Dog Heat Cycle Basics

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 six and a half months. But how long each cycle lasts is variable from female to female.

Don't count on any two females' cycles to be the same, even if they are sisters. It is good to remember that cycles are variable from female to female but consistent for each individual. Keeping records on a female's cycle will tell you what you can expect her to do next cycle.

The Three Parts of Heat Cycles

There are three parts to a heat cycle:

1. Coming in or proestrus
2. Standing heat or estrus
3. Going out or diestrus

Each stage of the average heat cycle can be as short as three days or as long as 21 days. How long she is between stages, and how long she stands will be the same the next cycle. This is why knowing your dogs individual pattern is important.

What is Ovulation?

Ovulation is the release of an egg from the ovaries. Most dogs ovulate at the end of standing heat. When ovulating, females do not want or need to be bred again. That is why they quit standing to be bred.

It's important to have live sperm there when she ovulates. Most breeding misses result from a failure to cover the eggs when they are ovulated. The semen viability in a female ranges from nine days for natural, five days for artificial insemination and three days 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 to Determine Ovulation

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 AI 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, mom 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.

Vitamin Deficiencies

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 lets 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. Doc Roy's^® 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 Doc Roy's^® Daily Care, will also help to provide these essential vitamins. Once she becomes pregnant make sure she continues to get the vitamins she needs. At this point a prenatal multivitamin such as Breeders' Edge^®Oxy Mate™ 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.

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.

The Effects of Aging on Heat Cycles

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.

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!

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. B
Don Bramlage, DVM, Former Director of Veterinary Services at Revival Animal Health

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The materials, information and answers provided through this website are not intended to replace the medical advice or services of your personal veterinarian or other pet health care professional. Consult your own veterinarian for answers to specific medical questions, including diagnosis, treatment, therapy or medical attention.