Evidence for retrograde flow of spermatozoa into the urinary bladder of bulls during electroejaculation.

Spermatozoa were not found in the urine collected from 12 bulls before electroejaculation, whereas spermatozoa were found in the urine collected after electroejaculation. The concentration of spermatozoa in four consecutive samples of urine collected during the first postelectroejaculation micturition did not differ (P > 0.80) within bulls, suggesting that the spermatozoa found in the urine were those that had flowed into the urinary bladder during electroejaculation. The mean percentage of retrograde flow was 21% and ranged from 1 to 50% for the 12 bulls. These findings demonstrate that there was a significant urinary loss of spermatozoa during electroejaculation.