Canine Hip Dysplasia (CHD)
A Discussion of Ethical and Real Life Concerns 

Well, this topic is one that most all Working Dog folks are intimately aware of and educated to the highest levels about.  I will bet that there is not one of you out there that has not either had some form of this disease in one of your own dogs or, for sure, in a dog that you are closely associated with.

So what is new in the realms of this common and often debilitating disease?  Well, to be honest, not a whole lot but what I plan here is a ethical discussion on the topic and maybe raise some new thoughts on the issue.

We all know the routine which involves having your dog’s hips x-rayed at about 6 months if you want some early indications of her chances of having the disease and than again at two years of age to get her OFA’ed. (PennHIP can, of course be used as well.) If the results come back as severe you can bet your dog is either limping now or will be shortly.  If they come back as excellent you can pretty much bet that there will be no dysplasia later in life.  But there are gradations in between these two extremes and I have seen dogs develop clinical signs when hips were judged to be fair to good and dogs I have seen dogs never take a short step in their lives that were judged to be mild to moderate.

These observations should certainly bring the big issue to bear and one that I have spoken on dozens of time. As a clinician and practicing veterinarian I consider hip dysplasia to be a clinical disease.  In other words, if the dog does not limp, she does not have it.  If she does limp and other tests support the diagnosis of which radiographs are the main supportive tests, than she has it.  But of course life is not so easy.  In the case of CHD, it is known for sure that there is a (read probably many) major genetic component.  This fact means that if your dog does not limp but has radiographic signs of CHD than it is probably not a good idea to breed her, even though by my definition your dog really does not have the clinical disease. 

The genetic links are strong and proven but just how strong are they and how do they manifest themselves individually?   That question has no million dollar clear cut answer. Remember when I said I had seen dogs that were graded good develop the clinic disease of hip dysplasia…well, I have seen dogs who were excellent bred to dogs that were excellent throw pups in the moderate to mild range.  Oh brother, and you have been taught that this OFA stuff is pretty black and white when breeding dogs on the extremes of the ranges.   NOT SO!  The reality of the situation is that the genetics are complicated and as we decipher the canine genome we will probably find that this disease is scattered about the multiple chromosomes and it takes several of these affected genes for the disease to manifest itself.

Of course this brings up the ethical concerns of CHD.  For the purists we should not be breeding any dog that has CHD.  Unfortunately even the purists have a hard time defining what CHD is.  Perhaps it is anything less than excellent hips?  In that case and we sterilized all dogs that were less than excellent than we would have about one and one quarter generations left of the German Shepherd Dog.  In fact, it is my opinion that about every dog in some breeds has at least some of the CHD genes in their genome.  And what about the dogs whose body is based on CHD?   English Bulldogs and the other smooshy faced breeds all have the disease….but again, is it a disease since all of them do not limp but all of them show radiographic signs.

I alluded to the canine genome earlier.  It will not be long before it has been mapped and we probably will know how many and which of the genes carry the CHD issue.  How many of you would be able to make all of your breeding plans based on that?   If your dog is doing great, scoring tripe 95’s and better but carries, say, 90% of the CHD affected genes what then?

 The last little issue to throw into the mix is environmental factors.   It is known beyond a shadow of a doubt that nutrition plays a huge role in the manifestation of the disease.  If you feed your dog too much and your dog carries certain genetic factors you could give him the clinical disease that he may not have had normally.  Physical injury can also exacerbate the clinical disease such as overwork on hard surfaces during the bone growth phases of life or excessive jumps or even falls.  How do these influences affect your decisions on the reproduction of your prized dog?  

I hope I have been able to shed light (actually I think I shed shadows) on the CHD topic.   At this point in our technological and medical understanding a good portion of our breeding decisions made about this disease are based on educated guesses. There are far too many factors, variations and gradations of the disease with far too many influences on it to make this issue black and white.  Not until we actually map out the genome will we know for sure what causes the problem and how to prevent it once and for all…although the elimination of a breed will probably not be an acceptable solution.  For now all we can do is try to eliminate the worst carrier  of it and make decisions based on the whole package.   There are things a whole lot worse out there than a mild or moderate radiographically diagnosed (no clinical signs) case of CHD that should take precedence to genetic modifications of the overall gene pool as there are some things that are so superior that they should not be removed from the gene pool.