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.