title: Determination of the appropriate delivery of prostaglandin F2α in the five-day CO-Synch + controlled intravaginal drug release protocol in suckled beef cows.
abstract: The objective of this experiment was to determine if 2 doses of prostaglandin F(2α) (PGF) administered concurrently at controlled intravaginal drug release (CIDR) removal was an efficacious method for delivery of PGF in the 5-d CO-Synch + CIDR protocol. Postpartum beef cows (n = 2,465) from 13 herds in 8 states were enrolled in the 5-d CO-Synch + CIDR protocol and assigned to receive 2 doses of PGF (25 mg/dose) 8 h apart with the initial injection given at CIDR insert removal (8h-PGF), 2 doses (25 mg/dose) of PGF delivered in 2 injection sites, both administered at CIDR insert removal (Co-PGF), or a single 25-mg dose of PGF at CIDR insert removal (1x-PGF). Cows were fixed timed-artificially inseminated (FTAI) 72 h after CIDR removal concurrent with GnRH administration. Estrus-cycling status (54% cyclic) was determined by evaluation of progesterone in 2 blood samples collected before CIDR insertion. Determination of pregnancy was performed by transrectal ultrasonography 39 ± 0.1 d after FTAI and at least 35 d after the conclusion of the breeding season. Fixed timed-AI pregnancy rates were greater (P < 0.05) for the 8h-PGF (55%) than the 1x-PGF (48%) treatment, with the Co-PGF (51%) treatment intermediate and not different (P > 0.10) from the other treatments. Contrast analysis demonstrated that cows receiving 50 mg of PGF (8h-PGF and Co-PGF) had greater (P < 0.05) FTAI pregnancy rates than those receiving 25 mg (1x-PGF). Pregnancy rates to FTAI were greater (P < 0.05) in cyclic (55%) than noncyclic (47%) and greater (P < 0.05) in multiparous (≥3 yr of age; 54%; n = 1,940) than primiparous cows (40%; n = 525). Luteolysis after PGF treatment was assessed in a subset of cows (n = 277) and treatment tended (P = 0.09) to affect the proportion of cows having luteolysis. The percentage of cows that had luteolysis was least in the 1x-PGF treatment (89%) and greatest in the 8h-PGF treatment (97%), with the Co-PGF treatment (94%) being intermediate. Breeding season pregnancy rate (88%) did not differ (P > 0.10) among treatments but was greater (P < 0.01) in multiparous (90%) than primiparous (78%) cows. In summary, 50 mg of PGF was required in the 5-d CO-Synch + CIDR protocol to maximize pregnancy rates; however, pregnancy rate did not differ when 50 mg of PGF was administered simultaneously with CIDR removal or split with 25 mg administered at 0 and 8 h after CIDR removal.
authors.affiliation: North Central Research and Outreach Center, University of Minnesota, Grand Rapids 55744, USA. gbridges@umn.edu
authors.forename: G A
authors.initials: GA
authors.lastname: Bridges
authors.forename: J K
authors.initials: JK
authors.lastname: Ahola
authors.forename: C
authors.initials: C
authors.lastname: Brauner
authors.forename: L H
authors.initials: LH
authors.lastname: Cruppe
authors.forename: J C
authors.initials: JC
authors.lastname: Currin
authors.forename: M L
authors.initials: ML
authors.lastname: Day
authors.forename: P J
authors.initials: PJ
authors.lastname: Gunn
authors.forename: J R
authors.initials: JR
authors.lastname: Jaeger
authors.forename: S L
authors.initials: SL
authors.lastname: Lake
authors.forename: G C
authors.initials: GC
authors.lastname: Lamb
authors.forename: G H L
authors.initials: GH
authors.lastname: Marquezini
authors.forename: R K
authors.initials: RK
authors.lastname: Peel
authors.forename: A E
authors.initials: AE
authors.lastname: Radunz
authors.forename: J S
authors.initials: JS
authors.lastname: Stevenson
authors.forename: W D
authors.initials: WD
authors.lastname: Whittier
mesh_terms: D000282:Administration, Intravaginal; D000818:Animals; D002417:Cattle / Q000502:physiology*; D003692:Delayed-Action Preparations / Q000008:administration & dosage; D015237:Dinoprost / Q000008:administration & dosage*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D007315:Insemination, Artificial / Q000662:veterinary; D003341:Luteolysis / Q000187:drug effects; D049590:Postpartum Period; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000097:blood; D013997:Time Factors; D014463:Ultrasonography
chemical_list: D003692:Delayed-Action Preparations; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D015237:Dinoprost