Freezing of Boar Spermatozoa: Fertilizing Capacity with Concentrated Semen and a New Thawing Procedure

Two hours after semen collection, aliquots containing 6×109 spermatozoa were centrifuged for 10 min at 300 g. The seminal plasma was removed and the spermatozoa were resuspended to 5 ml with Beltsville F5 (BF5) extender. The semen was cooled gradually to 5 C over a 2-hr period, 5 ml of BF5 containing 2% glycerol was added and the semen was mixed and frozen immediately into pellets of 0.15 to 0.2 ml on Dry Ice. The pellets were transferred to liquid nitrogen for storage. For each insemination 10 ml of pellets were removed from liquid nitrogen, dumped into an empty styrofoam shipping container and held for 3 minutes. The pellets were then dumped into a 250-ml beaker containing 25 ml of Beltsville thawing solution (BTS) at 50 C and were swirled in the beaker until thawed. The thawed semen was poured into an insemination bottle, the beaker was rinsed with 15 ml BTS and the rinse solution was added to the insemination bottle.