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Date Posted: 19:23:39 09/16/03 Tue
Author: Dan G.
Subject: Re: It DOES become clearer
In reply to: JB 's message, "Re: It DOES become clearer" on 12:43:51 09/16/03 Tue

I think I'm reiterating some of Johns points, but here it goes anyways.

I think all of the problems and complexities that are found with HD is because it is a polygenic trait rather than a monogenic one and because of its low heritability factor aside from a host of other factors. When they say polygenic, it is not yet known whether that means 5 different genes or 100 different genes especially since the hip joint has bone, ligaments, muscles, cartilage and possibly other factors that determine a tight hip or a loose hip. Then add to this other non-enviromental but physical factors that play a role in hip development, such as a dog that is straight legged in the rear (underangulated) which you tend to see alot of in the BB, which will transfer all of the pressure of movement on the hip joint and influence negative development.

Some of the other obstacles that geneticists and breeders are confronted with:
1) Dogs with DJD can also be affected in the knees, elbows, shoulders and vertebrae.
2) Some of these genes may be hidden genes that do not show up for several generations until HD comes up in your progeny once again.
3) Another possibility is that one set of genes may combine well with another set but yet combine badly with a different set of genes.
4) There can be a large variation in influence one gene may have over another. This alone throws a huge wrench into the discovery of the genetic markers for future testing.

Now if you go to the Penn hip site, you will come across this text:

"Hip dysplasia was first described in 1937. It is a disease of complex inheritance. Accordingly, veterinarians and dog breeders have attempted to eliminate CHD through selective breeding strategies. However, the reduction of CHD frequency in pure-breed dogs has been disappointing."

and this is from the OFA site:

"Do not ignore the dog with a fair hip evaluation. The dog is still within normal limits. For example; a dog with fair hips but with a strong hip background and over 75% of its brothers and sisters being normal is a good breeding prospect. A dog with excellent hips, but with a weak family background and less than 75% of its brothers and sisters being normal is a poor breeding prospect."

As you can see from all of this, the fact remains that there are still too many unknowns in regards to HD and the genetics behind it. What we do know is that selection does help, and I in no way advocate using poor specimens in breeding programs to overcome the ill effects of over saturation of a certain type within a breed. Quite the contrary, I think that it is important for people to consider the pedigree and the littermates of an individual when looking at hip evaluations as being the important and driving factor rather than just the individuals hip scores.

JB,

Sorry about the Bossman/bad hip comment. What I should have said is average hips, because saying that bad hips can be bred with is wrong as well. My point with "bad hips" meant that they were not acceptable hip scores for you. Again, bad choice of words, sorry.

I know very little about Greyhounds, so I won't touch that subject, except to say that they do have great hips. Maybe we should do a Greyhound X Boerboel!! LOL O.K., O.K. to the purist lynch mobs out there, I was only joking. :) But honestly the fact that the Boerboel does not seem to have as much of a problem with HD as some of the other Mastiff breeds may be to possibly having been crossed with the Ridgebacks in the past, which also have good hips or maybe its natural genetic variability due to SA breeding practices. Wouldn't that be ironic, intentionally or not, the same practices that they are criticized for, are the practices that also provide the breed with its healthy level of breed vigor. I mean, honestly, compare it to the EM or BM and what do you think? They didn't do such a bad job afterall?

Dan G.

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