Benefits of Frozen Semen
Frozen canine semen has gained in acceptance and demand since the American Kennel Club first recognized a litter conceived from frozen semen in 1981. The advantages to a breeding program using frozen semen are numerous. The most obvious benefit is long-term storage of a superior stud dog's genetic material. Researchers estimate that frozen semen could potentially remain viable for 10,000 years. Thus, frozen semen can bridge not only long distance breedings, international breedings, but also bridge the span of time. The preservation of select gene pools can help improve individual breeds and help eliminate problems that could develop within a breed.
Semen Longevity Factors
Breedings can be performed using three types of canine semen: fresh, fresh-chilled, and frozen. Fresh canine semen has the longest viable period and has been reported to live in the bitch's reproductive tract from 5 to 7 days.
Fresh chilled semen is a great alternative when the male bully is in a different location than the female and one does not wish to ship the female or travel great distances. The semen is collected at one location, mixed with a semen extender, and cooled down to 40'F. This process conserves the sperm's energy enough that it can be shipped overnight and artificially inseminated into the female. After warming back up to body temperature, fresh chilled sperm lives about 24 to 72 hours (we have seen longer).
Frozen semen uses liquid nitrogen to take the semen to the extreme temperature of -322'F. The semen is collected and analyzed for concentration and total numbers, morphology (normal structure), and motility. At CSBC the semen is preserved in precise units called "pellets". The pellets are then carefully labeled and stored in liquid nitrogen containers. After thawing, the sperm has a much shortened lifespan of only 12-24 hours, although possibly longer.
As you can see, mother nature gives us a large margin for error on our timing for natural breedings because of the fresh semen's long lifespan. However, when dealing with frozen semen, it is critical to know exactly when ovulation has occurred and deliver the frozen semen to the "eggs in waiting."
Factors Affecting Semen Quality
Many factors can affect the viability of frozen semen. While an older bully pitbull male can still be frozen, a better collection can be expected from a young, mature dog (two to six years old). Therefore, it is better to collect and store a dog at a young age based on potential, rather than wait until a male is in great demand but unfortunately much older. The overall health of a dog is extremely important as well. A sick, or stressed dog will not provide a quality collection. The quality of the collection can also be affected by the dog's libido (sex drive). Most dogs will perform better if a "teaser" dog (dog in active heat cycle) is present at the time of collection. Dogs that are accustomed to natural breedings may take several attempts to be collected. In most cases, with a teaser bitch and some patience the outcome is successful. Studies have shown, a dog's sperm count can decrease significantly after two ejaculations in a one-week period. A period of rest 10 to 14 days is suggested before semen freezing to restore the count to maximum potential. Also note, a dog that has not been used for breeding purposes for an extended time (several months) will benefit from having a collection performed 2 weeks prior to collecting for freezing. All dogs being collected for freezing must be checked for the bacterial infection Brucellosis. Brucellosis is highly contagious, causes infertility, abortion in females, and is zoonotic (people can catch too). Any male or female dog in an active breeding program should be tested yearly for brucellosis. It is wise to test in advance to collections or breedings, as false positives are possible and require retesting a month later.
Frozen Semen Insemination
Several breeding options exist for using frozen semen. Some individuals have reported success with thawing semen and inseminating intravaginally as with fresh chilled semen. This is usually performed on several successive days. While this method is less invasive, it also requires a greater amount of frozen semen. Most freezing centers would agree that a surgical insemination of the semen directly into the uterus provides a greater chance of pregnancy and increased litter size. This can be accomplished with a very small abdominal incision and injecting the semen directly into the two horns of a female's uterus. A newer method called transcervical insemination (TCI) involves using a camera on the end of a rigid scope. A catheter, which is guided through the cervix, also deposits the semen directly into the uterus. Most bitches in heat will tolerate this procedure without sedation. However, certain breeds can prove more challenging to inseminate by this method due to differences in visualizing the angle of the cervix. Regardless of the type of insemination, the most critical variable is the timing of the procedure to match the fertile period of the eggs. Accurate ovulation timing is accomplished by a series of blood tests to identify the most fertile period.