Department of Animal Production, University of Lleida, Lleida, Spain.
Theriogenology. 2010 Feb;73(3):293-9. doi: 10.1016/j.theriogenology.2009.09.012. Epub 2009 Oct 23.
Spontaneous reduction of advanced twin embryos has been described in high-producing, Holstein-Fresian (Bos taurus) dairy herds. The first objective of the current study was to determine whether management and cow factors could have an effect on such a reduction in twin pregnancies during the early fetal period. Because loss of a corpus luteum was noted in cows suffering twin reduction, we expanded our study to include multiple-ovulating cows carrying singletons. Pregnancy was diagnosed and confirmed from Days 28 to 34 and 56 to 62 postinsemination. Sixty-nine (23.5%) of 293 pregnant cows with two corpora lutea carrying singletons and 132 (28.4%) of 464 twin pregnancies recorded on first pregnancy diagnosis subsequently lost one of the corpora lutea or one of the embryos, respectively. Thirty-four (25.8%) of the 132 twin pregnancies suffering embryo reduction lost one corpus luteum along with the embryo. Corpus luteum reduction always occurred in the ovary ipsilateral to the gravid horn suffering embryo reduction. Binary logistic regressions were performed considering corpus luteum and embryo reduction as dependent variables in single and twin pregnancies, respectively, and several management- and cow-related factors as independent variables. In cows carrying singletons, the risk of corpus luteum reduction was 14.3 (1/0.07) times lower for a given herd, whereas the interaction season by laterality significantly affected corpus luteum reduction such that in cows with two corpora lutea ipsilateral to the horn of pregnancy, the risk of reduction decreased during the winter period. In cows carrying twins, ipsilateral twin pregnancies were 3.45 (1/0.29) times more likely to undergo the loss of one embryo than bilateral twin pregnancies. As an overall conclusion, both corpora lutea and embryos were vulnerable to the effects of stress factors during the early fetal period in cows maintaining their pregnancies. A strong unilateral relationship between the corpus luteum and the conceptus was also observed.
高产荷斯坦奶牛（Bos taurus）的奶牛场中曾描述过晚期双胎胚胎的自然减少。本研究的首要目的是确定在早期胎儿期，双胎妊娠减少是否与管理和奶牛因素有关。因为在发生双胎减少的奶牛中发现黄体丧失，所以我们将研究范围扩大到携带单胎的多排卵奶牛。妊娠于授精后第 28 至 34 天和第 56 至 62 天进行诊断和确认。在首次妊娠诊断时记录的携带两个黄体的 293 头怀有单胎的妊娠牛中，有 69 头（23.5％）和 464 头双胎妊娠中的 132 头（28.4％）随后失去了一个黄体或一个胚胎。在 132 头发生胚胎减少的双胎妊娠中，有 34 头（25.8％）失去了一个黄体和一个胚胎。黄体减少总是发生在发生胚胎减少的妊娠角同侧的卵巢中。在单胎和双胎妊娠中，分别将黄体和胚胎减少作为因变量，考虑了几个与管理和奶牛有关的因素作为自变量，进行二元逻辑回归分析。在携带单胎的奶牛中，给定牛群的黄体减少风险降低了 14.3（1/0.07）倍，而季节与侧别之间的相互作用显著影响了黄体减少，即对于黄体同侧的双胎妊娠奶牛，在冬季期间减少的风险降低。在携带双胎的奶牛中，同侧的双胎妊娠比双侧的双胎妊娠更有可能失去一个胚胎，风险增加了 3.45 倍（1/0.29）。总的来说，在维持妊娠的奶牛中，早期胎儿期的黄体和胚胎都容易受到应激因素的影响。黄体和胚胎之间也存在强烈的单侧关系。
