title: Administration of prostaglandin F2α 14 d before initiating a G6G or a G7G timed artificial insemination protocol increased circulating progesterone prior to artificial insemination and reduced pregnancy loss in multiparous Holstein cows.
abstract: The objectives of this study were to determine the effect of PGF2α treatment 14 d before the initiation of a G6G or G7G (PGF2α, 2 d, GnRH, 6 or 7 d, Ovsynch) protocol on ovarian response, synchronization protocol on ovarian response, progesterone (P4) concentration, pregnancy per AI (P/AI), and pregnancy loss in multiparous Holstein cows. Cows (3.6±1.1 lactations and yielding >30kg/d of milk) were randomly assigned to 1 of 4 timed artificial insemination (TAI) protocols: 1) G6G (n=240), one injection of PGF2α, GnRH 2 d later and a 7-d Ovsynch protocol (GnRH, 7 d, PGF2α, 56 h, GnRH 16 h TAI) was initiated 6 d later; 2) PG6G (n=250), PGF2α 14 d before the initiation of the G6G protocol; 3) G7G (n=200), one injection of PGF2α, GnRH 2 d later, and a 7-d Ovsynch protocol initiated 7 d later; and (4) PG7G (n=200), a PGF2α injection 14 d before the initiation of the G7G protocol. Blood samples from a subset of 269 cows were collected at the times of first and second GnRH, and PGF2α of the Ovsynch protocol to measure P4. Ultrasound examinations were performed to evaluate ovarian response to GnRH and PGF2α of Ovsynch, and to determine pregnancy status at 32 and 60 d after TAI. The proportion of cows with high (≥1ng/mL) P4 at first GnRH of Ovsynch was greater for PG6G and PG7G compared with G6G and G7G groups (combined 79.7 vs. 59.3%). In addition, mean (±SEM) plasma P4 concentration (ng/mL) at PGF2α of Ovsynch was also greater in PG6G (6.5±0.2) and PG7G (6.7±0.3) compared with G6G (5.1±0.2) and G7G (5.0±0.2). Cows given PGF2α 14 d before initiating a G6G or a G7G TAI (PG6G and PG7G) tended to have a greater P/AI at 32 d compared with those cows not receiving PGF2α (G6G and G7G). However, P/AI at 60 d was greater in cows subjected to PG6G and PG7G protocols (31.1 vs. 39.2%), with a lower pregnancy loss between 32 and 60 d (11.65 vs. 19.7%). In summary, administration of PGF2α 14 d before initiating a G6G or a G7G TAI protocol increased P4 concentrations before artificial insemination and late embryonic/early fetal survival in multiparous Holstein cows.
authors.affiliation: Department of Animal Science, Sari Agricultural Sciences and Natural Resources University, Sari, Mazandaran, Iran, PO Box 578. Electronic address: Dirandeh@gmail.com.
authors.forename: E
authors.initials: E
authors.lastname: Dirandeh
authors.affiliation: Department of Animal Science, University of Tehran, Karaj, Alborz, Iran.
authors.forename: A Rezaei
authors.initials: AR
authors.lastname: Roodbari
authors.affiliation: Department of Animal Science, Sari Agricultural Sciences and Natural Resources University, Sari, Mazandaran, Iran, PO Box 578.
authors.forename: M
authors.initials: M
authors.lastname: Gholizadeh
authors.affiliation: Department of Animal Science, Sari Agricultural Sciences and Natural Resources University, Sari, Mazandaran, Iran, PO Box 578.
authors.forename: H
authors.initials: H
authors.lastname: Deldar
authors.affiliation: Department of Animal Science, Faculty of Agriculture, University of Zanjan, Zanjan, Iran.
authors.forename: R
authors.initials: R
authors.lastname: Masoumi
authors.affiliation: Department of Animal Science, Sari Agricultural Sciences and Natural Resources University, Sari, Mazandaran, Iran, PO Box 578.
authors.forename: M
authors.initials: M
authors.lastname: Kazemifard
authors.affiliation: Livestock Research Branch, Alberta Agriculture and Rural Development, Edmonton, AB, T6H 5T6, Canada. Electronic address: marcos.colazo@gov.ab.ca.
authors.forename: M G
authors.initials: MG
authors.lastname: Colazo
mesh_terms: D000818:Animals; D002417:Cattle; D015237:Dinoprost / Q000008:administration & dosage*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000097:blood; D007315:Insemination, Artificial / Q000662:veterinary*; D007774:Lactation / Q000502:physiology; D008892:Milk; D010298:Parity; D011247:Pregnancy; D011270:Pregnancy, Animal; D011374:Progesterone / Q000097:blood*
chemical_list: D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D015237:Dinoprost
keywords: G6G; multiparous Holstein cow; progesterone; ultrasonography