Influencia de la selección espermática y el método de criopreservación sobre la criosupervivencia de espermatozoides epididimarios bovinos

Abstract

Bovine epididymal sperm cryopreservation protocols allow preserving the germplasm of valuable animals’ postmortem. This study aimed to evaluate the sperm selection and freezing method on the quality of bovine epididymal spermatozoa after cryopreservation. Fifteen pools (2 epididymides per pool) were used to recover sperm samples by retrograde washing, which were divided into two aliquots for cryopreservation by conventional slow freezing (SF) and ultra-rapid freezing (UF). Half of each aliquot was subjected to selection prior cryopreservation by density gradient centrifugation (200 µL of 40% and 80% Percoll). SF was performed by diluting the samples in TCG+EY+GLY medium (tris, citric acid, glucose + 6 % egg yolk + 5 % glycerol), while UF was performed by diluting in TCG+YH+Sucrose (100 mM). The results indicated that the freezing method and sperm selection affected (P<0.05) most of the kinetic and plasma membrane integrity parameters. Total and progressive motility, average and rectilinear velocity increased in post-freeze/thaw selected samples in both SF and UF(P<0.05). In addition, the proportion of spermatozoa with intact plasma and acrosomal membranes was significantly greater in samples selected and cryopreserved with both freezing methods (P<0.05). Neither head dimensions nor sperm DNA integrity were affected in either treatment (P>0.05). These results show that sperm selection before cryopreservation was effective for conventionally cryopreserved bovine epididymal spermatozoa.