FoundersA primary purpose of RymanSetters.com is to help foster an expanding gene pool of healthy Ryman-type setters. An important part of achieving that goal is providing breeders with good information about health issues in English setters and how to deal with them. One of the most challenging aspects of producing healthy dogs is the VAST amount of misleading and false information breeders have to wade through looking for answers. Of all the health issues facing them, hip dysplasia, by far, has the largest amount of conflicting, confusing, and incorrect information promoted online and elsewhere.
We’ll use the following article as an example because it is currently circulating around the web.
This article is yet another in the long line of publications rehashing the same old misconceptions that have been holding back progress in reducing the incidence of hip dysplasia for years! The mistakes made are a classic illustration of how easy it is to get off track in your thinking about HD- misunderstanding of genetic principles causes a misinterpretation of studies that leads to incorrect information and poor breeding choices. It begins with the commonly held, but false, premise that hip dysplasia (HD) persists as a problem despite decades of unproductive research looking for solutions, and despite breeders “doing their best to reduce the risk of producing affected puppies.” Then, within the context of believing that false premise, the author makes two critical errors that lead to a cascade of misinformation:
First– Like many writers and breeders, the author misinterprets heritability estimates in a way that confuses people into thinking environmental factors can be a cause, or even the main cause, of hip dysplasia. WRONG! By definition, heritability estimates do not separate inherited traits into genetically and environmentally controlled portions as implied in the article – if a trait is given a heritability it IS genetic. Here are a few references explaining what “heritability” means:
en.wikipedia.org/wiki/Heritability
The Use of Health Databases and Selective Breeding Pg. 7
extension.missouri.edu/publications/DisplayPub.aspx?P=G2910 Near the end there is a very good description of how heritability estimates are used.
Second– The author makes no distinction between HD and arthritis. They are not the same thing. Hip dysplasia is defined as abnormal formation of the hip joint. The most common major abnormalities are laxity (subluxation) and/or shallow acetabula. These abnormalities cause the hip joint to degenerate and eventually become arthritic. Again, arthritis is not HD, rather it is a consequence of HD. For instance, a dog with loose hips has hip dysplasia, whether or not it has developed arthritis yet.
So, keep these two things in mind when reading the Institute article:
1- When it says “hip dysplasia” substitute the word “arthritis”. That’s what the author is actually talking about in most of the article, not hip dysplasia.
#6 is a particularly egregious example of this. Data from a study on diet (Kealy et al 2002, Smith et al 2006, aka the Purina Life Span Study) is misrepresented to support the author’s beliefs, including ALTERING a chart from the study that represents the proportion of dogs with arthritic hips at various ages. Compare the altered chart:
Altered Chart
To Figure 1 from the study here:
Smith et al 2006
According to the altered version a high percentage of the dogs in the restricted group had “good hips” for most of their lives, which is obviously not what the study showed. The author also states “At four years old, less than 10% of dogs kept on a restricted diet (25% less than the control diet) were dysplastic…”. In reality 29% of the dogs in the restricted group were diagnosed as dysplastic at 2 years. The failure to understand the difference between arthritis and HD leads to the conclusion that dysplastic dogs in the study were NOT dysplastic!?! This reinterpretation is a gross misrepresentation of the data from the study. (We will be covering the Purina study thoroughly in a later post.)
2- No studies have shown that environment can cause HD. The only thing studies have been able to demonstrate with any confidence is that overfeeding dysplastic dogs MAY accelerate the onset of arthritis and increase it’s severity.
The mistakes in this article get to the root of why people don’t understand what to do about HD. Without those misunderstandings all of the seemingly logical advice about preventing HD through controlling environment falls apart. By all means, if you have a new puppy keep it thin and follow the other advice about optimizing the chances it will have a healthy life, but don’t fall into the trap of believing this will change whether the dog has HD. Nothing recommended will do anything whatsoever to reduce the genes for, or the incidence of, HD.
RymanSetters.com plans to do a series of in-depth posts on hip dysplasia. We will cover all of the above and more, including:
- What hip dysplasia is and how it presents in the individual dog.
- The known genetics behind it.
- Heritability.
- What is, and is not, known about environmental influences on the expression of the genes.
- How breeders CAN, and HAVE, reduced the incidence via selective breeding.
The selection methods that work are well established, they are straightforward, and you don’t have to worry about whether your customers feed their puppies a little too much or let them climb stairs.
Stay tuned.
RymanSetters.com series on Canine Hip Dysplasia. Our comprehensive guide to HD and the effective steps breeders and buyers can take to control it.
Upcoming Series on Hip Dysplasia
Old Age Arthritis is Not Normal, It Comes From Hip Dysplasia
Chronic Pain From Canine Hip Dysplasia: Can You Miss It?
There Is No Such Thing As “Environmental” Hip Dysplasia
Hips and Dysplasia and Heritability, Oh My!