# Questions about VWD



## Harley_chik (Nov 7, 2008)

What I think I know: There is a test that can tell if the dog is affected, a carrier or clear. Affected dogs should never be bred and carriers should only be bred to clear dogs. (correct me if any of this is wrong)

What I'm not clear about. If two clear dogs are bred are their offspring "clear by parentage"? If a carrier is bred to a clear, are the pups carriers, clear or a combination. Are there any estimates of how many dogs are carriers? For example, it's estimated that 70% of Maltese have non-symtomatic liver issues. Not breeding any of those dog would significantly reduce the gene pool. However, it's unkown how liver issues are passed on and there are not genetic tests at this point. I've heard people say if every breeder tested for VWB, the disease could be erradicated. I don't understand how that could happen if carriers produce more carriers. I'm not saying a carrier shouldn't be bred. I understand that a carrier may have a lot to offer and if they are bred to a clear, the offspring won't be affected.


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## cbrand (Aug 9, 2009)

Are you familiar with punnett squares? These predict the genetic make up of an individual and they are particularly helpful when we are talking about recessive genes that require two copies to produce an "affected" individual.

In the below punnett square, we will call "Carrie" a VWB carrier and Rusty a VWB clear. If we breed Carrie and Rusty, we can expect overall that 50% of our litter will be VWB carriers. If we test our puppies and try our best to pick "clears", then we can eliminate a recessive disorder in a couple of generations.

BTW... a punnet square is actually a predictor for an individual. So every puppy from the above breedng has a 50% of being a carrier. We just take that and extrapolate it out to the entire litter. In reality, in cases of bad luck, you could have an entire litter of VWB carriers.


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## thestars (May 2, 2009)

If one breeds clear to clear, the puppies are clear by parentage. However, I believe that every other generation be tested to ensure that all remain clear. Over time, as the frequency of clear dogs increases, it should be possible to breed mostly clear to clear, and to eventually eliminate the mutant vWD gene.

Some breeds are more difficult such as the Doberman since a high percentage of them are affected or are carriers. Valuable positive characteristics of the Doberman might be lost, or highly diluted if only just using clear dogs in the breeding programs. It is reasonable to breed carrier to carrier, if an acceptable clear dog is not available for breeding. This type of mating will produce 25% clear, 50% carrier, and 25% affected, on average. The puppies should be tested and the affected puppies not used for breeding. Breeding carrier to affected and affected to affected should be avoided if at all possible. The first breeding produces 50% affected on average, and the second produces 100% affected animals. Breeding clear to clear and clear to carrier, at least for the next two or three generations will result in more clear dogs over time.

The last stats I saw on Poodles, which was several years ago, had them being 90% clear, 9 % carriers and 1% affected.


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