Canine epididymal spermatozoa: A hidden treasure with great potential.

The hidden treasure represented by epididymal spermatozoa has great potential in the current reproductive technologies in dogs. In case of azoospermia or when a donor male accidentally dies or undergoes orchiectomy, the retrieval of epididymal spermatozoa opens new possibilities to generate progeny. Spermatozoa can be collected by different techniques from ex vivo or in vivo testicles and can be cryopreserved for a future use. Freeze tolerance of canine epididymal spermatozoa seems lower than that of ejaculated spermatozoa; however, puppies were born after artificial insemination with frozen epididymal semen, other than with fresh and chilled. Even though several aspects need to be further investigated, advances have been recently made in the use of epididymal spermatozoa in assisted reproduction in dogs.