Canine Artificial Insemination
Reproduction in dogs can be either planned as part of a breeding program or accidental. Either way, most breeding is successful and results in the birth of healthy puppies. For some dogs, natural breeding is unsuccessful and artificial methods are required.
Artificial insemination (AI) is the process of collecting semen and depositing it through artificial means into the vagina of the receptive bitch. AI is reserved for valuable purebred dogs that are unable to conceive through natural means due to various problems. In the bitch, abnormal vulvar or vaginal conformation, such as narrowing, may preclude coitus. Bitches may also be aggressive toward the intended sire and not allow breeding, for whatever reason. In the male, poor sex drive, weakness or pain when mounting due to arthritis or prostatic disease or aggression toward the female may result in the need for AI.
Another common reason for artificial insemination in breeding programs is the geographic separation of the dam and sire. Champion stud dogs may have semen frozen and shipped throughout the country, especially if transportation of the female to the male’s territory is not possible.
Semen Collection in Dogs
For successful AI, the semen must be collected and handled properly and placed into the female. Semen can be used fresh, it can be chilled and used within 24 hours, or it can be frozen. The more processing that is done to the semen, the less likely it will result in fertilization.
For fresh and chilled semen, it must first be determined that the female is receptive and near the time of ovulation. After that determination, semen can be collected by manual stimulation.
Most successful semen collection begins with the introduction of a teaser bitch – a dog in heat but not intended to be bred that day – or a bitch with a topical pheromone applied. This will increase the success of the stimulation and result in higher quality semen. Teasers, however, are not required and collection can be performed without them.
If a teaser is used, the male is allowed to sniff around the rear area and mount the bitch. The bitch should be muzzled and firmly restrained. Once the bitch is mounted, the person collecting the semen firmly grasps the penis through the prepuce (sheath) and begins rapid massage. If a teaser is not used, the person collecting the semen begins the procedure by grasping the penis and beginning the massage.
The remainder of the procedure is the same. The penis is not allowed to enter the teaser vagina. As the penis becomes erect, the prepuce is pushed back and a preformed rubber collecting cone with attached collecting tube is placed over the penis. The penis and collecting cone are firmly held in place with the collector’s hands, stimulating the constriction of the female during a normal breeding.
Ejaculation occurs in 3 parts. The first part is a small amount of clean fluid that does not contain semen. The next part is the sperm-rich cloudy fluid. Typically, vigorous thrusting is associated with this part of the ejaculation and results in 0.5 to 3 mls of semen. The final phase of the ejaculation is the addition of clear prostatic fluid. If the ejaculate is to be used immediately, the prostatic fluid is allowed to mix with the remainder of the semen. If the semen is to be stored for any length of time, the collecting cone is removed as soon as the prostatic fluid begins to discharge. The presence of prostatic fluid in stored semen will result in diminished motility of the sperm and reduce fertility.
The amount of semen that is required to give the best chance of a successful insemination varies depending on the size of the female.
After collection of the semen, a semen extender can be added to nourish the semen and to achieve the necessary amount of semen. For samples to be used within 24 hours but not immediately, an extender fluid is added to protect and nourish the sperm. This sample is then chilled and must be used within 24 hours. For samples intended for freezing, a different type of extended is added to protect the sperm from the effects of freezing.
After the collection cone is carefully removed from the erect penis, make sure the penis returns to normal size and is replaced into the prepuce.
Prior to insemination, the semen needs to be evaluated for quality. Over 70 percent of the sperm need to have normal forward motility, which correlates to 150 to 200,000 normal appearing sperm per sample.
Female Dog Preparation for Artificial Insemination
Knowing exactly when to inseminate the female can be quite challenging and, if not done properly, fertilization will not occur. In traditional breeding programs, with natural service, the bitch is bred at least three times on the 9th, 11th and 13th day after the vulva begins to swell and blood tinged discharge is seen. On average, bitches tend to ovulate on the 12th day after the onset of vulvar swelling. Unfortunately, this does not always occur and alternative methods may be required for some bitches to conceive. The goal of breeding is to inseminate the bitch four days before ovulation and then every two days until the final insemination at two days after ovulation. Insemination two days after ovulation results in the maximum litter size.
