Effects of glycerol concentration on the motility of equine spermatozoa after thawing

Abstract

The aim of this study was to evaluate the effect of different glycerol concentrations on stallion sperm motility after thawing. For statistical analysis 228 ejaculates were used. The semen was filtrated to remove gel fraction; macroscopic and microscopic evaluation was done. After evaluation the ejaculates were centrifuged, the supernatant was removed and the spermatozoa were re-suspended in French diluent with different concentrations of glycerol (2.0; 2.5; 4.0 and 6.0%). The choice of concentration of glycerol for a particular ejaculate was completely random. The spermatozoa were packed into 0.5 ml straws and placed for 2 h in a fridge (4 °C). Then the straws were placed in liquid nitrogen vapor (-80 to -100 °C) and after 10 min plunged into liquid nitrogen and stored at -196 °C for at least 48 h. The selected straws were individually thawed in a 38 °C water bath for 30 s prior to post-freezing analysis. Two progressive motilities using phase contrast microscopy (magnification × 400) were recorded: motility II immediately after thawing and motility III after 2 h incubation in a 38 °C water bath. The Spearmen/Kendall rang correlation test was selected to prove whether there is a correlation between the selected indices (glycerol concentration and motility II and motility III). Nonparametric multiple group analysis (Steel-Dwass test) was applied for finding the differences between groups. The Spearman/Kendall rang correlation proved a relationship between motility II and glycerol concentration. It can be stated that in this study the best glycerol concentration for freezing equine spermatozoa is with a concentration of 4.0% glycerol.