An update of artificial insemination with fresh, chilled, and frozen semen.

Two major limitations have been identified in semen extender technology in the dog; the longevity of canine sperm cells is greatly decreased by cooling or freezing, and the anatomy of the canine cervix acts as a barrier to intrauterine deposition of semen via a vaginal insemination. Currently, the ability to predict ovulation time indirectly by measuring serum progesterone levels has increased the success rate using both chilled and frozen canine semen. The American Kennel Club now routinely registers litters produced with both of these methods, and will allow foreign semen from recognized kennel clubs to be imported for domestic use.