Determination of ovulation can be done in a variety of ways. Traditionally, tissue cells of the vagina are microscopically evaluated. Based on the appearance of these cells, the time of ovulation can be estimated. Unfortunately, this is not the most accurate method of determining ovulation.
The measurement of progesterone levels is much more accurate but is time consuming and daily checks throughout the heat cycle is not always practical or affordable. The hormone progesterone can be measured within the blood. The most accurate measurements can effectively predict ovulation, but these tests are done in a laboratory. An in-hospital version of the progesterone level test is available, which can give the user a rough idea when ovulation is going to occur.
A combination of the two methods has a pretty good success rate. About 4 to 5 days after the beginning of vulvar swelling and blood tinged discharge, the cells of the vagina should be evaluated daily. Once 80 percent of these cells have the typical cornified appearance indicating ovulation is near, blood samples are drawn every 2 to 3 days to evaluate progesterone levels. At this point, if there is not a limit to the number of inseminations, the first insemination is performed. If only one insemination is possible, this one should be done 2 days after ovulation.
Further evaluation of the vaginal cells is no longer necessary. Every 2 to 3 days, blood samples should be evaluated for progesterone levels and insemination occurs. Once the progesterone levels reach ovulation level, one final insemination is done 2 days later. Pregnancy can then be confirmed about 25 days later with an ultrasound.
Progesterone levels can be determined either by a laboratory or by an in-hospital test kit. The laboratory can give specific values to the progesterone level. The in-hospital test kit can indicate levels of progesterone based on color changes.
For laboratory values, the serum progesterone is typically less than one ng/ml until 2 days before ovulation. At this time, the level of progesterone will rise to 1 to 2 ng/ml. On the following day (one day before ovulation), the progesterone level will be 2 to 4 ng/ml. On the day of ovulation, the progesterone will be 4 to 10 ng/ml. After ovulation, the progesterone levels rapidly rise and can be anywhere between 15 to 90 ng/ml.
For the in-hospital test, there are sample color changes that can help indicate approximately where in the ovulation process the dog is in currently.
Canine Insemination Process
Insemination is similar for fresh and chilled semen but is slightly different for frozen semen. This is due to the life span of the semen once processed. Frozen semen only lives for a few hours after thawing and insemination. Chilled semen lives for about 5 days in the bitch and fresh semen lives for about 6 days. Since frozen semen has such a short life span, an egg ready to be fertilized must be present at the time of insemination for fertilization to occur.
Once prepared, the semen can be deposited either in the vagina just in front of the cervix or just inside the uterus. Samples deposited just in front of the cervix result in the best success.
Placement of the semen into the proper area of the reproductive tract requires some specialized equipment. Long pipettes are recommended. For small and medium sized dogs, commercially made canine insemination pipettes are available. For large breed dogs, these pipettes are too short, so modified pipettes used in cattle are frequently used. Some people choose balloon catheters but the pipette is most commonly used.
To begin the insemination process, the male should not be around the female. Hold the bitch in a standing position. Draw the appropriate amount of semen into a sterile syringe and attach this to the appropriate pipette. The pipette is then guided into the upper vagina by a gloved, lubricated finger inserted into the vaginal canal. Once positioned, the semen is deposited. The syringe is then filled with air, which is used to inject the remaining semen that remained in the pipette after the initial push of the syringe. The pipette is then removed but the finger is not. The vaginal wall is stimulated with the inserted finger for several minutes. This should induce the vagina to begin contracting, which helps move the semen into the uterus. After stimulation, the finger is removed. At this point, the rear of the dog is elevated for 5 to 10 minutes. Do not push on the abdomen. Elevate the dog by grabbing the lower rear legs and elevating. Do not allow the dog to squat. After she has been elevated for 5 to 10 minutes, she can be allowed to walk around but do not allow her to urinate or jump for 30 to 60 minutes. After one hour, she can return to normal activity.
In selected cases, surgical insemination can also be done. After the uterus is surgically exposed, the semen sample is introduced into the uterus by a needle and syringe. This is not the most effective method of fertilization but may be required in highly valuable dogs in which puppies are in great demand.