Catahoula Issues » Hip Testing  

This is a very controversial subject, and there is a lot of misleading information being applied to approved tests. It is not my intent to add to the controversy, but to provide information that should be considered by both the breeders and owners of any breed of dog.

The greater majority of radiographs are sent to the Orthopedic Foundation for Animals (OFA) for a determination as to whether or not the dog in question has, or is prone to, Degenerative Joint Disease or Hip Dysplasia. This determination is made by randomly choosing three (3) of the twenty (20) Board Certified Radiologists working for OFA. If, in their opinion, the dog's hips fall within the average of the acceptable range, they are rated as Excellent, Good, or Fair. Dogs falling within these ranges are assigned an OFA Number. Dogs that are rated Borderline, Mild, Moderate, or Severe are considered Dysplastic by OFA Standards, and will not be given a number. Dogs failing OFA readings may be resubmitted with another radiograph for another evaluation by changing the method in which the original radiograph was taken. For example, if the dog was physically restrained for the first radiograph, then the next radiograph submitted should be taken with the dog chemically restrained, or anesthetized, and vice-versa.

It should be noted that the radiographs are viewed differently when the dog is restrained as opposed to being anesthetized. In Dr. Kelly's view, dogs that are restrained without the use of anesthesia are able to hide some faults, therefore, radiographs of restrained dogs that are awake during the radiography are viewed differently from those that are anesthetized. The examiners are aware of this because the OFA Card has a check box for both types of restraint, and the Veterinarian taking the radiograph must complete the form prior to submitting it to OFA.

Radiographs may be taken at any time and given a preliminary evaluation. Numbers will not be assigned to a dog that is under two (2) years of age. When getting radiographs taken, it is advisable that a bitch in heat not be tested. The reason given for this is that their hormone levels are increased, and that has a direct bearing on the relationship of the hip tests. That is a reasonable explanation, but what of a male to be tested? He undergoes a roller coaster ride of hormonal changes throughout his life. With a Female, you can obviously tell when she is in heat, but, with a male, you cannot determine what the hormone level is at the time of testing. Could that make a difference? What if the male being tested has been around a female in heat? Would that drive up his levels? Is the male unaffected by this rise in hormone levels? I could not get any answers to these questions from OFA or PennHIP, other than it was an "interesting point."

The radiograph examination and test results are a snapshot in time, and cannot predict the future. As was explained to me by Dr. Kelly at OFA, the radiograph is a single phenotypical picture by which a decision will be made. It is an average of opinions as to whether or not there are signs of DJD or HD. It does not, cannot tell you, if the dog is a carrier of the disease, and has the propensity to pass it on to its offspring. Even a dog that tests Excellent may carry the gene that will cause this disease to appear in its offspring. This polygenic disease may never be eliminated.

What is required to eliminate the disease is a genetic study of all of the dogs in a particular line of dogs. Essentially, it would take 12 to 15 years to study all of the dogs in one particular breeding line just to make a determination as to whether or not there is a predisposition for the disease. According to a study performed by the American Kennel Club, this would be about twice as long as most breeders remain in the business of breeding one particular breed of dog.

What needs to be determined in a breeding program is which dogs have the disease, and which dogs are carriers. When a dog is assigned an OFA number, we tend to become complacent about the presence of the disease. We receive a feeling of relief that the dog being tested does not have the disease. However, does it have the propensity to pass it on? Is it a carrier? That number gives us a feeling of security, but it does not eliminate the ongoing problem. For example: a dog that tests in the upper range is bred to another dog in the same or higher range, but it still produces a litter that has one dog that tests severe. This tells you that one or both of the parents were carriers of the disease. They may not display it, but they pass it on.

If the puppy that has been diagnosed as severe is bred, the disease is positively passed along. If the puppies that pass the testing are bred, they too, pass it on. If one pup in the litter is diagnosed with it, the others are positive carriers of the disease. In other words, you would have to study 12 years of lineage with a complete freedom from the disease in all of the litters before you could be certain that this line of dogs is not going to acquire or even pass along HD.

With PennHIP testing, the same holds true. It is a snapshot in time, only. There is no way of telling whether this dog will acquire or pass along the disease. In a conversation with one of the doctors at Synbiotics Corp., the previous owners of PennHIP, the following information was passed along to me: "When your dog is tested, it is only a picture, or snapshot in time, of that dog at that time. A determination as to whether or not it will develop HD later in life cannot be made. In addition, if a dog is diagnosed with HD, it cannot be determined whether it will worsen. It is known that it rarely ever improves. So, knowing that information, it would be advisable to have the tests performed at three different time intervals, and take the average of the tests."

