I spend a lot of time writing about the perils of inbreeding so it's interesting to find a report - albeit a preliminary one - that found that inbreeding did not lead to poorer health.
"One problem in modern dogs is a high occurrence of physical diseases, defects, and disorders. Many breeds exhibit physical problems that affect individuals already at young ages, and veterinary care and/or various drugs are in some cases needed throughout life," report the authors of the report in the Veterinary Journal of Behaviour . "A potential cause of these problems is inbreeding and loss of genetic variation that is known to reduce the viability of individuals and is associated with increased occurrences of hereditary disorders governed by autosomal recessive alleles. During recent years increasing conservation genetic focus has been devoted to domestic animal populations. This attention includes both scientific efforts and international and national policy work. Domestic populations are traditionally bred through strong selection. Only a few animals are used in breeding, resulting in considerable loss of genetic variation. Conservation breeding aims at reducing the rate of loss of genetic variation, and this includes reducing selective pressures. This research addresses the question of whether “unhealthy” dog breeds exhibit elevated rates of inbreeding and loss of genetic variation as compared to “healthy” breeds."The researchers used pedigree records from the Swedish Kennel Club database and classified the 14 breeds they looked at as "healthy" or "unhealthy" based on data from four Swedish pet insurance companies.
The “unhealthy” breeds were Bull Mastiff, Dogo Argentino, Bulldog, Mastiff, Neapolitan Mastiff, Irish Wolfhound and Shar Pei,. The “healthy” breeds were Finnish Lapphund, Norrbottenspitz, Norwegian buhund, Norwegian elkhound black, Småland hound and Coton de Tuléar.
The preliminary results did not find any difference between healthy and unhealthy breeds with respect to the average level of inbreeding among living animals. However, there were indications that the rate of loss of genetic variation was slightly higher among unhealthy breeds.
The authors stress that the results are preliminary. The pedigree data only went back to the start of the Swedish KC electronic database (around 1970) so may not be a true indicator of the breeds' level of inbreeding. The researchers also only looked at small-population breeds. But the findings are interesting nevertheless and serve to illustrate that inbreeding may not always result in a less-fit population.
"The plan is to also include breeds with larger population sizes and we hope to publish something more this winter," says co-author Mija Jansson, a population geneticist from the Institute of Zoology at Stockholm University.