by Robert Van Hutchinson, DVM
Historically, if multiple attempts for a natural breeding did not succeed, a last ditch effort of depositing semen in the vaginal tract was performed. Occasionally puppies resulted, often a smaller than average litter, but more often than not, the bitch did not conceive, and the artificial insemination was blamed.
The ability to accurately time the ovulatory pattern of the bitch has shown the canine breeder that artificial insemination can be as successful as natural breeding. Semen evaluation can be performed pre-breeding to assure the owner that the semen appears viable.
The routine use of "compromised life" semen such as fresh-chilled or frozen semen required artificial insemination to become common place. The need for frozen canine semen to be placed into the uterus rather than the vaginal tract necessitated the development of new methods for breeding the bitch.
The bitch is unique when her estrous cycle is compared to that of other domestic species. The bitch ovulates her eggs into a progesterone environment rather than estrogen as occurs in other domestic species. Estrogen measurement (vaginal smears, breeding guns), therefore, cannot be used for ovulation timing in the canine. When a natural breeding is performed, the semen is deposited in the vagina and "pumped" into the uterus by hormonal release stimulated by the tie. The lumen of the cervix in the average size bitch in estrous, is approximately the diameter of the insert in a Bic pen. The "Z"shape of the cervical lumen also prevents the insertion of even a small size catheter into the uterus.
The ova that the bitch ovulates are not ready for fertilization until a final meiotic division takes place. The time for ova maturation is a minimum of 48 hours post ovulation. This factor is especially important when short lived semen such as frozen semen is being used. Frozen semen is thought to only live 12-24 hours in the uterus after thawing and insemination. Frozen semen is only minimally effective when deposited vaginally (less than 20% conception success in one study), and not into the uterus. Is it any wonder that the initial impressions of canine frozen semen were less than spectacular!?
Currently, however, the use of frozen semen and fresh-cooled semen is every bit as effective as natural breeding. One of the main reasons for the conception success is the understanding by both breeders and veterinarians that the artificial insemination methods must be properly timed, properly performed and that certain bitches and types of semen require different methods of insemination.
If both breeding participants are present, fertile and ovulation timed ready, a natural breeding is performed. If for some reason a natural cannot be achieved, then a vaginal artificial insemination is used to breed the bitch. The technique requires specific procedures be performed.
The male's semen is collected. This is achieved by manual stimulation. The collector needs to obtain the second fraction of the ejaculate (the milky, sperm rich portion) stopping the collection when the third fraction starts (watery in appearance) which consists of prostatic fluid.
The bitch should have her rear end elevated for the artificial insemination procedure. This positioning facilitates the semen's deposition and flow to the cervical opening, a necessary for the semen being in position to be "pumped" into the uterus. The inseminator should digitally stoke the roof of the vaginal tract (also called "feathering") for 1-2 minutes after insemination. This technique simulates the tie of a natural breeding. The bitch's rear should be elevated for 2-3 minutes post-insemination.
The necessity to bypass the cervix and place the semen into the uterine lumen is beneficial in improving the conception rates in numerous situations. These include the use of frozen semen, fresh cooled semen, poor semen quality and in situations where examination of the bitch's uterus is desired.
Two methods are used to achieve the intrauterine deposition of semen, the transcervical insemination and the surgical insemination. These techniques each have their own usage guidelines and one does not replace the other as has been mistakenly represented to dog breeders.
The transcervical insemination (TCI) is performed with the bitch in a standing position. No sedation nor anesthesia is required. A fiber optic cystourethoscope is used vaginally to visualize the opening to the cervix. A flexible catheter is maneuvered through the cervix into the uterus. It is important that the breeder realize that the veterinarian is not visualizing the inside of the uterus and this technique does not allow for evaluation of the uterus.
The TCI procedure is visualized on a television monitor and does allow for examination of the vaginal tract, however. The semen is gently pushed through the catheter from a syringe. The veterinarian can visualize that the semen flows easily into the uterus and does not flow back into the vaginal tract.
The transcervical insemination does not replace the surgical insemination as it does not allow for uterine evaluation, but is a significant improvement over the vaginal method of artificial insemination. The TCI is recommended for any type semen, especially frozen and fresh-cooled and can significantly increase conception when poor quality semen and lowered sperm numbers are used. The TCI technique should be used in bitches less than 5 years of age where there is not a reason to suspect uterine changes or uterine disease.
The surgical method of artificial insemination is especially useful when breeding "middle age" and older bitches (5years of age and older). The unique biology of the bitch exposes the uterine lining to the inflammatory effects of progesterone for 60+ days, whether she is pregnant or not, accounts for the progressive changes in the uterus from a normal endometrium to cystic endometrial hyperplasia. These changes eventually render the bitch prone to such diseases as mucometrium and pyometritis. Pyometritis is a hormonal disease with a secondary infection, not a primary infection of the uterus.
The changes to the uterine lining can affect conception in many ways. The endometrial cysts can affect the semen's ability to reach the fallopian tubes where conception occurs (regardless of the method of insemination). The cystic changes can also prevent implantation of the fertilized ova, which occurs 17-18 days after ovulation and can inhibit placental development and growth.
A surgical insemination is a minor surgical procedure that allows the surgeon to inject the semen directly into the uterus. As the surgeon has the uterus in his hands, cysts, uterine wall thickness and muscular texture can be evaluated. There is no more accurate method to perform this vital examine. In many bitches, that have a surgical insemination, corrections can be made to the uterus that allow for conception to occur. A bitch's greatest chance of conception is by having a surgical semen implant.
A pre-surgical blood value examination is performed on the bitch, which is also beneficial to assure good prebreeding health. The surgical procedure is performed under sterile conditions.
The bitch is given a short acting intravenous injection of Propofol. An endotracheal tube is placed and the bitch is connected to a gas anesthetic, Sevothane. Even though the total surgical time is usually no longer than 10-15 minutes the bitch is connected to surgical monitoring.
A 2-3 inch incision is made on the abdomen through the skin and underlying muscle. The uterus is isolated and evaluated. The semen, whether fresh collected, fresh chilled or frozen, is inseminated though a small hypodermic needle into the uterus. The veterinary surgeon can see and feel the uterus fill as the semen is deposited. There is no incision in the uterus proper. The incision is sutured and in most cases the bitch is sent home within an hour post-surgically.
A bitch that has had surgical inseminations is not more prone to needing a ceasarean section nor having whelping difficulties. Having a surgical insemination does not decrease the number of times a bitch can be bred. A surgical insemination should be considered anytime there is a reason to evaluate the uterus (bitches 5 years and older) or where the semen being used can benefit from intrauterine implantation.
Our whole goal when breeding a bitch is to maximize the chances for conception. The manner and method that the semen is placed into the bitch should be evaluated critically as to whether a natural breeding, vaginal insemination, transcervical insemination or surgical intrauterine implant, gives the bitch the greatest chance of conception. Ultimately this will allow us to have the litter of which we have planned and dreamed.
http://classic.akc.org/vetoutreach/headlinenews_13.cfm
