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Canine Reproduction
Depending on the location and availability of the male and female dogs, semen may be collected for immediate use (fresh) or processed for use at a different location or later date (chilled or frozen). When using fresh semen, both the stud and bitch must be present, and ovulation timing using progesterone tests and vaginal cytology maximizes success rates in breeding. Artificial Insemination and Surgical Implantation Artificial insemination (AI) is the process of collecting semen and depositing it through artificial means into the vagina of the receptive female. In the female, abnormal vulvar or vaginal conformation, such as narrowing, may preclude coitus. Females 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.
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 12 hours after thawing and insemination. Chilled semen lives for about 3-5 days in the female and fresh semen lives for about 5-10 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. For semen to be placed directly inside the uterus, surgical methods are required. Frozen semen has a higher degree of success with surgical implantation. For this method, ovulation timing in the bitch is essential. Surgical implantation is frequently performed in English and French bulldogs due to extreme conformational difficulties.
Knowing exactly when to inseminate the female can be quite challenging and, if not done properly, fertilization will not occur. The goal is to inseminate the female 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 are microscopically evaluated. Based on the appearance of these cells cytologically, 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 are not always practical or affordable. The hormone progesterone can be measured within the blood and is the most accurate measurement to effectively predict ovulation. The turnaround time for this test is less than 24 hours. A combination of the two methods of cytology and laboratory tests have a pretty good success rate.
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. 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 later, an extender fluid is added to protect and nourish the sperm. This sample is then chilled and must be used within 10 days. For samples intended for freezing, a different type of extender is added to protect the sperm from the effects of freezing.
Semen Freezing Dr. Mark Sharp, a member of the Society for Theriogenology, routinely conducts artificial insemination utilizing fresh and chilled semen. Dr. Sharp also uses Minitube products in the collection, shipment and storage of frozen semen. Collecting and freezing semen from a stud dog has many different advantages. There are many different situations where the male may not be available: geography, show, illness, even death. Frozen semen precludes the necessity of travel for either male or female thus reducing stress on or danger to either animal. Frozen semen is stored in individual straws in liquid nitrogen at a temperature of -196 °C which allows the semen to be safely preserved for an indefinite period of time. Each straw is registered to the owner, and its use must be authorized. Therefore, breedings with frozen semen must be very carefully planned and ovulation timing in the bitch is essential. *Information on this page is adapted from information provided by PetPlace.com under the "Fair Use" Act. |
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