Effect of centrifugation and partial removal of seminal plasma on equine spermatozoal motility after cooling and storage

The objective of this study was to determine if centrifugation and partial removal of seminal plasma would improve spermatozoal motility in semen from stallions whose whole ejaculates have poor tolerance to cooling and storage. Stallions were divided into two groups (n = 5/group) based on the ability of their extended semen to maintain spermatozoal motility after cooling and storage. Group 1 stallions ("good coolers") produced semen in which progressive spermatozoal motility after 24 h of cooling and storage was reduced by less than or equal to 30% of progressive motility prior to storage. Group 2 stallions ("poor coolers") produced semen in which progressive spermatozoal motility after 24 h of cooling and storage was reduced by greater than or equal to 40% of progressive motility prior to storage. The sperm-rich portion of each ejaculate was divided into 4 aliquots. Two aliquots underwent standard processing for cooled transported semen and were examined after 24 and 48 h of cooling and storage in an Equitainer(TM). The remaining two aliquots were diluted 1:1 with semen extender, then centrifuged at 400 x g for 12 min at room temperature. After centrifugation, similar to 90% of the seminal plasma was removed, and the sperm pellet was resuspended in extender to a final concentration of 25 to 50 x 10(6) sperm/mL. These aliquots were then packaged as for the non-centrifuged aliquots and examined after 24 and 48 h of storage. The spermatozoal motion characteristics in fresh semen and after 24 and 48 h of cooling and storage was determined via computer-assisted semen analysis. Centrifugation and partial removal of seminal plasma increased the percentage of progressively motile spermatozoa and limited the reduction in progressive spermatozoal motility of "poor cooling" stallions after 48 h of cooling and storage. Results of this study indicate that centrifugation and partial removal of seminal plasma is beneficial for stallions whose ejaculates have poor tolerance to cooling and storage with routine semen dilution and packaging techniques, especially if the semen is stored for >24 h. (C) 2000 by Elsevier Science Inc.