Genetic Health of the Labrador Retriever

Who Does Health Testing and Why?

Responsible breeders test their dogs for diseases that are known to be hereditary prior to arranging a mating. Each breed is prone to a certain number of hereditary illnesses – but by ensuring only healthy, certified animals are bred, breeders can reduce or eliminate hereditary problems, and greatly increase the odds that their puppies live long happy lives.

Interested puppy buyers should ensure that the breeders they select are performing all necessary health tests suitable for their breed – this gives you the best possible chance for a healthy pup.   This page contains information on testing and clearances that Labradors should have done prior to being bred.

Health Tests for Labrador Retrievers

According to the Canine Health Information Center, all Labrador Retrievers being used in a breeding program should have their hips and elbows tested for dysplasia and their eyes checked against genetic defect by a canine opthamologist.  They should also be tested for EIC and testing for CNM is recommended. However, there are other conditions that are found in Labs that should also be considered even though they may occur less frequently. 

Two Types of Tests

There are two basic types of health testing available to Labrador breeders. Both are important and the differences are explained below.

These are:

  1. Genetic Tests
  2. Phenotypic Tests

Genetic Testing

In order to understand genetic testing, it is helpful to have a little bit of a background in how genes are inherited. Here is a very brief explanation that you can use to help you more readily absorb the information about testing that will follow.

Every dog’s genetic material is made up of hundreds of thousands of genes. A gene is a sequence on a chromosome that codes for a specific trait, in whole or in part. A gene is made up of two parts  called ‘alleles’, which are special sequences of DNA.  For each gene, a dog gets one allele from each parent. For each trait, there may be several possible alleles, and because the dog gets one from each parent, he is potentially carrying two types of genetic material for each trait. In most cases one allele is ‘dominant’ over others. Alleles that are not expressed in the presence of a dominant allele are called ‘recessive’. Recessive alleles are only expressed if both are matching at that specific gene. If a dog inherits one dominant allele from parent A and a recessive allele from parent B, the dog will show the trait from parent A but is said to be a ‘carrier’ of the other allele. That is because they will pass that allele on to 50% of his own offspring. A dog who has two matching recessive alleles will express that trait and in the context of disease, is said to be ‘affected’.

In Labradors, there are several diseases that have been identified as the result of a specific mutation to a certain gene. These are usually inherited recessively- meaning that the ‘normal’ healthy allele is dominant to the mutant allele. So, a dog who has one normal copy and one mutated copy of the gene will appear normal, but could pass the mutated allele to offspring. If a puppy receives a mutated allele from BOTH parents, they will be affected and will show symptoms of the disease.

Genetic testing is important because for these conditions where a genetic mutation has been identified, it is possible to run a DNA test to determine if the dog is clear, carrier or affected. This allows breeders to plan matings so that NO puppies affected for that condition are born. That means that with appropriate testing and planning, there are several diseases that formerly were very common in Labs that can now be 100% prevented. A breeder doing proper testing can definitely guarantee that their puppies will not be affected by those diseases. For recessive diseases, it is not even that hard to plan ‘safe’ breedings- as long as one parent has been tested ‘clear’ for the disease in question, there is no possible way for the puppies to end up with that disease. So – as a puppy buyer- that means that you should ensure that any breeder you are considering has PROOF (test results) of at least one parent’s ‘clear’ status for genetic recessive diseases. It is NOT enough to see that both parents appear healthy because they could potentially each have a mutated allele that could be passed on to the puppies- testing is the only way to know for sure.

Currently, there are genetic tests available for the following Diseases in Labradors:

Exercise Induced Collapse (recessive- at least one parent needs a ‘clear’ test)

CentroNuclear Myopathy – (recessive- at least one parent needs a ‘clear’ test)

Progressive Retinal Atrophy (recessive- at least one parent needs a ‘clear’ test)

Coat Dilution Alopecia (recessive- at least one parent needs a ‘clear’ test)

Degnerative Myopathy (recessive- at least one parent needs a ‘clear’ test)

Skeletal Dysplasia 2 (recessive- at least one parent needs a ‘clear’ test)

Hereditary Nasal Parakeratosis (recessive- at least one parent needs a ‘clear’ test)

Congenital macrothrombocytopenia – (recessive- at least one parent needs a ‘clear’ test)

Cystinuria – (recessive- at least one parent needs a ‘clear’ test)

Elliptocytosis – (recessive- at least one parent needs a ‘clear’ test)

Hyperuricosuria – (recessive- at least one parent needs a ‘clear’ test)

Myotubular myopathy 1 – (recessive- at least one parent needs a ‘clear’ test)

Narcolepsy – (recessive- at least one parent needs a ‘clear’ test)

Pyruvate kinase deficiency – (recessive- at least one parent needs a ‘clear’ test)

Retinal Dysplasia-Oculoskeletal Dysplasia – (dominant – BOTH parents need a ‘clear’ test)

*** Because the cause of these diseases has been identified and they can be completely prevented with genetic testing, we personally feel they are the most important tests a breeder can do. The diseases in bold print are the most likely of those listed in field type Labs. Some of the other conditions are much more common in show-type labs and some are equally infrequent in both types of labs. However infrequent, the fact that we can definitely and completely prevent them makes the testing worthwhile. ***

There are many different laboratories that can perform testing. We prefer to use the following laboratories due to their exceedingly high standards and reputations for zero errors: University of Minnesota, University of Alfort, UC Davis,  Optigen, Animal Genetics, and Paw Print Genetics.

