Motility activation of rainbow trout spermatozoa at pH 6.5 is directly related to contamination of milt with urine

Semen samples (collected using a catheter, n = 5) were experimentally contaminated with urine (10 – 30%) and incubated for 2 and 4 h. The percentage of sperm motility was measured at pH 6.5 and in D532 solution (pH 9.0). Contamination of rainbow trout milt with urine led to dose-dependent decrease in seminal plasma osmolality, from 301 ± 3 to 203 ± 2 mOsm/kg, for 0 and 30% contamination, respectively. Contamination with urine significantly reduced the ability of rainbow trout spermatozoa to be activated at pH 6.5 after 2 and 4 h of incubation. On the other hand, no changes of motility in pH 9.0 saline were observed at the same time. Our results suggest, that the ability of spermatozoa to activate motility at pH 6.5 can reflect sub-lethal changes of rainbow trout spermatozoa after urine contamination.