We care about osteoarthritis because it causes pain and disability in dogs
and in people,Dr. Smith explained.

 

Hip dysplasia is a polygenic trait and therefore very complex. The breeding
community has taken great efforts to reduce the incidence of the disease
through careful breeding. However, said Dr. Smith, in spite of these efforts,
they have not been very successful. In a prevalence study reviewing Orthopedic
Foundation for Animals (OFA) figures from 1981-1988, 21 percent of surveyed
German shepherds had hip dysplasia. During the subsequent eight years, that
figure was 23 percent. Likewise, the occurrence rates for Rottweilers, and
Labrador and golden retrievers which hovered in the range of 24 percent
did not significantly fall over time, as might have been expected if selective
breeding were effective. In a study of Airedale terriers in Berlin, the
prevalence rates of hip dysplasia in 1981, 1991 and 1996 were 45, 50 and 45
percent, respectively. A Finnish study of 10,335 German shepherds between 1981
and 1997 also showed no genetic headway in reducing the occurrence of hip
dysplasia.

 

Genetically, we're not getting anywhere fast, Dr. Smith concluded. But can we do things environmentally? The answer is yes.

 

Limiting the forces on a joint that is genetically predisposed to hip dysplasia
and/or osteoarthritis can reduce the occurrence and severity of disease, he
said. Several studies in the past have shown that restricting weight gain,
growth rate and exercise can produce small decreases in the occurrence of
degenerative joint disease.

 

Our understanding of hip dysplasia may be revolutionized by a longitudinal
study conducted at Nestle-Purina for which Dr. Smith was a coinvestigator. It
demonstrated for the first time that limiting a dogs intake of commercial
dog food throughout its life significantly reduces the occurrence and severity
of hip laxity and/or osteoarthritis. The study, which has not yet been
published, tracked 24 paired littermates of Labrador retrievers maintained at
Nestle-Purina for 14 years. For each pair of dogs, one was fed ad libitum for
15 minutes daily, while the other dog was fed 75 percent of
the quantity the first dog consumed. To increase the reliability of the
results, the hips were uniformly scored using several different diagnostic
methods.

 

At two years of age, 16 of the dogs fed ad libitum, and only seven of the
leaner, limit-fed dogs, had hip dysplasia. Other joints were affected by diet
as well: At eight years of age, 19 dogs in the ad-libitum group, and 12 dogs in
the limit-fed group, had osteoarthritis of the shoulder. In fact, 68 percent of
the ad-libitum dogs and ten percent of limit-fed dogs had both hip and shoulder
affected, and 77 percent of the ad-libitum dogs and ten percent of the
limit-fed dogs were affected in any two joints. Clearly dietary restriction has
a protective effect on other joints as well.

 

The study also demonstrated that the incidence of hip dysplasia increases
linearly with age such that normal hip conformation at two years of age is not
necessarily predictive of hip dysplasia risk in later years: About half of the
dogs with normal hips at two years of age became dysplastic later in life. The
study concluded that for dogs kept lean there was a 6:1 reduction in hip
osteoarthritis by two years of age and a 2:1 reduction by end of life. The
study also showed that leaner dogs that experience hip dysplasia generally have
a lower severity of the condition, and dysplastic dogs that are kept lean
maintain better use of their limbs, require less pain medication… and have a
better quality of life.

 

University of Pennsylvania - Bellwether 52 - Spring 2002