For the preparation of embryo transfer recipients, surgically vasectomized mice are commonly used, generated by procedures associated with pain and discomfort. Sterile transgenic strains provide a nonsurgical replacement, but their maintenance requires breeding and genotyping procedures. We have previously reported the use of naturally sterile STUSB6F1 hybrids for the production of embryo transfer recipients and found the behavior of these recipients to be indistinguishable from those generated by vasectomized males. The method provides two substantial 3R impacts: refinement (when compared with surgical vasectomy) and reduction in breeding procedures (compared with sterile transgenic lines). Despite initial promise, the 3Rs impact of this innovation was limited by difficulties in breeding the parental STUS/Fore strain, which precluded the wider distribution of the sterile hybrid. The value of a 3R initiative is only as good as the uptake in the community. Here we, thus, select a different naturally sterile hybrid, generated from strains that are widely available: the B6SPRTF1 hybrid between C57BL/6J and Mus spretus. We first confirmed its sterility by sperm counting and testes weight and then trialed the recovery of cryopreserved embryos and germplasm within three UK facilities. Distribution of sperm for the generation of these hybrids by in vitro fertilization was found to be the most robust distribution method and avoided the need to maintain a live M. spretus colony. We then tested the suitability of B6SPRTF1 sterile hybrids for the generation of embryo transfer recipients at these same three UK facilities and found the hybrids to be suitable when compared with surgical vasectomized mice and a sterile transgenic strain. In conclusion, the potential 3Rs impact of this method was confirmed by the ease of distribution and the utility of sterile B6SPRTF1 hybrids at independent production facilities.

为了准备胚胎移植受体，通常使用通过手术切除输精管的小鼠，这些小鼠是通过与疼痛和不适相关的程序产生的。无菌转基因菌株提供了一种非手术替代品，但其维持需要育种和基因分型程序。我们之前曾报道过使用自然不育的 STUSB6F1 杂交体来生产胚胎移植受者，并发现这些受者的行为与输精管切除的雄性受者产生的行为没有区别。该方法提供了两个实质性的 3R 影响：改进（与手术输精管切除术相比）和减少育种程序（与无菌转基因品系相比）。尽管最初有希望，但这项创新的 3R 影响受到亲本 STUS/Fore 品系育种困难的限制，这阻碍了不育杂交种的更广泛分布。 3R 计划的价值取决于社区的接受程度。因此，在这里，我们选择了一种不同的自然不育杂交种，该杂交种是从广泛可用的菌株中产生的：C57BL/6J 和Mus spretus之间的 B6SPRTF1 杂交种。我们首先通过精子计数和睾丸重量确认其不育，然后在英国的三个设施中尝试回收冷冻胚胎和种质。通过体外受精分配精子来产生这些杂种被发现是最稳健的分配方法，并且避免了维持活的M. spretus群体的需要。然后，我们在这三个英国设施中测试了 B6SPRTF1 不育杂交体对于产生胚胎移植受体的适用性，并发现与手术输精管切除小鼠和不育转基因品系相比，该杂交体更适合。 总之，该方法的潜在 3R 影响通过独立生产设施中无菌 B6SPRTF1 杂交体的易于分发和实用性得到了证实。