title: Insemination timing affects pregnancy rates in beef cows treated with CO-Synch protocol including an intravaginal progesterone insert.
abstract: Our objective was to determine the optimal time to artificially inseminate lactating beef cows (Bos taurus typicus) after using the standard CO-Synch protocol that also included a progesterone-releasing, intravaginal controlled internal drug release (CIDR) insert. Cows (N=605) at three locations were inseminated at four different times after CIDR insert removal and the prostaglandin F(2alpha) administration of the CO-Synch+CIDR protocol: 48, 56, 64, or 72h. Blood samples were collected 9 to 10 d before and on the day of CIDR insertion. Based on elevated (>1 ng/mL) serum progesterone concentrations, 60% of 605 cows had previously ovulated (were cycling) at the initiation of the study, with a range of 39.6% to 67.9% among locations (P<0.05). Age of cow, body condition score, and days postpartum affected (P< or =0.05) cycling status before ovulation was synchronized. Averaged across treatments, pregnancy rate to artificial insemination (AI) at Day 32 was affected (P< or =0.05) by pretreatment cycling status and body condition. Younger cows (< or =3 yr) tended to have greater AI pregnancy rates when inseminated at 56h, whereas older cows had similar pregnancy rates when inseminated at 56h or later (timing of AI by age interaction; P=0.085). Pregnancy loss between Days 32 and 63 was greatest (quadratic effect; P<0.05) when cows were inseminated at 48 and 72h. In summary, insemination times at or after 56h improved AI pregnancy rates when using the CO-Synch+CIDR program. Further work is warranted to examine age effects on timing of AI in the CO-Synch+CIDR program.
authors.affiliation: Department of Animal Sciences and Industry, Kansas State University, Manhattan, KS 66506-0201, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Dobbins
authors.forename: D R
authors.initials: DR
authors.lastname: Eborn
authors.forename: D E
authors.initials: DE
authors.lastname: Tenhouse
authors.forename: R M
authors.initials: RM
authors.lastname: Breiner
authors.forename: S K
authors.initials: SK
authors.lastname: Johnson
authors.forename: T T
authors.initials: TT
authors.lastname: Marston
authors.forename: J S
authors.initials: JS
authors.lastname: Stevenson
mesh_terms: D000282:Administration, Intravaginal; D000818:Animals; D001947:Breeding / Q000379:methods; D002417:Cattle / Q000502:physiology*; D015237:Dinoprost / Q000008:administration & dosage; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D007315:Insemination, Artificial / Q000379:methods / Q000706:statistics & numerical data / Q000662:veterinary*; D007774:Lactation; D008297:Male; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary*; D011247:Pregnancy; D011374:Progesterone / Q000008:administration & dosage* / Q000097:blood; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D011374:Progesterone; D015237:Dinoprost