This very quickly leads to an unfeasible number of unrelated ancestors at the n th generation, implying common ancestry and so inbreeding. 2 parents, 4 grand-parents, 8 great-grand-parents, and so on). Inbreeding is unavoidable in finite populations, since the number of ancestors increases exponentially per generation (2 n, where n is the generation, i.e. Indeed studies have empirically determined a large depletion in genetic diversity in some pedigree dogs breeds, and many breeds do suffer a high burden of genetic disease. It is widely believed that pedigree dogs are very inbred, due to closed registries and breeding practices, and that this has had a detrimental effect on the health and welfare of many pedigree breeds. Reports detailing results of the population analysis for each individual breed are publically available at. There was variation among breeds in the trend of rate of inbreeding over the period 1980-2014. Popular sires make large genetic contributions to subsequent generations and are the biggest influence on the rate of inbreeding. Evidence of popular sires was common in all breeds. The rate of inbreeding (or effective population size) showed no relationship with the actual population size, as judged by mean number of KC registrations. It is interesting that this coincides with the relaxation of the UK’s quarantine laws, and is possibly due to the more widespread use of non-UK animals for breeding. Since 2000 however, the general trend has been for the rate of inbreeding to decline to sustainable levels, with some modest restoration of genetic diversity in some cases. This study reports the general trends in the rate of inbreeding observed through population analyses of all 215 pedigree dog breeds currently recognised by the UK Kennel Club, over the period 1980 to 2014.įor all breeds, the trend was for the rate of inbreeding to be highest in the 1980s and 1990s, representing a major contraction in genetic diversity. Therefore the rate of inbreeding is a measure of the sustainability of a population.
The rate of inbreeding in a population relates to the risk of detrimental effects associated with inbreeding (such as loss of genetic diversity, inbreeding depression and the spread of deleterious genetic variants). Therefore some degree of inbreeding is inevitable in all populations it is how quickly this changes that is informative. The resemblance of relatives is a fundamental principle of genetics, and means that selected individuals will on average be more closely related than a random pair taken from across the population. Furthermore, selection within dog breeds for desirable traits will inevitably result in the breeding of individuals that resemble each other with respect to the traits under selection. In populations of a limited size, complete avoidance of breeding between individuals with a shared ancestry quickly becomes impossible. Inbreeding’ is widely viewed as being harmful to the wellbeing of individuals and populations. The theory of genetic contributions, which demonstrates the fundamental relationship of inbreeding and selection, implies that popular sires are the major contributor to high rate of inbreeding. The trends detected over 1980–2014 imply an initial excessive loss of genetic diversity which has latterly fallen to sustainable levels, even with modest restoration in some cases. The existence of popular sires was apparent in all breeds. Rates of inbreeding over the entire period 1980–2014 were not correlated with census population size. The trend was comparable in very common and rarer breeds, although was more pronounced in rarer breeds. The trend over all breeds was for the rate of inbreeding to be highest in the 1980s and 1990s, tending to decline after 2000.
Pedigree analysis of all 215 breeds currently recognised by the UK Kennel Club over the period 1980–2014 was undertaken to ascertain parameters describing the rate of loss of genetic diversity due to inbreeding, and the presence of any general trend across all breeds. Studies have shown some pedigree dog breeds to have high levels of inbreeding and a high burden of inherited disease unrelated to selection objectives, implying loss of genetic diversity may be a particular problem for pedigree dogs. Therefore, management of the rate of inbreeding at sustainable levels is required to avoid the associated detrimental effects of inbreeding. Inbreeding is inevitable in closed populations with a finite number of ancestors and where there is selection.