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The term 'inbreeding' refers to the mating of two dogs that are closely related to each other genetically, such as a mating of siblings or cousins, and selective deliberate inbreeding is something that has occurred for many decades in the pedigree dog world in order to maintain the purity of bloodlines and increase the number of dogs of a breed displaying certain desirable characteristics. Inbreeding of various bloodlines conceived of a relatively small gene pool is in fact how the desirable and distinctive characteristics of most modern breeds of pedigree dogs came into existence. But inbreeding is not without its associated problems, and is sometimes considered to be rather controversial in modern times, as our understanding of genetics, selective breeding and health and hardiness has increased.
First of all it's important to note that were it not for selective inbreeding, many popular breeds of pedigree dog would not exist today, or at least not in their current forms. All of the well known breeds of dog that are recognised under breed standards have at least some history of inbreeding in their heritage, due to the process of establishing a particular breed of dog, which evolves over many years and in some cases, centuries. Establishing a breed begins with a dog or dogs in a certain area having several desirable characteristics that are, when combined, unique to that small set of animals. This can include factors such as their temperament, distinctive looks, or a particular talent for a certain type of working activity such as herding, retrieving or guarding. The traits that make a particular dog or set of dogs desirable, mean that they will in turn become popular and in demand, as other people aspire to own a dog which possesses the same characteristics. This then leads to attempts to produce more dogs sharing the desirable traits of the original dog or dogs, and of course in order to do this it is necessary to produce pups from either a sire or dam (or both) with those traits. Of course, while there exists only a relatively low number of the original dogs with those traits, that also means that the gene pool from which new pups possessing the same traits can be produced is small. It is not uncommon at this stage of establishing a breed to inbreed dogs to produce pups with the same desirable traits as the parents, often by matings of siblings, cousins and other closely related dogs. Out crossing to unrelated dogs is also very likely to occur, and while this has many benefits that inbreeding does not have such as reduced likelihood of inherited flaws and genetic mutations developing, it also serves to potentially dilute out the desirable traits of the original dogs, and so a balance between the two factors must be reached. Sometimes, the genetic mutation is the desirable trait of the dog or dogs in question, such as in the case of the shar-pei dog's signature wrinkled skin and coat. When the genetic mutation is the desirable trait of the dog, inbreeding to a fairly high degree in the early stages of the establishment of the breed is necessary in order to establish the breed and make the mutation prevalent and the gene dominant within the breed. Inbreeding can also occur naturally in the wild, and is not always the result of selective breeding and human intervention.
While inbreeding to some extent has played a part in the establishment of all modern breeds of dog and will likely continue to do so, inbreeding also has a significant amount of potential problems and risk factors associated with it. Inbreeding results in an increased likelihood of undesirable traits being inherited into the subsequent offspring, and heightens the chances of recessive mutations occurring. While sometimes these mutations are a desirable effect of selective breeding, such as in the case of the shar-pei as mentioned above, the potential for undesirable and unforeseen mutations occurring alongside of these is considerably greater. Several hereditary conditions and illnesses which can be inherited by dogs only occur if the pups inherit the recessive gene from both their sire and dam, and the likelihood of them having two parents with the recessive gene which then causes the potential problem in the pup is of course much higher if the two parents are closely related in the first place. Conditions such as hip dysplasia and patella luxation are just two of the many potential congenital defects and hereditary conditions that can occur from inbreeding, which leads to all of the pedigree dogs of a given breed being genetically relatively closely related. Often a particular breed of a dog's breed guidelines does not allow certain colour variants or specific physical traits in order for an animal to be classed as a breed standard dog, which in turn can lead to a greatly reduced pool of potential parentage for new dogs of the breed, as those which possess the gene for the apparently undesirable colour or physical traits are bred out, thinning the gene pool further.
Some distinctive breeds which are popular as pets in the UK today have a significant history of inbreeding in order to achieve the desirable breed standard, to the point that they are at significant risk of other genetic mutations and problems which are well documented and which potential new owners of dogs of those breeds should be aware. Possibly the most obviously inbred dog commonly seen in the UK today is the pug, which has a significantly heightened chance of developing various different congenital conditions including problems with the eyes, hips, spine and breathing. Several other dogs such as the English Bulldog are also considered 'high risk' for congenital and hereditary problems, and in fact selective breeding to produce the bull dog's signature large head means that today it's highly unlikely that bulldog pups can be born naturally without the need for caesarean section delivery. Even hugely popular breeds such as the Labrador retriever have not escaped inbreeding unscathed, and are one of the breeds considered to have an elevated risk of developing hip dysplasia, and it is common practice for pedigree Labrador retriever dogs to undergo hip score testing prior to breeding to identify any potential problems which the offspring may inherit. As well as of course the problems of potential genetic health defects presenting themselves in later life if you buy a pedigree pup of a higher risk breed, insurance for pedigree dogs is generally rather higher than for mixed breeds, and significantly so in the case of well known selectively bred dogs such as the bulldog and pug. Due to the elevated risk factors associated with insuring breeds like these, insurance can prove to be very costly, and even then, sometimes insurance will not cover certain congenital and hereditary diseases and conditions due to their high level of prevalence within the breed. If you are considering buying a pedigree dog, it's important to check out its history first and learn about any potential hereditary risk factors, to make sure that the dog you buy is healthy, and that you are not storing up problems for yourself and your dog later down the line.
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