title: Estrus synchronization and pregnancy rates in beef cattle given CIDR-B, prostaglandin and estradiol, or GnRH.
abstract: Two experiments were conducted to determine estrous response and pregnancy rate in beef cattle given a controlled internal drug release (CIDR-B) device plus prostaglandin F2 alpha (PGF) at CIDR-B removal, and estradiol or gonadotropin releasing hormone (GnRH). In Experiment I, crossbred beef heifers received a CIDR-B device and 1 mg estradiol benzoate (EB), plus 100 mg progesterone (E + P group; n = 41), 100 micrograms gonadotropin releasing hormone (GnRH group; n = 42), or no further treatment (Control group; n = 42), on Day 0. On Day 7, CIDR-B devices were removed and heifers were treated with PGF. Heifers in the E + P group were given 1 mg EB, 24 h after PGF, and then inseminated 30 h later. Heifers in the GnRH group were given 100 micrograms GnRH, 54 h after PGF, and concurrently inseminated. Control heifers were inseminated 12 h after onset of estrus. The estrous rate was lower (P < 0.01) in the GnRH group (55%) than in either the E + P (100%) or Control (83%) groups. The mean interval from CIDR-B removal to estrus was shorter (P < 0.01) and less variable (P < 0.01) in the E + P group than in the GnRH or Control groups. Pregnancy rate in the E + P group (76%) was higher (P < 0.01) than in the GnRH (48%) or Control (38%) groups. In Experiment II, 84 cows were treated similarly to the E + P group in Experiment I. Cows received 100 mg progesterone and either 1 mg EB or 5 mg estradiol-17 beta (E-17 beta) on Day 0 and either 1 mg of EB or 1 mg of E-17 beta on Day 8 (24 h after CIDR-B removal), in a 2 x 2 factorial design, and were inseminated 30 h later. There were no differences among groups for estrous rates or conception rates. The mean interval from CIDR-B removal to estrus was 44.2 h, s = 11.2. Conception rates were 67%, 62%, 52%, and 71% in Groups E-17 beta/E-17 beta, E-17 beta/EB, EB/E-17 beta, and EB/EB, respectively. In cattle given a CIDR-B device and estradiol plus progesterone, treatment with either EB or E-17 beta effectively synchronized estrus and resulted in acceptable conception rates to fixed-time artificial insemination.
authors.affiliation: Department of Herd Medicine and Theriogenology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon.
authors.forename: M F
authors.initials: MF
authors.lastname: Martínez
authors.forename: J P
authors.initials: JP
authors.lastname: Kastelic
authors.forename: G P
authors.initials: GP
authors.lastname: Adams
authors.forename: E
authors.initials: E
authors.lastname: Janzen
authors.forename: D H
authors.initials: DH
authors.lastname: McCartney
authors.forename: R J
authors.initials: RJ
authors.lastname: Mapletoft
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003692:Delayed-Action Preparations; D015237:Dinoprost / Q000008:administration & dosage / Q000494:pharmacology*; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D004973:Estrus Synchronization / Q000187:drug effects*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D011247:Pregnancy; D018873:Pregnancy Rate
chemical_list: D003692:Delayed-Action Preparations; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D015237:Dinoprost