Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10980181 | Journal of Dairy Science | 2012 | 7 Pages |
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 (Re) 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 (Re = 0.07). Repeatability estimates for concentrations of P4 from cycle to cycle indicated low repeatability between d 4 (Re = 0.05) and 7 (Re = 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.
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Authors
M.H. Parr, M.P. Mullen, M.A. Crowe, J.F. Roche, P. Lonergan, A.C.O. Evans, M.G. Diskin,