Dog Heat Cycle Basics

Last updated: November 18, 2021 by Marty Greer, Doctor of Veterinary Medicine, and the Revival Education Team

Understanding your female dog's heat cycle doesn't have to be confusing and tricky. If a dog has healthy ovaries she will go into heat every six to eight months or so, depending on the breed. But how long each cycle lasts is variable from female to female.

Each female cycle is different and should be managed individually, even with sisters. It is good to remember that cycles are variable from female to female and may NOT be consistent for each individual. Keeping records on a female's cycle will tell you what you can expect her to do next cycle.

What Are the 4 Stages of a Dog in Heat?

There are four parts to a dog heat cycle:

1. Coming in or proestrus
2. Standing heat or estrus
3. Going out or diestrus
4. Between heat cycles or anestrus

Each of the canine heat cycle stages of the average heat cycle can be as short as three days or as long as 10 days. How long she is between stages, and how long she stands will be the same the next cycle.

Is There a Test to See if Your Dog is in Heat?

The average female will be receptive and fertile on days 10 to 14 of her heat. Watching her for her level of interest in the male or the male dog's interest in her is useful but not always accurate. The most accurate assessment of the stage of her heat cycle is a combination of vaginal cytology (a simple swab test done at the veterinary clinic) and progesterone testing (a blood test your veterinary professional can run or order for you). With these tests, usually done in a series every several days, your veterinary professional can tell you when she is ovulating.

There are several different types of tests and several different labs or machines that can be used to run these blood tests. There is a semi-quantitative test that estimates when she is ovulating based on a color change. The better tests are the quantitative blood tests, that report a numerical value. Different machines and different veterinarians may give you varying advice.

What Should a Dog Progesterone Level be to Breed?

In general, a progesterone under 3 ng/ml indicates she is still in proestrus. A progesterone between 4 and 10 ng/ml indicates she is ovulating. A progesterone between 10 and 30 ng/ml indicates she has ovulated and has entered her fertile period. A progesterone above 35 ng/ml indicates she have ovulated and is not likely fertile any longer. Unlike other species, dogs are not fertile the day they ovulate. Dogs are fertile two to five days post ovulation. For this reason, your veterinary professional will likely advise you to do the mating after her progesterone is above 5 ng/ml. if you are using frozen semen, the breeding will best be delayed to three days post ovulation, once the progesterone exceeds 20 ng/ml.

Do Dogs Have to Ovulate to Get Pregant?

Ovulation is the release of an egg from the ovaries. Most dogs ovulate during standing heat.

It's important to have live sperm in her reproductive tract two to three days after she ovulates. The most common causes of missed breedings are because of poorly timing the breeding and poor-quality sperm. The semen viability in a female ranges from five days for natural, two days for artificial insemination and one day for frozen semen. Timing to cover the eggs when ovulated is important and is the reason we breed every other day until they quit standing. Making sure viable semen is in the reproductive tract from three days before ovulation to two days after gives the best chance for conception.

How Do You Know When a Dog is Ovulating?

If it is not obvious when a female is ovulating, we can test the female's blood serum. Ovulation can be detected by checking progesterone levels in the female's blood. Scar tissue from the ovary-releasing egg (ovulation) makes progesterone that keeps the uterus quiet during gestation. When progesterone rises quickly to a certain level, we know the ovary has ovulated. That tells us we need to breed or inseminate immediately because eggs have already been released and we have a three day window to accomplish fertilization.

Luteinizing hormone (LH) testing can determine when an ovary is getting ready to ovulate but catching that LH spike in blood requires testing every day. When we catch the spike, the dam ovulates 48 hours later and we usually breed the next day. The LH test is often used with frozen or fresh chilled semen that is shipped overnight, as we have a narrow window to breed.

Do Dogs in Heat Need Supplements?

Vitamin deficiencies can cause a variety of problems, including missed heat cycles, irregular heat cycles and other heat cycle problems. Recognizing the signs of a deficiency can help you determine what your pet is lacking in their diet.

• All B Vitamins – Long or delayed heat cycle.
• B-1 Thiamine –The female in heat wants to be courted but she won't stand for the male. Oftentimes this is blamed on behavior but most often is a result of a thiamine deficiency. Thiamine is also needed for adequate swelling of female during heat.
• Folic acid deficiency can also cause a lack of pheromones or chemical signals that let males know when to breed. It also contributes to birth defects when deficient.

