How to maintain genetic diversity while reducing disease frequency in pedigree dog?
Scientists at the University of Edinburgh’s Roslin Institute who published an article earlier this year were aimed to answer this question. Encompassing all 215 dog breeds officially recognized by The Kennel Club in the UK, the study carefully lists 396 inherited diseases, provides available methods for the management of those diseases, and offers further specific recommendations for breeders.
“DNA tests for disease causing mutation(s) will be most informative and effective for disease management but must be combined with current screening schemes, pedigree information, and if possible genomic selection, to maximize the impact in the significantly reducing the number of inherited disorders and improving overall health in pedigree dogs.” Farrel LL et al. Canine Genetics and Epidemiology (2015) 2:3.
For the single gene disorders, the scientists strongly encourage the use of all available DNA tests to identify disease genes, but not to remove any individual from breeding stock based on the genetic testing alone. Even eliminating one allele from the breed this way could possibly increase the prevalence of other defects not yet known. For disorders with complex inheritance patterns, the additional use of genotyping is seen to further help reduce disease frequency. For example, patellar luxation is currently cared for using orthopedic screening schemes and relevant pedigree information.
The researchers emphasize the importance of heterogeneity within breeds by encouraging breeding with more individuals, while simultaneously limiting the use of any particular individual. They also recommend outcrossing with other breeds to further increase heterogeneity. The original breed type will quickly recover via backcrosses to original breed. In 10th generation backcross the genetic contribution of the original breed is 99.9%.
The researchers are less supportive toward the growing trend of “designer dogs” that specifically breed Poodles with various other breeds. While the heterogeneity is immediately increased with the crossbreeding, it does not always result in healthier offspring as many breeds are already highly susceptible to same disorders. As an example, they mention the Labradoodle – a mix of Labrador Retriever and Standard Poodle – in which individual from both parental breeds commonly represent of hip dysplasia and many eye and joint diseases. Therefore, thorough health screening and comprehensive genetic testing is equally important to ensure healthy puppies when cross–breeding.
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