What is the Canine Estrous Cycle?

Hey, fellow pet lovers!

My girls are currently in heat so I thought I should write a post that will help me learn more about what is happening to their bodies and the various stages of their cycle.

Having two female dogs we have had to watch the girls go through many heats so far, but I think this will be one of the last for them both as we are considering getting them spayed next year. We didn’t want to get them done when they were a puppy as I believe six months or anything under a year is far too early and you need to ensure your pup has fully matured before nurturing them. Depending on the breed and size of your pet will depend on how quickly they reach puberty, smaller dogs take less time, and larger dogs will take much longer.

Let’s jump straight in and understand what is happening to our pooches while they are in heat and the various stages of their estrous cycle? 

The Canine Estrous Cycle

closeup photography of adult short coated tan and white dog sleeping on gray textile at daytime

Photo by Christian Domingues on Pexels.com

An un-spayed female dog will go into heat or have an estrus cycle at least twice a year typically. If you’re a woman reading this, then you will know the pain and discomfort that comes with that time of the month, now imagine that being condensed into once or twice a year. Our pooches period must be so intense I cannot even imagine the discomfort my poor babies have to deal with!

Having a male dog is a lot easier when you think about it, no heats what so ever but I wouldn’t swap my girls for the world. I and my partner have been talking about getting the girls spayed for a little while now, as they are getting older and are fully matured and we certainly don’t have any plans to breed them.

Canine estrus cycles vary between certain breeds and the age and also the size of our canine friends determine when your pet will first come into heat. Some bitches have a short cycle and have little vaginal discharge, some have a longer cycle and have more vaginal discharge. It all depends on the pooch but most female dogs will reach sexual maturity (puberty) at around about the age of 6 to 12 months. However, for large breeds, it can take much longer and can be up to two years.

Both Nia and Lily have two cycles a year and they sync so they come into heat at the same time which is super handy. Lily, however, seems to be in a bit more discomfort, whereas Nia seems to be less bothered by everything.

The definition of the Estrus Cycle is the correlated phenomena of the endocrine and reproductive systems of a female mammal from the beginning of one period of estrus to the beginning of the next — called also estral cycle, estrus cycle

Merriam-webster.com. (n.d.). Definition of ESTROUS CYCLE. [online] Available at: https://www.merriam-webster.com/dictionary/estrous%20cycle [Accessed 11 Aug. 2018].

The Various Stages of the Canine Estrous Cycle


Photo by Pixabay on Pexels.com

There are various different stages to the canine reproductive cycle and these go on continually for the rest of your pets life or until you get her spayed.

  • Stage one of the cycle, Proestrus.

The first stage of our canines reproductive cycle is the Proestrus Stage; during this stage, follicles start to develop on the ovaries and the uterus lining forms. You will begin to notice changes in your pet, such as small amounts of bloody vaginal discharge and male dogs becoming more interested in your pet.

Females, however, are not interested in mating during the proestrus stage. Your pet may also have frequent urination and mark over other dogs scent, they may also become a bit more restless than usual.

The length of this stage varies between each pet, but the usual length is nine days. Your pet’s vulva will normally be swollen, and estrogen levels will peak during this stage.

  • Stage two of the cycle, Estrus.

The second stage of the cycle is called Estrus and this is when the ovarian follicles mature and are released from the ovaries. During this stage your pets estrogen levels are high and this is the stage your pet can become pregnant. Unlike the first stage Proestrus where females are not interested in mating, this is not the case and bitches want to mate with males and become pregnant.

During the second stage, you should expect to see less blood in the vaginal secretions and discharge may become more clear or straw-like coloured. During this stage, your pet will undergo many hormonal changes such as a surge in LH (Luteinizing Hormone), a decrease in Estrogen and an increase in Progesterone. Your pet will be willing to mate with males during this stage and ovulation normally occurs a few days before this cycle ends and is usually 24/48 hours after your pet has a surge in LH (Luteinizing Hormone).

The length of this stage is anywhere between 4-13 days but it normally lasts 9 days.

  • Stage three of the cycle, Diestrus/Pregnancy.

The third stage of your pets cycle is called the Diestrus stage, and this is when your pet’s body is preparing for potential fetal development. It is the period following mating and lasts about 56 to 60 days whether the bitch becomes pregnant or not. Your pet will no longer be interested or accept males, and they will have little or no vaginal discharge and progesterone levels will be high. Follicles in your pet’s ovaries become Corpus Luteum and produce progesterone to support a potential pregnancy.

During this stage, there is the chance that your pet might go into a false pregnancy (Pseudo-Pregnancy) which is very common in unspayed females, because the hormonal profile is pretty similar to a pregnant bitch during diestrus even if your pet isn’t pregnant. During a false pregnancy, your pet can gain weight, their mammary glands will develop and maybe even produce milk, and they may start hoarding toys and also exhibit a nesting behaviour.

It is worth noting that the occurrence of a false or ‘phantom’ pregnancy is a natural remnant hailing from our dogs days as wolves in the wild, within the structure of the pack only the lead female would be permitted to breed. With this in mind, you can see how all of the females in the group going into a false pregnancy and then producing milk to help raise the lead wolves offspring would play out as an evolutionary advantage.

