Mating and orthopedic problems

There is an inherited orthopedic disease for every breed of dog. Some traits are transmitted by a single dominant or recessive gene, while others are polygenic, i.e. transmitted by several genes. Polygenic traits are more difficult to control through mating, and in fact often result from human intervention in dog genetics.

Some diseases or malformations are the result of genetic mutation, but they are often the result of selection during mating to obtain a particular characteristic. For example, we select Bull Terriers and Pugs for an increasingly short nose, but the lower jaw remains the same size and projects forward.

Breeding for certain qualities has led to numerous malformations. Basset hounds have problems with radius closure, a forelimb disease, because they have been bred to have short limbs. Dachshunds have numerous back problems because of their long torsos. Hip and elbow dysplasia has become an important disease in large breeds, as they have been selected for rapid growth and large skeletons.

Mating between parent animals has led to other diseases. Retinal dysplasia or inner ear problems, which cause blindness or deafness, are common in Labrador Retrievers and are often the result of mating between individuals carrying the gene. The carrier animal is bred intensively, and three or four generations later there is mating between its offspring, resulting in the recessive trait and deformity. Often, the origin of a single disease can be traced back to a single pedigree. For example, if a racing animal is the best racer of all time, it will be bred many times, but if it has a bad characteristic, it will be reproduced throughout the breed in 8 to 10 generations.

OCD and osteochondrosis, which affect the joints of large-breed dogs, are other frequent orthopedic diseases. Patella luxation, legg-calv-perthes, femoral head necrosis and hemivertebrae are common in small breeds.

The only way to reduce the genetic transmission of these diseases is to examine breeding stock carefully. It is very important to test animals for these diseases before breeding them. Breeding stock should be taken to the vet before breeding. A general physical examination costs between €25 and €30. For more specialized tests, you can expect to pay a little more (for hip dysplasia, for example, from 90 to 120€). If the animal is diagnosed with an orthopedic disease, costs can be high. Prices range from $400 to $500 for an OCD, and up to €2,000 for a hip replacement. Corrective surgery does not make the animal fit for reproduction.

When choosing an animal for reproduction, the ideal is to examine the pedigrees as far back as possible, as it is still impossible to detect animals carrying a harmful gene. There is no such thing as a genetic marker, but genetic analysis will be the fashion of the future. A great deal of research is currently underway in the USA to fully describe human DNA and pinpoint the location of all traits. Perhaps in years to come, this science will be applicable to animals.

Vivianne Venisse MDV