Pedigree Dogs and Genetics
In August 2008 the BBC broadcast a documentary concerning dog breeding and showing. What a shocking documentary it was that highlighted pedigree breeding gone crazy. Some of the scenes were very upsetting to say the least, with dogs seemingly incapable of performing the most natural of dog traits; running, jumping and breathing!. How can a German Shepherd dog (once a superb, robust dog) that appears to be slightly lame and deformed win the most prestigious dog show in the world for its type?
This program also highlighted that the show scene and the success it brings to its owners completely blinded the breeders of these dogs to the problems they have created over the years. Luckily, Leonbergers being still a relatively rare breed, have not succumbed to these extreme breeding traits that have afflicted the Cavalier, GSD, Boxers, Bulldogs, Pugs and Ridgebacks to name the main ones featured on the program. Leonbergers can still run, jump and breath properly.
What it did highlight though, is the problems that pedigree dog breeding generates by default. Dogs from a limited gene pool will naturally be more prone to inherited diseases. It is a fact that we may not like to admit, but it is never the less a fact. Cross-breeds and mongrels are the most healthy. According to the geneticists, if left to themselves, breeding indiscriminately amongst themselves, then the dog would end up over the next couple of hundred years to looking like a 15kg brown whippet like animal with minimal if any inherited problem diseases!
We humans have created all these different wonderful breeds, originally for different purposes whether it was for hunting, stalking, going down rabbit holes etc. . However, we have also therefore created dogs with certain inherited problems that are kept within each breed because nature is not allowed to rectify the problem.
We limit which dogs will mate with which bitch within each breed type to maintain the same type of dog. In our case the Leonberger. By definition we therefore have to accept that we will always have a health problem within each breed that is virtually impossible to eradicate without bringing in fresh non-Leonberger blood. When reading the following paragraphs, let us not get carried away with our health problems, as major health issues are still comparatively rare with Leonbergers and you are likely to have your Leonberger into their old age.
We have tried and almost eradicated certain inherited diseases such as CHD (Canine Hip Dysplasia) from Leonbergers. What we don’t know is if by not breeding from dogs with bad CHD whether we have increased the other inherited diseases such as DCM (Dilated Cardiomyopathy), or Polyneuropathy or kidney disease for example? Why? Because by definition we are reducing the gene pool of the Leonberger by not breeding with those dogs with one known problem. It sounds contradictory and crazy, but that is something we just don’t know because we do not have the information about the genes responsible that cause our dogs diseases.
The following 4 paragraphs are examples of what could happen using theoretical inherited gene percentages, and assumes a dog does not have more than one inherited recessive gene. Please note I am not a geneticist, but have just done the maths!
Take this example:- Say we have 2,000 Leonbergers in this country, 1,000 males and 1,000 females. They have all at some point originated from a few Leonbergers from Europe, maybe as few as 30 or so dogs in total, that were left after the wars decimated the population. Those 30 or so dogs will have certain dominant problem genes and a certain number of recessive problem genes. Dominant genes will cause problems in the dog that have them, and only need the one parent to pass the problem onto the puppy; recessive genes need two of them one from each parent to cause a problem in the puppy. As the majority of our Leo’s inherited diseases are probably recessive because we have started from a very small population that appeared healthy, then by definition almost all of our current 2,000 Leonbergers have a recessive gene for any one of the diseases. These diseases however, will only appear when both recessive genes are joined in a puppy from two parents that both have that recessive gene.
Let us say for example that the DCM disease, of which the mode of transmission is not truly known, is passed on by two recessive genes. In other words, both the stud dog and the bitch will need to have the gene in order for some of the offspring to be affected by the disease. Even though neither parent shows signs of the disease themselves or will ever get it in their lifetime. If we say that approximately 25% of the Leo males and 25% of the Leo females have the recessive gene, then by the laws of probability every 16th litter will produce a litter of puppies that will be affected, of which approximately 2 out of 8 will get the disease. This equates to approximately 1 puppy in 60 puppies that will get the disease. (Taking average Leonberger litter size of 7.5 pups per litter).
The question now arises, when we eventually get the technology via genetics to identify the dogs carrying the recessive gene, should we breed from these dogs affected with the recessive gene? Your immediate emotional answer would be definitely not! However, now reflect and remember, this will mean losing 500 dogs from the current 2,000 dogs gene pool for breeding Leonbergers. These 500 dogs could well have the best hips/elbows, perfect eyes, fantastic characters and have no other inherited diseases. By taking them out of the breeding pool we lose these substantial health positives. Is it worth taking them out of the breeding pool and therefore eradicating the 1 puppy out of 60 that gets the DCM and all that heartache for that one owner, but potentially increasing the heartache for even more owners as other diseases that will inevitably become more prevalent?
Let us now assume that we have taken the 500 dogs with recessive DCM out of the breeding pool. We now have 1500 Leonbergers with which to breed from, and lets say that the Kidney disease recessive gene was prevalent in say 15% of dogs before. Now we have eradicated the DCM genes we now have only 1500 dogs remaining so the Kidney disease gene would be prevalent now in 20% of our remaining breeding pool (assuming DCM and kidney disease gene not in same dog). Before removing the DCM gene from our dog pool you were likely to get kidney disease in 1 litter for every 44 litters born; after removing the DCM dogs you are now likely to get kidney disease in 1 litter for every 25 litters born! That is almost a whopping 74% increase!