As well as your pet going into a false pregnancy, there is also a risk of pyometra which is an infection of the uterus. I plan on writing a post that talks more in-depth about pyometra as there are two different types such as open pyometra and closed, a benefit of getting your pet spayed is that they can no longer get pyometra.

  • Stage four of the cycle, Anestrus.

The final stage of your pets cycle is their resting stage and this is called the Anestrus stage and is a period of ovarian inactivity. Your pet will have no signs of being in heat and will also have a sharp decrease in progesterone.

This stages length varies between breeds and different sized pets but it can range anywhere between

  • 3 – 17 months but it normally lasts for about 4 or 5 months. 
  • Or 90 days.

This stage occurs regardless if the bitch is pregnant or not.

For a more in-depth read on the normal canine estrous cycle and canine puberty check out this webpage that I found very useful while writing this post. The Normal Canine Estrous Cycle and Canine Puberty.

Brief Recap of the Canine Estrous Cycle

Your pet will have their first-ever heat cycle when they have reached sexual maturity (puberty). This varies between each breed and of course whether your pooch is a small or large breed.

  • Proestrus normally lasts 9 days. This is when we notice our pets coming into heat/season and there will normally be a small amount of bloody vaginal discharge.

Pro-estrus:  Eggs develop in follicles on the ovaries and produce estrogen.

  • Estrus normally lasts 9 days, females are willing to breed and discharge becomes more clear or straw-like coloured.

The follicles release their eggs into the uterus and produce progesterone.

  • Diestrus/Pregnancy lasts typically 60 days; your pet is preparing for potential fetal development and is no longer interested in mating with male dogs.

Di-estrus:  The Heat is Over.

  • Anestrus normally lasts about four to five months and is a period of ovarian inactivity.

An-estrus:  Resting Time.

Your pet’s cycle will continually go on until you decide to get her spayed. 

Dog Breeding Information. (n.d.). The Dog Heat Cycle – Dog Breeding Information. [online] Available at: https://www.dogbreedinginformation.com/the-reproductive-dog-breeding-cycle/the-dog-heat-cycle/ [Accessed 11 Aug. 2018].

I found this YouTube video super informative while writing this blog post so if you want more information then head over there after finishing this post, Vaginal Cytology and Canine Estrous Cycle (Veterinary Technician Education).

Things to note when your dog is in season

Lily's puppy dog eyes

You need to take some precautions when your pet is in heat/seasons if you do not plan on breeding them.

These precautions are simple things like,

  • Keeping your pet on a lead at all times when you are out and about when they are in heat.

We never let the girls off the lead at the park or anywhere when they are in heat; you never know when a male dog might be around the corner, and you don’t want to frustrate other people’s dogs by getting all the males exited.

  • Having different types of food available.

This is something you probably won’t think about but make sure you have a verity of food options for your canine friend as they could become super fussy and turn their nose up at the food they would otherwise love.

My girl Lily gets so fussy when she comes into heat, so much so that she refuses to eat things that she usually loves like lamb or beef. Thankfully she hasn’t turned her nose up at chicken yet but just remember your pet’s appetite might increase or decrease depending on how they feel.

  • Your pet’s behaviour will change!

Something to note is that your pet’s behaviour will change, you will not know how they will act until they come into heat but they most likely won’t be the exact same pooch you know. Your pet could become more relaxed and want to sleep for most of the day or they could become depressed and unhappy.

It all depends on your pet and my girls get super needy when they come into heat, not kidding you some nights I have to cuddle them for most of the night. Your pet might get needier or less, just pay attention and keep an eye on how they are acting are at each stage of their cycle.

  • Keep your pooch away from male dogs if you’re not planning on breeding her.

One of the most obvious things to note is to keep your pet away from any male dogs during their heat cycle, especially during Proestrus and Estrus. Your pet cannot get pregnant at every stage of their heat, but it’s better to keep them away from any potential pregnancy if you don’t want your pet to have pups.

  • Keep an eye on your pet during Diestrus.

Diestrus is the stage of your pets cycle where they could potentially go into a false pregnancy or fall ill with pyometra. Keep a close eye on how your pet is feeling and also their overall behavioural changes if you notice anything that worries you take them to the vets for a quick check-up to ensure all is well.

  • All cycles can be different.

The last thing to note is the fact that each dogs cycle will be different, and there is no one set rule that is normal. Small dogs such as Chihuahua’s or Jack Russell will most likely have more heat cycles a year than say a large breed such as a German Shepherd or a Rottweiler. Don’t worry if your dog doesn’t fit the norm when it comes to her cycle, everyone is different, and there is no one set rule for your dog’s cycle. Now you understand your pets estrous cycle and can spot when they are actually in heat and could become pregnant.

Thanks for reading this post, I hope you all liked learning about your pets reproductive cycle and stick around for a post next week that is going to list the ways we can care for our pets while they are in heat.

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