Sperm selection by a climbing-over-a-wall IVF method reduces the incidence of polyspermic penetration of porcine oocytes

摘要

Effect of sperm selection according to the degree of motility after insemination on in-vitro penetration was examined by using a new in-vitro fertilization system designated as a climbing-over-a-wall (COW) IVF method. When the sperm penetration ratein the COW-IVF method was compared with a standard method at the same sperm concentration (5 X 10~5 cells/ml), the rates (95.1 +- 1.9 and 98.2 +- 1.0 percent, respectively) were similar, but the incidence of monospermic penetration was higher in the COW-IVF (25.5 +- 4.5 percent) than the standard method (10.4 +- 2.5 percent). When sperm concentration was changed from 0.5 X 10~5 to 10 X 10~5 cells/ml in the COW-IVF method, sperm penetration rate was higher at a higher concentration, whereas monospermicpenetration rate was increased at a lower concentration. The proportion of monospermic oocytes in matured oocytes was similar among sperm concentrations, 0.5 X 10~5 to 5 X 10~5 cells/ml, at fertilization in the COW method. These results demonstrate thattheCOW-IVF method, selection according to the degree of sperm motility after insemination, can increase the normal penetration of frozen-thawed boar spermatozoa into IVM oocytes without any reduction in the sperm penetration rate.