Colloidal Centrifugation for Dog Sperm Selection Prior Cryopreservation with Glycerol.

Background: Dog ejaculates are produced in three fractions: the first and third fractions contain prostatic fluid, which is harmful for cryopreservation. The second fraction is spermatozoa-rich. Collecting the second fraction of the ejaculate is complex; hence, colloidal centrifugation plus the addition of glycerol at three different concentrations (4, 6, and 8%) as cryoprotectant was evaluated as a method for sperm selection. Methods: In this study, 72 seminal samples from 6 crossbred dogs were evaluated at the University of Cuenca-Ecuador. Two aliquots were made from each sample, one for conventional centrifugation (Group 1), the other for colloidal centrifugation (Group 2). After centrifugation, each aliquot was subdivided into three parts, and 4, 6, and 8% glycerol were added, respectively. Three sperm evaluations were made (initial, pre-thawing, and post-thawing). Results: Sperm concentration was similar between the initial sample (IS) and Group 1 (P>0.05) after centrifugation, whereas fewer spermatozoa where observed in Group 2 (P <0.05). Evaluation of pre-thawing individual progressive motility (IPM) revealed that the spermatozoa in Group 1 underwent a 30% motility reduction in comparison to the IS and Group 2. Post-thawing IPM within the groups with different concentrations of glycerol (4, 6, and 8%) which underwent previous centrifugation with Percoll (Group 2), showed statistical differences (P <0.05). However, the HOS test produced similar percentages. Conclusions: Colloidal centrifugation prior freezing ensures better sperm selection and purification.