These sires inevitably carry at least a handful of genes that are likely to cause serious health problems and so become common in the whole population within just one generation. The effects of intensive inbreeding in pedigree dogs are hard to measure, though high prevalences of specific illnesses in specific breeds are well known. In this way, the welfare of much-loved pets can be highly compromised by standard breeding practices.
There is no complete solution to the problem. The best health outcome for dogs is diversity in mating, which is the opposite of what breeders want to do. Dog clubs have limited opportunities to make changes that are not widely supported by members. Ultimately they are like businesses and their customers the dog breeders can go elsewhere. It now offers an online tool that can report the relatedness of potential mates. Particular dog breeds and pedigree dogs exist due to deliberate and selective breeding for specific traits by dog breeders.
Breeding animals are primarily selected based on their physical appearance. Unfortunately, this primary focus on appearance often causes a number of health and welfare problems.
The breed standard mainly focuses on physical features and may also include a small section on temperament. Adherence to the breed standard is also used by judges in the dog show ring. Unfortunately, some of the breed standards require exaggerated looks such as flat faces, abnormally large eyes, excessively wrinkled skin or disproportionately short legs. Exaggerated features can cause pain and distress to dogs and seriously compromise their welfare and their ability to lead a normal comfortable life.
For some breeds overtime, these physical features have become increasingly exaggerated, for example, breeders have selected for even flatter faces or even shorter legs, further compromising animal welfare. Inbreeding also referred to as line breeding means mating animals that have one or more relatives in common, for example, mating a grandfather dog to his own granddaughter.
The researchers' analysis showed that, for example, Boxer dogs were so closely related to one another and had such little genetic variation between them that genetically, 20, dogs looked like a population of about In the Rough Collie breed, 12, dogs looked in genetic terms like a population of about Such small effective population sizes mean that the chances of a dog breeding with a close relative, resulting in birth defects and genetically inherited health problems, are high.
The researchers argue that those involved in breeding dogs should encourage breeding from a larger pool of potential mates in order to create greater genetic variation and lessen dogs' chances of inheriting genetic disorders.
They suggest measures such as limiting how many times a popular dog can father litters; encouraging mating across national and continental boundaries; and relaxing breed rules to permit breeding outside the pedigree.
Professor David Balding , the corresponding author of the research from the Division of Epidemiology, Public Health and Primary Care at Imperial College London, said: "The idea that inbreeding causes health problems in particular dog breeds is not a new one, but we believe ours is the first scientific study to explore this issue and analyse the extent of inbreeding in a systematic way, across many breeds.
We hope that following our work, dog breeders will make it a high priority to increase the genetic diversity within different breeds.
Particular dog breeds are believed to be prone to particular health problems and birth defects. For example, Dalmation dogs are predisposed to deafness, many Boxer dogs have problems with heart disease, and disproportionate numbers of German Shepherd dogs have an abnormal developmentof the hip joints known as hip dysplasia.
Inbreeding in pedigree dogs arises because certain dogs, prized for exhibiting the characteristics desirable for that breed, are used to father many litters of puppies. When dogs from these litters come to be mated, some will be paired with dogs having the same father from other litters. Over generations, more and more dogs across a particular pedigree are related to one another and the chances of relatives mating increase.
Recessive genetic variants only have adverse health effects such as deafness when an individual carries two defective copies of the gene. If a popular sire carries just one defective copy, he will not show the problem himself and nor will his puppies. However, the defect may become common in later generations if his grandpuppies and great grandpuppies are mated with each other, rather than introducing new genetic traits by breeding outside their relatives.
Although the problems associated with inbreeding have been known for many years, prior to the new study it had not been systematically measured. For this study, researchers from Imperial used mathematical modelling to analyse how dogs were related to one another within ten different dog breeds including the Boxer and Rough Collie.
They looked at the parentage of eight generations of dogs, using records collected from to the present day by the UK Kennel Club. The researchers' analysis showed that, for example, Boxer dogs were so closely related to one another and had such little genetic variation between them that genetically, 20, dogs looked like a population of about In the Rough Collie breed, 12, dogs looked in genetic terms like a population of about Such small effective population sizes mean that the chances of a dog breeding with a close relative, resulting in birth defects and genetically inherited health problems, are high.
The researchers argue that those involved in breeding dogs should encourage breeding from a larger pool of potential mates in order to create greater genetic variation and lessen dogs' chances of inheriting genetic disorders. They suggest measures such as limiting how many times a popular dog can father litters; encouraging mating across national and continental boundaries; and relaxing breed rules to permit breeding outside the pedigree.
Professor David Balding, the corresponding author of the research from the Division of Epidemiology, Public Health and Primary Care at Imperial College London, said: "The idea that inbreeding causes health problems in particular dog breeds is not a new one, but we believe ours is the first scientific study to explore this issue and analyse the extent of inbreeding in a systematic way, across many breeds. We hope that following our work, dog breeders will make it a high priority to increase the genetic diversity within different breeds.
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