Interview with Irene Sommerfeld Stur, DVM

Sommerfeld Stur


Prof. Dr. Irene Sommerfeld-Stur is an Austrian population geneticist. She is considered an expert in the field of dog breeding and published the book “Pedigree dog breeding, genetics for breeders and keepers” in 2016. From the completion of her veterinary studies until her retirement in 2012, she has worked at the Institute for Animal Breeding at the University of Veterinary Medicine in Vienna, where she has primarily dealt with questions of cynological genetics.

Sommerfeld Stur

The book “Pedigree dog breeding, genetics for breeders and keepers” is very useful divided into 12 chapters, which cover every important area of knowledge of dog breeding, from domestication to basic genetics, molecular genetics, behavioral genetics to population genetics, hereditary defects and also the area of agony breeding. Each topic is explained in a way that is easy to understand with the help of pictures and graphics, which in the end enable the reader to gain a deeper insight into the complex connections of dog breeding.


Question: Ms. Sommerfeld-Stur, since I started to deal more intensively with the idea of breeding myself, I have read countless scientific publications and several books on the subject. And the more I read and learned, the more aware I became of the great responsibility that I, as a breeder, have for my troubled breed.
You have summarized the many sometimes very complex relationships and problems we face in pedigree dog breeding in your book in a unique and understandable way. You managed to write a non-fiction book, which the reader does not want to put aside after a few pages with a headache, but a book that encourages to keep on reading. And even if you look at individual areas very critically at times, you do not become  judgmental, I was very impressed by that.
How long did it take you to write this book and what was your motivation to do so?

Answer: The book has occupied me for about a year and a half. With breaks in the active writing process, but almost around the clock with intellectual participation. As for motivation ... well, there were two points. A very personal one that had something to do with the need to leave a trail. At my age, you can no longer assume an unlimited lifetime. And there was something very motivating about the idea of ​​leaving sometime and leaving a trace, even if it was small but clear one. But of course there was also a very factual motivation. In the more than thirty years in which I have dealt with dog breeding professionally, on the one hand I have learned and experienced so much and on the other hand I have experienced so much ignorance on the part of those who are actively involved in dog breeding that it made sense to me to put my knowledge on paper in such a way that at least everyone who wants to become familiar with the theoretical basics of dog breeding has the opportunity to do so.

How to prevent damage?

Question: For further questions in this interview, I focused on one chapter in your book, population genetics, because I see a deep understanding of these dynamics as elementary in dog breeding.
“Breeding means thinking in populations, breeding means thinking in generations” are your introductory words in this chapter. A breeder is therefore not only responsible for the one mating that he decides on, but also for the effects that this mating can have on the overall population. In Shar Pei breeding there are some very conscientious, reputable breeders, but even more puppy mills and breeders, without a sound knowledge of breeding, genetics or the breed itself. How can the outnumbered, reputable breeders counteract the damage that the entire population is exposed to, especially since the number of puppies that come from reputable breeds is comparative small?

Answer: In my view, this is a question that cannot really be answered. Because it concerns the part of dog breeding, which I described in my book as the "less genetically than sociologically" influenced part of the breeding process. In many cases, the motivation to breed dogs is not based on an honest effort to maintain or improve a breed. Emotional, financial, prestige-related and also very naive points play a role. The only thing that can be countered by this problem is persuasion on a factual level. My book should contribute to this - but that at least presupposes the willingness of those involved to deal with the matter objectively.

Bottleneck in pedigree dog breeding

bottleneck effect
Tsaneda / CC BY (

Question: Modern western Shar Pei breeding has a short history. Almost all Shar Pei outside of China can be traced back to a handful of dogs in Hong Kong from the 1960s and 1970s. Few of these dogs were purebred or optically conformed to the old Chinese standard. In order to save the breed from the supposed extinction, breeding started there with the aim of purebredness and with a focus on dogs with a balanced temperament. The western race thus emerged from a genetic bottleneck situation. The genetic variance of the breed is therefore very small. What long-term effects can this have on a closed breeding population?

Answer: A genetic bottleneck is a problem for any population, especially if the bottleneck breeding continues in a closed population. Because even if you increase the population, there can be no expansion of genetic diversity. On the contrary, the genetic variance is decreasing from generation to generation and this process is faster, the smaller a population is. The reason for this is very simple. Every dog ​​that is not used for breeding and therefore has no offspring has one or more genes that other dogs in the population do not have. And these genes are irrevocably lost to the population. The only way to increase the genetic diversity again would be crossbreeding, which are strictly frowned upon in pedigree dog breeding.
The consequences of this ever decreasing genetic diversity result on the one hand from the more frequent homozygosity of harmful genes and on the other hand from a deterioration in the adaptability of the dogs. Frequent occurrence of genetic defects, increased susceptibility to infectious diseases, but also intolerance, autoimmune diseases, cancer, reduced fertility, and reduced life expectancy are the obvious consequences.

