Characteristics of Bovine Spermatozoa after Immobilization by Dehydration

Abstract

Extension of storage time of living animal spermatozoa is of great scientific and economical interest for the breeding industry in Norway. The extension of storage time will leave room to maneuver due to the time limit of artificial insemination of the animals. The aim of this study was to dehydrate semen in order to immobilize the spermatozoa, due to the fact that removal of water molecules leads to higher concentrations of cells and thus might contribute to the physical limitation of motility. Water was removed from diluted semen by air drying in a convection oven at approximately 33°C. The drying process was continued until there were less than 5% motile spermatozoa. The amount of total solids in the samples increased from approximately 14 to 35% during drying. After immobilization, experiments showed that with specific rehydration temperature (20°C), rehydration medium (skim milk diluents or Beltsville thawing solution), and rehydration rate, the spermatozoa recovered so that up to 70% motility was reestablished. At the female reproductive organ temperature, motile bull spermatozoa, that was dried and rehydrated, was observed for up to 50% longer periods of time compared to the reference sample. Membrane destruction caused by drying and/or rehydration of the spermatozoa was detected using plasma membrane integrity. The histograms of reference spermatozoa showed two limited populations, one living and one dead. For the dried and rehydrated samples a third population seemed to emerge. It is presumed that the cell membranes of these spermatozoa might be injured. It has been demonstrated that spermatozoa immobilized by drying and subsequent rehydration before insemination can cause fertilization and normal embryonic development in cattle.