Alternative Opportunities to Collect Semen and Sperm Cells for Ex Situ In Vitro Gene Conservation in Sheep

Abstract

The semen of domestic mammals is conventionally collected with an artificial vagina (AV) for artificial insemination (AI) or for short- or long-term storage. However, the procedure has certain drawbacks: animal training is not feasible in extensive animal care systems nor among wild species, as the trained animals sometimes fail to mount. Hence, there is a need for alternative semen collection methods. Electroejaculation (EEJ) and epididymal sperm recovery (ESR) are the two effective alternatives to AV. However, in recent years, animal welfare campaigners have called for the ban, in certain EU countries, of EEJ due to its inhumane nature. In this review, alternative methods of sperm collection (by EEJ and ESR, their qualities, and their freezing techniques) are highlighted, as well as the effects of EEJ on pre-freeze and post-thaw ram sperm quality parameters and the animal welfare progress made in EEJ between the 20th and 21st centuries. Additionally, the techniques for enhancing post-thaw sperm quality prior to freezing and for the freezing of EEJ and ESR spermatozoa are explored. ESR and EEJ are reliable alternatives to AV on certain occasions. EEJ is ideal for semen collection in wild or untrained animals, breeding soundness examinations, collection outside of the breeding season, and culling. At the same time, ESR is ideal in cases of castration, accidental death of elite sire, or postmortem for gene conservation purposes or assisted reproductive technologies (ARTs) studies.