Ginther O J
Department of Veterinary Science University of Wisconsin-Madison Madison, WI 53706 USA.
Theriogenology. 1983 Oct;20(4):383-95. doi: 10.1016/0093-691x(83)90199-1.
Brood-farm records were used to test several hypotheses concerning twinning and inequalities in the side of ovulation and embryo attachment. Ovulation occurred more frequently (P<0.05) from the left ovary (61% versus 39%) in maiden mares, but with equal frequency from either ovary in lactating and barren mares. The embryo attached more often (P<0.05) to the left horn in lactating mares (60%) and to the right horn in barren (59%) and maiden (67%) mares. Double ovulations and twin embryos were diagnosed more frequently (P<0.05) in barren mares (11% and 6%, respectively) than in lactating mares (5% and 1%). Pregnancy rates for double ovulations were affected (P<0.01) by the length of the interval between the two ovulations (0 days, 83%; 2 days, 87%; 4 days, 67%; 6 days, 54%; 8 days or more, 38%). Pregnancy rates were higher (P<0.01) for double ovulations 0 or 2 days apart (84%) than for single ovulations (54%). Twins were diagnosed more frequently (P<0.05) when double ovulations were two or more days apart (9 32 ) than when the ovulations were synchronous (0 19 ). These results support the conclusion that an embryo-reduction mechanism exists in mares for the elimination of excess embryos and indicate that the mechanism loses its effectiveness when the embryos originate from asynchronous ovulations.
利用繁殖场记录来检验几个关于双胎以及排卵侧和胚胎着床侧不平等的假说。初产母马中，左侧卵巢排卵更为频繁（P<0.05）（61%对39%），但在泌乳母马和不育母马中，两侧卵巢排卵频率相同。泌乳母马中，胚胎更多地（P<0.05）附着于左子宫角（60%），而不育母马（59%）和初产母马（67%）中，胚胎更多地附着于右子宫角。不育母马中双排卵和双胚胎的诊断频率（P<0.05）高于泌乳母马（分别为11%和6%对5%和1%）。双排卵的妊娠率受两次排卵间隔时间的影响（P<0.01）（间隔0天，83%；2天，87%；4天，67%；6天，54%；8天及以上，38%）。间隔0或2天的双排卵妊娠率（84%）高于单排卵（54%）（P<0.01）。当双排卵间隔两天或更长时间时，双胎的诊断频率（P<0.05）更高（9/32），而排卵同步时双胎诊断频率较低（0/19）。这些结果支持这样的结论，即母马存在一种胚胎减少机制以消除多余胚胎，并且表明当胚胎源自不同步排卵时，该机制失去效力。
