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The kink in the tail
If we wish our pedigree dogs to have good futures, we will need to step up and take our collective responsibility for it.

Text and illustrations: Ms MA J.H.C. Brooijmans-Schallenberg

Of late, more and more undocked dogs have made their appearance at dog shows as a result of the ban on tail docking. This is a good reason to once more direct some attention to the prevention of kinks in the tail. In itself, this might not seem very interesting, but the consequences for kennels certainly are.


The tail is the extension of the spinal column. The vertebrae in the spinal column are differently built depending on their function.
The coccygeal vertebrae (tail bones) are in line with one another, become increasingly smaller and gradually shorter. The last vertebra ends in a tip. There are also little joints and intervertebral discs between the vertebrae that stimulate agility and elasticity. The whole is kept together and in position by ligaments, tendons and muscles. A normal tail will approximately reach the hock.
Congenital aberrant tail shapes are found in various animal species. The tail could be too short due to e.g. vertebrae that are crooked or too short or due to the decrease of vertebrae. The tail then often has a blunt tip. The appendage can also be completely absent.
Another thing you may find are kinks in the tail that cannot be smoothed down, i.e. vertebrae that have grown together crookedly. Furthermore, we know the deficiency of half-vertebrae: the so-called hemivertebrae. A fixed curvature in the tail may occur (a ring grown crooked) or even a knot at the tip. Additionally, it is possible for the tail to consist only of fleshy parts without any bone in them. The congenital defects are found in e.g. dogs, cats, pigs and mice.

Scientific research has been done on mice with regard to the genetic background of this phenomenon. For dogs, cats and pigs, we mostly have only empirical data to work with. In many cases, the tail anomaly can be seen directly after birth but there are also reports of cases in which certain defects only occur after a few weeks (even up to eight or ten weeks).
The animal in question is not necessarily burdened by the defect as long as it is only the tail that is affected. The problem is that, when you breed with such a 'sufferer', it is possible for its offspring to develop serious defects in other parts of the body.

Hereditary background

Within the fertilised ovum (egg-cell), three germ layers are formed after the required cell divisions: the ectoderm, mesoderm and endoderm. Within the endoderm, the skin, the nervous system, the senses and the crown of the skull are shaped and within the endoderm, the digestive tract and the organs are formed. Within the mesoderm, which is the most important layer in this context, the entire skeleton (excluding the crown of the skull), the heart, the blood vessels and the urogenital system are shaped.

The shaping of these organ systems commences in an early stage of embryonic development. A great number of genetic factors pass on their information during this complicated process. In addition, interactions may take place between various genetic factors. After a temporary cartilage skeleton has formed, which ossifies for the most part, the skeleton takes the shape as we know it.

This development continues after birth. Genetic factors continue to play a part here. Whenever multiple genetic factors play a part, we call this polygenetic inheritance. With such a form of inheritance, various other factors jointly influence the phenotypical result.

Mutations occur frequently. When they take place in the reproductive cells, the changes are transferable to the descendents. Back mutations also occur often. The mutated allele can show dominant, incomplete dominant or recessive behaviour.
It is possible for mutations to produce good qualities that will e.g. allow the species to better adapt to changing circumstances. Sometimes, however, the mutation does not work out for the best. A hereditary disorder will then be the result, in rudimentary form at least. The DNA also contains so-called recovery genes or modifiers. These are able to undo the consequences of a negative gene defect. It is therefore important there is enough space in the DNA for the required recovery genes.


As a result of the polygenetic character of the inheritance, the phenotypical manifestation will vary. An example is the varying manifestation in diagnostics of hip dysplasia.
It is even possible for faulty genes to be present without this manifesting itself in the phenotype. In the event that it does reveal itself, however, at least we then know of the presence of one or more faulty genes and we are informed that there are possibly too few recovery genes present in the DNA.


So what can go wrong when breeding with dogs with kinked tails? Descendants can be born with tail defects: not such a big problem since the animals are generally not burdened by it. Because the entire skeleton, with the exception of the crown of the skull, is formed in the mesoderm, the same deformations can occur in the cervical, thoracic and lumbar vertebrae of the descendants. This can increase the symptoms considerably.
In other parts of the skeleton,
defects may occur as well, including crooked jaws, a crossbite, an open palate, fused and/or dented ribs, spina bifida (a split spine) and too many or too few toes, possibly fused. Without pretending to have been complete in my account, I would like to conclude the list of symptoms with the shortening (and sometimes connected with a curving) of the long bones.

We already know that, in addition to the skeleton, other organ systems are formed within the mesoderm. As a result of the complexity of the process and the interaction between genetic factors, abnormalities may occur in the organ systems of the descendents as well. Examples include the atrium septum defect (undersized septum in the heart), aortic stenosis (aorta too narrow in places), and the embryonic blood vessels that fail to disappear after birth.
Another symptom known in pups born from parents with kinked tails is that the urethras running from kidney to bladder have not been implanted in the bladder in the right way: past the sphincter. Females with this abnormality often display incontinent behaviour. Males have two sphincters and can suffer from this defect without it being evident.
Something else that is found in dogs is the absence of a septum between intestines and urethra, a cloaca, like birds have. Yes, sometimes the anus is completely absent.

This was a long list of defects but still this is only a small part of the total number of abnormalities. It is striking that different defects occur in different species. The kinked tail is one abnormality on the list but one that is visible and tangible externally.
A parent with a crooked jaw can produce descendents with e.g. kinked tails or ones with a defect in a different mesodermally-formed organ system.

