For purebred dog lovers, the idea of crossing two breeds causes alarm. However, it's possible that doing exactly that will improve the health and wellbeing of some breeds, particularly the toy-sized dogs. After all, many of our modern purebreds have been developed by carefully mixing breeds with specific characteristics.
Many purebreds have undergone radical changes in their appearance over the years through selective breeding, and in a number of cases, these changes have led to health concerns. The English Bulldog is an example. What was once a sturdy and athletic dog, is now a heavyset animal with breathing difficulties due to his short nose, and is unable to reproduce without assistance.
One serious problem that occurs in some breeds is the Chiari-like malformation, which occurs when the dog's skull is too small to contain the brain as it grows. The result is the back portion of the brain (the cerebellum and medulla) is pushed out of the small hole in the back of the skull, known as the foramen magnum. This blocks the normal circulation of cerebrospinal fluid and increases fluid pressure in the brain, resulting in pain and neurological symptoms.
This condition occurs most frequently in small breeds with the more dome-shaped heads, such as the Cavalier King Charles Spaniel, Brussels Griffon, and Chihuahua. Treatment usually involves the use of drugs to reduce cerebrospinal fluid pressure, but some individuals don't respond to this. They may need surgery to remove part of the skull at the back to improve cerebrospinal fluid flow.
Scientists from the University of Surrey have been evaluating whether careful crossbreeding could reduce the chances of a dog developing Chiari-like malformation. They worked with a knowledgeable breeder of Brussels Griffon and mated a dog with the malformation to an Australian Terrier. This breed resembles the Griffon in appearance, but has a longer skull. The offspring were then mated back to a purebred Griffon.
The study involved 27 dogs and occurred over a three-year period. Magnetic resonance imaging (MRI) was used to measure skull shape and angles. The outcome was that with careful crossbreeding, it was possible to produce first-generation offspring that closely resembled the Griffon. When those offspring were mated back to a purebred Griffon, the result was second-generation puppies that were very close indeed to the Griffon breed standard as described by the international kennel clubs, but with a lower risk of developing Chiari-type malformation. At this stage, researchers couldn't say that the offspring were completely clear of symptoms of the disease because the onset of pain and neurological abnormalities can occur later in life, and the offspring were MRI scanned at only twelve months of age.
Is this type of careful crossbreeding something that could benefit other breeds with health issues? It's possible, but the genetics of appearance isn't always an exact science. This means that the appearance of the cross-bred puppies may not be predictable, which would be a major issue with breed fanciers. It's certainly something that could be kept in mind as a potential solution to breed-related medical conditions.
Photo ©Nate Marsh, Flikr