O'Connell Anne R, Demmers Kristina J, Smaill Bronwyn, Reader Karen L, Juengel Jennifer L
Animal Science Group, AgResearch Ltd., Invermay Agricultural Centre, Mosgiel, New Zealand.
Animal Science Group, AgResearch Ltd., Invermay Agricultural Centre, Mosgiel, New Zealand.
Theriogenology. 2016 Sep 15;86(5):1285-93. doi: 10.1016/j.theriogenology.2016.04.069. Epub 2016 Apr 27.
In a naturally mated cycle, ova and viable embryo number as well as embryo size were assessed on Day 4, 10, 14, 18, and 30 of gestation in Romney ewes (n = 38-44 per gestational group). For Days 4-18 of gestation, embryos were recovered by flushing the reproductive tract after slaughtering of the ewe. Ovulation rate was determined by counting the number of corpora lutea present on both ovaries. For the Day 30 group, number of ovulations was measured by laparoscopic examination of the ovaries at Day 9-12 of the cycle, and number of embryos present was determined by ultrasound examination at approximately Day 30 of pregnancy. Most of embryo loss occurred before Day 14 of gestation with 6% loss before Day 4, and 12% loss between Day 4 and 14 of gestation. A similar proportion of viable embryos per number of ova ovulated were recovered on Day 14 and 18 (82%) and Day 30 (81%) of gestation. Fertilization failure was estimated at 1%. Conceptus and embryo size was most variable on Day 14, representing a period of rapid growth (conceptus length ± standard deviation); Day 4 (169 ± 8 μm), Day 10 (379 ± 93 μm), Day 14 (23 ± 32 mm), Day 18 (embryo length ± standard deviation; 5.0 ± 0.7 mm). Vaccination with commercially available fertility vaccines targeting androstenedione (Androvax and Ovastim) in previous seasons resulted in reduced conceptus size compared with controls. However, no difference in the proportion of viable embryos was observed between treatments, signifying maternal tolerance for considerable variation at this stage of development. Furthermore, the finding that most of loss occurs within the first 14 days of gestation highlights the importance of both oocyte quality and the uterine environment for the embryo to successfully overcome the challenges leading up to and including pregnancy recognition in the ewe.
在自然交配周期中，对罗姆尼母羊（每个妊娠组n = 38 - 44）在妊娠第4、10、14、18和30天评估卵子和存活胚胎数量以及胚胎大小。在妊娠第4 - 18天，通过在母羊屠宰后冲洗生殖道来回收胚胎。排卵率通过计数两侧卵巢上黄体的数量来确定。对于第30天组，在周期的第9 - 12天通过腹腔镜检查卵巢来测量排卵数，并在妊娠约第30天通过超声检查来确定现存胚胎数。大多数胚胎损失发生在妊娠第14天之前，在第4天之前损失6%，在妊娠第4天至14天之间损失12%。在妊娠第14天和18天（82%）以及第30天（81%）回收的存活胚胎与排卵卵子数量的比例相似。受精失败估计为1%。在第14天，孕体和胚胎大小变化最大，代表快速生长阶段（孕体长度±标准差）；第4天（169 ± 8μm），第10天（379 ± 93μm），第14天（23 ± 32mm），第18天（胚胎长度±标准差；5.0 ± 0.7mm）。在前几个季节用针对雄烯二酮的市售生育疫苗（Androvax和Ovastim）进行疫苗接种，与对照组相比，导致孕体大小减小。然而，在各处理组之间未观察到存活胚胎比例的差异，这表明在发育的这个阶段母体对相当大的变异具有耐受性。此外，大多数损失发生在妊娠的前14天内这一发现突出了卵母细胞质量和子宫环境对于胚胎成功克服直至包括母羊妊娠识别在内的挑战的重要性。
