1. Quality carriers of testable disease-causing recessive genes should be bred to normal testing mates and replaced for breeding with quality, normal testing offspring. 2. Quality dogs with a less desirable phenotype (such as fair or even mild hip dysplasia in breeds with high frequencies of dysplasia) should be bred to dogs with desir- ablephenotypes (goodor excellent hips) and replaced for breeding with offspring whose phenotype is better than the parent. 3. Quality non-affected dogs from lines expressing disorders that do not have genetic tests (such as epilepsy) should be bred to mates from families or litters not expressing the disorder and re- placed for breeding with a qual- ity, healthy offspring. In small population breeds with high frequencies of genetic disorders, breeders are often “frozen” from breeding for fear of producing disease. This causes continued breed decline due to population contraction. Breed improvement requires selection of the best breeding choices in matings that can reduce the frequency of ge- netic disease. As the population and breeding choices expand, the abil- ity to reduce the frequency of disease expands with it. Breed improvement involves: 1. Selection of Breeding Dogs; 2. Appropriate Pairing of Mates; 3. Breeding; 4. Replacement of Less Desirable Breeding Dogs with More Desirable Offspring. An unfortunate development in dog breeding are recommendations de- signed for the preservation of rare and endangered species. These involve outbreeding (reducing homozygosity and average inbreeding coefficients) and increasing minor gene or chro- mosome segment frequencies. Dog breeding requires diverse lines, and not a homogenized and randomized outbred population. Outbreeding will not reduce the frequency of breed- related genetic disease, as the caus-
ative genes are already dispersed in the breed gene pool. Genetic selection for quality and against undesirable traits is what causes homozygosity and reduces the frequency of minor genes and chromosomal segments. Blindly selecting for them without knowing their effect could signifi- cantly reverse selection-based breed improvement. Homozygosity is syn- onymous with pure breeds. It is not inherently correlated to impaired genetic health and does not have to be artificially controlled. Expanding populations with different breeders undertaking different types of matings and selecting on different lines, while monitoring and selecting against genetic disease provides for a healthy, diverse breed gene pool. Official genetic screening results should be made available to pro- spective breeders, and to the pet and breeding-stock purchasing public. This is facilitated through open ge- netic health databases like the OFA. It doesn’t matter whether a breeder is a large commercial breeder, or only breeds once. It is no longer acceptable to say that genetic disease “just hap- pens.” In today’s environment, not testing for documented breed-related hereditary diseases is irresponsible and unethical breeding. Breed-spe- cific pre-breeding health screening should become as universal as equine pre-purchase examinations. Maintenance and improvement of a breed requires: 1. A Large or Expanding Breed Population; 2. Avoidance of the Popular Sire Syndrome; 3. Avoidance of Extreme Pheno- types that Can Produce Disease Liability; 4. Monitoring of Health Issues in the Breed; 5. Constant Selection for Quality and Health. (This article was published in the Sep- tember 2016 Perspectives—AKC Dele- gates Newsletter. It can be reproduced with the permission of the author.)
ease-predisposing phenotypes have been actively selected for by breed- ers. The most evident and widespread is the brachycephalic obstructive airway disorder, seen in extremely short-muzzled breeds. Other extreme phenotypes include excessive skin, excessive skin folds, excessive hind limb angulation, excessive size, ex- cessive coat, dome-shaped skulls, and eyelid abnormalities. It is important that breed standards and selection practices specifically avoid selection for extreme phenotypes that cause disease liability. For the show ring, judges education should be directed towards rewarding moderation of disease-related extreme phenotypes. Regular breed health surveys should be conducted by breed clubs to moni- tor for the presence and changing prevalence of genetic disorders. The OFA offers on-line health surveys for breeds. Breed genetic health should be judged on breed health surveys that document the occurrence of genetic disease. Parent breed clubs should deter- mine realistic pre-breeding genetic screening requirements based on the prevalence and severity of testable disorders in the breed. Health test- ing requirements should be listed in the OFA CHIC and AKC Bred with H.E.A.R.T. programwebsites. Without direct selection against ge- netic disorders, the genetic health of breeds will decline. Breeders who refuse to do pre-breeding health screening should be directed to find a different hobby or profession that they can actually be good at. It is not ethical to breed dogs without selec- tion for genetic health. Selection of healthy breeding stock is themost im- portant aspect of maintaining breeds. Each breeder must prioritize their se- lection for positive traits and against disease traits with each mating. Some breeders feel that genetic screen- ing will reduce the genetic diversity of breeds. The proper use of genetic screening actually increases breeding choices by allowing quality dogs at higher-risk of carrying disease liabil- ity genes to be bred:
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