For 22 years, I have been working with large breeds of dogs in my veterinary practice. The numbers of giant and large breeds we see far exceed the numbers of medium and small individuals. One reason for this is my long history with this type of dog; another is that we do OFA hip radiographs without anesthesia, and for whatever reason, the owners and breeders of the large and giant breeds are, as a whole, far more sensitive to anaesthetic issues than those of smaller breeds.
Over the course of these years, the kennels of many clients who raise large numbers of giants have been our laboratory. Following these breeds, these breeding lines, and individuals within these lines over their entire lifetimes, certain facts have become incontrovertible to us.
We have never taken the time to go into our records and pull out the data to quantify these observations for professional journals, so the observations here must come under the heading of clinical findings. However, a few years back we looked into the records on Newfoundland dogs, and found our database held over 400 adult individuals. Several other large and giant breeds are represented in lesser, but still very substantial, numbers.
Internet sources on hip dysplasia include a selection of abstracts from Medline for the years 1966 to 1996.( Medline Literature Search: Canine Hip Dysplasia, 1966 - 1996. (http://www.working-retriever.com/library/chd6696.html ) At the end of this article are some of these abstracts found on that page which support observations made here.
Many other references are
present in the literature, but these suffice to illustrate the research
available making mention of the items we are interested in:
Dietary considerations
Influence of injury and pain
THE PREMISE
One frequently encounters discussions which assert that hip dysplasia is
50% genetics and 50% environment. We prefer to think of it as 100%
genetics, then 100% environment. Genetic considerations are the entirety
of what we must as breeders consider. Once that puppy is born,
environment is 100% of how well that puppy will do within the
possibility of his genetics. Dogs with very good hips, congenitally, may
have an injury and end up diagnosed as having 'unilateral hip
dysplasia'. Individuals with very shallow sockets may be mobile and free
of pain to an advanced age, if they have unlimited exercise. This is the
entirety of what the owner of that puppy needs to concern himself with
to provide the best possible care for his dog.
Over the years, our observations of the kennel populations of giant
breeds and their siblings living in private homes have led to the
conclusion that there is no such thing as congenital unilateral hip
dysplasia, but only acquired unilateral hip dysplasia. The kennel dogs,
whose exercise opportunities are maximized, with several dogs of a
similar age free to run and play all day and night in large paddocks,
show us some interesting things.
The implications of these observations are enormous, but very simple to understand. These large breeds grow much too quickly for their biology to keep up. They frequently show some degree of clinical rickets with some bowing of the forelegs, and have large soft joints due to the inability of the body to deposit calcium in the bone at a rate equal to the rate of growth. They often show uneven growth, with the rear end growing over a few weeks, then the front end trying to catch up. As the rear leg assembly grows disproportionately, and the puppy is 'high in the rear', the mechanical leverage that the muscles are able to exert across these straighter angles is much reduced. The result of this is a decreased ability of muscle to protect joints from injury.
The owners of giant breed pets tend to overfeed their puppies, having with the best of intention, the inner desire to see a 'big dog' and to do nothing which might risk the dog not attaining the greatest possible size. Try as they may, some owners are just unable to restrict their puppy's diet. Owners are cautioned that their puppy needs a good deal of exercise, but their work schedules often conflict with their desire to do this. The result is a period of intense exercise. A 3 mile run, or a half hour of Frisbee. When a single puppy who lies around all day welcomes his owners in the evening, he is ill prepared for either intense exercise, or the uncertainty of footing on slippery floors and his always changing joint angulation. His muscle tone is a small fraction of that of a puppy which plays with other active dogs all day long. The result is an injury.
When any dog has a hip dislocated, if it is not repaired within 48 hours, the socket begins to lose depth. When an injury occurs to a rear leg, whether it be a toe injury, a stifle injury, a soft tissue injury, or a hip injury, the result is often a decreased amount of weight bearing on that leg over a period of days to weeks or months. When this happens, the mechanical forces applied to the living bone tissue change, and the hips become asymmetrical, the injured hip becoming shallower in a similar fashion.
Many will find that a very controversial statement. Dr. Corley from the OFA would reply to observations such as this, that he could prove that unilateral hip dysplasia was genetic, since it was almost always the left hip which was shallower. My response to his statement was that this proves to me that most dogs are right handed. The left diagonal being the master limb, the one with which the dog pushes off most strongly, and the one which is most liable to injury, especially stifle injury.
