Estrus and Mating in Dogs

By Malcolm Weir, DVM, MSc, MPH; Ryan Llera, BSc, DVM; Ernest Ward, DVM

Breeding, Care & Wellness, Pet Services

When does a female dog first come into heat?

Puberty or sexual maturity in the female dog usually occurs around nine or ten months of age. Smaller breeds tend to go into estrus or 'heat' earlier, even as early as four months of age in some females, while in large and giant breeds, it can take up to two years. For many dogs, the first heat is 'silent' or does not have clinical signs associated with estrus. Additionally, many dogs' first estrus cycle is unlikely to allow successful breeding, therefore the standard practice is to wait until the second or third heat cycle before breeding.

How often do female dogs come into estrus?

On average, estrus occurs about twice a year, although it varies from dog to dog. Small breeds tend to cycle more regularly than larger breeds. The interval between heat cycles tends to be four to twelve months with an average of seven months. An exception is the Basenji and other sled dog breeds, as they tend to go into heat only once per year, typically in the spring.

What are the signs of estrus in dogs?

Vulvar swelling is the first physical indication of an impending estrus cycle. However, the most obvious recognizable sign is vaginal bleeding. This may not become apparent until a few days after the female has come into estrus. Some female dogs experience heavy vaginal bleeding during estrus, while other dogs have minimal bleeding. If you are concerned about your dog, consult your veterinarian.

"...the most obvious recognizable sign is vaginal bleeding."

From the beginning of a female’s estrus period, she will be attractive to male dogs, though she will usually not be receptive or allow mating until seven to ten days into her cycle. As the cycle progresses, the color and appearance of the discharge change. In the beginning, it is usually quite bloody and thick in appearance, then gradually changes to a watery, blood-tinged discharge. The receptive period for mating usually corresponds to this change in the appearance of the discharge.

You may also find your female dog is passing small quantities of urine more frequently. The urine contains pheromones and hormones, both of which signal interested males that she will be receptive soon.

How long does an estrus cycle last?

Cycle length varies, averaging two to three weeks for most dogs. The cycle begins with the first signs of vulvar swelling or vaginal discharge. It ends when all discharge ceases and the vulva has returned to its normal size.

How do I determine the best time to mate my dog?

This can be difficult. Most dogs ovulate and are receptive around the eleventh day of estrus. The discharge is usually less bloody (often described as a salmon color) and the female will be actively looking for a male. The female may stand and present her hind end for the male to be mounted or she may tuck her tail to the side. However, ovulation may occur either early or late during the heat cycle.

Are there any tests to determine when to mate my dog?

Yes. There are two simple tests that your veterinarian can perform:

1. Vaginal cytology or vaginal smears. A simple microscopic examination of vaginal cells will detect changes in cell appearance and numbers. This technique has been used for many years and is reasonably reliable. It is non-invasive and does not cause discomfort to the female. Most vaginal smears are performed over several days to look for changes in the cells that predict ovulation and the best time for breeding.

2. Serum progesterone test. This test measures the progesterone level in the blood. It is very sensitive and has become popular due to its accuracy. Some dogs will require several tests done over a series of days to predict ovulation. Some veterinarians prefer another daily blood hormone test, LH (luteinizing hormone), instead of serum progesterone. Your veterinarian will discuss the different testing options and which is best for your dog.

"The serum progesterone test is a good indicator of when mating is most likely to be successful."

Your veterinarian may be able to perform both tests at the clinic, though sending samples out to a laboratory provides more accurate results. The serum progesterone test is a good indicator of when mating is most likely to be successful. It is useful for females with a history of unsuccessful mating or females who will be traveling a considerable distance to the male dog.

What can I do to ensure mating is successful?

Surprisingly, male dogs appear to be more stress-sensitive than females during mating. Successful matings are more common when the male dog is in his own environment. For this reason, females are usually taken to the male dog's home for breeding.

The time of mating is extremely critical, and it is highly recommended to have your female tested to determine the optimal days for breeding. For most females, the best time for breeding is between the tenth and fourteenth day of estrus. However, some females ovulate as early as the third or fourth day or as late as the eighteenth day.

It is normal to arrange for two matings (also called stud services) for your dog, often 24 to 48 hours apart. Check these details with the owner of the male when making initial inquiries. Also, be sure to ask what will happen if your female dog does not become pregnant as a result of the stud service. It is common for the owner of the male dog to offer a free service next time.

I was told that my female had tied well with the dog. What does this mean?

During coitus, part of the dog's penis (bulbis glandis) swells and enlarges. The female's vaginal muscles contract against the bulbis glandis, preventing the penis from being withdrawn. This is the 'tie' that is considered a desirable feature of successful mating. It is important to note that pregnancy can occur without a tie. Once tied the male dog will often step over the female or be turned by handlers into a position so that the dogs are back-to-back. The tie will usually last for five to ten minutes.

What should I do if I find my dog tied to another during a mismating?

There is little point in trying to separate animals that are locked together in this way. Buckets of cold water, water pistols, cap guns, and so forth do little to speed up the process of separation and merely upset or potentially injure the dogs. In fact, forced separation can result in serious injury to the female and should be avoided. If a mismating occurs, consult your veterinarian as soon as possible so your options can be reviewed.

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