If you can remember that far back, you may recall learning reproductive biology in school. Being humans, we have a slight advantage in understanding human reproduction and can be forgiven for finding animal reproduction a little more challenging. Of particular relevance for owners of female dogs is the dog oestrus cycle. Today we will explain how this cycle works, what the signs are, and what you should do when your dog is in heat.

Back to School…?

The oestrus cycle is a series of changes within a female’s body that prepares her for pregnancy. It is driven by chemicals called hormones that tell different parts of the body to do something. In human females, this happens every 28 days on average. However, dogs are different in that they generally only have one or at most two complete cycles a year, known as their season.

To summarise the cycle: it starts with hormones telling the ovaries to develop egg cells, and the uterus to grow and prepare for a potential pregnancy. This continues until egg cells are released into the uterus, known as ovulation. Around ovulation, if a female mates with a male, sperm from the male can reach the eggs to fertilise them, allowing them to grow into puppies. However, if there is no mating and the eggs are not fertilised, the oestrus cycle continues. This period when she is fertile is called her heat. 

Dogs are again unusual because even if they are not pregnant, they have a period of ‘pseudopregnancy’ or false-pregnancy where the body thinks it is pregnant (we think this allowed wild dogs could produce milk even if they weren’t pregnant, so they could foster other females’ pups). After a complete pregnancy (or false-pregnancy), the uterus lining stops being a healthy environment for fertilised eggs and breaks down.

This completes the oestrus cycle. In humans, the cycle starts up again with the ovaries producing more eggs. However, dog ovaries ‘ shut down’ after an oestrus cycle for around 5 months. This is known as anoestrus, and she cannot become pregnant during this time. 

Is She in Heat?

Now you know the overall cycle, let’s start getting more relevant to you as an owner. Is your dog in heat?

Firstly, is your dog a girl? If not, she probably won’t be in heat! Next, is she entire or has she been neutered via a spay? Remember that a spay removes the reproductive organs meaning your dog cannot get pregnant and will not enter heat. 

Finally, how old is your dog? Your dog will first come into heat around puberty – however, puberty in dogs is highly variable, ranging from less than a year to almost 2 years old. Generally, the larger breed your dog is, the later they will enter puberty. Ask your vet if you need a more specific answer.  On the opposite end of the scale, older dogs are likely to have reduced fertility – dogs do not have a menopause and can cycle until they die, but the cycles will become less regular.

So if you have an entire female dog who has reached puberty, she is capable of having a heat. What are the specific signs of heat? The signs are incredibly varied but watch out for: changes in behaviour such as unusual playfulness, nervousness or aggression; increased urination; a swollen vulva; red or yellow coloured non-smelly discharge from the vulva; ‘flirting’ with males; standing when male dogs mate her; changes in tail position; changes in diet. Some dogs do have ‘silent’ heats, where there are almost no signs at all. To be certain, vets can take cell samples from the vagina or test her blood if you require an accurate answer.

She’s In Heat! What Do I Do?

Firstly, don’t panic! Although the changes in behaviour can be distressing, heat is perfectly normal in dogs. However, if the behaviour is getting too much to handle, ask your vet for assistance. And of course, if you suspect there may be something else going on, let us know.

The first decision to make is whether you are wanting to breed from your dog or not? 

A dog in heat is fertile and receptive to mating, so an entire male could get her pregnant. If you are interested in breeding we recommend doing plenty of research well before your dog gets into heat – dog breeding is complicated and can be expensive or even dangerous if it goes wrong. Check out our previous blogs and please ask your vet for advice if you think you’d like to breed your dog. 

If you are not wanting puppies (and as cute as they are we know they are a handful!), then ensure you avoid all entire male dogs. Dogs can be sneaky and even if you think you are paying attention they can mate under our noses. Keep your dog on a lead and don’t let unfamiliar dogs approach her – male dogs can sometimes be aggressive, and female dogs in heat can be aggressive back. Avoiding males for a few weeks on either side of her heat is safest. 

Regardless of whether you want puppies or not, prepare for a little mess 

The discharge produced during a heat can stain carpets and furniture. In human females, the shedding of the uterus lining is commonly known as a period – note that the bleeding when a dog is in heat is not the same as a period, which dogs do not get. We would recommend puppy pads, keeping your dog in an easy-to-clean area, or even consider dog nappies. Remember that she cannot help making a mess, so don’t get angry with her. 

Accommodate her behaviour too 

If she is a little grumpy, try to give her some space. If she is being needy, give her some cuddly toys or a blanket, or spend extra time with her. Make sure she has plenty of food, water, and exercise, so routines aren’t disrupted. We would also recommend you keep in good contact with your vet during this time for extra advice or in case anything doesn’t seem quite right.

What Happens After Her Heat?

Remember that female dogs have a ‘false pregnancy’ after their heat if they are not pregnant. During this time, her body thinks that she is pregnant so her behaviour can change accordingly. This can present as: aggression or nervousness; nesting behaviour; being possessive with toys; mammary gland enlargement; milk production. A pseudopregnancy will usually end after around 70 days post-heat. Not all dogs will show obvious signs of a pseudopregnancy.

Pseudopregnancies can be left alone if the behaviour is manageable until it naturally ends. You can discourage certain behaviour if it helps, such as removing nesting material and toys. Alternatively, your vet can dispense drugs to end the pseudopregnancy within a week or two. The options depend on what you and your vet feel is best for your dog, so seek their advice if her false pregnancy is becoming an issue.

Can I Stop Heats? 

If you don’t want puppies and don’t want heat signs, there are options to prevent heat altogether.

By far the most common is a spay, where a vet will surgically remove your dog’s reproductive organs. She will never be able to become pregnant, have a heat, or have a false pregnancy, and it carries a number of other significant benefits as well. It is permanent, however, so ensure you never wish to breed from your dog. We preferably want to spay during the long anoestrus period, as the operation is much easier and safer, so we cannot use a spay to prevent the current heat cycle. 

There are also short-term medical options for preventing heat and pregnancy or to cause abortion. These drugs often carry side effects and of course are not a long-term solution. We would only recommend these for emergency contraception or for particularly difficult heats, prior to permanent spaying. Talk to your vet if these may be of interest.

Final Thoughts

Phew, that was complicated! We hope that it has given you a better understanding of what heat actually is, what it looks like, and your options for managing and preventing it. As we said above, planning well in advance is always important, so talk to your vet now about heat, particularly if you have a young puppy who might soon be having her first heat. 

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