What Is Health Testing and Why Is It Important?

You may have heard such phrases as “puppies come from health tested parents” or “puppies are completely health tested” on advertisements for Labrador Retriever puppies and wondered what that meant. The fact is, if you’re entering the world of breeding Labrador Retrievers this is something you need to understand, and furthermore, something you need to do with your breeding dogs.

First, we will take a look at genetic health testing. In 2005, MIT’s Broad Institute finished the daunting task of sequencing the entire canine genome and published their results in the journal Nature. What this did was open up the opportunity for scientists to pinpoint where genetic diseases lie on the canines genome, and allow for testing to be developed that tested those specific genes. This also allowed breeders to evolve and become more responsible for the genetic health of their dogs. Now that it is possible to know exactly what genetic diseases each dog may carry, be affected by, or be clear of, we as breeders can make more informative decisions as to our breeding practices.

Today, we have a variety of laboratories offering canine genetic testing, and many even offer panels that are specific to the Labrador Retriever breed. So what diseases are most common in Labradors and what diseases should be tested for? According to the AKC the genetic health testing requirements for Labradors is only Exercise-induced collapse (EIC). This usually non lethal disease causes a dog to collapse due to muscle weakness after a period of vigorous exercise. This disease is unfortunately very common in Labradors and the incidence of this disease continues to rise, so it is indeed important that any breeder test for this disease. However, it is far from the only genetic disease a breeding dog needs to be tested for.

The Orthopedic Foundation for Animals (OFA) goes a couple steps further, and advises two additional genetic tests that Labradors should be tested for. Centronuclear Myopathy (CNM) and Progressive Retinal Atrophy, Progressive Rod-Cone Degeneration (PRA-prcd). Puppies born with CNM seem normal at birth but will quickly fall behind their littermates with gaining weight and will have decreased muscle tone. This grows progressively worse as the puppy grows giving an awkward gait and an intolerance to exercise. These puppies require special care their entire lives, and while their lives may not be shortened, they will have to battle the symptoms of CNM everyday. PRA-prcd causes cells in the back of the dogs eyes to die leading to night blindness. This is unfortunately followed by the cone cells losing their ability to function and eventually leads to complete blindness in both eyes.

It is important to note that all the diseases described above are autosomal recessive diseases. This means that both parents must carry the disease (though they are not outwardly affected by it) in order for the disease to be passed and develop in their offspring. This is why the power of genetic testing was so groundbreaking when it was released, and why it is is so crucial that breeders use this tool. Now, we can take a glimpse into the genetics of our breeding dogs and know what diseases they may be carrying that we couldn’t see with the naked eye before. Genetic testing gives us the power to eradicate these diseases if only everyone would test their breeding dogs.

Now, let's quickly take look at some the leading laboratories that offer genetic disease testing. Note that they all offer testing for many more diseases than those described above, and that while the disease above are vital to test for, they are not all encompassing. There are many other diseases that one should test their Labrador for, and it will be up to each breeder to decide what to include in their breeding program.

Broken down it seems Embark is the best investment, and offers every disease their competitors offer plus many more. The Embark kit also offers breed identification and physical traits such as coat color.

While we’ve discussed why genetic testing is an essential part in any breeding program, let's look at another aspect of health testing that is similarly important- hip and elbow evaluations. For the sake of this article I am going to mainly focus on hip dysplasia, as it is more common in Labradors, and many of the same preventatives for hip dysplasia also correlate to elbow dysplasia. Hip dysplasia is a condition where the abnormal formation of the hip socket leads to lameness and arthritis in the joint.  Hip dysplasia, unlike the genetic diseases described above, is polygenic, meaning it has more than one source. While genetics does play a part in the hip health of a dog, the environment also plays a large role. Hip dysplasia is unfortunately common in many larger breeds, Labradors included, and hip evaluations are one way that breeders can help ensure they set up any puppies they produce to have healthier hips.

There are two main evaluations breeders can choose to have their dog’s hips examined. These are through OFA or PennHIP. OFA uses a seven-point scoring system and has three independent radiologists interpret a radiograph of the dog’s hips. These radiologists each assign a score and the dog will then be given a rating of Excellent, Good, Fair, Borderline, Mild, Moderate, or Severe. OFA considers Excellent, Good, and Fair as passing and will issue these dogs OFA numbers. Note that veterinarians do not need to be certified to take an xray for OFA nor does the dog need to be anesthetized, though it is recommended. Also, OFA is the only method accepted by AKC at this time.

PennHIP differs from OFA in a few critical ways. Unlike OFA, PennHIP only allows those veterinarians who are certified by them to take an xray, and they also require three radiographs verses OFA’s one. They also require that the dog be anesthetized while the xrays are taken. Another big difference between OFA and PennHIP is that OFA only allows those dogs that are 24 months or older to receive a final score. PennHIP, however, will test dogs as young as 16 weeks and the report is seen as final.

PennHIP looks at joint laxity  and each hip is given a score (called the distraction index or DI) between 0-1. Hips that are tighter will score closer to 0 while hips that are looser score closer to 1, with the breed average for Labradors being .47 at the time of this writing. PennHIP does not offer a pass or fail, but most consider a dog falling greatly higher than the breed average as not passing.

It is again up to the breeder to decide which method they will use to have the hips of any dog they are considering breeding evaluated. However, one study done by researchers from the University of Pennsylvania School of Veterinary Medicine found that the PennHIP method was more accurate in indicating a dog’s odds of developing osteoarthritis (OA) and stated, “Dogs judged as phenotypically normal by the OFA harbored clinically important passive hip joint laxity as determined via distraction radiography. Results suggested that OFA scoring of HE radiographs underestimated susceptibility to osteoarthritis in dogs, which may impede progress in reducing or eliminating hip dysplasia through breeding.” It is also important to note that PennHIP does not offer evaluations for elbows and that OFA is currently the only option to check for elbow dysplasia. Unlike hip dysplasia, dogs are only given the rating of Normal if no dysplasia is seen on the radiograph.

Let us remember though that hip health is not due solely to genetics, and even dogs that have excellent hips with OFA or extremely low DI’s with PennHIP can produce a puppy that develops hip dysplasia. This is because, as mentioned earlier, hip dysplasia is polygenic and the environment in which the puppy is raised can greatly affect their hip health. The Norwegian School of Veterinary Science suggests that it is the period between birth and three months old that may greatly impact the overall health of a dog’s hips and suggests preventive measures to improve their hip health. They offered that daily low impact exercise in gentle terrain, combined with the absence of any stairs, could greatly improve the prevention of hip dysplasia.

Health testing, which includes genetic testing as well as hip/elbow evaluations, is indispensable when it comes to improving the Labrador Retriever breed as a whole. Breeders that have programs of any size should feel the obligation to completely health test any dog they plan on breeding. It is only with diligent health testing, especially testing for genetic diseases, that the possibility of the extinction of those diseases in the Labrador breed can one day happen. Even hip and elbow heath, which is much more complicated than a simple test, could be improved with assiduous testing along with understanding conditions that could possibly harm a young dog’s joints. As more time goes by, and more tests become available, breeders should feel it is their responsibility to conduct these tests. Not only for the dogs they may one day produce, but for the future owners of those dogs, and to ensure that we keep moving the Labrador Retriever breed ahead.