Sperm quality and selected biochemical markers of seminal plasma at the beginning of the reproductive period of common carp, Cyprinus carpio L.

Changes in semen quality and selected biochemical markers were analyzed during a week of spawning season of common carp Cyprinus carpio L. Semen was obtained twice, on May 30 and on June 7, and each time it was collected 24 h after hormonal stimulation using Ovopel [(d-Ala⁶, Pro⁹ NEt)-mGnRH + metoclopramide] in 1 pellet kg^?1. The total volume of semen (ml), volume of semen per kg of body weight (ml kg^?1 b.w.), sperm concentration (×10⁹ ml^?1), total number of sperm per kg of body weight (×10⁹ kg^?1 b.w.), pH of semen, pH of seminal plasma, seminal plasma osmotic pressure (mOsm kg^?1) and the total protein content in seminal plasma (mg ml^?1) were determined. A 10 mM Tris buffer containing 100 mM NaCl with 0.5 % BSA (pH 9.0, osmolality 200 mOsm kg^?1) was used to activate sperm. The following computer-assisted sperm analysis (CASA) parameters were determined: percentage of motile sperm (MOT, %), progressively motile sperm (PRG, %), curvilinear velocity (VCL, μm s^?1), straight-line velocity (VSL, μm s^?1), movement linearity (LIN, %), wobbling index (WOB, %), amplitude of lateral head displacement (ALH, μm) and beat cross-frequency (BCF, Hz). The volume of semen per kg of BW, total number of sperm per kg of BW and semen pH were significantly lower at the second semen sampling compared to the first semen sampling. Volume of semen at the second sampling correlated positively with CASA parameters. A lack of differences among CASA parameters between both collection periods indicates good quality of carp sperm hormonally stimulated with Ovopel twice at a 1-week interval.