Dogs and Hybrid Vigour

Why does is seem that certain breeds of dogs are more likely to develop specific health problems than other breeds? For example, why are Doberman pinchers more likely to have heart problems than other breeds? You may or may not be familiar with the term “hybrid vigour”, but you have probably run across this concept before. In this article we will discuss how this term can be used to explain why various dog breeds are predisposed to developing certain health issues.

How are dog breeds created? If you think about it, all dog breeds descended from a single ancestor related to the modern wolf. The Chihuahua and the Great Dane, as well as the Yorkshire terrier and the Bull Mastiff all came from the same genetic background.

Genes are pieces of DNA that are located deep in each cell of the body. All of the information used to create appearance, and to a certain extent to influence behaviour, is written on genes. Therefore, in order to create different types of dogs, we created a process called “genetic selection”. All this means is that over the years we selected animals with similar characteristics, and by doing so we selected animals with similar genes.

As we said above, in order to create different breeds, dogs with the desirable personality and physical traits were selected. These dogs were bred together. To ensure that the breed characteristics were consistent, hundreds of years of breeding narrowed the gene pool. What this means is that there was a lot of what we would consider “in-breeding”. Dogs were bred to their relatives to make sure that the breed remained “pure”, which means that they have very similar genes. Therefore this in-breeding (genetic selection) allowed us to create distinct and different breeds. However, as you can imagine, in-breeding also brought with it some health issues.

Why does this form of breeding, or genetic selection, contribute to health problems? When dogs with similar genes are bred together, any “faulty” genes get combined. These faulty genes may predispose the animal to a health problem. A dog that has more faulty genes is at a higher risk of developing the health problem.

“Hybrid vigour” can also be considered like a dilution effect. When two dogs with different genetic backgrounds are bred together, it is unlikely that they have similar faulty genes. Therefore, the genes from one parent will usually compensate for the faulty genes from the other parent. This implies that the term hybrid vigour refers to the increased overall health of the puppies when animals with different genetic backgrounds are bred together. This includes many shelter mutts.

Hybrid vigour is not an easy concept to understand. But what it boils down to is that purebred dogs have similar genes. And for the same reason that dogs with similar genes tend to look the same, they also tend to be predisposed to developing the same medical problems. Labrador Retrievers are at a higher risk of developing hip dysplasia, Yorkshire terriers tend to get collapsing trachea, and Cocker Spaniels often develop ear problems.

For these reasons, if you own a purebred dog, it is always a good idea to be aware of the medical problems that your breed is predisposed to. This way you can be aware of your options and look for signs of problems in case your pet does develop the medical issue. Not all individuals of a certain breed will develop the problem; they are simply at a higher risk. If you are not prepared to take that chance, perhaps you may want to consider getting a mixed breed dog. If you have questions about hybrid vigour or breed predispositions, you have a couple of options for sources to provide you with information. Books or websites specifically devoted to your breed, good breeders, breed clubs, and of course your veterinarian are all good places to find information about a specific breed.