Motility parameters assessment of bovine frozen semen by biospeckle laser (BSL) system

Motility evaluation is a necessary step in semen analysis by artificial insemination centres, once it can be related to sperm fertility; a widespread method to evaluate spermatozoa progressive movement and velocity is light microscopy (LM). Limitations of the routine methods unfolded new approaches of evaluations mainly in optical branches. The incidence of laser light on specimens exhibiting biological activity generates an interference image named biospeckle which has been used to investigate biological activity such as in plants, animals and human beings. The aim of this work was to evaluate frozen semen kinetics of bovine species, comparing LM with biospeckle analysis. Thirty straws were thawed and semen was illuminated by He-Ne laser just after LM evaluation. Biospeckle images were processed using a second order statistical approach obtaining a summary value named inertial moment (IM). Data were statistically analyzed using Spearman correlation and box plots. IM approach was correlated (r = 0.904) to sperm cell velocity (p < 0.0001). In addition, percent sperm cell motility and mobile sperm cell concentration presented positive correlation (r = 0.977; r = 0.815; respectively, p < 0.0001), evidencing coherence between semen activity features and IM values. Sperm cell concentration did not influenced IM values (r = 0.262; p > 0.05). These data indicate that biospeckle laser system should be considered a reliable tool for semen motility assessment contributing as an alternative method to sperm cell fertility investigation.