Hybrid Vigor Myth

This article is to clarify the Myth of Hybrid Vigor. Hybrid vigor in dogs does NOT exist. It only exists in theory - much like Communism. Health problems cannot be avoided by mixing breeds - they can only be reduced through responsible breeding. Additionally, purebreds are not unhealthy due to inbreeding. That is also a myth. Unhealthy purebreds are a result or poor and irresponsible breeding. Mixed breeds are NOT any healthier than pure bred dogs. A mixed breed dog can be just as unhealthy as any poorly bred pure breed dog. See links on so you think you want a dog for more info.

Unfortunately, most purebreds that you see in pet stores, on the side of the road, in the Wal-mart parking lot, or advertised on some puppy buying website are in terrible shape - thus the notion that purebred dogs are unhealthy due to inbreeding. They have poor structure. They are in poor health. Those are the ones that people are spending a small fortune on. Unfortunately, that's the general public's view of purebred dogs - just the poorly bred ones. And more unfortunately, the general public is only exposed to irresponsible breeders, rarely do they encounter the responsible ones. I would say that 98% of breeders are irresponsible across the board. That only leaves a handful of the good ones - the ones that are actually improving the breed. See links on so you think you want a dog for information on responsible versus irresponsible breeding.

The main concern with hybrid vigor is that is tends to give the public the notion that they can breed their dogs with anything and anyone and it will automatically be "healthier." This cannot be further from the truth. Two unhealthy dogs do not produce healthy puppies. The types of "breeders" (term used loosely) that push the "hybrid vigor" myth are the types that get poor purebred quality dogs, then produce poor quality mixed breeds. No responsible breeder would do that. And there is not a single breed club in America that endorses that practice nor do I know of a single vet that endorses that practice. The people who do that are only after the mighty dollar.

Hybrid or cross-breed vigor can only work in theory if two high quality dogs that are not affected NOR carriers of the disease are bred. However, this is not what happens in practice. What happens is that said "breeder" will buy some dogs, breed them, sell puppies as designer dogs. That's actually what most of them do with purebreds as well. They are essentially outcrossing two unhealthy gene pools. They do NOT get health certificates on their dogs. Many of the hereditary diseases are asymptomatic. They do NOT know the dog's pedigree, thus not know if the dog is a carrier or not. They are basically going into it blind as a bat with only $$$ in mind. Hybrid vigor in dogs now is really just another marketing ploy.

They are also making the mistake that all diseases are randomly distributed. They ASSUME that due to random distribution, acquiring a dog and NOT doing health clearances, will mean that their dog should have the same risks of producing diseases as any other dog. Wrong assumption. Genes are not randomly distributed - genes are inherited from the sire and damn. Puppies cannot have genes that the parents DON'T have. It isn't possible. Puppies can only inherit the genes the parents do have. If the parents have unhealthy genes, then it isn't too hard to see what the puppies will inherit. This is taught in a basic probability class. What happens when you mix 2 bad sets of genes? You get puppies with bad genes! Duh! 2 unhealthy parents don't make 1 healthy puppy, unless it was a miracle. And seeing how I haven't won the lottery, miracles aren't all that common.

Having a small gene pool has nothing to do with health problems. Having a gene pool full of genetic disorders - large or small - and breeding irresponsibly is a problem. Many breed clubs actually have programs in place that track the health of the breed. There's always www.offa.org and the chic registry. Most breed clubs also do a mass survey to owners every 3-5 years to track trends in health. Then it is up to the breeders to try to breed away from those problems. But remember, those are the responsible ones. The irresponsible people probably don't even know that a breed club exists.

Additionally, many diseases can be multigenetic or plietropic, but there hasn't been a documented one in canines that is protagonistic plietropic. Multigenetic means it multiple genes have been linked to a disease. An example would be canine hip dysplasia. Plietropic means that the gene has multiple effects. An example of this in humans would be PKU (phenylketonuria) that can cause mental retardation, reduced hair, and skin pigmentation. An example of this in canines are colored linked diseases. There are many diseases in canines that have been linked to light colored coat or lack of pigmentation. Most of the time, what we see in dogs and humans is antogonistic plietropic. Antagonistic pleiotropy refers to the expression of a gene resulting in multiple competing effects, some beneficial but others detrimental to the organism. This flies in the face of people who say that the bigger the gene pool, the fewer risk of diseases. Just not true.