The aim of this study was to evaluate whether the RI and PI values would help in choosing the best embryo recipient, and observe whether CL vascularization would influence P4 production. During the breeding season 2018/2019, the study was conducted using 35 mares, which is used for reference to collect data for the project on the day of embryo transfer. The utilized mares were divided into five groups followed by the day after ovulation, with D0 being the day of ovulation. Therefore, the five groups are as follows: D4—mares that were on the 4th post‐ovulation day; D5—mares that were on the 5th post‐ovulation day; and doing so successively for D6, D7 and D8. On the day of embryo transfer, the CL of the mares that selected as recipients was evaluated by B‐mode and power flow mode ultrasonography and the right and left dorsal branches of the uterine arteries by spectral Doppler ultrasonography. Blood samples were taken on the day of the embryo transfer for a dosage of P4 concentration by radioimmunoassay. No statistical difference was found between the variables when the mares were separated into pregnant and non‐pregnant mares, or when they were separated by age groups. When the groups of mares were compared by the day of embryo transfer, the statistical difference was found between the groups D5 × D6 (p  = .0053) and D6 × D8 (p  = .0036) in RI variable. In PI variable, the statistical difference was found between the groups D4 × D8 (p  = .049), D5 × D6 (p  = .0446) and D6 × D8 (p  = .0024). We conclude that the mares with RI measurement of uterine arteries near 1.0 are correlated to mares with high CL vascularization and elevated P4 concentration.

中文翻译：

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频谱多普勒超声选择马胚胎接收器。

这项研究的目的是评估RI和PI值是否有助于选择最佳的胚胎受体，并观察CL血管形成是否会影响P4的产生。在2018/2019繁殖季节，使用35匹母马进行了研究，以供参考以在胚胎移植当天收集该项目的数据。被利用的母马被分为五组，随后是排卵的第二天，D0是排卵的一天。因此，这五个组如下：D4-排卵后第4天的母马；D5-排卵后第5天的母马；然后依次对D6，D7和D8执行此操作。在胚胎移植的那天，被选为接受者的母马的CL通过B型和功率流超声检查，并通过频谱多普勒超声检查子宫动脉的左右背分支。在胚胎移植当天通过放射免疫测定法采集血样，测定一定剂量的P4浓度。当母马分为怀孕母马和非怀孕母马，或按年龄组分开时，变量之间没有统计学差异。在母鼠胚胎移植当天比较母马组时，发现D5×D6组之间的统计差异（当母马分为怀孕母马和非怀孕母马，或按年龄组分开时，变量之间没有统计学差异。在母鼠胚胎移植当天比较母马组时，发现D5×D6组之间的统计差异（当母马分为妊娠母马和非妊娠母马，或按年龄组分开时，变量之间没有统计学差异。在母鼠胚胎移植当天比较母马组时，发现D5×D6组之间的统计差异（p  = .0053）和 RI变量中的D6×D8（p = .0036）。在PI变量中，在D4×D8（p  = .049），D5×D6（p  = .0446）和D6×D8（p  = .0024）组之间发现了统计差异。我们得出的结论是，子宫动脉RI测量接近1.0的母马与CL血管化程度较高和P4浓度升高的母马相关。