26th August 2008

 

The hot topic at the moment seems to be the BBC Pedigree Dogs program that was broadcast last week.

 

What a shocking documentary 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.

 

Us humans 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 very likely to have your Leonberger well 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? Cancer, Sudden death heart failure, Polyneuropathy, 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! …….. Continue to next page….