Ciernia L A, Perry G A, Smith M F, Rich J J, Northrop E J, Perkins S D, Green J A, Zezeski A L, Geary T W
University of Missouri, Columbia, MO, USA.
South Dakota State University, Brookings, SD, USA.
Anim Reprod Sci. 2021 Apr;227:106723. doi: 10.1016/j.anireprosci.2021.106723. Epub 2021 Feb 17.
Two experiments were conducted to examine the effect of plasma concentrations of 17β-estradiol (E) preceding and progesterone (P) subsequent to ovulation on proportions of beef cows pregnant following embryo transfer. Timing of ovulation (d 0) among postpartum cows was synchronized and cows that expressed estrus were removed from each study. In Experiment 1, plasma E concentration on d 0 was used to classify cows (n = 353) into Low, Medium, and High E groups. Pregnancy rate for cows with Low, Medium, or High E concentrations were different (P < 0.05). In Experiment 2, there were multiple administrations of PGF to evaluate the independent effects of Low or High E before ovulation and Low or Normal (no treatment) P after ovulation on proportions of cows pregnant. Treatment groups in Experiment 2, therefore, were: Low E-Low P (LL; n = 71), Low E-Normal P (LN; n = 69), High E-Low P (HL; n = 74), and High E-Normal P (HN; n = 73). Concentrations of P on d 7 subsequent to ovulation were less (P < 0.05) in cows of the HL compared to HN, and in LL compared to LN groups. Concentrations of E on d -2, 0, and change in E (d -2 to d 0) had a positive effect (P < 0.008) on pregnancy rates. In summary, relatively greater E concentrations preceding ovulation; and relatively greater P concentrations subsequent to ovulation combined with lesser E concentrations preceding ovulation had a positive effect on proportions of postpartum cows pregnant.
进行了两项试验，以研究排卵前血浆中17β-雌二醇（E）浓度和排卵后孕酮（P）浓度对胚胎移植后肉牛怀孕比例的影响。产后母牛的排卵时间（第0天）进行了同步化处理，每个研究中发情的母牛被剔除。在试验1中，根据第0天的血浆E浓度将母牛（n = 353）分为低E组、中E组和高E组。低E、中E或高E浓度母牛的怀孕率不同（P < 0.05）。在试验2中，多次注射前列腺素F2α以评估排卵前低E或高E以及排卵后低P或正常（未处理）P对母牛怀孕比例的独立影响。因此，试验2中的处理组为：低E-低P（LL；n = 71）、低E-正常P（LN；n = 69）、高E-低P（HL；n = 74）和高E-正常P（HN；n = 73）。与HN组相比，HL组母牛排卵后第7天的P浓度较低（P < 0.05），与LN组相比，LL组的P浓度也较低。第-2天、第0天的E浓度以及E的变化（第-2天至第0天）对怀孕率有积极影响（P < 0.008）。总之，排卵前相对较高的E浓度；排卵后相对较高的P浓度以及排卵前较低的E浓度相结合，对产后母牛的怀孕比例有积极影响。
