Female dogs can easily have heat cycle abnormalities. It just happens. These can be prolonged heats, split heats, silent heats, or even absent heats. At times, heat cycles can also be irregular.

Most bitches follow the heat cycle pattern of their dams if they live together. But there are situations in which a young bitch might skip a heat period. In fact, many females tend to have silent or irregular heats as well. Their cycle will however regulate itself within a couple of years but the situation does differ from time to time.

In this comprehensive article, we’ll cover the main dysfunctions occurring in a bitch cycle, including:

Absent Heat — a missed heat

— a missed heat Silent Heat — an undetectable heat (from a human perspective)

— an undetectable heat (from a human perspective) Split Heat — a heat happening in two distinct periods of times split by a break

— a heat happening in two distinct periods of times split by a break Prolonged Heat — a too long heat compared to the breed’s average

— a too long heat compared to the breed’s average Prolonged Interestrus Interval — a too long window between two heats

— a too long window between two heats Shortened Inter Estrous Interval — a too-short window between two heats

— a too-short window between two heats Premature Ovarian Failure — ovarian functions lessening or stopping at an early age

Just like with women, female dogs can have irregular heats their first few times. You must have these checked by your vet just to confirm or inform your suppositions. However, don’t worry since these first cycles become normal after a couple of heats.

Diagram showing two healthy heat cycles, back to back.

Absent Heat

You have absent heat when the heat is completely missed (ie. failure to cycle.)

There are many situations where a bitch younger than 2 years of age will not be able to get a cycle. Mostly because they are immature from a sexual standpoint, in fact, this does tend to appear in the case of those larger breeds.

If your female will not start to have heats after 2 years of age, it’s important to work with a professional and examine her to check if everything is ok.

It’s crucial to note that heat will not take place when a female was spayed, so you will need to inform your vet. This matters if you got a dog with very little history and background. Usually, a sign to spot if the bitch is spayed is a visible scar on the lower abdomen region. Also, females treated with progesterone and androgen will not be able to have a cycle during the treatment and for a few months after. Corticosteroids treated females will have to deal with a similar issue as well.

Moreover, debilitated or malnourished females will not be able to have a cycle. This will usually be progressively back to normal once the bitch is in a more stable and positive great state of mind and health.

Hypothyroidism can also be a cause when it comes to the absence and loss of heat. You can usually determine this via a thyroid blood test. There are uncommon causes too, the Cushing’s syndrome being one of them, but in this case, females should have around 8 years or more so basically they won’t really be able to reproduce any longer anyway.

Abnormal heat cycles usually happen several times in a bitch’s life.

Ovarian hypoplasia is a disease in which the ovaries do not reach sexual maturity and are unable of producing sufficient amounts of estrogen. The mammary glands and vulva remain small and underdeveloped. Ovarian hypoplasia may be the result of sex chromosome abnormalities. Immune-mediated inflammation of the ovaries may be responsible for a few cases of absent heat. Tumors of the ovary have also been associated with absent heat.

The absent heat can be confirmed by professionals using weekly progesterone assays or vaginal cytology. Most of the time you will see a high LH in the case of females that have absent ovaries or ovarian hypoplasia. A process such as ultrasonography could show the appearance of an ovarian tumor or immature uterus.

Then there’s also the analysis of the dog’s chromosomes called Karyotyping which does come in handy for the females that don’t have any cycle within half a year of research. And even if chromosomes have a normal value and the cycle won’t appear within 2.5 years, estrus and ovulation can be induced by FSH and hCG in a protocol determined by your veterinarian.

If your female has massive problems with infertility, it’s a very bad idea to think about breeding her.

TREATMENT — There is no treatment for the occasional absent heat. For recurring absent heats, a hormonal medication may be prescribed to try and regulate her heat cycle.

A wrong diagnosis is often made about an absent heat by thinking it is a silent heat. A silent heat is biologically normal but not exposed, an absent heat is just not happening.

Silent Heat In Dogs

A silent heat is a heat cycle that is very hard to detect from a human perspective. A dog in normal heat shows several signs alerting the dogs around (and us) that she is in heat. With a silent heat, these external and internal symptoms such as vaginal bleeding, discharges, and swollen vulva are barely visible, if at all.

The female in a silent heat might show no interest in male dogs around unless the bitch is actually ovulating which represents a window of a week or so. Smaller breeds who reach an early sexual maturity often have one or two silent heats before show an obvious and more regular cycle.

It’s very hard to figure out if there is vaginal bleeding because the female will usually lick herself clean. It’s a habit, most dogs do it and sometimes they will also lick the floor for any drop of blood.

Many owners and breeders don’t inspect their bitch’s vulva when she is in a normal state, out of her heat. It’s an error because you then can’t really compare if the vulva is swollen or not. After all, some bitches only show one sign and if you can’t read it, you’ll misjudge the situation. You can always Google some vulva images for your breed just for visual representation but it will be far from being accurate.

A bitch in heat usually has some red-ish or yellow-ish discharges on her vulva so be on the lookout for these. You may also bring in a stud dog every few days and observe how both dogs behave and react. If the male is being extremely insistent and the female receptive and submissive, then she might be in silent heat (therefore still in heat.)

TREATMENT — Using vaginal cytology and progesterone measurements, your vet will be able to accurately tell you whether the bitch is cycling or not.

Split Heat In Dogs

When a female dog is in a split heat, she will start her heat, stop it for a few days, and resume and finish it then.

On the first stage, the bitch will naturally attract male dogs and you will usually see vaginal bleeding and vulvar swelling. Up until now, it seems like a very normal heat.

The problem is that the female does not move to the normal oestrus phase but instead goes out of heat without being receptive and ready for breeding. The second and final phase of the cycle will roughly take place 2 weeks to 3 months later.

