The pedigree problem

by Jo-ann Hodgson in At home on 21.08.08

No one would encourage a grandfather to mate with his granddaughter. But inbreeding among dogs is common practice within pedigree circles, often with disastrous consequences.

This week a study by Imperial College London formed the basis of a saddening BBC documentary into the deformation and disease-prone nature of today’s pedigree dogs - dogs which frequently win Crufts and other championship shows.

The programme compared images of pedigree breeds a hundred years ago with today’s show-pieces and found that many are now anatomically different. Many German Shepherds, for example, have abnormal development of the hip joints and the shape of Bull Terriers‘ skulls barely resembles what it did when the standards for the purebreds were original set.

As anyone with a basic knowledge of genetics will know, defects and disease become more common the more closed the gene pool becomes.  Inbreeding is rare in nature - close relatives rarely mate and will only do so if they have little choice. So the fact that pedigree studs father dozens of litters in their lifetime, to relatives as close as daughters and granddaughters, is not good news.

The study found that Boxer dogs are so closely related to one another that genetically, 20,000 dogs looked like a population of just 70. And a population of 12,000 Rough Collies looked like that of 50.

Among the problems that have arisen due to this practice are that Boxers are prone to heart disease and epilepsy - a particularly disturbing bit of footage from the documentary showed a two-year-old Boxer being held down and comforted by his owners whilst suffering numerous fits on the kitchen floor - Dalmatians to deafness and Golden Retrievers to cancer. 

And as much as 20 to 30% of one of England’s favourite lap dog breeds, the Cavalier King Charles Spaniel, suffers from what has been described in humans as one of the most painful conditions you can have.

Syringomyelia is caused by a malformation in the Cavalier’s skull and reduces the space available to the brain, often forcing it out through the opening into the spinal cord. Basically, the spaniel’s brain becomes too big for its skull.

Veterinary neurologist Clare Rusbridge said on the BBC programme: “If you took a stick and beat a dog to create that pain, you’d be prosecuted. But there’s nothing to stop you breeding a dog with it.”

The exaggeration of prize-winning features in pedigree breeds can also cause health problems. For example, Bulldogs have become so oddly proportioned that they now find it hard to mate or give birth naturally; the squashed faces of Pugs can bring about breathing problems; and the folds of flesh on Basset Hounds‘ increasingly short legs can cause skin complaints.

And the effects of inbreeding on temperament has lead to some purebreds being abandoned in re-homing shelters due to owners not being able to cope.

To prevent the deterioration of pedigree dog health, researchers suggest that there be a limit to how many times a stud can father a litter and that breed rules should be relaxed. They are also encouraging owners to mate their dogs with those from abroad.

Meanwhile, maybe programmes such as this might help us appreciate the happier, healthier non-pedigree dogs. A new era of mongrel chic, perhaps?

IMAGEs by Flickr users tanakawho and DMBfreakNo41