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So not to offend anyone involved with various breeds, I am going to use fictional breeds. In keeping with simple explanations, I am going to use a simple dominant/recessive issue. Bear in mind,
most things regarding dogs are polygenetic; this means there are various gene pairs involved. The more genes, the more complex. However, for here: simple Punnet Squares would predict simple explanation with
what ideally would come from a four-pup litter. Remember, dogs do not read the books and nature is funny. A litter can end up with all clear, all carriers, all affected or any combination of them.
On to the example!
Person has four dogs:
Two Belgian Chocolate Hounds - BCH - (male and female from unrelated litters)
One French Caramel Terrier – FCT - (male)
One Mexican Vanilla – MV - (female)
The breeder thinks it would be neat to "create" a few "new breeds" (designer mutts) so he wants to cross:
BCH x MV and create ChoVans
FCT x BCH and create ChoCars
He assumes that since he is crossing breeds that health is no worry, after all he knows from reading things on line that crosses are healthier. In addition, he got his dogs from friends who made sure
the parents all saw the vet regularly and certainly the vet would know if the dogs were not healthy.
Belgian Chocolate Hounds have a genetic issue called Purple Blotch Syndrome (PBS).
This is a recessive problem and causes varying degrees of purple blotching and hair loss at the site. All of the parents showed no blotches so it was assumed they were fine. In one litter that produced the BCH male, the parents were carriers. The male inherited both recessives. However, PBS affects to varying degrees, some affected dogs have no apparent signs. This BCH had no blotches. The litter the female was from the sire was clear and the dam a carrier. This female is a carrier.
BCH male – pp (affected)
BCH female – Pp (carrier)
PBS has never been documented in the other breeds owned.
The ChoVan litter produced four puppies.
All are PBS carriers. No puppy is affected because the disease is recessive – but they all carry the PBS gene. Technically, the pups are healthier than the PBS parent is because they will not be affected. The ChoCar litter produces four puppies as well. Two puppies are clear and two are carriers.
ChoVan Litter – Pp, Pp, Pp, Pp ChoCar litter – PP, PP, Pp, Pp
As luck would have it, one ChoVan pup was kept and one ChoCar pup was given to a friend who was interested in breeding. The ChoVan pup is a carrier and as luck would have it, the ChoCar pup was one
of the two carriers.
When they grew, the two friends crossed the pups together. In the litter of four puppies, there was one clear, two carriers and one affected with PBS.
ChoVan Pp x ChoCar Pp – PP, Pp, Pp, pp
Now, during this time, the FCT and MV were crossed to create French Vanillas. Again, assumption was the pups would be healthier.
However, both breeds are known to have Crazy Butt Syndrome (CBS). Both of these dogs are carriers of it. In the litter of FVs, one was clear, two were carriers and one was affected.
Yes, these are made up breeds with made up health issues, but the reality is there. This happens daily when dogs are bred: pure or cross.
When breeders cross breeds together, are they truly creating healthier offspring or just putting undesired genes into a new generation of dogs? The more this is done, the greater the chances of a
health issue exploding even in a crossbred population.
Next time someone insists crosses are healthier than purebreds please remember basic genetics. It really is not true. A crossbred dog can have the same chance of inheriting a health issue as a
purebred if the genetics are right or wrong depending on your point of view.
Regardless of what is being bred, health and genetic testing is necessary.
*please note - not all health issues in breeds have genetic tests therefore you must know what can be screened for and not. If there is a genetic test, is the breeder using it? Ask the breeder for what
they are testing and how.
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