Bovine embryo growth involves a complex interaction between the developing embryo and the growth-promoting potential of the uterine environment. We have previously established links between embryonic factors (embryo stage, embryo gene expression), maternal factors (progesterone, body condition score), and embryonic growth to 8 d after bulk transfer of Day 7 in vitro-produced blastocysts. In this study we recovered blastocysts on Days 7 and 15 after artificial insemination to test the hypothesis that in vivo and in vitro embryos follow a similar growth program. We conducted our study using 4 commercial farms and repeated our study over 2 yr (2014, 2015), with data available from 2 of the 4 farms in the second year. Morphological and gene expression measurements (196 candidate genes) of the Day 7 embryos were measured and the progesterone concentration of the cows were measured throughout the reproductive cycle as a reflection of the state of the uterine environment. These data were also used to assess the interaction between the uterine environment and the developing embryo and to examine how well Day 7 embryo stage can be predicted from the Day 7 gene expression profile. Progesterone was not a strong predictor of in vivo embryo growth to Day 15. This contrasts with a range of Day 7 embryo transfer studies which demonstrated that progesterone is a very good predictor of embryo growth to Day 15. Our analysis demonstrates that in vivo embryos are 3 times less sensitive to progesterone than in vitro-transferred embryos (up to Day 15). This highlights that caution must be applied when extrapolating the results of in vitro embryo transfer studies to the in vivo situation. The similar variance in measured and predicted (based on Day 15 length) Day 7 embryo stage indicate low stochastic perturbations for in vivo embryo growth (large stochastic growth effects would generate a significantly larger standard deviation in measured embryo length on Day 15). We also identified that Day 7 embryo stage could be predicted based on the Day 7 gene expression profile (58% overall success rate for classification of 5 embryo stages). Our analysis also associated genes with each developmental stage and demonstrates the high level of temporal regulation of genes that occurs during early embryonic development.

牛胚胎生长涉及发育中的胚胎与子宫环境促进生长的潜力之间的复杂相互作用。我们先前已经建立了胚胎因子（胚胎期，胚胎基因表达），母体因子（孕酮，身体状况评分）和胚胎移植到体外培养的第7天囊胚移植至8天后的8 d之间的联系。在这项研究中，我们在人工授精后的第7天和第15天回收了胚泡，以检验体内和体外胚胎遵循类似生长程序的假说。我们使用4个商业农场进行了研究，并在2年内（2014年，2015年）重复了我们的研究，并在第二年从4个农场中的2个农场获得了数据。测量第7天胚胎的形态和基因表达（196个候选基因），并在整个生殖周期中测量奶牛的孕酮浓度，以反映子宫环境的状态。这些数据还用于评估子宫环境与发育中的胚胎之间的相互作用，并检查从第7天的基因表达谱可预测第7天的胚胎阶段有多好。孕酮并不是第15天体内胚胎生长的强力预测因子。这与第7天胚胎移植研究的范围形成鲜明对比，后者研究表明，孕酮是第15天胚胎生长的很好预测因子。我们的分析表明，体内胚胎对孕激素的敏感性比体外移植的胚胎低3倍（至第15天）。这突显了将体外胚胎移植研究的结果外推至体内情况时必须谨慎行事。第7天胚胎期的测量值和预测值（基于第15天的长度）具有相似的方差，表明体内胚胎生长的随机扰动较低（较大的随机生长效应会在第15天产生较大的标准胚胎长度标准偏差）。我们还确定，可以基于第7天的基因表达谱（在5个胚胎阶段的分类中，总成功率为58％）可以预测第7天的胚胎阶段。我们的分析还将基因与每个发育阶段相关联，并证明了在早期胚胎发育过程中发生的基因的高水平时间调控。