Two topics that I have been thinking a lot about recently have been preservation and diversity. For some people, preservation means preserving the breed as it is known, but others place importance on genetic diversity. Sometimes these can be in conflict. There are those who believe in the concept which has been promoted that diversity is merely a case of numbers. They have stated that all litters should be outcrossed to keep the COI (Coefficient of Inbreeding) below a set number. The COI number of 5.0 is claimed to improve breed health and longevity. This has not been proven scientifically, and some have gone so far as to suggest that many breeds may need to be crossed with another to increase genetic diversity and save them from extinction.
The biggest problem I see with this belief system is that it does not take into account the fact that different breeds have different needs. With modern advances in molecular biology and DNA profiles now available, they do not take into consideration that DNA testing becomes an essential component. If a breed has a genetic defect that has become widespread in that breed, investing in the identification of the genes involved becomes essential. It can then be determined if it would be possible to breed away from that disease within the purebred dogs available or if a carefully chosen outcross to another breed would be necessary.
One thing that has always puzzled me is the idea that after several generations of breeding within the stud book that ancestors are actually lost. To the average person it suggests that the total genome of a single dog has been eliminated, but this cannot be true. The canine genome has 38 chromosome pairs plus the X and Y sex chromosomes, and each chromosome contains several hundred genes. Those genes in turn have multiple variables called alleles. To complicate things further, chromosomes in the living cell come in pairs, one from each parent. In order to reproduce, these pairs must divide, with a single strand in the sperm and a single strand in the ovum combining to create a fertilized egg. Every fertilized egg is unique in its DNA and will contain varying combinations of genetic material. That is how, if breeds allow multiple colors, you can have a litter with puppies of different colors. Breeders will make selections in every generation as to which dogs and bitches should be bred from, and which puppies should be retained for future breeding. Some genes may be lost, and others may be duplicated, but individual breeders will select for different things. Some people look at the ancestral loss coefficient to quantify the loss of genetic diversity, but in my opinion, that is too formulaic.
Calculated by taking the total number of dogs in a generation and dividing by the number of unique individuals does not take into consideration the number of random combinations over that number of generations, plus the variable choices made by individual breeders. It would take a blackboard with a math professor like the character in Numbers (the television series) or a supercomputer analyzing the DNA of every individual dog in a litter to figure out the potential loss.
I am not a mathematician, and I am not a geneticist, but I read about new discoveries and learn from them. I am a big believer in BREED-SPECIFIC DNA tests for health defects. Some breeds have a long list of applicable tests, but some have none—my own breed, Afghan Hound, included. Using a commercial screening program that tests for diseases that are not applicable is a waste of time and money, in my opinion, but when they exist, use them. The idea of outcrossing willy nilly, which would spread defective genes throughout a breed, is dangerous. Defective genes can become so widespread that only DNA research can save them.
Having followed ongoing research as I have done, I was blown away when researching this column as to how far things have advanced. I do all my own research and do NOT use AI. I do not want a bot giving me information, which they have learned from their training modules and which they have been programmed to provide.
I’ve found information from international sources, and one took me completely by surprise. I came across the most complete trove of information in their national language with a drop-down menu to choose your language of choice. One click, and the whole page switched to English from Chinese! That was not a country that I would have thought of where canine genetics is concerned. It only goes to show how fast and how far things have changed. Many things that were taught 20 years ago no longer apply.
Now I want to move on to the topic of preservation. We all want to preserve our breeds, but just what do we as individuals want to preserve? Some want to preserve physical characteristics and others are more concerned with performance and working activities—and both choices are good! Breeding for dual-purpose dogs is the hardest thing of all. Remember, when egg meets sperm, two single strands of DNA combine to create a unique individual. Good qualities can be preserved and defects eliminated, but there are limits as to how close to an ideal can be replicated. Being too fixated in either direction can be a loss to the breed.
Outcrossing in the name of diversity with the aim of reducing the COI is unlikely to produce excellence in either performance or show quality, and could even spread unwanted characteristics across the gene pool if every pedigree ends up being a mishmash of the same ancestors. Linebreeding, and yes, inbreeding are necessary when creating good workers, high performers, and Best in Show winners, as long as good health and temperament are also given a high priority. This cannot be done just with breeding by number. It includes knowing the pedigrees, knowing the bloodlines that went into the creation of the breed, and knowing as much as we possibly can historically about the dogs involved. Each one will have had a unique combination of breed points and abilities. Combining these in the best way possible is not a case of mathematics, it is one of art.
Here is a fictional story that I hope you enjoy, how one dog can affect a breed: https://itsthatwomanagainallaboutdogs.wordpress.com/2025/07/29/an-amusing-story-fiction-about-the-rare-transylvanian-fluffball/
