Motility of Fresh and Frozen-Thawed Stallion Sperm from Three Segments of the Epididymal Cauda and the Effect of Post-Thaw Seminal Plasma Addition on Motility

Preservation of epididymal spermatozoa is an advantageous method to preserve genetic material of endangered species or valuable breeding animals after sudden death and injuries. Despite lower pregnancy rates, fertilization with epididymal sperm has been proven successful. Variable sperm quality after cryopreservation among individual stallions and the usually terminal chance to preserve epididymal sperm are opportunities for the development of a freezing procedure suitable for the majority of stallions. To evaluate the effect of the preservation procedure, we analyzed the sperm motion characteristics after every step of processing. In addition, we investigated the influence of seminal plasma on motility of frozen-thawed semen. We compared three segments of the cauda epididymidis and harvested spermatozoa by retrograde flushing (most caudal part) and mincing (more cranial segments) to augment the number of spermatozoa. During processing, there were differences in sperm motion characteristics depending on the segment of the cauda epididymidis. Distinct increases in motility due to different extenders and the effect of seminal plasma suggest that motion characteristics of raw and frozen-thawed spermatozoa are strongly influenced by microenvironment and must be interpreted with caution.