Sakaguchi M, Geshi M, Hamano S, Yonai M, Nagai T
National Agricultural Research Center for Tohoku Region, NARO, Morioka, Iwate 020-0198, Japan.
Anim Reprod Sci. 2002 Aug 15;72(3-4):209-21. doi: 10.1016/s0378-4320(02)00090-8.
One or two in vitro-produced (IVP) Japanese Black (JB) cattle embryos at 8 days after in vitro fertilization were transferred to the contralateral uterine horn of previously bred Japanese Shorthorn (JSH) or JSH-JB cross recipients, and then the occurrence of early embryonic death, abortion during mid- and late gestation, and calving loss were recorded. The survival rate of embryos, including indigenous ones, was not affected by the number of embryos transferred, and a significantly higher twinning rate (68% of pregnant recipients at 80 days after transfer) was achieved when two IVP embryos were transferred, as compared with the rate when one IVP embryo was transferred (24%). In late ET (recipients at 8.5-9.0 days after the onset of oestrus), the embryo survival rate (22%) and the pregnancy rate (42%) at 80 days after ET were significantly lower than those rates in the synchronous ET (recipients at 8.0 days after the onset of oestrus; 47 and 79%, respectively). In the early ET (recipients at 6.0-7.5 days after the onset of oestrus), no significant differences from the synchronous ET were detected in these rates. Twenty-six percent of twin pregnant recipients were aborted during mid- or late-pregnancy, and 39% of twin calves were stillborn. The mean gestation length of the twin-bearing JSH dams (276 days) was 1 week shorter than that of the single-bearing JSH dams, and it was 2 weeks shorter than that of the JB dams bearing a single JB calf derived from the IVP embryos. The longer gestation length of single JB calves derived from IVP embryos resulted in a significantly higher mean birth weight than that of in vivo control calves with the standard length of gestation. In conclusion, the number of embryos to be transferred did not affect the embryo survival rate, and the transfer of two IVP embryos to previously inseminated recipients induced a significantly higher twinning rate during early pregnancy than that of one IVP embryo transfer. The incidence of embryonic losses during early pregnancy increased when Day 8 embryos were transferred to the recipients later in the oestrous cycle (>8.0 days). The results suggested that one cause of the high rate of abortions and stillbirths in twin-bearing dams is the difference in the mean gestation length between the native JSH and JB foetuses derived from transferred IVP embryos.
将体外受精8天后的一两个体外生产（IVP）日本黑毛（JB）牛胚胎，移植到先前已配种的日本短角牛（JSH）或JSH-JB杂交受体的对侧子宫角，然后记录早期胚胎死亡、妊娠中期和晚期流产以及产犊损失的发生情况。包括本地胚胎在内的胚胎存活率不受移植胚胎数量的影响，与移植一个IVP胚胎时的比例（24%）相比，移植两个IVP胚胎时获得了显著更高的双胎率（移植后80天怀孕受体的68%）。在晚期胚胎移植（发情开始后8.5 - 9.0天的受体）中，胚胎移植后80天的胚胎存活率（22%）和妊娠率（42%）显著低于同期胚胎移植（发情开始后8.0天的受体；分别为47%和79%）。在早期胚胎移植（发情开始后6.0 - 7.5天的受体）中，这些比率与同期胚胎移植相比未检测到显著差异。26%的双胎怀孕受体在妊娠中期或晚期流产，39%的双胎犊牛死产。怀有双胎的JSH母畜的平均妊娠期（276天）比怀有单胎的JSH母畜短1周，比怀有来自IVP胚胎的单头JB犊牛的JB母畜短2周。来自IVP胚胎的单头JB犊牛较长的妊娠期导致其平均出生体重显著高于具有标准妊娠期的体内对照犊牛。总之，移植胚胎的数量不影响胚胎存活率，将两个IVP胚胎移植到先前已授精的受体中，在妊娠早期诱导的双胎率显著高于移植一个IVP胚胎。当将第8天的胚胎移植到发情周期较晚（>8.0天）的受体中时，妊娠早期胚胎损失的发生率增加。结果表明，怀有双胎的母畜中高流产率和死产率的一个原因是本地JSH和来自移植IVP胚胎的JB胎儿之间平均妊娠期的差异。
