The aim of the present study was to determine the most suitable embryonic stage and embryo freezing technique for commercial implementation of frozen embryo trading by small-scale sheep producers. There was a 2 × 2 factorial design utilized for conducting the study consisting of two embryo stages (2-8 cells or morula/blastocyst) and two cryopreservation protocols (vitrification or slow-freezing). For the in vivo produced embryos, there were treatments of crossbred donor ewes to induce superovulation. Embryos were recovered surgically on either Day 2 or 5.5 after estrous onset. The embryos were cryopreserved using either a vitrification or slow-freezing method before there was transfer to recipients. Ovarian response, embryo survival and lambing outcomes were analyzed. There were no differences in number of recovered and fertilized embryos at the two embryonic developmental stages. There were no effects of embryonic stages and cryopreservation methods on pregnancy rate, twinning rate, fetal birth weights and lamb weight at 1 month of age. When there was use of vitrified embryos for transfers, there was a greater lamb weight at 2 months of age (8.38 ± 0.20 compared with 7.78 ± 0.21 kg; P =  0.044) than when there was transfer of embryos cryopreserved using slow freezing procedures. Considering economic and practical benefits to small-scale sheep farms, morula/blastocyst stage-embryo collection and transfer into the uterus is more efficacious than transferring 2-8 cells embryos into the oviduct. Results of this study may contribute to the genetic improvement in the flocks of small-scale sheep producers.

中文翻译：

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转移玻璃化和慢速冷冻胚胎后的农场产羔结果。

本研究的目的是确定最合适的胚胎阶段和胚胎冷冻技术，以供小规模绵羊生产者商业实施冷冻胚胎交易。有2×2析因设计用于进行研究，包括两个胚胎阶段（2-8个细胞或桑ula /胚泡）和两个冷冻保存方案（玻璃化或缓慢冷冻）。对于体内产生的胚胎，有处理杂交供体母羊以诱导超排卵的方法。发情后第2天或5.5天通过手术恢复胚胎。在将胚胎转移给受体之前，先用玻璃化法或慢速冷冻法将其冷冻保存。分析了卵巢反应，胚胎存活和产羔结果。在两个胚胎发育阶段，回收和受精的胚胎数量没有差异。胚胎期和冷冻保存方法对1个月大的妊娠率，孪生率，胎儿出生体重和羔羊体重没有影响。当使用玻璃化的胚胎进行移植时，与使用慢速冷冻程序冷冻保存的胚胎进行移植相比，在2个月大时的羔羊体重更大（8.38±0.20，而7.78±0.21 kg； P = 0.044）。考虑到小型绵羊养殖场的经济和实际利益，桑ula /胚泡阶段胚胎的收集和转移到子宫比将2-8个细胞的胚胎转移到输卵管更有效。这项研究的结果可能有助于小型绵羊生产者群体的遗传改良。