This is only two diseases. What if we take all the other inherited diseases into account? Osteosarcoma, Glaucoma, Polyneuropathy, Epilepsy, Hermangiosarcoma, Liver disease, skin ailments etc. etc. We could end up with hardly any Leonbergers left to breed with. Those that would be left would still have their own problems that may well not have been genetically discovered yet and we will then all suffer from a few dogs left to breed that will increase the inbreeding factor to over 40% with all the associated problems that will cause.
Humans of course want to produce healthy puppies all the time, and try to eradicate all the nasty diseases that afflict our Leonbergers. We do this with the greatest of intentions, but have we stopped to think about the long term consequences of our actions. Within a limited number of dogs (approx. 2,000 for the Leonbergers), by eradicating one disease, we are making another more likely to appear because we have reduced the number of breeding dogs available. We have often heard that other diseases within Leonbergers are on the increase, and could this be due to our eradicating Canine Hip Dysplasia from our dogs for example? We have done this of course to prevent distressed dogs being crippled on terrible and painful hip joints, but have we inadvertently increased other diseases coming through?
We have had this conversation with several older vets who all broadly agree with the analysis, they have seen the same thing happen in other animals such as pigs and cows, where humans have interfered with the breeding patterns, tried to eradicate one problem, only to increase the incidence of another. Humans seem to have this arrogance that we can always change things for the better, and can always solve a problem we have created with another solution. Not so with genetics, not for the next century at least with a limited gene pool. It is the lack of dogs to breed with that is the problem.
Is there an answer to the problem of inherited disease within pedigree dogs? At the moment no matter what we like to think we are doing to improve health, in reality we are just storing up problems in other diseases for later on. We do not have the genetic technology to solve the problem, and are using just guesswork and supposition and rumour to use what we think are healthy lines. If we injected new blood every so often from other breeds related to ours, like Newfoundland's, St.Bernards etc. then we may improve the gene pool, but you cannot guarantee that you have not injected a whole new bunch of bad genes instead as these breeds have their own health issues due to a limited breeding pool.
Our Leonbergers are relatively free from major disease problems as yet, but then we are young in this country at only 30 years old, and have only just started to screen our dogs in the past 10 years or so against CHD, ED and cataracts. Unfortunately, there is a real possibility that our health problems will increase like all other pedigree breeds as time continues as the effects of limiting our breeding pool continues. So maybe we should stop at the current health screening requirements? We have great hips, great elbows and great eyes, to go any further starts to make me nervous for the reasons given. This is a very interesting topic for debate!
When they DNA tested the 10,000 pugs in this country, they discovered that only 50 had unique genes!! Interpolating, that would leave Leo’s with just 10 unique dogs for the whole country! …. Not a lot to work with ….. But it is going to be roughly the same for all pedigree breeds.
The only temporary solution I can think of at present is for us breeders and owners and potential owners to take a share of the responsibility for wanting a pedigree dog. We are all guilty of wanting a Leonberger because they are fantastic …. big, cuddly, funny, loyal and beautiful. Nothing compares. But we have created a very unnatural but magnificent dog, and are keeping it selfishly the way we want it because they are so brilliant. Nature would not give us these dogs, but we can produce them time and again through selective breeding. We must take responsibility for the risk we are taking in owning or buying one. We must inform all new potential Leo owners of the risks in owning this beautiful dog and they must accept them or not get a pedigree dog! The risks are not huge, we should not overplay them, but they are there. Insurance companies know the extra risks and increase the premiums accordingly compared to a mongrel (sometimes double).
Everyone must understand that they come with in-built health issues by definition, and we must stop slandering and slighting the poor breeder who occasionally gets the 1 in 16 litter and produces heart problems, or 1 in 44 litter that produces Kidney disease because with a recessive gene problem they had no way of knowing it was going to happen. They could use the same bitch with a different dog for the next 15 litters to produce litters with no problems whatsoever (please do not comment on this as obviously no one will breed their bitch this many times!).
It is very easy to slander a breeder who has had these problems, especially when you are smug and have never experienced them yourself…… YET!! (the laws of probability will catch up with everyone given enough time).
We should not start complaining when our beautiful Leonberger at 3 years old suddenly comes down with an inherited disease that neither parent has got. We have to accept the heartache and sadness and be grateful for the time we had with them. For all the reasons stated above, you have to do your own homework and accept the risks …… otherwise don’t get a pedigree dog, and stick to a mongrel.
Many a time you come down in the morning to see your beautiful Leonberger lying motionless on the floor at peace, having unusually not heard you, then you suddenly panic that he could have died in the night from giant breed sudden heart failure with no warning ….. And then suddenly he moves and realises you are there, he wags his tail, gets up, and your stomach goes back to normal, you take a deep breath and grab hold of him and give him a big hug! This is just one of the risks we know exist with our beautiful Leonberger, we either chose to live with it, or we don’t get a Leonberger……..but then think how empty your life would be…….
Leonmoor Leonbergers Telephone: 01706 220292 firstname.lastname@example.org