title: Two doses of prostaglandin improve pregnancy rates to timed-AI in a 5-day progesterone-based synchronization protocol in beef cows.
abstract: The objective was to compare reproductive performance of Angus-cross beef cows synchronized with GnRH, a progesterone-based intravaginal insert (Controlled Internal Drug Release, CIDR) for 5-d, and one dose of either dinoprost (PGF) or cloprostenol (CLP, a PGF analogue) or two doses of PGF on the day of CIDR withdrawal. All cows (N=830) at six locations received 100microg of GnRH and a CIDR on Day 0. Within farm, cows were randomly allocated to receive 25mg of PGF at the time of CIDR insert removal on Day 5 (1xPGF; N=277), two 25mg doses of PGF, the first given on Day 5 at the time of CIDR removal and the second 7h later (2xPGF; N=282), or 500microg of CLP at the time of CIDR removal on Day 5 (1xCLP; N=271). All cows were given 100microg of GnRH on Day 8 (72h after CIDR removal) and concurrently inseminated (5-d CO-Synch+CIDR). Cows were fitted with a pressure-sensitive estrus detection device at the time of CIDR withdrawal. Timed-AI pregnancy rates were greater (P<0.0001) in the 2xPGF (69.0%) than the 1xPGF (52.0%) and 1xCLP (54.3%) treatments. However, breeding-season pregnancy rates were not different among treatments (87.0% for 1xPGF, 92.9% for 2xPGF and 87.5% for 1xCLP; P>0.1). In conclusion, cows that received two doses of PGF on the day of CIDR removal in a 5-d CO-Synch+CIDR synchronization protocol had excellent timed-AI pregnancy rates that were greater than in cows receiving a single treatment with either PGF or CLP.
authors.affiliation: Department of Large Animal Clinical Sciences, Virginia Maryland Regional College of Veterinary Medicine, Duckpond drive, Phase II, Blacksburg, VA 24061, USA. drram@vt.edu
authors.forename: R
authors.initials: R
authors.lastname: Kasimanickam
authors.forename: M L
authors.initials: ML
authors.lastname: Day
authors.forename: J S
authors.initials: JS
authors.lastname: Rudolph
authors.forename: J B
authors.initials: JB
authors.lastname: Hall
authors.forename: W D
authors.initials: WD
authors.lastname: Whittier
mesh_terms: D000282:Administration, Intravaginal; D000818:Animals; D001823:Body Composition; D001947:Breeding; D002417:Cattle; D003008:Cloprostenol / Q000008:administration & dosage; D015237:Dinoprost / Q000008:administration & dosage; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D008297:Male; D011247:Pregnancy; D011374:Progesterone / Q000008:administration & dosage*; D011453:Prostaglandins / Q000008:administration & dosage*; D011460:Prostaglandins F / Q000008:administration & dosage; D012621:Seasons
chemical_list: D011453:Prostaglandins; D011460:Prostaglandins F; D007987:Gonadotropin-Releasing Hormone; D003008:Cloprostenol; D011374:Progesterone; D015237:Dinoprost