Phenotypic Testing

The other type of testing that is done is called ‘phenotypic’ testing. Phenotypic testing checks for outward signs of the disease.  and occurs for conditions that are believed or known to be heritable, but where the genes responsible have not yet been identified. Since DNA testing can’t be done, the next best thing is to thoroughly examine the parent dogs and avoid breeding dogs that have the signs/symptoms of the disease in question.  Breeders also use testing information to avoid breeding healthy dogs who have many relatives who show symptoms of the disease.

It has been proven that breeding dogs who are free of clinical OR subclinical signs of the following diseases helps reduce the odds of disease in the puppies, but cannot eliminate the chance completely. In some cases of these disease, it is known that environmental factors (nutrition, exercise, injury, etc) can cause the disease to appear so while this testing is important, it’s not a guarantee that the puppy will be healthy and each puppy owner needs to do their best to make sure they do not inadvertently cause symptoms to appear through poor management.

For all of these conditions, BOTH parents need to be tested free of disease-

Hip Dysplasia – Hips are x-rayed and films sent to specialists for evaluation and grading. The most common certifying body  is the Orthopedic Foundation for Animals (OFA) Hips are graded as either dysplastic (affected by hip dysplasia – not suitable for breeding), fair, good, or excellent.  Because these films look at the actual bones of the dog, it is important for the dog to be done growing to get an accurate evaluation. The OFA will examine x-rays on a preliminary basis in younger dogs but only offers an official grade to dogs over 2 years of age. Another certifying body is PennHip. This organization uses a combination of x-rays and measurements to determine hip quality and looseness. The measurements determine if the hip is better or worse than other dogs of the same breed and it is recommended to breed only dogs who are rated as better than average. Note that many young dogs have evidence of hip dysplasia on x-ray long before the symptoms start to appear- so it’s not enough to just visually check a dog for signs of limping- you need to have the speicalist look for those early signs of disease to rule out current AND future problems before a dog is considered as a viable breeding candidate.

Elbow Dysplasia – these are also x-rayed and films are sent to the OFA. Elbows are graded as various grades of dysplasia or normal (which means no dysplasia). In Labs, only dogs with normal- rated elbows are recommended for breeding.

Eye diseases –  Dogs who are intended for breeding should have their eyes examined annually, or at minimum, within 12 months prior to breeding. Eyes are examined by a canine opthamologist and checked for cataracts, lens and retina irregularities, and any other sign of disease. Several types of eye diseases are believed to be heritable in Labs but few have genetic tests available so having eyes examined helps identify issues as soon as they arise to eliminate affected dogs from breeding. Results from the exams are sent to OFA for recording and dogs who pass the test (no disease found) are issued a certificate good for one year.

There are all kinds of other conditions that can be examined phenotypically for signs of potential disease, such as shoulders, knees, hearts and thyroid. Generally, it is considered a rule of thumb for breeders to test hips, elbows and eyes, and other tests may be required depending on what concerns are specific to the lines or future job description of the puppies (for example, we also screen our dogs’ shoulders since so many go on to compete in the rigorous sport of agility).  Remember that phenotypic tests do not provide the ability to guarantee healthy offspring, though testing is part of a responsible breeder’s due diligence and wise planning should certainly decrease the odds of those diseases over time.

PROOF OF TESTING

It is perfectly acceptable and expected that you (as a puppy buyer) ask a potential breeder for proof of health testing. In fact, breeder’s who engage in health testing are very excited to show the documentation to interested people. We are proud of the fact that our dogs have been objectively evaluated in this way. You can see copies of our dog’s health certifications on our website, and if you visit, we’ll be happy to show you the hard copies too. Another way to check testing results is to search online. Hip, elbow and eye testing results can be verified at the Orthopedic Foundation for Animals website HERE. In fact, breeder’s have the option to submit other types of testing results too.  Some DNA testing laboratories also publish test results online, such as Paw Print Genetics. So, you are able to verify test results there. Here is Ruger’s Paw Print page . The key point is this: As a puppy buyer, you have the right AND obligation to check test results either by using an online option or seeing copies of the actual health test results. A breeder that says ‘oh ya, his hips are fine’  or ‘my vet says he’s healthy’ is not the verification you need, and if those are the answers you get to the question, you may be dealing with a breeder who is so inexperienced they don’t even know that they should be testing their dogs. You deserve a healthy puppy so take the time to make sure you are sourcing your pup from a knowlegable breeder who will do everything they can to produce only healthy puppies.

 

CLEAR BY PARENTAGE

When you are researching breeders and health test results, this is a term you may come across. Clear by parentage is a term used to describe a dog who has not personally been tested for a specific genetic condition for which DNA testing is available but is known to be ‘clear’ because both of his parents were tested and were ‘clear’. In this case, because neither parent had any mutant alleles to pass along, it is safe to say that we know that their offspring are also clear of mutant alleles.  You can still verify this by asking for copies of the parent’s health test results. For example, our “Viper” is clear by parentage for the condition of PRA. We know that she is ‘clear’ because her mother Verona was tested and is clear, and her sire Chester was also tested clear. So, though there is no specific paperwork for Viper herself, you can verify ‘clear by parentage’ by viewing the test results for Verona and Chester. Generally speaking, most breeders will do testing at least every other generation so that puppy buyers don’t have to go very far up the family tree to get the verification results. Please note that ‘clear by parentage’ is not a valid claim for phenotypic conditions- those are the conditions where no DNA test exists. For example, you should expect that each and every Labrador used in a breeding program has had their hips tested for hip dysplasia. Hips, elbows, and eye exams must be done on each dog because they are not DNA tests, so there is always the possibility that a particular dog could be affected even if both parents are clear.

 

We know this can be a confusing topic but we urge and BEG you not to give up. Study this page and email me if you have questions. Please don’t overlook health testing during your breeder search if you find it confusing, ask for help- we are happy to assist.

 

 

 

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