Phenotype traits, positive or negative are are the result of a combination of alleles, not a single locus. That means they occur in a continuous range of severity (hip dysplasiais is an example). In fact, in many cases the setter may be borderline and be normal or near normal. So included in our discussion we have the concept of threshold, where at a certain level the animal develops the disorder and below they are normal, although at risk of producing unsound offspring.
Also, another influencing factor is heritability, which in the narrow sense expresses the extent to which phenotypes are transmitted from parents to offspring. The higher the heritability of a trait the greater the accuracy of positive selection or in the case of negative genetic maladies the higher the risk of inheriting it. To add to the complication, many traits are multi factorial with environmental influences (non-genetic).
Finally, there is the important concept of liability, which is the severity of the genetic disease i.e. whether it is disabling (Progressive Retinal Atrophy) or life threatening (Addison Disease) or a relatively modest malady having mild effects such as skin allergies or easily corrected by surgery such as umbilical hernias. And in the latter cases recurrence risk should be considered, in other words is this an occasional occurrence or a frequent one. Modest maladies with a high recurrence should be considered of a higher liability. All of this leads to the decision to cull or retain an individual or blood line for breeding.
The term culling is a livestock breeders’ term which is a screening out of undesirable animals. Screenings are done using estimates of an individual’s risk to an average population. They are only estimates. Decisions are normally made by comparison. If our goal is to improve the breed (population) or to improve bloodlines, the individuals culled should be of a high liability or in more modest cases of high recurrence risk in comparison to the average.
Now when we consider an individual that for example is below the threshold of a high liability genetic malady i.e.,normal phenotypically, we could mistakenly retain that setter because we don’t have adequate information. Information pertaining to the our breed population is nearly impossible to obtain because of the lack of transparency. And we don’t have a strong breed club collecting information by willing breeders.
So the next best alternative comes from family members-parents, grand sires and grand dams, and full siblings.These close relatives carry as much as 50% of the genetics of individuals under consideration and therefore they are a window into the genetic health and soundness of any individual setter. But once again, collecting health data from other breeders is difficult and in many cases impossible. Only a breeder producing several generations of setters, recording feedback observations from clients, will have enough data on a significant number of progeny to draw inferences on genetic soundness.
But we don’t have many breeders. We have scores of individuals mating setters without an adequate selection criteria or in regard to our particular discussion the accurate generational health history of the setters being mated. The usual practice is repeatedly buying setter puppies from many other “breeders” with no first hand knowledge of the health and soundness of the family and bloodline. And ending up with a high risk dog with a smorgasbord pedigree.
In the past, it was common to have large commercial kennels line breeding specific well known bloodlines. “Big kennels” that carried the familiar kennel name for many generations with an occasional strictly selected outcross. Today the overwhelming structure is “backyard breeders” with a few setters (many times only two or three), with no long term business history but a website with a fancy kennel name.
Besides pioneering and incorporating genetic testing with UC Davis Genetics Lab, we’ve been hunting, training and breeding our Llewellin setters for 24 years. We’ve paid attention to and recorded all maladies from feedback by our clients. And we have produced significant numbers of progeny to evaluate. We’ve been very fortunate to have foundation setters of extremely good health and soundness. And it has been over the years the top priority our breeding program. No sporting dog kennel has put the effort we have and had the success of our health and soundness program.