title: Effects of administration of prostaglandin F at initiation of the seven-day CO-Synch+controlled internal drug release ovulation synchronization protocol for suckled beef cows and replacement beef heifers.
abstract: Two experiments were conducted to determine the effect of administering PGF at the initiation of the 7-d CO-Synch+controlled internal drug release (CIDR) fixed-timed AI (TAI) protocol on pregnancy rates of suckled beef cows and replacement heifers. Within location, cows were stratified by days postpartum (DPP), BCS, and parity (Exp. 1; = 1,551) and heifers were stratified by BCS (Exp. 2; = 999) and randomly assigned to 1 of 2 treatments: 1) CO-Synch+CIDR (100-μg injection of GnRH at CIDR insertion [d -10] with a 25-mg injection of PGF at CIDR removal [d -3] followed by injection of GnRH and TAI on d 0) or 2) PG-CO-Synch+CIDR (a 25-mg injection of PGF on d -10 of the CO-Synch+CIDR protocol). Follicle diameter and corpus luteum (CL) development were assessed on d -10 and -3, and pregnancy status was determined on d 30 to 35. Blood was collected on d -20, -10, -3, and 0 relative to TAI to determine concentrations of progesterone (P4). In Exp. 1, TAI pregnancy rates did not differ ( = 0.667) between treatments and were affected by BCS ( = 0.003) and DPP ( = 0.006). Concentrations of P4 were greater ( < 0.0001) on d -3 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (4.1 ± 0.2 and 3.4 ± 0.2 ng/mL, respectively). Follicle diameter on d -3 differed ( = 0.05) between PG-CO-Synch+CIDR (13.4 ± 0.3 mm) and CO-Synch+CIDR (12.5 ± 0.3 mm) treatments. Cows with P4 > 2.5 ng/mL on d -10 had greater ( = 0.024) pregnancy rate to TAI (56.5%) compared with cows with 2.5 ng/mL < P4 > 1 (43.0%), whereas cows with P4 < 1 ng/mL were intermediate (51.6%). Cows with a CL on d -10 had greater ( = 0.012) pregnancy rates to TAI than cows without a CL (66.3 vs. 39.4%, respectively). In Exp. 2, TAI pregnancy rates did not differ ( = 0.316) between treatments. Concentrations of P4 differed ( < 0.0001) on d -3 with greater concentrations of P4 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (3.75 ± 0.20 ng/mL and 3.60 ± 0.21 ng/mL, respectively). Follicle diameter was similar ( = 0.749) between treatments on d -10 and -3. Regardless of treatment, cyclic status tended ( = 0.062) to improve pregnancy rates to TAI (55 vs. 45%, for cycling and noncycling heifers, respectively). We concluded that addition of PGF to the 7-d CO-Synch+CIDR protocol decreased concentrations of P4 in cows and heifers and increased follicle diameter at CIDR removal in cows but failed to increase TAI pregnancy rates.
authors.forename: V R G
authors.initials: VR
authors.lastname: Mercadante
authors.forename: L E
authors.initials: LE
authors.lastname: Kozicki
authors.forename: F M
authors.initials: FM
authors.lastname: Ciriaco
authors.forename: D D
authors.initials: DD
authors.lastname: Henry
authors.forename: C R
authors.initials: CR
authors.lastname: Dahlen
authors.forename: M R
authors.initials: MR
authors.lastname: Crosswhite
authors.forename: J E
authors.initials: JE
authors.lastname: Larson
authors.forename: B E
authors.initials: BE
authors.lastname: Voelz
authors.forename: D J
authors.initials: DJ
authors.lastname: Patterson
authors.forename: G A
authors.initials: GA
authors.lastname: Perry
authors.forename: R N
authors.initials: RN
authors.lastname: Funston
authors.forename: T L
authors.initials: TL
authors.lastname: Steckler
authors.forename: S L
authors.initials: SL
authors.lastname: Hill
authors.forename: J S
authors.initials: JS
authors.lastname: Stevenson
authors.forename: G C
authors.initials: GC
authors.lastname: Lamb
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003692:Delayed-Action Preparations / Q000494:pharmacology; D015237:Dinoprost / Q000494:pharmacology; D004334:Drug Administration Schedule; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007315:Insemination, Artificial / Q000662:veterinary*; D007774:Lactation; D006080:Ovarian Follicle / Q000187:drug effects; D010060:Ovulation / Q000187:drug effects*; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000097:blood; D011460:Prostaglandins F / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D003692:Delayed-Action Preparations; D011460:Prostaglandins F; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D015237:Dinoprost