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Veterinarians and the veterinary team should be knowledgeable about which genetic disorders have appropriate testing available, and in what patients they should be run (see 3.4 Predicting and Eliminating Disease Traits). If parental documentation of genetic testing is not available, certain breeds should undergo genetic testing early in life (see 3.6 Genetic Testing). For example, patients from breeds with an incidence of von Willebrand disease should be tested so that measures can be taken to prevent excessive hemorrhage during surgery or injury. Patients at risk of carrying the mdr1 mutation (mostly herding breeds) should be tested before drug treatment. Owners of large‐breed puppies can be counseled to feed lower calorie “large‐breed growth or puppy” foods to provide for a more uniform growth rate and better joint development. Boxers should be tested while young for the dominant arrhythmogenic right ventricular cardiomyopathy (ARVC) gene. Carriers can be auscultated for arrhythmias through life, and if they occur can be put on antiarrhythmic drugs to prevent heart failure.

As more research is being done, more disease liability genes are being identified. Some of these genes occur in only a small “familial” population of a breed or only in a research setting while some cause breed‐wide disease.

The focus of molecular genetic testing is now shifting to panel (multiplex) testing that includes many mutations found across all breeds. It is much less expensive to use a gene chip that runs hundreds of genetic tests for mutations, traits, and ancestry on a single sample. This is what is found with several commercial genetic testing companies for dogs and cats. With the results of such testing, genetic counseling becomes more important. Many genetic mutations that cause disease in some breeds have no health consequences in other breeds. An example is the sod1 mutation test for liability to develop degenerative myelopathy (DM). This is a significant clinical disease in eight breeds, although the sod1 mutation is found across all breeds and mixed‐breed dogs. The presence of the gene mutation is not predictive for clinical disease if the breed is not actually predisposed to the disease. Genetic testing companies should provide some genetic counseling based on the breed or mixed‐breed status of the specific patient. Decisions based on inappropriate test interpretation may be worse than having no test at all.

The expression of some genetic disorders cannot be altered. If a genetic test is available, it should be utilized prepurchase so that owners are not burdened with predictable genetic disease. However, for owned animals, it is a personal decision whether the owner wants to know if their pet is likely to develop a nontreatable genetic condition later in life. These include polycystic kidney disease (PKD) in Persian, Himalayan and related cats, lysosomal storage diseases, and the (poorly penetrant) liability gene for DM in susceptible breeds. These genetic tests can also assist with ruling out diagnoses in clinical patients with suspected genetic disease.

Dietary recommendations should be offered for identified genetic predispositions such as feline lower urinary tract disease in cats, dogs and cats with nonstruvite bladder stones or “crystals,” and obese “prediabetic” cats. Behavioral counseling and early training recommendations should be offered for breeds or individuals demonstrating aberrant or pathological behaviors.

Owners may also bring results of direct‐to‐consumer genetic tests or tests of ancestral breed background for interpretation (see 3.6 Genetic Testing).