Many breeders are very serious when it comes to breeding their dogs. The hobby has proven to be a lucrative one. The process by which most breeders impregnate a female dog can vary from natural insemination to artificial insemination. Since there are so many variables with nature, many breeders choose to go the artificial route. Freezing dog sperm makes it possible for cross country insemination between two dogs that have never been in the same room, or for a female to become pregnant with pups sired by a male that has already passed.
Dog semen has a "use by" date. The best time to collect the semen is when the dog is between the ages of 18 months and 4 years. After 4 years, the probability of the dog having prostate disease increases, which results in poor quality semen. Older males can still be used, but a better quality sample can be expected from a younger, adult dog. If an older dog is used, it is advised to have an evaluation of the semen done first before committing to storing large amounts of semen.
After collection of the semen, a sample is looked at under a microscope to determine the mobility, concentration, and forward motion of the sperm. If the semen is declared poor quality, it will be determined what the cause is. If the sample meets the minimum requirements, the sperm portion of the ejaculate (dog semen consists of three parts: lubricant, sperm, prostatic fluid) is separated from the rest of the fluid and is mixed with an "extender." The extender contains egg yolk, antibiotics and chemicals to protect and nourish the sperm during the cooling, freezing and thawing process. Once mixed, the sperm is then cooled slowly over a few hours to 4ºC.
The cooled sperm is then loaded into straws and quickly frozen to -196ºC in liquid nitrogen. After freezing, a single straw is thawed. This is done to make sure that the sperm survived the freezing and thawing process. Using a microscope, the sperm is assessed on mobility and forward motion again immediately after thawing and again at 10 and 30 minutes. The number of straws frozen per collection varies from breed to breed, but an average of 5 to 10 straws is the norm. Once frozen, the semen can be stored indefinitely in liquid nitrogen.