Tippenhauer C M, Steinmetz I, Heuwieser W, Fricke P M, Lauber M R, Cabrera E M, Borchardt S
Clinic for Animal Reproduction, Faculty of Veterinary Medicine, Freie Universitaet Berlin, Koenigsweg 65, 14163, Berlin, Germany.
Department of Dairy Science, University of Wisconsin, Madison, 53706, United States.
Theriogenology. 2021 Mar 1;162:49-58. doi: 10.1016/j.theriogenology.2020.12.020. Epub 2020 Dec 29.
The objective of this study was to evaluate the effect of two prostaglandin F (PGF) treatments 24 h apart (500 μg of cloprostenol) and treatment with a double PGF dose on d 7 (1000 μg of cloprostenol) during a 7-d Ovsynch protocol on progesterone (P4) concentration and pregnancy per artificial insemination (P/AI) in lactating Holstein cows. We hypothesized that treatment leads to a decreased P4 concentration at the second GnRH treatment (G2) and an increase in P/AI compared to the traditional 7-d Ovsynch protocol. A secondary hypothesis was that the treatment effect is influenced by the presence of a corpus luteum (CL) at the first GnRH treatment (G1). Two experiments were conducted on 8 commercial dairy farms in Germany. Once a week, cows from both experiments were assigned in a consecutive manner to receive: (1) Ovsynch (control: GnRH; 7 d, PGF; 9 d, GnRH), (2) Ovsynch with a double PGF dose (GDPG: GnRH; 7 d, 2xPGF; 9 d, GnRH), or (3) Ovsynch with a second PGF treatment 24 h later (GPPG: GnRH; 7 d, PGF; 8 d, PGF; 32 h, GnRH). All cows received timed AI (TAI) approximately 16 h after G2. Pregnancy diagnosis was performed by transrectal palpation (38 ± 3 d after TAI, experiment 1) or transrectal ultrasonography (35 ± 7 d after TAI, experiment 2). Whereas farms from experiment 1 used a Presynch-Ovsynch protocol (PGF, 14 d later PGF, 12 d later GnRH, 7 d later PGF, 2 d later GnRH, and 16-18 h later TAI) to facilitate first postpartum TAI, no presynchronization protocol was used on farms from experiment 2. In experiment 1, we enrolled 1581 lactating dairy cows (60 experimental units) from 2 dairy farms. At G2, blood samples were collected from a subsample of cows (n = 491; 16 experimental units) to determine P4 concentration at G2. In experiment 2, we enrolled 1979 lactating dairy cows (252 experimental units) from 6 dairy farms. Transrectal ultrasonography was performed to determine the presence or absence of a CL at G1. In experiment 1, treatment affected P/AI (P = 0.01) and P/AI was greater for GDPG (38.2%) and GPPG (38.9%) than for control cows (29.8%). Both, GDPG and GPPG cows had decreased P4 concentration at G2 compared with control cows (P < 0.01). Whereas both treatments increased the percentage of cows with very low P4 concentration (0.00-0.09 ng/mL) at G2, only the GPPG treatment decreased the percentage of cows with high P4 concentration (≥0.6 ng/mL) at G2 compared to the control group. In experiment 2, P/AI was greater for GPPG (37.4%) than for control cows (31.0%; P = 0.03) and tended to be greater than for GDPG cows (31.8%; P = 0.05). Cows from the GDPG group had similar (P = 0.77) P/AI compared to the control group. Pregnancy per AI did not differ between cows with a CL at G1 and cows without a CL at G1 (34.1% vs. 32.6%; P = 0.50). There was no interaction between treatment and presence of a CL at G1 on P/AI (P = 0.61). Combining data from the 2 experiments but excluding cows from experiment 1 receiving presynchronization before first TAI (n = 2573; 312 experimental units), P/AI was greater for GPPG (40.3%; P < 0.01) than for control (31.8%) and GDPG cows (33.4%). Between GDPG and control cows, P/AI did not differ (P = 0.46). We conclude that overall the addition of a second PGF treatment on d 8 during a 7-d Ovsynch protocol increased P/AI compared to the traditional 7-d Ovsynch including a single PGF dose on d 7 and to a double PGF dose on d 7. Doubling the PGF dose on d 7 in a 7-d Ovsynch protocol did not affect P/AI. Use of a presynchronization protocol, however, seems to influence the effect of a dose frequency modification of PGF treatment in an Ovsynch protocol. Presynchronized cows receiving first postpartum TAI had similarly increased P/AI treated with a double PGF dose compared with treatment with a second PGF dose. Future studies need to elucidate whether the treatment effect is modified by presynchronization of the first postpartum TAI.