Popular sire in small populations

Question: The Popular Sire Syndrome is a controversial discussed topic. Meaning a popular stud dog that is used disproportionately often for mating. This leads to a further restriction of the genetic variance, which is already low in Shar Pei. The inbreeding level of the total population increases and one or more genetic defects can spread widely in the population if the stud dog is heterozygous for them. What would be the benefits of a popular sire?

Answer: I can't see any real advantage of a popular sire in a small closed dog population. In sufficiently large populations, one could at best see an advantage in the fact that a large number of the offspring of a male is a good source of information about his genetic potential but above all about his possibly existing genetic load. This would, however, presuppose that relevant information about their state of health is also available with as large a part of his offspring as possible. Unfortunately, that is hardly ever the case in dog breeding.

popular sire
By using popular stud dogs, more genetic diversity is lost in a population from generation to generation.

Inbreeding, incest breeding and line breeding

Question: I read the section on inbred resistance and genetic purging with great interest. With the word inbreeding, the alarm bells start ringing directly with most breeders. For this reason alone, one should deal with the topic much more, since it is above all the negative consequences that we are afraid of. Since the terms inbreeding, incest breeding and line breeding are often confused, could you briefly explain them to us?

Answer: These three terms are terms from the animal breeding textbook. The term inbreeding is defined as any mating in which the mating partners are more closely related than two animals randomly selected from the population.
Line breeding is a more precisely planned form of inbreeding, in which mating is usually carried out within a smaller group of animals of one breed. In line breeding, males are often paired with female offspring from the second or third generation. Line breeding is generally also carried out in combination with targeted selection for certain characteristics.
Incest is the mating of first-degree relatives, i.e. mating between father and daughter, mother and son and between full siblings.

Genetic purging as a consistent direction?

Question: You say that the more often a recessive defect gene is present in a breed, the more it becomes homozygous at a defined inbreeding level and leads to a phenotypic manifestation. Populations with such a high genetic burden therefore only tolerate a very low level of inbreeding, whereas populations with a low genetic burden have a much higher tolerance. In this context, you also point out additional factors, such as environmental influences, which can lead to a different tolerance of inbreeding. One mechanism is genetic purging. To what extent can this be controlled by breeders and is this useful?

Answer: Genetic purging or, as the analogous technical term in animal breeding is called - mass selection - would be a very useful measure in pedigree dog breeding, which in many cases is carried out with more or less consistency. It means nothing more than that dogs that carries traits of a genetic defect should never be used in breeding. If you consistently follow this measure, you cannot eliminate genetic defects from a population, but you can keep them at a very low frequency.There is a nice example from the breeding of the Irish Terrier. A genetic defect that used to be very common in this breed, called “Corny Feet”  hyperkeratosis of the paw pads, was reduced to a very small percentage by a relatively simple selection measure, namely a paw control for all Irish Terriers that came to an exhibition. There has recently been a genetic test for this defect, and the first results show that the defect gene only occurs in the breed at the exact frequency that was to be expected on the basis of mass selection.

Learning from livestock breeding?

Question: Finally, I would like to address the area of crossbreeding, because this is also a taboo topic in pedigree dog breeding. If you look at how the spectrum of genetic diseases has widened in recent decades, using the example of western Shar Pei, you can see this more than clearly, then serious breeders ask themselves how they can still save their breed. The connection between an ever decreasing genetic variance and the increase in genetic diseases and inbreeding depression symptoms are obvious. In livestock breeding, however, crosses are a very proven tool. What can pedigree dog breeding learn from livestock breeding?

Answer: Dog breeding should simply stop seeing purebredness as dogma and crossbreeding as fundamentally evil. Crossbreeding, like inbreeding, is a breeding tool that has advantages and disadvantages. Dog breeding should begin to deal with the theoretical basics of the different crossing systems and to think about which types of crosses are suitable for which situations. 

Crossbreeding as possible measures?

Question: Continuous and discontinuous crossings are two options in breeding. One enables the greatest possible preservation of genetic diversity within a population, the other extends the genetic variance by introducing genes from a foreign population. Which options should be chosen in which situations? Can such measures counteract the increase in genetic diseases?

Answer: Continuous crossings could be practically performed on the spot in some breeds. Every breed in e.g. separate color shifts are ideal for this. Discontinuous crossings e.g. in the form of an occasional immigration crossing to expand genetic diversity, or, the ingenious example of the creation of LUA-Dalmatians by the American geneticist Robert Schaible, who immigrated a gene missing from all Dalmatians by crossing a pointer and thus eliminated a serious disturbance of the purine metabolism and prevented the affected Dalmatians of a before needed lifelong diet and the risk of urethral occlusion
by uric acid stones, are simple and easy to implement options. The paradox, however, is that the LUA Dalmatians are regarded by the purebred breeding society as mixed breeds and are therefore not recognized as Dalmatians.

Question: Your book has only been published in German so far, are there any plans for an English edition?

Answer: No, there are currently no plans for an English edition. 


I could ask you a lot more questions about the many chapters in your book. But that would go beyond the scope of this interview.
Thank you very much for taking the time to answer the questions so thoroughly.