| Reproduction in the dog is unique and very different from our other typical domestic species. In order to understand and deal with the reproductive processes in the dog, one must appreciate not only the uniqueness of the canine reproductive cycle but also how much variation we see between normal individual bitches. |
| Puberty in the dog is defined by initial sperm production. Sperm production may begin as early as 5-6 months of age but usually peaks in numbers and quality at the age of 2 years. Dogs continue to produce sperm throughout their lives although the quality of sperm tends to deteriorate over time after the age of 5-7 years. Although some dogs will retain their fertility into their senior years, most will decline in fertility over time until they can no longer produce puppies. If one wants to preserve semen in a dog for future use by freezing, it is best to do this between the ages of 2-4 years, when the dog is producing his maximum number of normal sperm. |
| Puberty in the bitch is defined by her first heat cycle. Most bitches cycle every 5-7 months thereafter throughout their life (normal cycles range anywhere between 4 and 12 months). Once a pattern is established for an individual bitch, she will usually continue with this pattern. When her heat cycle begins, the bitch’s vulva will become swollen and she will have a bloody discharge that usually lasts 14-21 days (normal ranges can be 7-28 days). She will be receptive to mating by a dog the last half or so of this time. Another important aspect of the bitch’s cycle is her progesterone phase that occurs after every heat. Progesterone is the hormone of pregnancy. The bitch will have elevated blood levels of progesterone for 2 months after every heat cycle, approximately the length of a pregnancy. In other words, the bitch will either be pregnant or pseudopregnant after every heat cycle. Pseudopregnancies, or false pregnancies, are normal and expected in bitches. Some bitches show very pronounced signs of a false pregnancy (mammary gland enlargement, mothering of toys, etc.) while other bitches show almost no visible signs. |
| Traditional breeding management in the bitch involves behavior monitoring. Mating with the dog is performed soon after the bitch will accept the dog, and every 2-3 days until she will no longer accepts him. Vaginal cytology has been used for decades in canine breeding management and is a technique that requires microscopic slides, cell stains, and a microscope, most often performed by a veterinarian. There are typical changes noted in the vaginal cells which indicates the presence of estrogen from the ovary, the approximate ideal time for breeding, and when she is no longer in the receptive stage of her cycle. Modern breeding management has evolved over time to include the monitoring of blood levels of the bitch’s hormones during her cycle, specifically progesterone and luteinizing hormone (LH-the hormone that causes ovulation). Blood is collected every other day for progesterone and daily for LH, usually starting around Day 5 of her cycle;Day 1 is the first day of vulvar bleeding. It is very helpful to detect the initial and continued rise of progesterone during a bitch’s heat cycle. When progesterone reaches 2 ng/ml, this is good indirect evidence that there has been a release of LH that initiates the ovulation process. The continued rise of blood progesterone is evidence of ovulation and helps determine the optimal timing of breeding. Knowing the time of ovulation also gives an accurate due date for whelping. Ovulation occurs when the blood progesterone levels reach 5 ng/ml (range 4-10 ng/ml). For best fertility, a minimum of 2 breedings should take place around the time of ovulation (+ 48 hours). Cooled shipped semen can be utilized in the bitch using progesterone testing to best determine when the semen should be collected and shipped. With overnight shipping, we can now ship the semen instead of shipping the animals for a breeding. Cooled shipped semen breedings can be managed identically to natural matings. Frozen semen is a little more labor intensive than natural/fresh or shipped cooled semen breedings. Progesterone testing is mandatory to utilize frozen semen successfully. The timing for frozen semen insemination is approximately 5-6 days post LH peak and/or 3 days post-ovulation. An additional requirement of frozen semen use is that the thawed semen must be placed directly into the uterus by either transcervical insemination or by surgical insemination. The whelping due date will be approximately 61 days (+/- 48 hours) post-ovulation. Knowing when to breed a bitch and when she is due to whelp is valuable information to have for management of the bitch and her puppies. |
| Pregnancy diagnosis is usually performed by abdominal palpation around 4 weeks post-ovulation and mating. More accuracy is gained with the use of ultrasonography, which can give a good estimate of the numbers of puppies, as well as the viability of the fetuses. An additional tool that can be utilized is radiographs (X-rays) performed during the last week of pregnancy. An X-ray can be quite accurate in predicting the number of puppies within the uterus. Some accuracy is lost when there is a large litter present, ex. 10 or more puppies. |
| Using some or all of the above mentioned tools will help facilitate canine breeding management, taking a lot of the guess work out of the process. These tools also make it possible to use frozen or shipped cooled semen successfully in the bitch. Having a good working relationship with a Veterinarian is a much needed asset in ensuring a positive outcome of a pregnancy. |
