Line Breeding Dogs … Why Dog Breeding Genetics Say Not To!
Many show dog breeders seem oblivious to the dangers of line breeding dogs, and in fact, hotly defend the practice.
What Show Breeders Mean by “Good for the Breed”
Well, as registered dog breeders we are told that we must continually strive to “improve” our breed. What does this mean exactly?
It means how closely the resultant progeny conform to the documented “Breed Standards” of the breed in conformation, coloring, size, weight, ear set and a dozen other parameters.
And how is this measured? By how well such dogs succeed in the Show Ring against others of their breed.
Naturally, anyone who is a serious show breeder will do whatever it takes to produce dogs that win, self righteous in the knowledge that they are supported by their Kennel Club for dutifully “improving the breed”.
Where Does Line Breeding Dogs Fit Here?
Motivated by trying to produce the perfect dog that conforms exactly to the associated breed standards, such breeders deliberately breed outstanding show animals back to their close relatives in order to both stabilize and stamp their line with its special characteristics.
This is line breeding.
In the words of one respected breeder:
Linebreeding is a method that breeders will use to improve upon and try to eliminate structural and health problems from their dogs.
It is the breeding together of dogs that have a well bred superior common ancestor who has attributes that the breeder is attempting to reproduce and improve upon in their own dogs.
Linebreeding is an attempt to concentrate the genetic contribution of an outstanding ancestor in the resulting offspring.
As well once started one must continue the linebreeding process or all will be for naught. (Underlining my own)
Yes, serious respectable show breeders are very committed to line breeding... it gives them the results they are looking for.
Here is an excerpt on this topic from the BBC documentary "Pedigree Dogs Exposed" :
Such breeders declare that linebreeding is not inbreeding, as in inbreeding, close relatives not separated by more than one generation are bred e.g. brother to sister or mother to son.
And even inbreeding is considered OK by many show dog breeders if done sparingly in the hands of “very experienced breeders”.
Line breeding dogs is considered "safe" by show dog breeders if the superior common ancestor that is used repeatedly in a genetic line appears to be healthy, and turns out (in retrospect!) to have lived a long life.
But is it really?
A real linebreeding example
Let’s look at a real example of line breeding dogs in the light of
basic dog breeding genetics
to see what the implications of this practice might be.
In this example, two outstanding show dogs appear several times in the one 4 generation pedigree. One is the daughter of the other who on his own assumes the position of 5 ancestors in the pedigree.
Consider this scenario:
• This super male dog (shown as a white box) carries a genetic defect i.e. genes are Dd. Because most defects are recessive, he will appear healthy and the defect will be completely unapparent and unexpressed.
• Every other dogs in the pedigree, including his super daughter who appears twice in it (pink box), is genetically free of the gene i.e. genes are DD (unlikely though that is!).
• The defective gene is inherited by 50% of the offspring (which is what would happen normally under the laws of inheritance).
Here’s the scenario represented as a pedigree:
You can see that while every dog in the ancestors of the resultant litter are perfectly healthy, no doubt with many show winners amongst them, half of the litter resulting from this pedigree scenario would be affected by the genetic disease i.e. dd (and the other half would be carriers for it i.e. Dd).
The Message Here...
The incidence of genetic diseases in purebred dogs is relatively high.
When dogs carrying the same genetic weakness (highly likely in closely related animals of the same breed) are mated together, the risk that they will have offspring that actually expresses and therefore suffers from the weakness is very high.
So, while line breeding does produce some “outstanding” show animals, it also results in just as many defective “duds” not suited to any purpose, least of all as innocent people’s beloved pets.
Another thing to suffer in any animal with closely related parentage is what is called in genetics “vigor”. Vigor refers to the fecundity (fertility), health and life expectancy of the animal.
Inbred animals are more prone to not only genetic defects, but also poor reproductive performance, have smaller litters and are simply not as robust and long-lived as out-bred animals.