The effects of urine concentration, and cushion centrifugation to remove urine, on the quality of cool-stored stallion sperm

Urine-contaminated stallion semen is a clinical problem due to a variety of causes. The effect of the level of urine contamination on the longevity of sperm quality has not been evaluated. The aim of this study was to determine the effects of urine concentration level (0%, 10%, 20%, 30%, and 40%) and cushioned centrifugation and resuspension of the sperm pellet in fresh extender, on measures of sperm quality, immediately after semen collection (T0), after 1 hour of storage at room temperature (T1), and after 24 hours of cooled storage (T24). In general, most sperm quality measures declined with increasing urine concentration starting at T0. Cushioned centrifugation (CC), but not simple dilution, generally maintained sperm quality at T24 as compared with T1. At T24, total sperm motility was higher in all urine-contaminated CC samples compared with uncentrifuged samples (P < 0.05); sperm viability was lower in CC than uncentrifuged at a urine concentration of 20%, but higher at 30% and 40% (P < 0.05); and DNA quality was decreased (higher % cells outside the main population) in all urine concentrations (P < 0.05). Immediate extension in semen extender, followed by cushioned centrifugation and resuspension of the sperm pellet in fresh extender, provided the best option for preserving sperm quality of urospermic semen.