The Reproductive Cycle In Dogs - A Guide to Dogs in Heat

As responsible owners we all need to know about dogs in heat; what it means for the dog and, importantly, how we can care from our pets during this time.

Like any other animals, dogs also undergo their own unique reproductive cycles. The cycle in dogs is known as the estrus cycle. This cycle is the time when female dogs display interest in mating and is the fertile period.

The Canine Heat Cycle

There are 4 phases in the female canine reproductive (estrous) cycle:

• proestrus: part of "dog in heat" cycle
• estrus: part of "dog heat" cycle
• dietrus
• anestrus

Males are attracted to the female dog starting with the proestrus cycle.

The reproductive cycles in dogs begins at puberty, generally when the dog is about 7-10 months of age. This is the average age of puberty and may vary according to the breed of the dog.

For small breeds, this process starts at around 5-6 months of age. While for the large breeds, it can start when the dog is about 2 years old.

Female dogs normally have only 2 reproductive cycles in a year.

During the cycle, they will experience bloody vaginal discharges that last for 4-9 days. After this duration, the female dog will begin to stand for breeding and accept the male.

Depending on the breed, this receptive stage can last for a couple of days to as long as 1-2 weeks. Counting from the first day of the vaginal discharges, the most fertile days are the 9th, 11th and 13th.

Female reproductive organs that are part of the female dog in heat cycle
The pictures in this section are reprinted with permission by the copyright owner, Hill's Pet Nutrition, from the Atlas of Veterinary Clinical Anatomy. These illustrations should not be downloaded, printed or copied except for personal, non-commercial use.

How Dogs React to Heat Cycle

Females are very restless and receptive to males. They even have the ability to attract male dogs from far distances. You may notice that your female dog is always moving around and is sometimes very irritable.

Dog Heat Symptoms and Changes in Behavior

First Week of Dog in Heat:

• change in mood during first week of heat cycle or pre-heat. Some bitches may prefer to be left alone while others seek more affection
• increase in urination
• vulva becomes swollen and may have some blood spotting
• tail tucking, using the tail to guard the vulva

In the 2nd week:

• vulva expels lighter pink substance
• tail wagging to alert other dogs

In the 3rd week:

• behavior starts to return to normal

Caring for Your Dog

It is important to know how to handle female dogs in heat. As a responsible pet owner, you will obviously be concerned with their health and safety. Here are some ways on how to take care of your dog.

• During the third or fourth week of the cycle, your dog will release pheremones, which will attract male dogs even at far distances. So it is best if you keep your dog indoors.


• Even if you keep your dog indoors, male dogs can still smell the pheremones and may wait on the doorstep. If your dogs in heat is going outside to urinate, you must accompany her to protect her from male dogs in the neighbourhood


• If you are planning to mate your dog during this time, remember that as a general rule, it is not best to breed female dogs on their first heat period. Her reproductive organs are still not very mature yet and becoming pregnant may cause some health problems. It is better to wait until the next cycle or the third cycle before breeding your dog.


• To prevent future health problems to the mother and to her future puppies, it is better to have her checked by the vet. This will ensure that she is in a good condition to handle a pregnancy and to make sure that she doesn’t have any medical problems that can be passed on to the future puppies.


• Pregnancy can put strain on the mother. So it is never wise to breed her in every cycle. Give her time to relax and go back to the non-pregnant state for a while before planning to breed again. Consecutive pregnancies may harm her health.

Preventing Dog Pregnancy

Most dogs should be sterilized that are not used for breeding due to the pet over population problem and the financial and time burden of raising puppies.

The best methods of dog contraception are spaying (OHE) for the female (called ovariohysterectomy) or neutering (castration) for the male dog. In OHE the female canine reproductive organs are removed. In males the testicles are removed. For males there is a medication called Neutersol that can be injected into the testicle with 99.6% effectiveness in causing sterility. No anesthesia is required for this procedure. Both can be performed at age 6 to 8 weeks with little health risk to the dog.

OHE is particular will prevent dog heat behavior and reduce canine medical problems such as uterine infection and cancer. Male dog castration reduces the tendency to roam, and eliminates the risk of tumors in the testicles.

Temporary Dog Pregnancy Prevention

There are prescription medications available that can temporarily prevent the dog heat cycle. The medications are based on the hormone progesterone and anabolic steroids. For example, the brand Ovaban claims a 32 day treatment. There are some side effects including:

• weight gain
• increased appetite
• pyometra (female dog uterine disease, pus discharge symptom and others
• high blood sugar
• dog mammary tumors (neoplasia

After treatment stops, the dog will resume the heat cycle.

Fact Sheets on Dogs in Heat, Breeding, Spaying and Neutering

Dog Pregnancy Prevention: Guide to Dog Spaying and Neutering (PDF Download, Source: UC Davis)

Dog Breeding Management: Dog breeding management (PDF Download, Source, UC Davis)

Articles Related to Dogs in Heat

Dogs In Heat And Canine Reproduction 

Breeding - An Overview 

Breeding Labrador Retrievers 

From Dogs in Heat To Spaying And Neutering 

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