Testicles

[michaelundinaeichhorn]

Sorry,
as a vet I can tell you that in most cases you can´t directly compare human genetics of the genetic defects with canine genetics, the genetic background of kryptorchism in dogs is varified. The newest theories are that the reason is a hormonal caused dysfunction of the descendus testis, that is caused by a factorcomplex. Genetic-statistic research (Wiesener, Willer) has prooved that one of the most important factors is genetic. In former times they thought it was a autosomal-recessive way, nowadays it is thought to be polygenic.
Carriers of that disease should not be used for breeding (kryptorchids themselves and females or males with an above-avarage high amount in their offspring).
Breeds with high incidence are: Minituare and Toy Poodles, German Shepherd, Welsh-Corgi, Smooth-haired Foxterriers, Greyhound, Whippet, Pomeranian, Maltese, Boxer.

In breeds where kryptorchids have been used for breeding (Boxer) the incidence increased clearly, so even if not every case may be genetic you shouldn´t take the risk.

Regards Ina

[Dharkwolf]

First off, don’t be sorry for stating an opinion Ina, it’s yours and one of the great things we can enjoy is the fact we can say what we think! (So long as we stay civil)

Now as for the genetic determination, I still beg to differ, so I will expand on my previous argument, I’ll try to keep it simple, but I apologize in advance if it gets a little technical.

Statistical analysis of the type which Wiesner and Willer must have used (roughly 20 years ago I presume?) is based on the observation of phenotypes. You don’t actually take into account the genetic make up of the animal at all, but you infer genetic information from the phenotypes which you observe.

Now this approach is theoretically perfect, but it is very difficult with this kind of approach to take into account environmental effects, especially those environmental effects that you cannot foresee.

Let me give you a somewhat silly but illustrative example. Lets say there is an isolated colony of female birds (we shall call them fems for now). Now these fems have a number of traits which are genetically determined, their plumage can be blue or grey, their tails can be long or short and their eyes can be black or grey. Now every so often a male fem flies in to mate. Every year it is this same male (lets call him prince charming) who comes to mate. Prince charming has a preference for female birds which have short tails and blue plumage. If you carried a study out on the reproductive success of these birds, you would reach the conclusion that you are faced with a situation where there is a strong correlation with genetics, and a multigenic situation at that. Fair enough. But then prince charming dies and now it’s the black prince who comes to visit the colony, and the black prince has a penchant for females who have grey plumage and black eyes. If you were to continue your study your data would become rather skewed, and you would have lots of trouble defending this data. The reason? You were using a statistical analysis to measure an environmental factor (the preferences of prince charming) even though this factor does have a genetic basis.

My argument is that something very similar applies to dogs and cryptorchidism. The basis for this argument is the actual process of testis migration, which is not only complex but takes place outside the womb, which is a relatively well controlled environment. It takes place in the living, kicking running puppy!

One must also take into account that the environmental conditions in which dog breeds evolve are particularly odd. The selection of which animal breeds successfully is almost entirely up to human discretion, thus it is the animals which best fit the arbitrary (from a darwiniean point of view anyhow) requirements of their owners. This arbitrary environment would probably not be taken into account in a statistical study which would take place today, much less in one which took place twenty years ago, quite simply because it was taken as a given.

Alright, lots of blabbing, but one can wonder, what the whole point of it all is? Lets say that having a certain shape of a pelvis is going to be a significant factor in whether a dog is cryptorchid or not. So what? Even though it is a morphological feature it is still clearly determined by genetics.

The importance of this sort of thinking is, that if you start to think that the determining factors are perhaps environmental and not fundamentally genetic, you get into a different mindset, and are able to better understand where the actual problem lies, and would thus be in a better position to determine whether a given dog should or should be used for breeding.

I cannot resist but ask… would the morphology of the hindquarters be significantly different in those races with a high degree of cryptorchidism (which you just mentioned) and those which have a low incidence of this? Anyhow, as always, just my idea.

