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Genetic Diversity

Genetic diversity is a topic in dog breeding that is becoming increasingly interesting. Genetically speaking, races are closed populations. This means at the time when a breed was established as such and the studbooks were closed, a status quo of genetic material was determined. If no foreign breed is crossed in anymore, there is no gain in genetic material. On the very contrary, with every selection made in the breeding, genetic material is lost. Over time, this leads to a steadily increasing inbreeding level and a loss of genetic diversity. The least concern of many is that each selection not only consolidates desired features and characteristics, but also those we do not want, such as (hidden) disease-causing gene variants that are increasingly used in a breed. However from a breeding point of view as many different genes and variants as possible should be present and preserved in a breed. So for example, there should be a high degree of heterozygosity in order to be able to maintain a breed as long as possible. Because genetic diversity is the basis for vitality, disease resistance and fertility.

From a genetic diagnostics perspective, measuring genetic diversity has been a major challenge for many years. Means to determine the diversity for each dog based on its genes and not on the pedigree. Today we can do this quite easy by testing hundreds of thousands of genetic markers. These markers are evenly distributed small areas on each dog’s DNA. They tell us whether a dog has inherited different genes from its parents or not, and if so, to what extent. You can also determine how related two dogs are to each other. It is a very precise way of predicting relationships between two dogs based on DNA data. This is completely independent of pedigrees. With these kinship analyses, the degree of consanguinity of dogs can be determined without any information about them. The result can be that there is no relationship or relationship that we would expect to be for parents to descendants, full siblings, grandparents to grandchildren etc. This information can also be used for breeding or for mating. For example, those dogs with the lowest degree of kinship and thus the genetic diversity in the offspring are consciously increased or kept high for instance.

In addition to the relationship analyses, the analyses allow to determine genomic inbreeding coefficients. So far, the IK is the best-known way to differentiate between the different varieties and to calculate the genetic diversity. However, so far it is been done based on the pedigree. From a genetic point of view, it makes a mathematical forecast of the likelihood of two identically alleles (gene variants) at a specific gene location are from a common ancestor. The more the level of the IK increases the closer is a blood relationship of the individuals, and the more likely it is that they share a certain amount of similar gene combinations. The increase of the level of inbreeding leads to a decrease of genetic diversity. Since years the calculations of the IK based on the pedigree is the usual way. This way of calculating has its limitations as sometimes not all pedigrees are complete or the actual ancestor differs from the one stated in the pedigree (lack of parental testing) which leads to a miscalculation of the IK. The evaluation of the genetically IK is not affected by this, because it is based on the actual genetically status of a dog. The inbreeding coefficient can be re-calculated up to 50 generations, and therefor can be used in detail as effectively breed-and diversity management within a breed.

Today’s genetic procedures and possibilities offer us for the first time the opportunity for extensive and long-term breeding management. Many breeds already show a highly restricted genetic diversity with a high degree of inbreeding. It is all the more important to manage the remaining genetic material in a sensible and breed preservation manner. Just as testing should be a matter of course, a well-thought-out and breed-specifics adapted breeding management is required to maintain and preserve a breed as long as possible.