Many factors contribute to the likelihood of pregnancy when using artificial insemination, including type of semen (fresh or frozen), semen quality and quantity, age and fertility of both the stud dog and bitch, site of semen deposition (intrauterine or vaginal), and time of insemination.

TYPES OF SEMEN

Insemination can be performed using three types of canine semen: fresh, fresh-chilled, and frozen.

FRESH

Fresh ejaculated canine semen has the longest viability. Semen from young, fertile stud dogs can survive for up to 5-7 days in the bitch’s reproductive tract.

FRESH-CHILLED

Fresh-chilled semen involves the dilution of ejaculated semen in special canine extenders which contain egg yolk and buffers that protect the sperm during the cooling process. The extended semen is then slowly cooled to 4˚C and can remain viable at 4˚C for up to 3-4 days. (Semen from some stud dogs has been reported to maintain viability and fertility after storage at 4˚C for 10 days). Chilling semen conserves the sperm’s energy and hence prolongs its longevity and viability.

Preserving semen at fridge temperatures facilitates the shipment of canine semen either within the United States or internationally to Canada or Mexico. It is a great alternative to shipment of either the stud dog to the bitch or vice versa when each are located at a distance from each other, which can be very costly and impractical.

FROZEN

Frozen semen is stored in liquid nitrogen at the extreme temperature of -196˚C. Semen is preserved in a frozen state in either “straws” or “pellets.” The freeze-thawing process causes some degree of sperm damage, greatly reducing the lifespan of the sperm to only 12-24 hours in the bitch. Therefore, when dealing with frozen semen, it is critical to know exactly when ovulation has occurred so that we can make sure the frozen semen is deposited into the uterus when the oocytes or “eggs” are ready to be fertilized.

TIMING OF INSEMINATION: MONITORING YOUR BITCH’S HEAT/ESTROUS CYCLE

Timing of insemination is very important. Monitoring your bitch’s heat, or estrous cycle, to determine the optimal time to inseminate involves carrying out one or a combination of the following procedures:

• Blood samples to measure the hormone progesterone
• Vaginal smears for cytologic evaluation to help determine when to inseminate and evaluate for infectious or inflammatory processes
• Vaginoscopy to assess the vaginal vault which correlates to the stage of the estrous cycle and is a very helpful tool for timing. Vaginoscopy can also rule out anatomic abnormalities (strictures, septa, persistent hymen) prior to breeding.

The number of samples that need to be taken to determine when to inseminate varies between bitches. We recommend starting testing approximately 5 days after the onset of heat (first observable sign) and then every second or third day until we determine when the bitch has released her ovulatory hormone called “luteinizing hormone” or “LH.” The day this occurs is called the “LH surge” or “LH Day 0” and coincides with a progesterone level around 2 ng/ml.

The day or days on which we recommend artificial insemination to be carried out depends on the type of semen that is to be used. For example, insemination with frozen-thawed semen is carried out on “Day 5” (post LH 0) when only one insemination is to be carried out, or on Days 4 and 6 or 5 and 6 (post LH 0) if two inseminations can be performed.

SITE OF SEMEN DEPOSITION: ARTIFICIAL INSEMINATION TECHNIQUES

TRANSCERVICAL INSEMINATION

The intrauterine insemination technique that we recommend when using frozen-thawed semen or low numbers of potentially compromised fresh or chilled semen is transcervical insemination, where semen is deposited directly into the uterus to maximize the chance of pregnancy.

This internationally-recognized technique was developed in 2001 by Dr. Marion Wilson in New Zealand. It has the advantages of being anesthetic and sedation free, non-surgical, and relatively stress free. It also has the distinct advantage, in comparison to surgical artificial insemination, that more than one insemination can be carried out during the bitch’s heat.

Transcervical insemination may not be a feasible option for some bitches, typically for behavioral reasons.

There have been some developments with the canine transcervical insemination endoscope. A new longer and slimmer scope is specifically designed for transcervical insemination in dogs. This facilitates transcervical insemination in large and giant breeds, as well as maiden bitches.

VAGINAL INSEMINATION

When using fresh or chilled semen with adequate sperm numbers and sperm quality, deposition of semen into the very end of the vagina can result in pregnancy and litter sizes equivalent to natural mating.

There are many different types of catheters that can be used for vaginal artificial insemination. We insert a special artificial insemination catheter into the very end of the vagina. At this point a bulb at the end of the catheter is inflated to mimic the swelling of the dog’s bulbus glandis during mating. This not only prevents back flow of semen, but stretches the vaginal wall resulting in oxytocin release and stimulation of vaginal and uterine smooth muscle contractions, facilitating transport of the sperm into the uterus. After the bulb is inflated, fresh semen is slowly injected down the catheter into the far end of the vagina. This is then followed by warm canine semen extender which functions to help flush the semen into the uterus in the same way prostatic fluid does during natural mating.

This is a technique that can be used in all bitches, is non-invasive, requires less skill and equipment than intra-uterine artificial insemination techniques, and therefore is also more economical. It is often used in maiden bitches and studs that fail to “tie” or mate, which can be due to several reasons.

Vaginal artificial insemination is not the preferred method for use of frozen-thawed semen. As well as the greatly reduced lifespan mentioned previously, frozen semen breeding units contain significantly lower numbers (i.e. 100 million motile sperm per “AI dose”) than a fresh or chilled insemination dose. Therefore, deposition of low numbers of fragile frozen-thawed sperm into the hostile vaginal environment results in low numbers migrating through the cervix into the uterus and reaching the fallopian tubes (oviduct), the site of fertilization. This obviously results in a lower pregnancy rate and litter size.

SURGICAL INTRA-UTERINE INSEMINATION

We do not recommend surgical insemination, nor do we perform this insemination technique at CSU. This technique involves a general anesthetic and surgery with associated risks. An incision is made into the abdomen, the uterus is then identified and exteriorized. The semen is then injected directly into the uterine horns. It can only be carried out once during the bitch’s heat. Further, surgical insemination does not increase conception rates or litter sizes.

IMPORTANCE OF SEMEN HANDLING AND ASSESSMENT

No matter what type of semen (fresh, fresh-chilled, or frozen) or the method of artificial insemination that is used to deposit the semen, careful and skillful handling of the semen is essential. Furthermore, assessment of a sample of semen by a qualified and knowledgeable professional prior to insemination plays a critical role in the maximization of pregnancy rates.

Artificial insemination is a very useful reproductive management tool. It allows the transport of semen both nationally and internationally. Management of both the stud dog and bitch is critical to maximize both pregnancy rate and litter size after artificial insemination.

ARTIFICIAL INSEMINATION TIMELINE

This is a sample timeline for transcervical insemination using frozen semen. Because the lifespan of frozen semen once thawed is limited, timing of insemination is critical. The process using fresh or fresh-chilled semen is similar, and this timeline reflects the most regimented version of the artificial insemination process.