When you consider the costs of OFA and/or PennHIP tests, performing repeated tests on the same dog could get very expensive, and you still will not have a guarantee that the disease will not appear in the offspring of the dogs being bred. OFA costs, including Veterinarian charges for the radiograph, can vary from $75.00 to $135.00. PennHIP tests average about $175 per dog, per x-ray.

A top breeder of Labrador Retrievers, who has been involved with OFA testing and various other forms of testing for over 20 years, has decreased the number of appearances of HD in his line of dogs, but, even after 20 years of testing and scrutiny, HD will still rear its ugly head in 20% of the offspring.

A comparison study of tests was performed by me with the help of a few other breeders involved with testing, and the results were confusing, to say the least. There were dogs that tested Excellent that were bred to dogs that tested Fair, and they produced an offspring that displayed HD at the age of 7 months. Then, there were dogs that tested Mild for the disease that were bred to dogs that tested Good, and they produced puppies with PennHIP readings of 3.1, with no HD. Dogs testing Good bred to others testing Good produced puppies that tested Good. The same pair also produced a litter that had one case of HD. This would conclude that ALL of the dogs tested and produced were carriers of HD. Based on this, how could a breeder guarantee that a dog will not get HD?

I am all for eliminating this and any diseases that affect our dogs, but be assured that this type of testing is only the first step. Testing is a tool, not a guarantee, which should be used as an aid in the production of better dogs. Until we have funding that will support a study to isolate any genetic or polygenic diseases, we are left with an educated guess as to what will be produced.

When diagnosing lineages, most registered Catahoulas will go back to just a few (three or four) bloodlines that were accepted at the start of the registry. Regardless of the kennel name on the papers, its lineage may go back to those few lines, creating a limited gene pool. Fortunately, at Abney Catahoulas, we have the privilege of having a line of dogs that goes beyond those three or four original lines, and which are totally unrelated. This has aided us in the production of our line of dogs.

In an effort to reduce HD, without destroying other positive traits, the program used at Abney Catahoulas is very similar to the one utilized by the AVMA study listed below. Given the limited gene pool that is available to most registered Catahoula breeders, it would be advisable for breeders to incorporate this study into their breeding program, and not remove a dog that has good traits. Instead of removing the dog, you should attempt to "breed up." Breed to a dog that is better, or has better test scores. Do not eliminate positive traits just to achieve one thing. Breed to achieve all that you can.

A published report appearing in the Journal of American Veterinary Medical Association, vol.217, No.5, September 1, 2000, presented a chart on the frequency of Hip Dysplasia from a study beginning in 1972 through 1993. The dogs that were used in this study were the English Setters (1091), Portuguese Water Dogs (1101), Chinese Sharpeis (1070), and Bernese Mountain Dog (2941). These breeds were chosen because of the high percentages of breeding animals for which test scores were available and demonstrated a high degree of HD. The study concluded that dogs that had OFA Scores of Excellent when bred together still had a 2.3% ratio of producing HD in their offspring. Since the disease is believed to be polygenic, its elimination is not likely. Reduction of its appearance is possible with careful breeding, but elimination is not possible at this time. These breeds have reduced the number of appearances of HD with the use of programmed breeding.

In the chart below, the upper group of boxes indicates Females and the outer group of boxes indicates Males, each with the OFA reading of the dogs being bred. Using the chart as you would to find a location on a road map, bring the two together to meet within the inner boxes. The inner boxes indicate the percentages of dysplasia that appeared because of that breeding. All dogs that tested Borderline (4) were eliminated from this study.

In spite of the readings shown in the chart above, AVMA reports that neither male nor female are more prolific in producing dysplasia, and that both contribute equally to this polygenic disease.

Some breeders, in an effort to reduce the number of appearances of HD, are using the information contained here very successfully. Do not throw out a good dog because of one problem. Attempt to eliminate the problem and maintain the positive traits that are already there. Given the limited Gene Pool of the Catahoula, we cannot afford to discard dogs with other positive traits and qualities. We do not have to rebuild the Catahoula, but we should attempt to perfect it.

Orthopedic Foundation for Animals

PennHIP

American Veterinary Medical Association