Department of Pathology, Reproduction and One Health, School of Agricultural and Veterinarian Sciences, São Paulo State University, Via de acesso Prof. Paulo Donato Castellane, s/n, CEP 14884-900 Jaboticabal, SP, Brazil.
Department of Veterinary Medicine, Federal University of Viçosa, Av. Peter Henry Rolfs, s/n, CEP 36570-000 Viçosa, MG, Brazil.
Reprod Biol. 2024 Sep;24(3):100920. doi: 10.1016/j.repbio.2024.100920. Epub 2024 Jul 5.
At present, the success of non-surgical embryo recovery (NSER) and transfer (NSET) hinges upon the cervical passage of catheters, but penetration of the uterine cervix in ewes is problematic due to its anatomical structure (i.e., long and narrow cervical lumen with misaligned folds and rings). It is a major obstacle limiting the widespread application of NSER and NSET in sheep. While initial attempts to traverse the uterine cervix focused on adapting or re-designing insemination catheters, more recent studies demonstrated that cervical relaxation protocols were instrumental for transcervical penetration in the ewe. An application of such protocols more than tripled cervical penetration rates (currently at 90-95 %) in sheep of different breeds (e.g., Dorper, Lacaune, Santa Inês, crossbred, and indigenous Brazilian breeds) and ages/parity. There is now sufficient evidence to suggest that even repeatedly performed cervical passages do not adversely affect overall health and reproductive function of ewes. Despite these improvements, appropriate selection of donors and recipients remains one of the most important requirements for maintaining high success rates of NSER and NSET, respectively. Non-surgical ovine embryo recovery has gradually become a commercially viable method as even though the procedure still cannot be performed by untrained individuals, it is inexpensive, yields satisfactory results, and complies with current public expectations of animal welfare standards. This article reviews critical morphophysiological aspects of transcervical embryo flushing and transfer, and the prospect of both techniques to replace surgical methods for multiple ovulation and embryo transfer (MOET) programs in sheep. We have also discussed some potential pharmacological and technical developments in the field of non-invasive embryo recovery and deposition.
目前，非手术胚胎回收（NSER）和移植（NSET）的成功取决于导管通过宫颈，但由于绵羊的宫颈解剖结构（即长而狭窄的宫颈管，褶皱和环错位），其宫颈穿透存在问题。这是限制 NSER 和 NSET 在绵羊中广泛应用的主要障碍。虽然最初尝试穿过子宫颈的方法侧重于适应或重新设计授精导管，但最近的研究表明，宫颈松弛方案对于绵羊的经宫颈穿透至关重要。在不同品种（例如多伯羊、拉卡努羊、圣塔因尼斯羊、杂交羊和巴西本土品种）和不同年龄/配种的绵羊中，应用这些方案使宫颈穿透率增加了两倍以上（目前为 90-95%）。现在有足够的证据表明，即使反复进行宫颈通道也不会对绵羊的整体健康和生殖功能产生不利影响。尽管有这些改进，但适当选择供体和受体仍然是维持 NSER 和 NSET 高成功率的最重要要求之一。非手术绵羊胚胎回收已逐渐成为一种商业上可行的方法，尽管该程序仍不能由未经培训的人员进行，但它成本低廉，效果令人满意，并且符合当前公众对动物福利标准的期望。本文回顾了经宫颈胚胎冲洗和移植的关键形态生理学方面，以及这两种技术在绵羊中替代多排卵和胚胎移植（MOET）程序的手术方法的前景。我们还讨论了非侵入性胚胎回收和沉积领域的一些潜在药理学和技术发展。
