Current and Emerging Advanced Techniques for Breeding Donkeys and Mules

Donkeys and mules have historically played an important role in agriculture and are now gaining recognition for their contributions to animal conservation, milk production, tourism, and equid-assisted services. However, their distinctive reproductive challenges pose obstacles to breeding management. As a result, the application of assisted reproductive technologies (ARTs) could help address these challenges, enhancing their roles in both traditional and emerging industries. This review examines the current and emerging in vitro techniques for breeding donkeys and mules. Key methodologies such as sperm cryopreservation, innovative sperm preservation technologies, embryo transfer, ovum pick-up (OPU), oocyte maturation, and vitrification are discussed, emphasizing their importance in optimizing ARTs. Advances in in vitro embryo production technologies such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and somatic cell nuclear transfer (SCNT) are reviewed, with particular attention to its success in producing the first donkey and mule blastocysts or foals. Despite significant progress in the last decade, standardization of protocols for gamete conservation and embryo transfer are still required in long-ear equids. Advancing these technologies in combination with established in vitro embryo production could significantly improve reproductive outcomes and enhance the genetic management of donkey and mule populations.