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By Dr. Becker
Researchers from the Institute of Animal Breeding and Genetics at the University of Veterinary Medicine Hannover, Germany, have identified important genetic variants and their interrelated pathways for the development of canine hip dysplasia (CHD). at the house of German Shepherds.
The genes responsible for hip dysplasia are involved in the formation of bones and cartilage. More than 1,000 German Shepherds were genotyped, and scientists examined a large number of single-nucleotide polymorphisms (SNPs) (the most common type of genetic variation) to determine their association with coronary heart disease. The results of the study were published in the journal PLOS ONE.1
Canine Hip Dysplasia Explained
Canine hip dysplasia is what we call a polygenetic multifactorial disease, meaning there is a genetic component to the disease, more than one gene is involved and it is caused by a number of factors, not all of which have been identified.
Dogs carrying genes that cause hip dysplasia may or may not develop the disease; a dog without CHD genes is in the clear.
A dog can have excellent OFA and PennHIP scores (which measure hip health) and still carry genes for the disease, meaning future generations of puppies can develop CHD even if previous generations did not. ‘show no signs of it.
A dog is diagnosed with coronary artery disease if the ball and socket joint of the hip is malformed, causing the two bones in the joint to separate. In most cases, the socket is not deep enough for the ball to fit snugly into place.
In a dog with healthy hips, the ball (the head of the femur) at the top of the leg bone fits perfectly into the socket. In animals with CHD, the imperfect fit causes the bones to separate. This separation is the result of abnormal joint structure combined with weakness in the muscles, ligaments, and connective tissue that support the joints.
The result is a joint that rubs and grinds rather than sliding smoothly during movement. Often the body tries to compensate for an ill-fitting joint by producing hard bone material in and around it to try to stabilize it. This modification can have the opposite effect, creating an even less natural fit.
Seal wear due to friction and grinding eventually results in degenerative joint disease (DJD), which can be extremely painful and debilitating for the dog.
Symptoms of hip dysplasia
According to PennHIP,2 A dog with coronary heart disease may exhibit one or more of the following symptoms:
The disorder appears between 5 and 12 months for the severe form; later for the chronic form Low exercise tolerance Abnormal gait Reluctance to climb stairs Running bunny hop “click” audible when walking Thigh muscle atrophy Increased width between hip points Pain The diagnosis of hip dysplasia is usually made either because a dog is exhibiting symptoms or following a standard hip exam.
If your pet is exhibiting symptoms, there will be signs of mobility issues and pain. The veterinarian will perform a complete physical exam and take x-rays. Joint problems are often easily seen on x-rays of dogs exhibiting symptoms. Your veterinarian may also be able to feel looseness in your dog’s hip joint and note pain when a rear leg is extended or flexed.
In asymptomatic dogs, CAD is often diagnosed during the OFA and/or PennHIP certification process intended to establish the health of an animal’s hips.
Which dogs develop coronary heart disease?
Some large breeds are more prone to coronary heart disease than others, including the Newfoundland, Saint Bernard, Old English Sheepdog, RottweilerGerman Shepherd, Golden Retriever, Alaskan Malamute, Labrador Retriever and Samoyed.
Hip dysplasia also occurs less commonly in small breed dogs and cats.
Other markers of CHD may include:
- A body longer than tall
- High BMI (body/mass) ratio
- Spayed or neutered
- Dogs less than 1 year old diagnosed with hip joint injuries and hip orbit microfractures
- Young to middle-aged dogs with osteoarthritis-related pain and lameness
Whether or not a dog develops coronary heart disease and DJD/osteoarthritis, and their severity, depends on both nature (a genetic component) and nurture (environment and nutrition).
Environment, nutrition and canine hip dysplasia
There are things you can do as a pet owner to help prevent or reduce the severity of hip dysplasia in your dog. For example, if you are considering getting a large breed or giant breed puppy, find breeders who certify their dogs with PennHIP. OFA certification remains the established standard, but PennHIP is a much better indicator of hip health.
The amount of calories your dog consumes, especially between 3 and 10 months of age, can have a significant impact on whether a puppy carrying the CHD genes will develop the disease. Diets high in calories and carbohydrates can cause the body to grow too quickly for the body’s cartilage to keep up, especially in large breed puppies. A portion-controlled, balanced, species-appropriate diet will provide your pet with proper nutrition in the right quantities throughout its life.
In a 1997 study of Labrador Retriever puppies, “free-fed” dogs had a much higher rate of hip dysplasia than their littermates who were fed the same food, but in controlled portions that made up 25% of less than free-fed puppies.3
The free-fed dogs were also a bit heavier as adults than the portion-controlled group — by about 22 pounds on average.
Obesity can increase the severity of dysplasia. Extra weight can accelerate joint degeneration. Dogs born with genes that make them prone to hip dysplasia, if they become overweight, will be at a much higher risk of developing the disease, and subsequently arthritis as well.
Exercise your dog with activities like running and swimming. The goal is to maintain good muscle mass, which can decrease the incidence and severity of coronary heart disease.
Avoid activities that require your pet to jump, change direction abruptly, or stop. Don’t let your dog exercise or spend a lot of time on slippery surfaces.
A study will encourage better breeding choices
According to Lena Fels, co-author of the study, dog breeding will benefit considerably from this research:
“Despite the use of Estimated Breeding Values (EBV) for CHD, dogs with CHD are not uncommon and often unexpected based on parental EBVs. This poses big problems for dog breeders. Handling dogs with coronary heart disease is often difficult and dogs frequently suffer from this painful condition.
Fels believes that coronary heart disease can be prevented much more effectively thanks to the results of this study.
The genome-wide CHD test is available at the Institute of Animal Breeding and Genetics and can be provided to all German Shepherd breeders and owners. Further details can be found here.
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