Now this may not be a question you’ve ever considered, but if you breed, or are planning to breed from your dog, or if you’re new to owning female dogs, then it may become more relevant. To say a dog has ‘periods’ is actually not true. Periods are a human trait, and although dogs appear to go through the same thing, physiologically, they are actually very different. 

What is a human ‘period’?

Now I’m a vet, not a doctor, but I am a woman, so I like to think I have some experience talking about human periods…. 

  • A woman’s menstrual cycle lasts for an average of 28 days
  • The cycle consists of a 14-day follicular phase followed by a 14 day luteal phase
  • At the junction of the two phases is when ovulation occurs, and coincides with a rise in oestrogen.
  • Once ovulation has occurred, oestrogen begins to drop and progesterone begins to rise. 
  • During this time, the lining of the uterus starts to thicken, ready for the ovulated egg to embed if it is fertilised. 
  • If the egg is not fertilised, the progesterone levels fall, which triggers menstruation – the shedding of the thickened lining of the uterus and the unfertilised egg. This is the bleeding that we see and tends to last, on average, for around 5-7 days. 

What is a canine ‘period’?

Although externally, it appears that female dogs also experience periods, there are stark differences…

  • A dog’s oestrus cycle lasts for around 6 months
  • The cycle consists of four phases – pro-oestrus, oestrus, dioestrus and anoestrus. 
  • Pro-oestrus
    • Bleeding begins along with swelling of the vulva. This stage is controlled by high oestrogen levels and will last for around 9 days.  
  • Oestrus (being ‘in season’)
    • At the start of oestrus, ovulation occurs and the progesterone starts to rise. This is the fertile period and is characterised by an easing of the bleeding. Again, it will last for around 9 days. 
  • Dioestrus
    • Once female dogs no longer want to mate, they are said to have entered dioetris. Progesterone remains high for the duration which tends to be for 2-3 months. 
  • Anoestrus
    • This is the ‘rest’ phase where progesterone falls and remains low. Anoestrus lasts for 4-5 months on average. 

When does a dog have her first season?

As with people, this can be very variable. On average, a bitch’s first heat will be at around 6 months of age, but it’s not uncommon for them to reach this point as early as 4 months, or as late as 18 months. Sometimes this first season is what we call ‘silent’, in that the dog doesn’t show many obvious external signs, so it can be missed by the owners. 

Do dogs go through the menopause?

Older dogs don’t go through a menopause as it’s described in human medicine, but we do find their seasons can become less frequent and more sporadic as they age. 

So as you can see, physiologically, dog and humans are quite different when it comes to their reproductive cycle. But why does it matter? Well, if you’re looking to breed from your female dog, you need to have a basic understanding of the timings in order to predict the most fertile time to mate her. On the other hand, if you’re thinking of spaying her, then we use the facts of the cycle to plan the safest time to perform the operation – generally 3-4 months after a season (oestrus), as we aim to be as close to half way between seasons as possible.

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