Wijma R, Stangaferro M L, Giordano J O
Department of Animal Science, Cornell University, Ithaca, New York, USA.
Department of Animal Science, Cornell University, Ithaca, New York, USA.
Theriogenology. 2016 Jun;85(9):1660-1668. doi: 10.1016/j.theriogenology.2016.01.025. Epub 2016 Feb 4.
Our objectives were to evaluate circulating progesterone (P4) concentration dynamics and test the feasibility of inducing luteal regression after intravaginal (IVG) instillation of the PGF2α analogue dinoprost (PGF) in lactating dairy cows. In two experiments, cows were synchronized using the Ovsynch protocol to induce the formation of a corpus luteum (CL). Cows with at least one functional (P4 ≥1 ng/mL) CL ≥15 mm 7.5 days after Ovsynch remained in the studies. In experiment 1, cows (n = 31) were stratified by parity group and received 5 mL of saline IVG (SAL-IVG, n = 6), 25 mg of PGF intramuscular (IM) (PGF25-IM, n = 7), 25 mg of PGF IVG (PGF25-IVG, n = 6), 50 mg of PGF IVG (PGF50-IVG, n = 6), and 125 mg of PGF IVG (PGF125-IVG, n = 6). Experiment 2 was conducted to test the hypothesis that IVG instillation of two 25 mg doses of PGF 12 hours apart would be more effective than a 25- or 50-mg dose in a single application. Cows (n = 32) were stratified by parity and received SAL-IVG (n = 7), PGF25-IM (n = 7), PGF25-IVG (n = 6), and PGF50-IVG (n = 6) as in experiment 1, whereas another group received two IVG instillations of 25 mg of PGF 12 hours apart (PGF25-2X-IVG, n = 6). Blood was collected at -1 hour, every 6 hours from 0 hour to 24 hours, and every 12 hours up to 96 hours after treatment (trt). In experiment 1, there was an effect of trt (P < 0.01), time (P < 0.001), and an interaction between trt and time on P4 concentrations (P < 0.001). All PGF-treated groups had lower (P < 0.05) concentrations of P4 than cows in the SAL-IVG group from 12 to 96 hours after trt. Although an initial decline in P4 concentrations was induced in all PGF-treated cows, some cows in the IVG-treated groups presented a rebound in plasma P4, indicating CL recovery. More cows in the PGF25-IVG and PGF125-IVG groups than in the PGF50-IVG and PGF25-IM groups presented CL recovery, suggesting that greater doses of PGF may not necessarily improve CL regression. In experiment 2, there was an effect of trt (P < 0.001), time (P < 0.001), and an interaction between trt and time on P4 concentrations (P < 0.001). All PGF-treated groups had lower (P < 0.05) P4 than the SAL-IVG group from 12 to 96 hours after trt. Cows in the PGF25-2X-IVG group had a P4 profile that was similar to that of cows in the PGF25-IM group and the lowest P4 concentrations after treatment among the IVG-treated groups, and all cows presented complete CL regression (defined as P4 <0.4 ng/mL). We conclude that CL regression can be induced through IVG instillation of PGF in lactating dairy cows and that instillation of two IVG doses of 25 mg of PGF 12 hours apart was the most effective strategy.
我们的目标是评估循环孕酮（P4）浓度动态变化，并测试在泌乳奶牛阴道内（IVG）灌注前列腺素F2α类似物地诺前列素（PGF）后诱导黄体退化的可行性。在两项实验中，使用Ovsynch方案使奶牛同步发情，以诱导黄体（CL）形成。在Ovsynch处理7.5天后，至少有一个功能正常（P4≥1 ng/mL）且直径≥15 mm的CL的奶牛被纳入研究。在实验1中，奶牛（n = 31）按胎次分组，接受5 mL生理盐水IVG（SAL-IVG，n = 6）、25 mg PGF肌肉注射（IM）（PGF25-IM，n = 7）、25 mg PGF IVG（PGF25-IVG，n = 6）、50 mg PGF IVG（PGF50-IVG，n = 6）和125 mg PGF IVG（PGF125-IVG，n = 6）。进行实验2以检验以下假设：间隔12小时两次阴道内灌注25 mg PGF比单次应用25 mg或50 mg剂量更有效。奶牛（n = 32）按胎次分层，与实验1一样接受SAL-IVG（n = 7）、PGF25-IM（n = 7）、PGF25-IVG（n = 6）和PGF50-IVG（n = 6），而另一组接受间隔12小时两次25 mg PGF的IVG灌注（PGF25-2X-IVG，n = 6）。在处理（trt）前1小时、处理后0小时至24小时每6小时以及直至96小时每12小时采集血液。在实验1中，处理（P < 0.01）、时间（P < 0.001）以及处理与时间之间的交互作用（P < 0.001）对P4浓度有影响。所有PGF处理组在处理后12至96小时的P4浓度均低于SAL-IVG组的奶牛（P < 0.05）。虽然所有PGF处理的奶牛均出现P4浓度的初始下降，但IVG处理组的一些奶牛血浆P4出现反弹，表明黄体恢复。PGF25-IVG和PGF125-IVG组中出现黄体恢复的奶牛比PGF50-IVG和PGF25-IM组更多, 这表明更高剂量的PGF不一定能改善黄体退化。在实验2中，处理（P < 0.001）、时间（P < 0.001）以及处理与时间之间的交互作用（P < 0.001）对P4浓度有影响。所有PGF处理组在处理后12至96小时的P4均低于SAL-IVG组（P < 0.05）。PGF25-2X-IVG组奶牛的P4变化曲线与PGF25-IM组奶牛相似，且在IVG处理组中处理后P4浓度最低，所有奶牛均出现完全黄体退化（定义为P4 <0.4 ng/mL）。我们得出结论，在泌乳奶牛中通过阴道内灌注PGF可诱导黄体退化，且间隔12小时两次阴道内灌注25 mg PGF是最有效的策略。
