title: Presynchronization using a modified Ovsynch protocol or a single gonadotropin-releasing hormone injection 7 d before an Ovsynch-56 protocol for submission of lactating dairy cows to first timed artificial insemination.
abstract: Presynchronization strategies, such as Presynch-Ovsynch and Double-Ovsynch, increase fertility to timed artificial insemination (TAI) compared with Ovsynch alone; however, simpler presynchronization strategies could reduce costs and simplify reproductive management. Lactating Holstein cows (n=601) were randomly assigned to 1 of 2 presynchronization treatments before beginning an Ovsynch-56 protocol (GnRH at 70 ± 3 DIM, PGF2α 7 d later, GnRH 56 h after PGF2α, and TAI 16 h later at 80 ± 3 DIM) for first TAI. Cows (n=306) in the first treatment (Double-Ovsynch; DO) were presynchronized using a modified Ovsynch protocol (GnRH at 53 ± 3 DIM, 7 d later PGF2α, and GnRH 3 d later) ending 7 d before the first GnRH injection (G1) of an Ovsynch-56 protocol. Cows (n=295) in the second treatment (GGPG) were presynchronized using a single injection of GnRH 7 d before G1 of an Ovsynch-56 protocol at 63 ± 3 DIM. Blood samples were collected at G1 and the PGF2α injections of the Ovsynch-56 protocol to determine progesterone (P4) concentrations. Pregnancy diagnosis was performed using ultrasonography 32 d after TAI, and pregnant cows were reexamined 46 and 70 d after TAI. Overall, DO cows had more pregnancies per artificial insemination (P/AI) compared with GGPG cows 32 d after TAI (53 vs. 43%). Overall, P/AI did not differ by parity (primiparous vs. multiparous), and pregnancy loss did not differ between treatments or parities. More DO cows had P4 in a medium range (>0.5 to <4 ng/mL) at G1 of the Ovsynch-56 protocol compared with GGPG cows (82 vs. 50%), and more DO cows had high P4 (>4 ng/mL) at the PGF2α injection of the Ovsynch-56 protocol compared with GGPG cows (67 vs. 36%). Thus, presynchronization with a modified Ovsynch protocol increased P/AI after TAI at first AI by increasing synchrony to the Ovsynch-56 protocol compared with presynchronization using a single injection of GnRH.
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: P D
authors.initials: PD
authors.lastname: Carvalho
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: J N
authors.initials: JN
authors.lastname: Guenther
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: M J
authors.initials: MJ
authors.lastname: Fuenzalida
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: M C
authors.initials: MC
authors.lastname: Amundson
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: M C
authors.initials: MC
authors.lastname: Wiltbank
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706. Electronic address: pmfricke@wisc.edu.
authors.forename: P M
authors.initials: PM
authors.lastname: Fricke
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D015237:Dinoprost / Q000008:administration & dosage; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage*; D007315:Insemination, Artificial / Q000662:veterinary*; D007774:Lactation; D008297:Male; D008892:Milk / Q000378:metabolism*; D010298:Parity; D011247:Pregnancy; D011374:Progesterone / Q000032:analysis; D013312:Stress, Physiological; D013696:Temperature
chemical_list: D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D015237:Dinoprost
keywords: Double-Ovsynch; Ovsynch; presynchronization