Departamento de Reproducción Animal, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Madrid, Spain.
J Dairy Sci. 2010 Mar;93(3):1022-9. doi: 10.3168/jds.2009-2605.
Infertility in dairy cattle is a multifactorial problem that may be linked to follicle development and the quality of the ovulated oocyte, to sperm transport and fertilization, to the reproductive tract environment, or to a combination of these factors. Using a state-of-the-art endoscopic embryo transfer technique, the aim of this study was to compare the ability of the reproductive tract of postpartum dairy cows and nulliparous heifers to support the development of early embryos to the blastocyst stage. Bovine embryos of 2 to 4 cells (n=1,800) were produced by in vitro maturation and fertilization of oocytes derived from the ovaries of slaughtered cattle. The estrus cycles of nulliparous Holstein heifers (n=10) and postpartum Holstein cows (n=8, approximately 60 d postpartum) were synchronized using an 8-d controlled internal drug release device coupled with prostaglandin injection. On d 2, one hundred 2- to 4-cell embryos were endoscopically transferred to the oviduct ipsilateral to the corpus luteum. Five days later, on d 7, the oviduct and uterus were flushed nonsurgically to recover the embryos. The number of embryos developing to the blastocyst stage was recorded immediately at recovery and following overnight culture in vitro. A representative number of blastocysts from heifers and cows were stained to assess cell number. Progesterone concentrations were lower in cows than in heifers on d 5, 6, and 7 (d 7=2.39+/-0.33 vs. 5.34+/-0.77ng/mL, respectively). More embryos were recovered from heifers than cows (79.0+/-7.0 vs. 57.2+/-11.4%). Of the embryos recovered, 33.9+/-3.6% had developed to the blastocyst stage in the heifer oviduct compared with 18.3+/-7.9% in the postpartum cow oviduct. There was no evidence of a difference in blastocyst quality as evidenced by total cell number in the blastocysts (71.2+/-5.7 vs. 67.0+/-5.3, respectively). In conclusion, the reproductive tract of the postpartum lactating dairy cow may be less capable of supporting early embryo development than that of the nonlactating heifer, and this may contribute to the lower conception rates observed in such animals.
奶牛不孕症是一种多因素问题，可能与卵泡发育和排卵卵母细胞的质量、精子运输和受精、生殖道环境或这些因素的组合有关。本研究采用最先进的内镜胚胎移植技术，旨在比较产后奶牛和初产小母牛生殖道支持早期胚胎发育至囊胚阶段的能力。通过体外成熟和受精从屠宰牛卵巢中获得的卵母细胞，产生 2 至 4 细胞的牛胚胎（n=1800）。使用 8 天的控制内部药物释放装置和前列腺素注射同步初产荷斯坦小母牛（n=10）和产后荷斯坦奶牛（n=8，产后约 60 天）的发情周期。在第 2 天，将 100 个 2 至 4 细胞胚胎经内镜转移到与黄体同侧的输卵管。5 天后，即第 7 天，非手术冲洗输卵管和子宫以回收胚胎。在回收时和在体外过夜培养后立即记录胚胎发育至囊胚阶段的数量。从小母牛和奶牛中选择代表性数量的囊胚进行染色以评估细胞数量。与小母牛相比，奶牛在第 5、6 和 7 天的孕激素浓度较低（第 7 天=2.39+/-0.33 对 5.34+/-0.77ng/ml）。从小母牛中回收的胚胎多于奶牛（79.0+/-7.0 对 57.2+/-11.4%）。在回收的胚胎中，与产后奶牛输卵管中 18.3+/-7.9%相比，小母牛输卵管中 33.9+/-3.6%的胚胎发育至囊胚阶段。囊胚的总细胞数表明囊胚质量没有差异（分别为 71.2+/-5.7 对 67.0+/-5.3）。总之，产后泌乳奶牛的生殖道可能不如非泌乳小母牛支持早期胚胎发育的能力强，这可能导致此类动物的受孕率较低。
