What is the importance of consanguinity and how can it be assessed by DNA testing?

In recent centuries, the creation of dozens of new dog breeds has popularized the use of inbreeding, also known as "consanguineous mating," as this is a quick way to produce puppies that look very similar to each other in just a few generations. Therefore, this choice to breed related dogs has become a common method for breeders to select pairs.

However, with the scientific growth of the entire field of genetics, including canine genetics in the last decade, numerous scientific evidences are now available demonstrating the deleterious effects of excessive inbreeding. Official bodies and breeders in first-world countries, who generally have easier access to science, are already aware of these effects and are working to select dogs with the lowest possible degree of relatedness for mating.

Based on several scientific articles comparing the offspring of dogs with different degrees of kinship, it has been possible to determine that excessive inbreeding is related to reproductive difficulties, an increased chance of genetic diseases, impaired immune efficiency (leading to diseases such as atopic dermatitis, food allergies, and autoimmune diseases), decreased longevity, and a higher chance of early-onset cancer.

Therefore, it is important to have a way to assess a dog's inbreeding to understand if it is within normal limits for the species or if it exceeds the limits recommended for a healthy dog. One way to do this is through an estimate made using the names of the father's and mother's relatives, evaluating the names present in both pedigrees : the more names are repeated, the higher the inbreeding value, and if this value exceeds 10%, it is recommended that the breeder not proceed with the mating. Geneticists specializing in breeding perform this calculation and use this information in genetic counseling for the breeder.

However, a much more accurate way to assess a dog's degree of consanguinity is through DNA analysis, which will indicate the degree of genomic consanguinity . When evaluating an animal's DNA, it's possible to count how many analyzed points are identical through the paternal and maternal lines. Dogs with high levels of genomic consanguinity will have a higher risk of all the health problems already reported, which is very important information for the owner. After all, once they know that their pet has a higher risk for any of these diseases, which are not assessed by genetic testing, ideally they should take this information to the veterinarian. The professional will be able to direct the performance of more frequent health exams to detect any health changes in the initial phase and promote more effective treatment.