title: Sire effect on the pregnancy outcome in beef cows synchronized with progesterone based Ovsynch and CO-Synch protocols.
abstract: The objective was to determine the sire effect on the pregnancy outcome in beef cows in which stage of estrus was synchronized with progesterone based fixed-time artificial insemination (AI) protocols. Three Angus sires with more than 300 breedings were evaluated for differences in pregnancy outcome from 1868 inseminations. Angus cross beef cows (N=1868) were synchronized with Ovsynch-CIDR or CO-Synch-CIDR protocols for fixed-time AI. Cows in both groups that showed estrus on day 9 before 1500 h were designated to Selectsynch-CIDR group and were inseminated according to AM-PM rule. Results indicated that Sire 2 had lower fixed-time AI pregnancy rate compared to Sire 3 (48.1% versus 58.7%; P=0.01). Significant sirexsynchronization program and sirexlocation interactions were observed for fixed-time AI (P<0.05). Sire 2 had a lesser fixed-time AI pregnancy in both Ovsynch-CIDR and CO-Synch-CIDR groups compared to Sire 3. In two of four locations, Sire 2 had a lesser fixed-time pregnancy rate compared to Sire 3. No sire differences were observed in AI pregnancy for cows in Selectsynch-CIDR group. In conclusion, evidence in this study suggest that there are differences in sire fertility when they were used in fixed-time AI protocols, possibly due to the sire differences in sperm capacitation process. Further studies are needed to investigate association of the sire differences in fixed-time AI protocols with sire differences in the sperm capacitation process.
authors.affiliation: Department of Large Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Duckpond Drive, Phase III, Blacksburg, VA 24061, USA. drram@vt.edu
authors.forename: R
authors.initials: R
authors.lastname: Kasimanickam
authors.forename: J B
authors.initials: JB
authors.lastname: Hall
authors.forename: J F
authors.initials: JF
authors.lastname: Currin
authors.forename: W D
authors.initials: WD
authors.lastname: Whittier
mesh_terms: D000818:Animals; D002417:Cattle; D015237:Dinoprost / Q000008:administration & dosage / Q000494:pharmacology*; D004343:Drug Implants; D004973:Estrus Synchronization / Q000187:drug effects*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007315:Insemination, Artificial / Q000662:veterinary; D008297:Male; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects / Q000502:physiology*; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D004343:Drug Implants; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D015237:Dinoprost