Ball B A
Department of Clinical Sciences, New York State College of Veterinary Medicine, Cornell University, Ithaca.
Vet Clin North Am Equine Pract. 1988 Aug;4(2):263-90. doi: 10.1016/s0749-0739(17)30641-7.
Fertilization rates were similar for normal and subfertile mares, and much of the difference in fertility between normal and subfertile mares was due to embryonic loss. Fertilization rate estimates for mares ranged from 71 to 96 per cent. The incidence of embryonic loss detected by ultrasonography between Days 11 and 50 was approximately 9 per cent for normal mares, and the estimated incidence of embryonic loss before Day 14 was also 9 per cent. Therefore, the estimated incidence of embryonic loss in normal mares between fertilization and Day 50 is approximately 18 per cent (Fig. 1). In subfertile mares, the corresponding estimate for embryonic loss between fertilization and Day 50 is 80 per cent, with most embryonic losses occurring before Day 14 in subfertile mares (Fig. 1). The high rate of early embryonic loss in subfertile mares could be related to embryonic defects, oviductal environment, or uterine environment. Oviductal embryos from subfertile mares were less viable than embryos from normal mares; therefore, embryonic defects were important in early embryonic losses in subfertile mares. These defects might be inherent within the embryo or might arise from the early oviductal environment. The uterine environment of subfertile mares was adequate to support normal embryos in early gestation; however, the relationship between the uterine environment and the increased metabolic demands of the conceptus in the late embryonic or early fetal periods requires further study. The uterine environment is also altered in mares with endometritis; therefore, endometritis may also be an important factor in embryonic loss in some mares. Uterine-induced luteolysis, as well as the effect of the pathogen or the resulting inflammation, may lead to embryonic loss. An increased susceptibility of some subfertile mares to endometritis could result in embryonic loss secondary to a postcoital endometritis that persists until the embryo reaches the uterus at Days 5 or 6 postovulation. Although progesterone is critical to embryonic survival, the cause-and-effect relationship between progesterone and spontaneous embryonic loss remains unclear. Reduced progesterone concentrations could be related to endometritis, failure of maternal pregnancy recognition, or luteal insufficiency. Progesterone supplementation may be indicated for some mares, but the value of exogenous progesterone for prevention of spontaneous embryonic loss has not been critically tested. A number of other factors have been associated with embryonic loss in mares.(ABSTRACT TRUNCATED AT 400 WORDS)
正常和亚生育能力母马的受精率相似，正常和亚生育能力母马在生育力上的差异很大程度上是由于胚胎丢失。母马的受精率估计在71%至96%之间。通过超声检查在第11天至50天期间检测到的正常母马胚胎丢失发生率约为9%，在第14天之前估计的胚胎丢失发生率也是9%。因此，正常母马在受精至第50天期间估计的胚胎丢失发生率约为18%（图1）。在亚生育能力母马中，受精至第50天期间胚胎丢失的相应估计发生率为80%，亚生育能力母马的大多数胚胎丢失发生在第14天之前（图1）。亚生育能力母马早期胚胎丢失率高可能与胚胎缺陷、输卵管环境或子宫环境有关。亚生育能力母马的输卵管胚胎比正常母马的胚胎活力更低；因此，胚胎缺陷在亚生育能力母马早期胚胎丢失中很重要。这些缺陷可能是胚胎固有的，也可能源于早期输卵管环境。亚生育能力母马的子宫环境在妊娠早期足以支持正常胚胎；然而，子宫环境与胚胎后期或胎儿早期胎儿代谢需求增加之间的关系需要进一步研究。患有子宫内膜炎的母马子宫环境也会改变；因此，子宫内膜炎在某些母马的胚胎丢失中也可能是一个重要因素。子宫诱导的黄体溶解以及病原体或由此产生的炎症的影响可能导致胚胎丢失。一些亚生育能力母马对子宫内膜炎易感性增加可能导致性交后子宫内膜炎继发胚胎丢失，这种炎症一直持续到排卵后第5或6天胚胎到达子宫。虽然孕酮对胚胎存活至关重要，但孕酮与自发性胚胎丢失之间的因果关系仍不清楚。孕酮浓度降低可能与子宫内膜炎、母体妊娠识别失败或黄体功能不全有关。对于一些母马可能需要补充孕酮，但外源性孕酮预防自发性胚胎丢失的价值尚未经过严格测试。许多其他因素也与母马的胚胎丢失有关。（摘要截取自400字）
