Until now, there have been no reports of foals born through embryo transfer after artificial insemination using frozen semen in Japan. The aims of this study were to develop a riding crossbred horse and evaluate the prospects of embryo transfer technology in multiplying horse population. In both donor and recipient mares, luteolysis was induced by the administration of 0.1 mg Cloprostenol to synchronize the onset of estrus, and ovulation was induced by administering 2000 IU human chorionic gonadotropin (hCG) or 0.75 mg Deslorelin. Frozen semen from an Irish Connemara pony stallion was used to breed a Hokkaido native pony mare by deep-horn artificial insemination (dose, 400 × 106 sperm). A non-surgical technique was used to collect embryos from the donor mare at day 7 post-ovulation and transfer them transcervically into the uterus of recipient mares (n = 4) immediately after collection. Weekly blood samples were collected from the recipients throughout pregnancy. A total of four embryos were recovered from seven collection attempts (57% recovery) from a donor mare in a single breeding season. Three of the four transferred embryos maintained successful pregnancy and delivered a healthy live foal (75% birth). A normal progesterone profile was observed throughout gestation in recipient mares. In conclusion, for the first time, to the best of our knowledge, this study describes the birth of foals through non-surgical transcervical embryo transfer in Japan after artificial insemination using frozen semen. We expect that this new crossbreed (Connemara pony × Hokkaido native pony) will be a good riding breed.

中文翻译：

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在日本使用冷冻精液人工授精后通过胚胎移植诞生第一批小马驹

迄今为止，在日本还没有使用冷冻精液人工授精后通过胚胎移植出生的小马驹的报道。本研究的目的是开发一匹骑术杂交马，并评估胚胎移植技术在马群繁殖中的前景。在供体和受体母马中，通过施用 0.1 毫克氯前列醇以同步发情，诱导黄体溶解，通过施用 2000 IU 人绒毛膜促性腺激素 (hCG) 或 0.75 毫克地洛瑞林诱导排卵。来自爱尔兰康尼马拉小马种马的冷冻精液通过深角人工授精（剂量，400 × 106 精子）用于繁殖北海道本地小马母马。使用非手术技术在排卵后第 7 天从供体母马收集胚胎，并在收集后立即将它们经宫颈转移到受体母马 (n = 4) 的子宫中。在整个怀孕期间每周从接受者收集血液样本。在一个繁殖季节，从一匹供体母马的七次收集尝试中总共回收了四个胚胎（回收率为 57%）。四个移植的胚胎中的三个保持成功怀孕并产下了健康的活马驹（75% 出生）。在受体母马的整个妊娠期间观察到正常的孕酮谱。总之，据我们所知，这项研究首次描述了在日本使用冷冻精液人工授精后通过非手术经宫颈胚胎移植出生的小马驹。