 15.4mm was measured and an average diameter of corpora lutea was 18.7mm on day of follicular aspiration. In the experiment, a follicular remove by ultrasound-guided aspiration, the ovarian response was significantly enhanced when animals were superovulated in the aspiation of a dominant follicle compare with animals superovulated non-aspiration of a dominat follicle. In the aspiration of a dominant follicle donors yieleded more corpora lutea(14.44.7 vs 8.63.4) and transferable embryos(8.94.2 vs 5.42.7) than control. In cows in which the dominant follicle had been aspirated under sonographical control 2 days before superovuation, the number of corpus lutea and transferable embryos were significantly enhanced compared with animals superovulated in the presence of a dominant follicle (14.44.7 vs 6.92.7, ; 8.94.2 vs 3.31.6). After 7 days of artificial insemination, the embryos at 7 days were cllected by uterine flushing after dominant follicle insemination, the embryos at 7 days were collected by uterine flushing after dominant follicle aspiration and superovulation treatment, and evaluated their quality by morphological criteria. Sixteen embryos with excellent and good grade were transferred into 8 recipient cows. Six pregnancies were identified at 60 and 120 days of gestation by rectal palpations. In conclusion, the present study showed that 1) the presence or absence of a dominant follicle signficicnatly affects superovulatory responses, and 2) ultrasound-guided follicular aspiration of the dominant follicle and superovuation treatment provides an accurate and procedure to increase ovarian responses in HanWoo.

The objective of this study was to evaluate the effect of GnRH or estradiol in a CIDR-based timed Al (TAI) protocol on follicular turnover, synchronized ovulation and pregnancy rates in Holstein cows. Cows were treated at random stages of the estrus cycle with an insertion of an intravigal progesterone (1.9 g) device (CIDR, Day 0) and either no other treatment (control group; n=10), injection of 100 ug fertirelin acetate (GnRH group; n=10) or 4 mg estradiol benzoate (estradiol group; n=10). Seven days later devices were removed and an injection of 25 mg PGF2a was administered. On Day 9, 100 ug GnRH was administered. Cows received a fixed-time insemination 16 h after injection of the GnRH.