title: Follicular wave emergence, luteal function and synchrony of ovulation following GnRH or estradiol benzoate in a CIDR-treated, lactating Holstein cows.
abstract: This study evaluated the effect of GnRH or estradiol benzoate (EB) on follicular wave emergence and progesterone concentrations, and following a second injection of GnRH, synchrony of ovulation, and pregnancy rates in a controlled internal drug release (CIDR)-based timed AI (TAI) protocol in lactating Holstein cows. Cows received a CIDR device without hormone (controls), with an injection of 100 microg GnRH or with an injection of 4 mg EB. Thereafter, all received PGF(2 alpha) at the time of CIDR removal on Day 7, GnRH on Day 9, and TAI 16 h later. Follicular wave emergence occurred within 7 days in 19/20 GnRH-treated, 14/20 EB-treated and 5/20 control cows (P < 0.05). The interval to wave emergence was the shorter and less variable (P < 0.01) in the GnRH group (2.9 +/- 0.2 days) than in the EB (4.7 +/- 0.5 days) or control (4.8 +/- 1.0 days) groups. Serum progesterone concentrations from Days 4 to 7 were higher (P < 0.01) in the GnRH-treated cows that ovulated than in those that did not ovulate, or in control and EB-treated cows. The diameters of dominant follicle on Day 7 differed among groups (P < 0.01), and the diameters of the preovulatory follicle on Day 9 were larger (P < 0.01) in the control and GnRH groups than in the EB group. The proportion of cows with synchronized ovulations did not differ among groups, but pregnancy rate to TAI was higher (P < 0.05) in the GnRH group (65%; 13/20) than in the control (30%; 6/20) or EB (35%; 7/20) groups. Results suggest that GnRH treatment of CIDR-treated lactating Holstein cows will result in synchronous follicular wave emergence, large preovulatory follicles and synchronous ovulation, resulting in an acceptable pregnancy rates to TAI.
authors.affiliation: Laboratory of Theriogenology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk 361-763, South Korea.
authors.forename: Ui-Hyung
authors.initials: UH
authors.lastname: Kim
authors.forename: Guk-Hyun
authors.initials: GH
authors.lastname: Suh
authors.forename: Hyun-Wook
authors.initials: HW
authors.lastname: Nam
authors.forename: Hyun-Gu
authors.initials: HG
authors.lastname: Kang
authors.forename: Ill-Hwa
authors.initials: IH
authors.lastname: Kim
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000187:drug effects* / Q000502:physiology; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage* / Q000031:analogs & derivatives*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage*; D007315:Insemination, Artificial / Q000662:veterinary; D007774:Lactation; D006080:Ovarian Follicle / Q000033:anatomy & histology / Q000187:drug effects* / Q000502:physiology; D010060:Ovulation / Q000187:drug effects* / Q000502:physiology; D011247:Pregnancy; D011374:Progesterone / Q000008:administration & dosage / Q000097:blood; D013997:Time Factors
chemical_list: D004343:Drug Implants; C074283:estradiol 3-benzoate; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol