Use of concanavalin A for coating the membranes of stallion spermatozoa

Semen from three ejaculates from each of 4 stallions was frozen in liquid nitrogen. Morphology was evaluated by coating the spermatozoa with fluorescein-labelled Concanavalin A (FITC-ConA2) and motility was measured by computer-assisted image analysis. Coating was performed at each step of the freezing procedure (dilution, cooling, addition of glycerol and freeze-thawing) and observations were made after each step, to evaluate changes, or after subsequent steps, to determine protection provided by the coating method. All the parameters showed progressive changes during the freezing procedure. Mean track speed of the spermatozoa, the proportions of normal and motile spermatozoa and lateral head displacement all decreased, whereas the proportions of spermatozoa exhibiting non-fluorescence in the equatorial segment and wrinkled acrosome membranes increased. The results demonstrated that coating stallion spermatozoa with ConA2 provides some degree of protection for acrosome membranes and it helps to preserve motility after freezing and subsequent thawing.