World of Cats & Dogs

Recommendations for Breeders

What can a breeder, owner, or veterinarian do if it is not known if a condition is inherited? First, a firm veterinary diagnosis needs to be established. This should be done for stillborn or fading puppies and kittens as well. If a disorder is not reported in a breed chapter; is it reported as an inherited condition in other breeds or other species? You should search widely to confirm whether the condition occurs at an increased frequency within a family or within the breed. Even if a mode of inheritance is not determined, knowledge that a condition is genetic allows for specific breeding recommendations.

The best methods for ensuring the health and diversity of any breed’s gene pool are to: 1) Avoid the popular sire syndrome. 2) Utilize quality individuals from the breadth of the population to expand the gene pool. 3) Monitor genetic health issues through regular health surveys. 4) Do genetic testing for breed-related disorders. 5) Participate in open health registries.

The most important goal of managing genetic disease is to avoid producing affected individuals. The secondary goal is to reduce the frequency of carriers of defective genes in the population. At the same time, recommendations should allow perpetuation of breeding lines, in order to preserve the genetic diversity of the population. Historically, genetic counseling has ranged from recommendations to not repeat a mating and to outbreed, to recommendations for elimination of all relatives of affected animals from the breeding pool. Neither of these two extremes serves the best long-term interest of specific breeds. Outbreeding may prevent the production of animals affected with rare recessive diseases, but it will propagate and further disperse the detrimental recessive genes.

With widely dispersed or high frequency defective genes, it must be recognized that carriers are spread across the gene pool. Eliminating unique breeding lines because some individuals carry a single defective gene may adversely affect gene pool diversity more than a process that allows a limited number of carriers to reproduce. Conversely, with recently mutated or low frequency defective genes, it is advisable to strictly limit breeding, to avoid dispersion of the defective gene further in the population.

With each new generation, breeders ask, “How can I continue my line and improve it?” Aside from selecting for conformation, behavior and general health, breeders must consider how they are going to reduce the incidence of whichever genetic disorders are present in their breed. There are no answers that will fit every situation. There are, however, guidelines to preserve breeding lines and genetic diversity while reducing the risk of producing animals that carry defective genes, or are affected with genetic defects.