[michaelundinaeichhorn]

genetical (and other) research in dogs is still done and never stopped, though I don´t know when the last statistics of this disease has been done I doubt very much that they are 20 years old. Even if you take in count the different tastes of human beings it is very clear that there are breeding lines and breeding dogs that have an highly increased amount in cryptorchids in their offspring. As you wrote before: it doesn´t really matter if it is the pelvic-construction - what I don´t think is very likely- or hormonal problems (that are thought to be the main reason at the moment). As long as we don´t know enough about the genes themselve we have to go for statistics and most statistics on genetic diseases in dogs are done on a quite big population. In Germany German Shepherds, Poodles and Boxers have a very big population, most of their puppies don´t stay with breeders but with normal families, that didn´t buy the dog because it is from a special breeder or out of a special breeding line but it is from the next breeder around or the only puppy available at the moment. It is not very likely that especially this cryptorchid-lines have been selected or influenced by a special enviourment differently to all the others.
If you look at the breeds they have very different pelvics (dog pelvics aren´t that different anyway) but are all out of breeds that are in the unlucky situation to have breeders that go for special looks and therefore didn´t select very thoroughly for health, most of those breeds have over-avarage health problems of very different kinds. German Shepherds for example don´t only have orthopedic problems but almost every other disposition you can think of. Boxers didn´t only use sires with cryptorchid problems but also with heart problems, just because they were thought to be beautiful. The offspring of this sires caused problems till today.
Interesting new points of thinking and looking at problems are always worth a discussion and research, but shouldn´t change breeding policy to a weaker selection before they are proofed to be right. We had a lot of intersting new theories in veterinary medicine the last years, most of them turned out to be totally wrong a few years later, very few of them have been right.

Regards Ina

P.S. Sorry for the sorry, in some ways it is very difficult for me to write in English and some translations are wrong or may be unpolite.

[Dharkwolf]

Note that I never gave any advice either way as to whether a dog should or should not be bred, I do not consider myself qualified to give that sort of advice (though perhaps to people who read what I write might get the wrong impression) For final breeding advice go to see your vet. Maybe get a second opinion if necessary.

What I was doing was speculating, which I enjoy doing. Seems like the hip structure is not really a solution, that was just an example though, my basic thought was that you were up against a *physinomical* cause as a primary cause or at least a significant cause as opposed to a genetic cause. ie most or at least many of these cases are caused by the physionomy of the animal rather than his genetics. Naturally hormonal problems are a fairly obvious possibility (though hormonal problems again are not necessarily linked to genetics) and you can also have situations where there is a malformation or even an absence of the testis (though I doubt that dogs are routinely checked to see if this was the problem or if simply the testis ended up migrating to the wrong spot and never ended up in the scrotum, correct me if I'm wrong) Bottom line is: Eight years of experience working with the genetics of several species (Humans and rats as models, but also and primarily protoozooan parasites) give me the hunch that this sort of issue is not a primarily genetic one. There just seems to be an underlying trend to pretend it is (and it is quite possible for a statistical analysis to show up a "false" genetic correlation)

Enjoyed the discussion I have to say.

PS Didn't I tell you not to be sorry? You don't have to be sorry about being sorry either... and no need to apologize about your English I can assure you it is perfectly understandable and far far better than my german.

[slarman]

Hi,
Why not ask a genetics expert regarding the inheritance of kryptorchidism.In humans,it is the woman who passes on the genes to produce testicles in male children NOT the man as you would assume-I think you may find the same occurs in most animals.
Simon

[Dharkwolf]

Hi Slarman... interesting idea, just two comments.

1) It is not a question of "passing on the testicles" but rather a question of the correct migration of the testicles into the scrotum
2) What is a genetics experts? Ina is a veterinarian who seems to know pretty well what is going on, and I, well I have eight years of research experience does that count?

Incidentally I'm really curious about that idea of "passing on the testicles" being due to the female... do you have a reference for that?

[slarman]

Hi,
Perhaps my wording was wrong.In humans,the woman passes on the genes to produce the males testes-my reference is biology books and science shows,the woman also passes on the size of the testes,and this can be heavily influenced thru environment,diet and the overall health of the pregnant woman.I don't say it's all the woman,the man has to influence the gene pool of the child,however,the final expression of the testes are more directly influenced by the pregnant woman in utero.
As far as expertise goes I can e-mail an animal genetics professor at the University of New England,Australia,who has authored a book on the genetics of the dog to find out more onthis subject.
Simon

[michaelundinaeichhorn]

Originally Posted by Dharkwolf

(though I doubt that dogs are routinely checked to see if this was the problem or if simply the testis ended up migrating to the wrong spot and never ended up in the scrotum, correct me if I'm wrong)

In some way they are routinely checked. Abdominal testicles have a high tendency to envolve tumors. For that reason they normally are removed by surgery, at least when this happened. the abscence of one testicle is extremly rare.

Ina