Freezing equine semen: the effect of combinations of semen extenders and glycerol on post-thaw motility.

The research study investigated how different combinations of semen extenders and glycerol affect the post-thaw motility of frozen equine semen. It was found that the combination of the extender INRA 96 and 4% glycerol provided the highest sperm mobility after freezing and thawing.

Research Methods and Materials

• The researchers used a randomized 2 x 3 block design for the experiment.
• Semen were collected from four stallions, with a total of six collections per stallion.
• Two commercial semen extenders, namely dried skim-milk glucose extender (EZ Mixin Original Formula) and chemically defined, milk-free diluent (INRA 96), were used.
• Each of these extenders was combined with one of three concentrations of glycerol (2%, 3%, or 4%) in a standard commercial freezing medium.
• Sperm motility was assessed using microscopy both in fresh and post-thaw semen.

Results and Findings

• There was a significant difference in post-thaw sperm motility between the two extenders. INRA 96 provided a motility of 48.9% while EZ Mixin OF yielded 38.6%.
• The highest post-thaw motility was achieved when 4% glycerol was used in the freezing medium.
• Three out of the four stallions exhibited significantly improved post-thaw motility when INRA 96 was used, and two of the four stallions demonstrated higher motility with 4% glycerol.
• The combination of INRA 96 and 4% glycerol in the freezing medium resulted in the highest average post-thaw motility of 51.5%.

Conclusions

• The study concluded that INRA 96, when combined with 4% glycerol, provides the optimal conditions for post-thaw sperm motility in equine semen. This combination resulted in an average recovery of progressively motile sperm consistently above the desired 35%.