Immunoreactive relaxin in seminal plasma of fertile boars and its correlation with sperm motility characteristics determined by computer-assisted digital image analysis

Ejaculates from 10 mature fertile large white Yorkshire boars were used to examine the correlation between immunoreactive relaxin levels in seminal pl asma and sperm motility characteristics. Seminal plasma levels of immunorea ctive relaxin were measured by a time-resolved fluoroimmunoassay (TR-FIA). Motility characteristics were assessed using a CellSoft computer-assisted d igital image analysis system. The mean +/- SD level of immunoreactive relax in in seminal plasma was 2.61 +/- 0.62 ng/mL. When the correlation between seminal plasma levels of immunoreactive relaxin and parameters of sperm mov ement was examined, it was found that relaxin levels were significantly cor related with the percentage of motile spermatozoa (r = 0.687, p < 0.05), cu rvilinear velocity (r = 0.745, p < 0.05), straight line velocity (r = 0.651 , p < 0.05), mean amplitude of lateral head displacement (mean ALH) (r = 0. 844, p < 0.01) and the maximum amplitude of lateral head displacement (max ALH) (r = 0.830, p < 0.01), but not with linearity, beat-cross frequency, o r percentage of circular cells. Among these parameters, seminal plasma leve ls of immunoreactive relaxin showed the strongest correlation with the ALH parameter related to fertilizing ability. These results indicate that immun oreactive relaxin in boar semen may be necessary not only for normal sperm motility but also for normal fertility, suggesting that determination of th e profile of immunoreactive relaxin in ejaculates may have value as a poten tial marker for predicting sperm fertilizing ability of boars.