The genetic package of the species is largely homozygous: two dogs will always produce dogs. Two humans will produce humans. The extent of homozygousness is even greater in pedigree dogs. After all, two Borzois will produce Borzois.
This purity of breeding is required for the protection of the species and the breed. However, in order to preserve a breed, you also need genetic variability. Put simply: the less variability, the less room there is for recovery genes and more for the manifestation of genetic defects. Apart from the other consequences of inbreeding depression, sufficient variability is required to stay healthy.
Not surprisingly, this is the reason why the number of animals in a population needs to be as varied as possible. For too long did we fawn on strict inbreeding and line breeding in the pedigree dog breeding world.
By understanding the need for variability, breeders are able to stimulate the animals' health. In addition, it is of great importance for the breeders to be open and to report which defects they find in their litters. Naturally, dogs with abnormalities should not be used for breeding. If breeders should be permitted to continue breeding (in different combinations) with seemingly healthy parents that have produced pups with abnormalities is a serious question and warrants careful consideration. Multiple aspects play a part in the answering of this question.

It may be a good idea to pay some attention to external factors here. We know of e.g. 'softenon babies', skeletal defects as a result of poor nutrition and a cleft palate as a result of insufficient vitamin B intake. It is good to realise that - small though it is - genetic influence does play a part. The intake possibilities of nutritional elements, for example, are genetically determined. The cleft palate is shown to be hereditary but a certain threshold value is also a factor.
If the mother dog is given antibiotics in an early stage of gestation without any extra vitamin B, many or all pups will be born with an open palate. This will not happen when an adequate dose of vitamin B is administered, but the genetic defects will still be present in the pups.
It is dangerous to reason as follows: "if it has not been proven to hereditary, we will not treat it". It is better to say: "if it has not been proven to be hereditary, we
will treat it".

The judge

In the struggle to keep our pedigree dogs as healthy as possible, judges also play a significant part. Judges are not veterinary surgeons: they do not have to make diagnoses. In this case, it is about being able to find every deviation from the standard.
In the Netherlands, every judge has been instructed in all aspects of this standard: we can all see if the eyes look normal and dry, if the teeth are set in the jaw evenly and straight and if they have developed normally. We can see and hear if their breathing is normal and regular without any snoring background noise. In breeds with short muzzles, we check if the nostrils are wide enough.

In connection with the issue described in this article, there are a number of points that deserve attention: an important one is feeling the tail for deformities or bumps, to see if it has developed properly, but the proper top line is also very important. The back should always be straight and the possibly desired curve should be above the loins. If the curve is present in the centre of the back, it is of the utmost importance that this curve smoothes out during movement. In other words, when the dog starts walking, the back should be able to straighten. A back grown crooked is, in fact, a hunchback and extremely problematic. Additionally, the ribs should not be deformed in any way and there should not be any dents in the rib cage. Also, the toes should be all there.

And finally the proportions: in normal-legged dogs, the depth of their chests should be equal to the length of their front legs, measured from their elbows to the ground, the elbow being level with the bottom of the chest. In certain breeds, including the
Dachshund and the Welsh Corgi, the lower leg is sometimes so much shorter than desirable that you can even feel a slight curve in it. De abnormality of undersized lower legs also occurs in e.g. ponies and small ruminants.


Breeders and judges should feel responsible for the collective pursuit of healthy breed populations.
I have already gone into the part of the breeder. The contribution of the judge is at least as important, however. Particularly in this day and age, in which winning is considered to be so dreadfully important. If abnormalities are found, it is sensible to mention this in the judge reports, if only to account for the lower qualifications. Breed associations and breeding committees therefore have the possibility to incorporate a few things in their registration.
Remarks like "well, that eye is indeed wet but it is still a very beautiful dog and a dog is more than just an eye" or "yes, I did see a crooked jaw but I looked the other way there for a moment because I love the type and if I am as strict as I should be, I will not be allowed to judge as often" will no longer pass in this day and age in which sufficient knowledge is available. If we wish our pedigree dogs to have good futures, we will need to step up and take our collective responsibility for it.

Grüneberg, Hans (1963).
The pathology of development. A study of inherited skeletal disorders in animals.
Hutt, Frederick B. (1979).
Genetics for dog breeders.
Leschot, Nico J. and Mannens, Marcel (2001).
Genen in beweging.
Wiesner, Ekkehard and Willer, Siegfried (1983). BI-LEXIKON. Genetik der Hundekrankheiten.

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CV J.H.C. Brooijmans-Schallenberg.

I am born in Indonesia and repatriated after the war to The Netherlands.
In 1953 I am licenced as a veterinary surgeon.
Under the prefix "Absyrtos" I bred wirehaired Dachsies, Welsh Corgi Pembroke and Cardigan and Entlebucher Sennenhunden.
Since 1965 I am a judge and now licenced for all the breeds of FCI group I, X, several breeds of FCI group II and a few breeds of FCI group V.
In 1970 I was elected as a member of the board of the Dutch Kennel Club and happened to be President between 1983 and 1998.
Besides running a practice in small animal surgery I did scientific research on hip dysplasia in dogs at the Utrecht University especially about the genetic background.
I am still a teacher in confirmation and locomotion just as in genetics for candidate judges.

J.H.C. Brooijmans-Schallenberg. (1926-2010)

English version of this article copyright Trudy Zantingh & Henny van den Berg
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