Effect of urine contamination on semen quality variables in Eurasian perch Perca fluviatilis L.

The objectives of the present study were to determine values for semen quality variables in the Eurasian perch (i.e., osmolality of seminal plasma as well as sperm motility characteristics analyzed with CASA system) in response to (1) the method of milt collection (stripping or catheterization) and (2) experimental contamination of catheterized semen with urine (0%, 5%, 10%, 20%, 30% and 50% of contamination). Additionally, the effect of short-term chilled storage of experimentally contaminated semen (during the 24 h post semen collection period) on motility characteristics was investigated. Use of a typical stripping procedure resulted in about 5%-10% contamination of semen with urine, what is much less compared with other species. Markedly lesser values of straight line velocity (VSL) and consequently less linearity of spermatozoa movement (LIN) in perch semen, however, occurred as a result of stripping (46 ± 4 μm/s and 38 ± 4% for VSL and LIN, respectively), when compared to sperm collected by catheterization (87 ± 5 μm/s and 77 ± 2% for VSL and LIN, respectively), indicate that even a 10% contamination of semen with urine may have negative effects on quality. Exposure of semen to urine resulted in a significant dose-dependent decrease in the percentage of motile spermatozoa (MOT) and both velocity variables (VSL and VCL). Amount of urine contamination also affected MOT, VCL, VSL and LIN value during short-term storage. In conclusion, it is important to avoid semen contamination by urine when using the stripping procedure in the Eurasian perch, either for controlled reproduction or sperm preservation.