Dog Estrus, the heat cycle

Explanation, occurrence, and symptoms of the dog Estrus, the heat cycle.


During my many years working in veterinary medicine,

I couldn’t begin to count the number of times I handled upset owners whose dogs were “bleeding.” Others would tell me they thought their dog was “menstruating.” In a way, they weren’t that far off. What they were describing was the Estrus or heat cycle of their female dog.

Once I explained that all unsprayed female dogs go through this at least once, usually twice a year, they then wanted to know how long they were going to have to put up with the mess and the neighborhood Romeos.

The average estrus cycle in a dog is approximately twenty-one days and this cycle usually occurs every six to seven months. The first cycle will often depend on the size of the dog. Small breeds such, as Chihuahuas or Toy Poodles will come into heat between five and seven months. Large breeds like the Collie, Mastiff or Great Dane may have their first heat cycle at six months but it isn’t unusual for them to delay until they are a twelve to sixteen months. Larger dogs develop at a much slower rate than small dogs.

There are three distinct stages of the heat cycle. The first one is the “Proestrus” and it is during this stage the owner will often notice the bleeding from the vulva. The bleeding itself can be slight or she can leave evidence of her condition everywhere she sits or lays. For those owners who keep their dogs in the house, many pet stores carry dog panties that hold special canine sanitary napkins to eliminate the mess.  In addition to bleeding, the vulva will also swell and the dog will usually have an increase in urination. The most obvious sign to most owners are the increase in population of male dogs around their house. This proestrus part of the cycle will last between seven and ten days and the female will make it clear she wants no part of the male during this time. Unfortunately for the owner, the male dogs don’t know how to take no for an answer. They will climb or dig under fences, attempt to breed through the fence if the female strays close enough and often serenade the dog and owner into the wee hours of the night.

The second stage or actual “Estrus” stage of the heat cycle will often begin between the eight and tenth day after the first sign of color (bleeding). During this time the color of the blood has gone from bright red to pink and then to an almost clear discharge. It is during this stage most females will allow a dog, in fact ANY dog to breed her. The estrus stage can last between four and seven days and it must be remembered the female can become pregnant with mixed litters. Just because you bred your purebred collie to another collie doesn’t mean she can’t have puppies with the Doberman next door and the German Shepherd up the street. Your best bet is to keep her confined in the house during the entire estrus cycle or take the easy way out and board her for the necessary time. If you keep her at home, you may want to purchase a crate to keep her in. I had one collie that attempted to chew the front door down to get to the male outside. When that didn’t work, she leapt through our front window as soon as I went to pick up the kids at school. After her rendezvous with my male collie outside, she went over the fence because she had taken a liking to the chow that had been panting after her for over a week.  
If you do decide to breed your dog, she will show her willingness to be bred by “flagging” whenever you scratch the area directly above her tail. By flagging, she will actually stand still and lift her tail up and out of the way. For those breeds that have had their tails docked, you will just have to wing it although a veterinarian can do a vaginal smear. Each stage of the cycle will have different types of cells appear on the slide.
The third stage of the heat cycle is the “Diestrus.” This is when the female is going out of heat. During this time she will still be giving off the heat “scent” and males will still be congregating for her attentions. Once again she will be out of the mood and will snap at the males or sit and lie down when they try to mount her. The diestrus stage will last approximately seven to ten days. Once it is over, the dog will remain out of heat for approximately six to eight months.

During my work, I have seen many dogs have unwanted puppies, develop uterine infections or pyometria. I have assisted in countless C-sections through the middle of the night, often delivering dead puppies because the owner waited too long to bring the dog in. If you do not plan on breeding your dog, get her spayed. This can be done during the heat cycle although there is a greater risk of complications and many vets will charge extra for the surgery. Spaying not only removes the chances of unwanted pregnancies and complications, if done BEFORE the first heat cycle, it greatly reduces the risk of mammary (breast) cancer later on in life.