Migration/sedimentation sperm selection method used in bovine in vitro fertilization: Comparison with washing/centrifugation

Sperm selection methods are usually considered for in vitro fertilization (IVF) programs. To achieve a population of viable, motile and morphologically normal spermatozoa, seminal plasma and contaminants must be removed. In this study 2 sperm selection methods were compared with regard to conventional parameters: 1) repeated washing/centrifugation, and 2) migration/sedimentation. Their effect on the fertilization of oocytes aspired from ovaries of slaughtered cows was determined. Frozen-thawed semen was used for all assays (n=8). The sperm concentration was adjusted to 1.0x10(6) cells/ml for in vitro insemination. Selected oocyte-cumulus complexes were matured in vitro for 24 h and were co-incubated with spermatozoa prepared by the 2 different methods. Presumptive zygotes were co-cultered in TCM-199. The percentage of motile, viable and morphologically normal spermatozoa was markedly higher (p<0.05) with the migration-sedimentation method. Triple stain showed that the integrity of the acrosome was significantly better maintained after migration/sedimentation (68.3%) than after washing/centrifugation (53.2%; p<0.05). In accordance with these results, a high fertilisation rate was achieved after application of the migration/sedimentation method (92.5 vs 69.1%; p<0.05). It is concluded, that this method is very promising for obtaining spermatozoa with optimal fertilization capacity.