An important thing to note here is that split heats often appear in younger females and are created by lack of pituitary output of LH. Basically, the low LH will not allow ovaries to generate ovulatory follicles and thus the overall serum progesterone will have a very low value which stops or hinders the heat.

TREATMENT — Most times it happens, no medication will be given or required and the upcoming cycle will retain the normal schedule. If you notice it happens on a regular basis, you will need to specify it to your vet.

Split Heat: when a bitch starts her heat, stops it for several days, and eventually finishes it.

Prolonged Heat

Prolonged heat is when the bitch has a heat cycle longer than 3 weeks or 21 days, and still shows the signs and symptoms she was showing earlier on (ie. vaginal swelling, discharges, appealing to males, etc.)

Most of the time, prolonged or even shorter heats often occur during the first cycles of a bitch’s life but everything goes back to normal after a few heats.

The main causes of prolonged heats are based on a hormonal dysfunction such as a persistent elevation of estrogen, caused by:

an estrogen-producing ovarian cyst , or

, or by a granulosa cell tumor of the ovary

Ovarian tumors require surgical intervention to be removed as soon as possible. Ovarian cysts need some observation time to see whether they regress or not; if not, surgery will be required. You vet will use ultrasonography to show an ovarian tumor or cyst and get it fixed.

TREATMENT — The prolonged heat can be terminated by using the estrus suppression method explained below.

Estrus Suppression

Veterinarians can end your bitch’s prolonged heat using mibolerone, an androgen preparation, that will be given over the course of three or four months. This is called an estrus suppression. Once the heat is over, females will start a new cycle around 4 months later and they will be able to breed without a problem. Another option is to breed the female by adding in hCG or Gn-RH that has a human provenience. In addition to that, there’s also the possibility to use spaying to save your bitch and yourself some further trouble.

Interestrous Interval

This interestrus interval is basically the period of time in between two heat cycles. The normal interval really depends on the breed and size of the dog but it usually is anywhere from 5-10 months. However, no need to worry if the interval is longer or shorter, it also changes from dog to dog and throughout a bitch’s life.

An abnormal interestrous interval occurs if the difference between two heat cycles is either more than a single year or less than 4 months. Such dysfonctionnements are usually caused by genetics.

The interestrus interval is also referred to as anestrus; it is the resting stage in between two heats (or one pregnancy and a heat) where the dog’s body recovers from the proestrus and estrus stages or the pregnancy.

Hormone levels throughout canine heat cycle. (credits: peteducation)

Prolonged Interestrous Interval

A prolonged interestrous interval happens when a female had a regular heat but is still not starting her next heat after 16 months or more.

Usually, the cause is an ovarian cyst that will start producing progesterone, a hormone similar to androgen, both either stopping a heat or preventing it from happening.

Another thing to note here is that conditions like Cushing’s syndrome and even hypothyroidism can generate long term anestrus. However, you can detect hypothyroidism via a dedicated thyroid blood test. Cushing’s syndrome isn’t an issue that will affect reproduction and is commonly affecting older bitches.

TREATMENT — Mixing bitches cycling normally with bitches not cycling on time can actually be beneficial to the abnormal females that naturally will try to be in sync with the other healthy females. They may slowly become more appealing to males and get back to a normal fertility and heat cycle.

If such a stratagem fails, you can opt for karyotyping — the study, analysis, and detection of chromosomal abnormalities. If the karyotype returns normal, estrus and ovulation may be induced by your vet if certain conditions are met.

Shortened Interestrous Interval

A shortened interestrus interval happens to females starting their next heat cycle less than 4 months after the previous one ended.

Not to be mistaken for a split heat, a shortened anestrus can be diagnosed by noticing both cycles getting fully completed and going well over the proestrus phase (ie. the second stage of the heat).

A shortened anestrus or interestrus interval can have dramatic repercussions on the bitch’s fertility, especially if repeated several times. Heat cycles and progesterone damage the female’s body, and a shorter anestrus between two heats does not allow proper recovery of the lining of the uterus (called the endometrium.)

When the bitch’s body hasn’t recovered fully from the progesterone-induced damage, the mucous membrane lining the womb is not hormonally receptive to embryo implantation therefore the bitch will face difficulties to become pregnant.

TREATMENT — For older female dogs with a short interestrous interval, your vet may suggest the use of androgen to suppress the current or next heat before ovulation so the endometrium gets enough time to recover until the next heat. Most young bitches regulate their abnormal interestrous intervals as they grow older thus treatment is not recommended nor required.

Premature Ovarian Failure

Female dogs will start to get lesser ovarian functions after 6 years and usually won’t have heat cycles by the time they reach 10 years old, more or less. Most females will see their ovaries and fertility on or before 6 years of age resulting in permanent anestrus.

Using a simple blood test to quantify the FSH and LH concentrations will help confirm the premature ovarian failure in the bitch. LH and FSH are at much higher levels when approaching or in a permanent anestrus.

TREATMENT — There is no treatment for premature ovarian failure.

Shareable summary of the most common abnormalities of a dog heat cycle.

Take-aways

Abnormal heat cycles in dogs are more common than you think and younger bitches tend to regulate their cycles as they mature. So no need for panic if you have a 6 to 24 month-old bitch, cycles should get better naturally.

Older and senior females inevitably lose fertility and ovarian functions as they grow and the vet may recommend a hormonal treatment or spaying your female dog to give her body some rest for her last years.

For females in their adult years, you must observe each abnormal cycle and make sure it does not become a repeat occurrence. If so, you can see with this article that most abnormalities have their treatment, more or less heavy, so there are solutions regardless of the type of abnormal heat your dog being the victim of.