Optimizing ovulation to first GnRH improved outcomes to each hormonal injection of Ovsynch in lactating dairy cows
Optimizing ovulation to first GnRH improved outcomes to each hormonal injection of Ovsynch in lactating dairy cows
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DOI：
10.3168/jds.s0022-0302(06)72378-5
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发表时间：
2006-09-01
影响因子：
3.5
通讯作者：
Pursley, J. R.
中科院分区：
文献类型：
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作者：
Bello, N. M.;Steibel, J. P.;Pursley, J. R.
对Ovsynch第一个GnRH的排卵反应是奶牛成功同步排卵的关键决定因素。我们在本研究中的目的是开发一种Ovsynch前治疗，增加对Ovsynch首次注射GnRH作出反应的排卵奶牛的百分比。为了实现我们的目标，我们在Ovsynch的第一个GnRH之前评估了由PGF（2 α）和GnRH组成的激素策略。将泌乳奶牛（n = 137）分配为在Ovsynch（对照）之前不接受治疗，或在开始Ovsynch方案前4（G4 G）、5（G5 G）或6（G6 G）天给予25 mg PGF（2 α）（PreP），2天后给予100 μ g GnRH（PreG）。进行经直肠超声检查以评估卵泡大小和排卵情况，并在每次激素注射前立即采集血样以测量孕酮和雌二醇的循环浓度。在Ovsynch的最终GnRH后16 h的固定时间对奶牛进行授精。35天后通过直肠触诊子宫内容物进行妊娠诊断。对于G4 G、G5 G、G6 G和对照组，排卵至Ovsynch第一个GnRH的奶牛比例分别为56.0%、66.7%、84.6%和53.8%，G6 G组高于对照组奶牛。所有给药奶牛对Ovsynch PGF（2 α）的黄体溶解反应均高于对照奶牛（G4 G、G5 G、G6 G和对照分别为92.0%、91.7%、96.2%和69.2%）。G6 G奶牛与Ovsynch的同步率（分别为92%和69%）高于对照奶牛。此外，与未排卵的奶牛相比，对Ovsynch的第一次GnRH有反应而排卵的奶牛对Ovsynch的PGF（2 α）有更大的反应（分别为92.7%和77.1%），对总体方案的同步率更高（分别为87.9%和62.9%）。Ovsynch的PGF（2 α）的孕酮浓度和Ovsynch的最终GnRH的雌二醇和卵泡大小被确定为人工授精后35天妊娠概率的重要预测因素。总之，与对照奶牛相比，基于PGF（2 α）和GnRH的Pre-Ovsynch策略（包括PreG和Ovsynch首次GnRH之间的6天间隔）分别导致对Ovsynch首次GnRH和PGF（2 α）的排卵和黄体溶解反应更大。这反过来又优化了与Ovsynch的同步速率。
Ovulatory response to the first GnRH of Ovsynch is the critical determinant for successful synchronization of ovulation in dairy cows. Our objective in this study was to develop a pre-Ovsynch treatment that increased the percentage of cows that ovulated in response to the first GnRH injection of Ovsynch. To accomplish our goal, we evaluated a hormonal strategy that consisted of PGF(2 alpha) and GnRH before the first GnRH of Ovsynch. Lactating dairy cows (n = 137) were assigned to receive either no treatment before Ovsynch (control) or 25 mg of PGF(2 alpha) (PreP) followed 2 d later by 100 mu g of GnRH (PreG), administered 4 (G4G), 5 (G5G), or 6 (G6G) d before initiating the Ovsynch protocol. Transrectal ultrasonography was performed to assess follicular size and resulting ovulation, and blood samples were collected to measure circulating concentrations of progesterone and estradiol immediately before each hormonal injection. Cows were inseminated at a fixed time 16 h after final GnRH of Ovsynch. Pregnancy diagnosis was performed 35 d later by palpation per rectum of uterine contents. Proportion of cows that ovulated to first GnRH of Ovsynch was 56.0, 66.7, 84.6, and 53.8% for G4G, G5G, G6G, and controls, respectively, and was greater for G6G than for control cows. Luteolytic response to PGF(2 alpha) of Ovsynch was greater in all treated than control cows (92.0, 91.7, 96.2, and 69.2% for G4G, G5G, G6G, and control, respectively). Synchronization rate to Ovsynch was greater (92 vs. 69%, respectively) in G6G than in control cows. In addition, cows that ovulated in response to first GnRH of Ovsynch had greater response to PGF(2 alpha) of Ovsynch (92.7 vs. 77.1%, respectively) and greater synchronization rate to the overall protocol (87.9 vs. 62.9%, respectively) than those that did not ovulate. Concentrations of progesterone at PGF(2 alpha) of Ovsynch, and estradiol and follicle size at final GnRH of Ovsynch, were identified as significant predictors of probability of pregnancy 35 d after artificial insemination. In summary, a PGF(2 alpha)-and-GnRH based pre-Ovsynch strategy consisting of a 6-d interval between PreG and first GnRH of Ovsynch resulted in a greater ovulatory and luteolytic response to first GnRH and PGF(2 alpha) of Ovsynch, respectively, compared with control cows. This, in turn, optimized synchronization rate to Ovsynch.