Department of Animal Science, Michigan State University, East Lansing 48824.
Department of Animal Science, Michigan State University, East Lansing 48824.
J Dairy Sci. 2018 Nov;101(11):10505-10525. doi: 10.3168/jds.2018-14410. Epub 2018 Sep 7.
The objective of this experiment was to determine the effect of high versus low progesterone (P4) during the pre-dominance or dominance phase (or both) of ovulatory follicle development on follicular dynamics and fertility of lactating dairy cows. Progesterone (P4) was manipulated to reach high (H) or low (L) serum concentrations during the pre-dominance phase (d 0 to 4 of the wave) and dominance phase (d 5 to 7 of the wave) of a second follicular wave ovulatory follicle, creating 4 treatments: H/H, H/L, L/H, and L/L. Luteolysis was induced with PGF on d 7 of the wave and ovulation was induced with GnRH 56 h after PGF. Cows (n = 558) received artificial insemination (AI) 16 h following GnRH. Pregnancy was determined at 6 intervals during gestation and at calving to quantify pregnancy loss beginning at d 23 post-AI utilizing pregnancy-specific protein B (PSPB) in novel within-cow comparisons. Cows with single ovulations assigned to the L/L treatment had greater pre-ovulatory follicle diameter compared with cows assigned to the L/H or H/L treatments. Cows with single ovulations had greater pre-ovulatory follicle diameter compared with cows with double ovulations. Low P4 in H/L, L/H, and L/L increased double ovulation rate compared with H/H. Cows with double ovulations had greater pregnancies per AI (P/AI) on d 23 post-AI compared with cows with single ovulations but had greater losses if ovulations were unilateral. Cows with low P4 during the entire period of the ovulatory follicle development also had greater P/AI on d 23 post-AI compared with cows with high P4 during both phases. However, full-term P/AI was not different between treatments. This was a result of the greater incidence of pregnancy losses between d 35 and 56 of gestation for cows with unilateral double ovulations compared with bilateral double ovulations and single ovulatory cows. Cows with single ovulation and low circulating P4 during the dominance period of follicle development had increased pregnancy losses between d 35 and 56 of gestation compared with cows with single ovulations and high P4. The PSPB measurements on d 16 and 23 post-AI were highly accurate in the prediction of pregnancy at d 28. The PSPB differed on d 23 and 28 between cows that had versus cows that did not have pregnancy losses between d 28 and 35 of gestation. In summary, circulating concentrations of P4 during ovulatory follicle development affected numbers of follicles ovulated and timing of subsequent pregnancy losses.
本实验的目的是确定在优势卵泡发育的前期（d0 至 4）或优势期（d5 至 7），或在两者期间，高（H）或低（L）孕激素（P4）对泌乳奶牛的卵泡动态和生育能力的影响。通过在第二个卵泡波的优势卵泡中，使 P4 达到高（H）或低（L）血清浓度，从而达到对 P4 的处理，产生了 4 种处理方式：H/H、H/L、L/H 和 L/L。在波的第 7 天用 PGF 诱导黄体溶解，并在 PGF 后 56 小时用 GnRH 诱导排卵。奶牛（n=558）在 GnRH 后 16 小时接受人工授精（AI）。在妊娠期间利用妊娠特异性蛋白 B（PSPB）进行 6 次间隔和分娩时的妊娠确定，以在 AI 后第 23 天开始量化妊娠损失，以在 AI 后第 23 天开始量化妊娠损失，以进行个体内比较。与 L/H 或 H/L 处理相比，分配给 L/L 处理的单排卵奶牛的排卵前卵泡直径更大。与双排卵奶牛相比，单排卵奶牛的排卵前卵泡直径更大。与 H/H 相比，H/L、L/H 和 L/L 中的低 P4 增加了双排卵率。与单排卵奶牛相比，双排卵奶牛在 AI 后第 23 天的每 AI 妊娠（P/AI）更高，但如果排卵是单侧的，则损失更大。在整个排卵卵泡发育期间 P4 水平低的奶牛在 AI 后第 23 天的 P/AI 也高于在两个阶段 P4 水平高的奶牛。然而，各处理之间的足月 P/AI 没有差异。这是由于单侧双排卵奶牛与双侧双排卵奶牛和单排卵奶牛相比，在妊娠第 35 天至第 56 天之间的妊娠损失发生率更高。与排卵前卵泡发育的优势期有高循环 P4 的单排卵奶牛相比，在妊娠第 35 天至第 56 天之间，妊娠损失增加。在 AI 后第 16 天和 23 天的 PSPB 测量值在预测妊娠第 28 天的妊娠方面非常准确。在妊娠第 28 天至第 35 天之间有妊娠损失的奶牛与没有妊娠损失的奶牛之间，在妊娠第 23 天和第 28 天的 PSPB 有差异。总之，在排卵卵泡发育过程中循环 P4 浓度影响排卵卵泡的数量和随后妊娠损失的时间。