本研究的目的是评估在为期7天的同期发情方案中，间隔24小时进行两次前列腺素F（PGF）处理（500μg氯前列醇）以及在第7天使用双倍PGF剂量处理（1000μg氯前列醇）对泌乳荷斯坦奶牛孕酮（P4）浓度和每人工授精受胎率（P/AI）的影响。我们假设，与传统的7天同期发情方案相比，该处理会导致第二次促性腺激素释放激素（GnRH）处理（G2）时P4浓度降低，且P/AI增加。第二个假设是，处理效果受第一次GnRH处理（G1）时黄体（CL）的存在情况影响。在德国的8个商业奶牛场进行了两项试验。每周一次，将来自两个试验的奶牛依次分配接受：（1）同期发情方案（对照：GnRH；第7天，PGF；第9天，GnRH），（2）双倍PGF剂量的同期发情方案（GDPG：GnRH；第7天，2xPGF；第9天，GnRH），或（3）24小时后进行第二次PGF处理的同期发情方案（GPPG：GnRH；第7天，PGF；第8天，PGF；32小时后，GnRH）。所有奶牛在G2后约16小时接受定时人工授精（TAI）。通过直肠触诊（TAI后38±3天，试验1）或直肠超声检查（TAI后35±7天，试验2）进行妊娠诊断。试验1的奶牛场采用预同期发情-同期发情方案（PGF，14天后PGF，12天后GnRH，7天后PGF，2天后GnRH，16 - 18小时后TAI）以促进首次产后TAI，试验2的奶牛场未使用预同期发情方案。在试验1中，我们从2个奶牛场招募了1581头泌乳奶牛（60个试验单元）。在G2时，从一部分奶牛（n = 491；16个试验单元）采集血样以测定G2时的P4浓度。在试验2中，我们从6个奶牛场招募了1979头泌乳奶牛（252个试验单元）。在G1时进行直肠超声检查以确定CL的有无。在试验1中，处理影响P/AI（P = 0.01），GDPG组（38.2%）和GPPG组（38.9%）的P/AI高于对照奶牛（29.8%）。与对照奶牛相比，GDPG组和GPPG组奶牛在G2时的P4浓度均降低（P < 0.01）。两种处理均增加了G2时P4浓度极低（0.00 - 0.09 ng/mL）的奶牛百分比，与对照组相比，只有GPPG处理降低了G2时P4浓度高（≥0.6 ng/mL）的奶牛百分比。在试验2中，GPPG组的P/AI高于对照奶牛（31.0%；P = 0.03），且倾向于高于GDPG组奶牛（31.8%；P = 0.05）。GDPG组奶牛与对照组相比，P/AI相似（P = 0.77）。G1时有CL的奶牛和G1时无CL的奶牛之间的每人工授精受胎率无差异（34.1%对32.6%；P = 0.50）。处理与G1时CL的存在情况对P/AI没有交互作用（P = 0.61）。合并两项试验的数据，但排除试验1中首次TAI前接受预同期发情的奶牛（n = 2573；312个试验单元），GPPG组的P/AI高于对照组（31.8%）和GDPG组奶牛（33.4%）（40.3%；P < 0.01）。GDPG组和对照组奶牛之间，P/AI无差异（P = 0.46）。我们得出结论，总体而言，在7天同期发情方案中，与传统的在第7天使用单次PGF剂量以及在第7天使用双倍PGF剂量的7天同期发情方案相比，在第8天添加第二次PGF处理可提高P/AI。在7天同期发情方案中第7天PGF剂量加倍对P/AI没有影响。然而，预同期发情方案的使用似乎会影响同期发情方案中PGF处理剂量频率改变的效果。接受首次产后TAI的预同期发情奶牛，与使用第二次PGF剂量处理相比，使用双倍PGF剂量处理时P/AI同样增加。未来的研究需要阐明首次产后TAI的预同期发情是否会改变处理效果。