The conclusion from these observations is that the single most important environmental factor in a puppy's life is exercise, continuous and strenuous. Since this is often impossible for owners to arrange, the next considerations are to drastically restrict the diet of the growing puppy and to avoid strenuous exercise which will exhaust his muscles and leave him unable to protect his joints from injury. The puppy should be given frequent moderate exercise instead. This requires a different kind of time commitment from the owner.
NUTRITIONAL CONSIDERATIONS
R. D. Kealy, S. E. Olsson, K. L. Monti, et al. Effects of limited food
consumption on the incidence of hip dysplasia in growing dogs. J Am Vet
Med Assoc, 1992;857-63. Forty-eight 8-week-old Labrador Retrievers were
allotted to 2 groups of 24 dogs each; 1 group was fed ad libitum and the
other group was given 25% less of the same feed until the dogs were 2
years old. Radiography of the hip joints was done when the dogs were 30,
42, 54, 78, and 104 weeks old. Subluxation was measured by the Norberg
angle on radiographs made with the dog in the standard (extended limb)
position. Independent of age at which the radiography was done, there
was less subluxation of the femoral heads in the limit-fed dogs. Using
the Swedish method of hip joint evaluation on the same radiographs, it
was found that fewer dogs on limited food intake had signs of hip
dysplasia. Radiographs done when dogs were 2 years old, for all the
methods used (Norberg angle in standard and frog-limb position, the
Orthopedic Foundation for Animals [OFA] score, and the Swedish score),
revealed less hip dysplasia (less joint subluxation and less
degenerative joint disease) in the limit-fed dogs. Using the OFA method,
7 of the 24 limit-fed dogs and 16 of the 24 ad libitum-fed dogs were
diagnosed as having hip dysplasia. Similarly, using the Swedish method,
5 of the 24 limit-fed dogs and 18 of the 24 ad libitum-fed dogs were
diagnosed as having hip dysplasia. The food-intake-related differences
were significant both for the OFA score and for the Swedish score.
H. Kasstrom. Nutrition, weight gain and development of hip dysplasia. An experimental investigation in growing dogs with special reference to the effect of feeding intensity. Acta Radiol Suppl (Stockh), 1975;135-79. Thirty-one dogs from 5 litters with a high parental frequency of hip dysplasia were used in the investigation. Each litter was split in two groups, of which one was put on a high caloric intake, the other one on a low caloric intake. Each member of a group had a paired litter mate in the other group. The litter mates were paired on the basis of the result of a palpatory examination of the hip joints before 12 weeks of age. If possible, paired mates were of the same bodyweight at the time of palpation, and of the same sex. In the groups made up of pups from 3 of the litters, the protein intake was kept at an optimal level, regardless of the amount of calories given. It was found that hip dysplasia was more frequent, occurred earlier, and became more severe in the dogs with a rapid weight gain caused by increased caloric intake than in the dogs which had a low weight gain because of restricted feeding. The final diagnosis was closer correlated with feeding and weight gain than with tightness or laxity of the hip joints before 12 weeks of age.
OFA
The OFA provides a necessary service. It is a level playing field for
evaluating hip films and elbow films submitted by veterinarians of
widely varying ability to read the films themselves. They are a fairly
administered database for the use of breeders, and they have taken on
the task of administering other genetic databases. This is good since
the OFA’s track record in handling databases is excellent.
The OFA is not, however, perfect. Dogs with good hips are occasionally labeled as dysplastic and dysplastic dogs are occasionally passed. Since the panel of film readers changes quarterly, there is an inherent inconsistency factor, but this rotation also ensures that no bad panel will be in effect forever. While we should give them credit for all of their good services, this should not blind us to occasions and situations where they fall short. Occasionally they misread films and they have broadened the Elbow Dysplasia diagnosis in a manner harmful to those trying to breed good dogs.
ELBOW DYSPLASIA
The trouble with Elbow Dysplasia is that the OFA has labeled any x-ray
with some sclerosis as dysplastic. Sclerosis is the result of
degenerative changes and will appear in any joint over time. It results
from normal wear and tear. You had some by the time you hit twenty.
Eventually the joints showing mild sclerosis will develop
osteoarthritis. This is arthritis as a result of wear and tear. Dogs
with the three conditions the OFA cites will develop massive sclerosis
in a very short time. However, some breeds show a slight degree of
sclerosis in the elbow joint by two years of age without any of the
elbow conditions the OFA describes being present. These dogs are not
painful in these joints.