title: Relationship between pregnancy per artificial insemination and early luteal concentrations of progesterone and establishment of repeatability estimates for these traits in Holstein-Friesian heifers.
abstract: Pregnancy per insemination is a major determinant of reproductive efficiency in cattle and is affected by concentrations of progesterone (P4) during early pregnancy. The relationship between pregnancy per artificial insemination (P/AI) and early luteal concentrations of P4, and repeatability of concentrations of P4 was examined on d 4, 5, 6, and 7 (day of standing estrus=d 0) in 118 Holstein Friesian heifers following 2 rounds of AI to 1 high-fertility sire. Repeatability estimates (R(e)) for P/AI were established following 4 rounds of AI. We found a linear and quadratic relationship between P/AI and concentrations of P4 on d 4 to 7 after estrus, as well as a linear and quadratic relationship between P/AI and the change in concentration of P4 from d 4 to 7 and from d 5 to 7. Optimum concentrations of P4 to maximize probability of P/AI were 2.5, 4.0, 5.0, 5.2, and 3.5 ng/mL for d 4, 5, 6, and 7, and the change from d 4 to 7, respectively. Repeatability of P/AI following 4 rounds of AI was low (R(e)=0.07). Repeatability estimates for concentrations of P4 from cycle to cycle indicated low repeatability between d 4 (R(e)=0.05) and 7 (R(e)=0.20). These data indicated the importance of P4 in the early luteal phase for pregnancy survival, but also demonstrated that high concentrations of P4 on these days have a deleterious effect on embryo viability. Early luteal (d 4 to 5) concentrations of P4 were a reasonable predictor of concentrations on d 7 and could be used as a diagnostic tool to identify animals at risk of subsequent embryo loss.
authors.affiliation: Animal and Grassland Research and Innovation Centre, Teagasc, Mellows Campus, Athenry, Co. Galway, Ireland.
authors.forename: M H
authors.initials: MH
authors.lastname: Parr
authors.forename: M P
authors.initials: MP
authors.lastname: Mullen
authors.forename: M A
authors.initials: MA
authors.lastname: Crowe
authors.forename: J F
authors.initials: JF
authors.lastname: Roche
authors.forename: P
authors.initials: P
authors.lastname: Lonergan
authors.forename: A C O
authors.initials: AC
authors.lastname: Evans
authors.forename: M G
authors.initials: MG
authors.lastname: Diskin
mesh_terms: D000818:Animals; D002417:Cattle; D003338:Corpus Luteum / Q000502:physiology; D003340:Corpus Luteum Maintenance / Q000502:physiology*; D004972:Estrus Detection / Q000379:methods; D004973:Estrus Synchronization / Q000379:methods / Q000502:physiology; D005260:Female; D007315:Insemination, Artificial / Q000502:physiology / Q000662:veterinary*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood / Q000502:physiology*
chemical_list: D011374:Progesterone