title: Pregnancy rates of postpartum beef cows that were synchronized using Syncro-Mate-B or the Ovsynch protocol.
abstract: We compared pregnancy rates of beef cows subjected to the traditional Syncro-Mate-B protocol or the new Ovsynch protocol and timed insemination. Multiparous Angus cows (n = 436) were stratified by age, postpartum interval, and AI sire and were randomly divided into two treatment groups for synchronization of estrus/ovulation. Approximately half of the cows (n = 216) received the traditional Syncro-Mate-B protocol with 48-h calf removal from the time of implant removal until breeding. The remaining cows (n = 220) received the Ovsynch protocol, which consists of an injection of GnRH (100 microg) on d -10, an injection of PGF2alpha (25 mg) and 48-h calf removal on d -3, another injection of GnRH and calf return on d -1, and timed insemination 24 h later (d 0). Blood samples were collected from all cows before treatment to identify anestrous and cyclic females. Pregnancy rates were higher (P < .025) for Ovsynch-treated cows (54%) than for Syncro-Mate-B-treated cows (42%). Pregnancy rates of cyclic Ovsynch-treated cows (59%) were higher (P < .005) than pregnancy rates of cyclic Syncro-Mate-B-treated cows (38%). Pregnancy rates of anestrous cows also tended to favor synchronization with the Ovsynch protocol. From these data, we conclude that the Ovsynch protocol is capable of inducing a fertile ovulation in cyclic and anestrous beef cows and that pregnancy rates to a timed insemination are higher than those obtained with synchronization of estrus using Syncro-Mate-B.
authors.affiliation: Department of Animal Sciences, Colorado State University, Fort Collins 80523-1171, USA.
authors.forename: T W
authors.initials: TW
authors.lastname: Geary
authors.forename: J C
authors.initials: JC
authors.lastname: Whittier
authors.forename: E R
authors.initials: ER
authors.lastname: Downing
authors.forename: D G
authors.initials: DG
authors.lastname: LeFever
authors.forename: R W
authors.initials: RW
authors.lastname: Silcox
authors.forename: M D
authors.initials: MD
authors.lastname: Holland
authors.forename: T M
authors.initials: TM
authors.lastname: Nett
authors.forename: G D
authors.initials: GD
authors.lastname: Niswender
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D015237:Dinoprost / Q000008:administration & dosage*; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives*; D004966:Estrogens, Conjugated (USP) / Q000008:administration & dosage; D004973:Estrus Synchronization; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage*; D007273:Injections, Intramuscular / Q000662:veterinary; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate; D011282:Pregnenediones / Q000008:administration & dosage*; D011374:Progesterone / Q000097:blood; D045167:Progesterone Congeners / Q000008:administration & dosage; D013997:Time Factors
chemical_list: D004343:Drug Implants; D004966:Estrogens, Conjugated (USP); D011282:Pregnenediones; D045167:Progesterone Congeners; D007987:Gonadotropin-Releasing Hormone; C100284:norgestomet; D011374:Progesterone; D004958:Estradiol; D015237:Dinoprost