When Is A Female Dog Most Fertile?

when is a female dog most fertile

The answer to the question “when is a female dog most fertile?” is not one that can be understood in isolation. Before you can answer that, a brief education is required to understand how estrus actually happens in female dogs.

Puberty and the reproductive cycle in dogs, bitches to be precise, is a really interesting topic. While humans begin puberty after a number of years, dogs hit puberty in a number of months. By 9 or 10 months of age, the average female dog would have reach sexual maturity and experienced her first heat. However, this age varies from breed to breed and from bitch to bitch.

In smaller breeds, this age can even be much younger as some of them get their first heat at around 4 months. Larger breeds, on the other hand, might be up to two years of age before they experience their first heat.

Because the first heat is typically silent, that is without any clinical symptom, breeders and dog owners are usually advised to delay breeding until the second or third breeding to increase the chances of success.

Having laid the background, therefore, let’s attempt to answer today’s question.


How A Female Comes Into Heat

Typically, heat in female dogs occurs twice a year. However, as usual, this is just generally speaking. It varies from dog to dog and from breed to breed.

As you might have guessed, small breeds cycle more often than larger breeds. So, while a smaller breed might have 4 months between cycles, a larger breed might have up to 12 months between each cycle.

The only small breed exceptions to this rule are the sled dog breeds and the Basenji. In these breeds, heat tends to happen only once yearly, and that in the spring.

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Signs Of Heat In A Female Dog

Before we go into the essay part of this sub, check out this video below. It explains everything you need to know about your dog’s heat cycle including flagging, smear tests, and zeroing in on your dog’s most probable fertile days.

The first sign of heat in a female dog is usually the physical swelling of the vulva. This indicates that the heat cycle is about to begin. However, this sign is not as obvious as that of vaginal bleeding.

Vaginal bleeding usually happens about a few days after the dog has fully entered into estrus.

Now, vaginal bleeding shouldn’t bother you as a dog owner as it varies from dog to dog. Some dogs bleed heavily naturally but others have only minimal bleeding. If you think the bleeding is abnormal though, see your vet.



Another thing you might notice is that male dogs seem to be more attracted to her even though she might not necessarily be receptive to their advances just yet. This is because, when in heat, female dogs give off pheromones that male dogs can pick up.

As estrus continues to progress, the bloody discharge gives way to a less bloody and a more watery discharge.

Finally, a female dog might begin to pass urine more frequently. This urine contains the pheromones we talked about which the male dogs pick up.


How Long Does A Female Dog Stay In Heat?

Estrus or heat cycles vary among dogs and breeds. However, typically, a female dog stays in heat for about 14 to 21 days.


When Is A Female Dog Most Fertile? – Best Time To Mate Your Dog

dog tail

Well, pinning it down to the exact day can be a bit difficult. However, for most dogs, ovulation usually occurs at about the 11th day of estrus. So, this means that the female dog is usually most fertile at about that time.

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At about this time, the vaginal discharge is less bloody and has taken up a more salmony color. The female dog might also begin to actively search for a male partner and begin flagging.

She will stand and present her rear end for the male to mount her. Or she might move her tail to one side or the other (flagging).

However, like we said, these things vary, and in some dogs might either occur early in the cycle or late in the cycle. This is why the best way to confirm is to take tests.


Are There Tests To Determine When A Female Dog Is Most Fertile?

There are actually two tests that a veterinarian can perform to confirm that your dog is fertile.

1. Vaginal Cytology and Vaginal Smears

One way your vet can confirm if your dog is ready to mate is by a microscopic exam of the vaginal cells. In this exam, your vet will be able to observe the changes in the appearance of numbers of cells in the vagina.

This method is somewhat reliable and has been used in the veterinary world for many many years now.

On the other hand, there are vaginal smears that can predict fertility as well. Unlike the vaginal exam, this one is performed over a number of days. 

In the vaginal smears, the vet looks for changes in the vaginal cells as well. These changes predict ovulation as well as the peak of fertility and the best time for breeding in dogs.


2. Serum Progesterone Test

This test is used to measure progesterone levels in the female’s blood. It is a super-sensitive, super-accurate test which is the reason it has found rampant use in today’s world of veterinary medicine.

For some dogs, this test will have to be carried out several times over a number of days for an accurate prediction of ovulation and fertility.

Some vets do not use the serum progesterone test and instead prefer to test for levels of luteinizing hormone (LH). Whatever your vet prefers, they will discuss the various options with you and, together, you’ll select which test works best for your dog.

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In some cases, in fact, your vet might even use both tests.

Generally, though, the serum progesterone test is highly effective at predicting when the female dog is most fertile and when breeding is most likely to succeed. It’s also useful for dogs with a history of unsuccessful mating as well as females who might have to travel some distance to breed with the male dog.


What To Do To Ensure That Mating Is Successful

when is a female dog most fertile

Interestingly, female dogs are less likely to be stressed during mating periods than male dogs. In fact, if a male dog is outside his comfort zone, unsuccessful mating is significantly common. This is why, most times, the female is taken to the home of the male dog for mating.

One way to ensure a successful mating is to test your female for fertility first. When it comes to the success of mating in dogs, timing is critical. If mating does not occur at the right time, it will, most likely, not be successful.

For most female dogs, this critical time will fall between the tenth day and the fourteenth day of heat.

However, there are dogs for which that time falls as early as on the third or fourth day or as late as on the eighteenth day.

Because of these variations, it is extremely important to confirm your dog’s fertility using the tests listed above

This video gives a roundup of everything we’ve discussed so far about ensuring a successful mating process.

Oftentimes, female dog owners would arrange for two services (matings) with 24 – 48 hours in between both services. You want to arrange for that with the owner of the male dog performing the stud services. 

Also, make sure you have an understanding with the owner of the dog concerning what happens if it so happens that your dog does not get pregnant after mating. Many times, the dog owner would give you a free service next time.

Prepare for the coming of your new pup, click here to read our article on dog supplies necessary for welcoming home a new pup.