title: Inclusion of an intravaginal progesterone insert plus GnRH and prostaglandin F2alpha for ovulation control in postpartum suckled beef cows.
abstract: Four experiment stations (IL, KS, MN, and MO) conducted experiments to determine effects of introducing a CIDR (controlled internal device release) into an ovulation control program for postpartum suckled beef cows. Five hundred sixty cows were assigned randomly to two treatments: 1) 100 microg of GnRH (i.m.) followed in 7 d with 25 mg of PGF2alpha, followed in 48 h by a second injection of GnRH and one fixed-time insemination (Cosynch; n = 287) or 2) Cosynch plus one CIDR during the 7 d between the first injection of GnRH and PGF2alpha (Cosynch+P; n = 273). Cows at three stations were inseminated at the time of the second GnRH injection (n = 462), whereas 98 cows at the fourth station were inseminated 16 to 18 h after that injection. Blood samples were collected at d -17, -7, 0, and 2 relative to PGF2alpha to determine concentrations of progesterone. Ultrasonography was used to monitor follicle diameter on d 2 and to determine the presence of an embryo at 30 to 35 d after insemination. Pregnancy rates were greater (P < 0.05) for Cosynch+P- (58%) than for Cosynch-treated (48%) cows. No station x treatment interaction occurred; however, cows at MO (62%) and KS (60%) had greater (P < 0.05) pregnancy rates than those at IL (47%) and MN (44%). Cows that had follicles > 12 mm on d 2 had greater (P < 0.01) pregnancy rates than those with follicles < or = 12 mm regardless of treatment. Pregnancy rates were similar between Cosynch and Cosynch+P treatments when cycling cows had elevated concentrations of progesterone at d 0, but pregnancy rates were greater (P < 0.05) in the Cosynch+P (79%) than in the Cosynch (43%) treatment when cycling cows had low concentrations of progesterone on d 0 (at PGF2alpha injection). Similarly, among noncycling cows, pregnancy rates were greater (P < 0.05) in the Cosynch+P (59%) treatment than in the Cosynch (39%) treatment. Cows in greater body condition at the onset of the breeding season experienced improved (P < 0.001) overall pregnancy rates. Pregnancy rates for cows that calved > 50 d before the onset of the breeding season were greater (P < 0.01) than those for cows that calved < or = 50 d. Thus, treatment of suckled cows with Cosynch yielded acceptable pregnancy rates, but addition of a CIDR improved pregnancy rates in noncycling cows. Body condition and days postpartum at initiation of the breeding season affected overall efficacy of the Cosynch and Cosynch+P protocols.
authors.affiliation: North Central Research and Outreach Center, University of Minnesota, Grand Rapids 55744, USA. clamb@umn.edu
authors.forename: G C
authors.initials: GC
authors.lastname: Lamb
authors.forename: J S
authors.initials: JS
authors.lastname: Stevenson
authors.forename: D J
authors.initials: DJ
authors.lastname: Kesler
authors.forename: H A
authors.initials: HA
authors.lastname: Garverick
authors.forename: D R
authors.initials: DR
authors.lastname: Brown
authors.forename: B E
authors.initials: BE
authors.lastname: Salfen
mesh_terms: D000282:Administration, Intravaginal; D000822:Animal Husbandry / Q000379:methods; D000818:Animals; D002417:Cattle / Q000502:physiology*; D003692:Delayed-Action Preparations; D015237:Dinoprost / Q000008:administration & dosage* / Q000097:blood; D004973:Estrus Synchronization / Q000187:drug effects; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage*; D007315:Insemination, Artificial / Q000662:veterinary; D006080:Ovarian Follicle / Q000000981:diagnostic imaging; D010062:Ovulation Induction / Q000662:veterinary*; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000008:administration & dosage* / Q000097:blood; D011897:Random Allocation; D014463:Ultrasonography
chemical_list: D003692:Delayed-Action Preparations; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D015237:Dinoprost