Iron is an important mineral during pregnancy; however, it does not have anything to do with heat cycles. A female dog's red blood cells increase by 25 percent when pregnant and puppies are forming red blood cells late in the pregnancy. An iron deficiency in a female is hard on mom and can result in puppies born anemic and weak.

The good news is there are easy solutions to fix a vitamin deficiency. Breeder's Edge^® B Strong is a daily liquid vitamin and mineral supplement that includes all B vitamins, including thiamine and folic acid. Giving a daily multivitamin, such as Breeder's Edge^® In Between For Her, will also help to provide these essential vitamins. Once she becomes pregnant make sure she continues to get the vitamins she needs. And don't forget the need to support her nursing and recovery once the newborns are on the ground. Breeder's Edge^®Oxy Momma™ is ideal.

To Trigger Heat Cycle or Not to Trigger Heat Cycle

Manipulating hormones is never easy on moms. It also doesn't make heat cycles consistent. Manipulating hormones is harder on mom than getting her healthy and letting her do her job naturally and effectively. If the female is deficient in some nutrient and that is causing her to delay or stay out of heat, manipulating hormones has low success.

You want to supplement with vitamins while on a good diet and get mom's ovaries healthy. Then if she does not start cycling – likely anestrus – trigger her to start. Once started and healthy, she will cycle normally on her own.

The long term goal is to get the ovaries as healthy as we can, manage issues and deficiencies, keep supplements simple and give her only what she needs. When we do that, mom will do her job consistently and with success. It's not enough to get her pregnant, we must get her healthy so her babies are born alive, healthy and wean with no issues. All babies just want to be healthy and have a chance at life. Your job is to be sure they get that chance. Manage mom well and they live!

Skipping Heat Cycles

Inconsistency in breeding is never a good thing for females. Skipping a heat cycle is not easier on mom. The uterine and hormone changes happen if you breed or not breed. We don't want to get her older and then ask her to raise a litter. Anestrus from not breeding or skipping heat is normal in wild dog packs. We do not want to trigger this non-cycling as it can last for several years. Better to get moms as healthy as possible, get her genetics out and retire young.

At What Age Should You Stop Breeding a Dog?

Dogs don't go through menopause like humans do. They cycle as long as they are healthy. However, as they age, they typically aren't as consistent.

Canine reproductive specialist, Dr. Robert Hutchison, recommends that once the female is fertile, she should be bred at every heat until she is done. He says skipping cycles does not benefit the uterus and a female should be done breeding when you see a sharp decline in the litter size or when you do not want to breed her again. Hutchison states statistically, females over six years of age have a 33 percent decrease in success of carrying to term.

Older moms get "kid worn" and usually are not as tolerant or consistent as young moms. We want to get mom's genetics out while she is young and then retire her. A female's fertility peaks around age five and we retire at six years.

Can an Unspayed Dog Get Pregnant?

Yes. If you elect to wait to spay your dog or to breed her when she is older, you should not assume that she is ever safe around a male dog while she is in heat. She is also never safe when she is outside unsupervised, even in a fenced in yard or when leashed. A breeding can happen in a split second, so she and the male should never be allowed in the same room unless one is in a crate or pen. Even those cute panties you can put on her during a heat cycle to keep your home clean are not sufficient to prevent a mating. These panties are only for preventing discharge from ending up on your carpet or furniture; they are not a chastity belt.

The most common way to prevent pregnancy in dogs is to spay. Of course, this is a permanent solution and should only be done if you are certain she should not have puppies in her future. Most dogs should not be bred and do not need to be bred. Gone are the days when we said having one litter of puppies was a good thing for her.

If you have any other questions on heat cycles, give our Pet Care Pros a call at 800.786.4751. They are expertly trained to provide you with the answers you need.

-Dr. Bramlage
Donald Bramlage, Doctor of Veterinary Medicine, Former Director of Veterinary Services at Revival Animal Health

Donald Bramlage, Doctor of Veterinary Medicine, practiced veterinary medicine for 30+ years and is known for his work in managing parvovirus. He received his Doctor of Veterinary Medicine from Kansas State University in 1985. He served as Revival's Director of Veterinary Services from 2011 until his retirement in 2019.

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