IDENTIFICATION OF CRYODAMAGE ON PLASMA MEMBRANE INTEGRITY IN BULL SPERMATOZOA AND ITS RELATIONSHIP WITH FIELD FERTILITY Identificación de daño criogénico sobre la integridad de la membrana plasmática del espermatozoide de toro y su relación con la fertilidad en campo

The aim of this study was to investigate the effect of cryopreservation on the membrane integrity (MI) in the bull sperm, and determine the relationship between intact cryopreserved sperm and field fertility (FF). The eosin nigrosin exclusion and the hypo-osmotic swelling test were combined in a single test (HOS-EN test) to identify the spermatozoa with four types of MI. After cryopreservation, there was a marked decline (21.3%) in the percentage of spermatozoa with head membrane intact/ tail membrane intact (Type IV MI), and a significant increase in those with head membrane damaged/ tail membrane damaged (Type I MI) (P<0.001), whereas type II MI (head membrane intact /tail membrane damage) and type III MI (head membrane damage/ tail membrane intact) ocurred sparingly. A significant correlation was observed between the percentage of Type IV MI and FF (r=0.49, P<0.014). Cryopreservation causes a important demage in the plasmatic membrane of the spermatozoa. Intact MI is closely related to FF.