EVALUATION OF SPERM DAMAGE AND TECHNIQUES FOR SPERM CLEANUP

The cryopreservation of bull semen adversely affects the metabolism, m otility and membrane integrity of the spermatozoa, thereby decreasing the fertilizing ability of the processed sample. The present review co vers methods available for examining the functionality of bull spermat ozoa after thawing, including the use of fluorophores in combination w ith morphological examination. Procedures for clean-up, separation and selection of morphologically-normal, viable spermatozoa in vitro are also reviewed. Among the reviewed procedures are methods for dilution and washing and the selective fractionation of sperm subpopulations (e specially density-gradient centrifugation in silica-bead suspensions), as well as methods based on adherence to glass (differential filtrati on) and sperm self-migration (particularly swim-up through hyaluronic acid). Emphasis is placed on assessing the value of these techniques f or diagnostic purposes and for optimizing the methodology of in vitro fertilization.