Health Testing
Introduction
Before breeding a litter of puppies, a breeder should ensure the sire and dam of the litter are as healthy as possible. This would seem to be stating the obvious but all too frequently this does not happen and the results can be heart breaking.
Even with every health test performed and with the correct results achieved, problems can arise. After all, dogs are living creatures and the study of biology teaches us that good health cannot be guaranteed. However, responsible breeders should be doing everything possible to increase the chance that the puppies will be healthy.
What does this mean in practice? As mentioned in another blog post, the parents should be fit and healthy and a good example of their breed both in conformation and temperament. Dogs suffering from chronic disease such as atopic dermatitis should not be bred from as it is likely there is a genetic component playing a part.
DNA testing
Health testing can be done by DNA testing. Most breeds now have DNA tests available for various eye, neurological conditions and others. These are done once in a dog’s life and the results can be as follows :“clear”, “carrier” or “affected”. The conditions for which DNA testing is available are those known as “autosomal recessive”. This means an affected dog will have two “copies” of the affected or mutated gene, a carrier will have one and a clear dog will have none. A carrier dog will not be affected by the condition but if mated to another carrier could produce affected offspring.
DNA test results are recorded on the KC website and can be found by following links to “breeding“ and “health test result finder”. To access these results, the exact KC registered name of the parents needs to be known.
Some of the conditions caused by defective or mutated genes can cause catastrophic conditions such as renal failure and blindness. The whole canine genome has now been identified and new DNA tests are being added all the time. The cost of the tests is reasonable and the tests themselves are non invasive only requiring a swab to be taken from inside the dog’s mouth.
Some genetic conditions (known as polygenic conditions) are caused by a number of genes acting together or in combination with other factors such as diet and exercise. DNA testing is unlikely ever to be available for these.
Eyes, hips and elbows
Many pedigree dogs require an annual eye test to screen them for conditions affecting the lens, retina and other structures including the eyelids. These certificates are issued by vets specialising in ophthalmology. Some breeds require a test for glaucoma known as gonioscopy.
Hip dysplasia (HD) and elbow dysplasia (ED) are both polygenic conditions. Both HD and ED have been described in most breeds of pedigree dogs. Cross breeds can also be badly affected. Large and giant breeds are the ones most severely affected by either HD or ED (or occasionally both). The main abnormality found in affected hips is laxity of the joint. In other words, the hip is a poor fit in the socket (known as the acetabulum). This results in uneven wear in the joint and can cause lameness in a young developing animal. Often, the lameness improves once the dog is fully grown but at some point in the future osteoarthritis develops. If a young dog is very badly affected by HD and if funds allow, often the only satisfactory treatment is a total hip replacement. This surgery is not for the faint hearted. The lengthy recovery time, usually requiring strict cage rest, can have a profound effect on a dog’s temperament.
Elbow dysplasia is also usually seen in young growing dogs. Again, the dog will present with a lameness, this time involving a fore limb. Often both limbs are affected. This is a very painful condition which often requires surgery. Even with surgery, most affected dogs will go on to develop arthritis.
This brief summary of the impact of hereditary conditions on a dog’s life should hopefully underline the importance of health testing.
To reduce the risk of producing affected puppies a hip scoring scheme has been in existence since the early 1980s. The elbow scoring scheme came into existence at the end of the 1990s.
Each breed has a “median” hip score based on the number of dogs scored. This data is available on the KC website. The more animals that are scored, the more reliable this data will be. Dogs with a low score or at least a score less than the median for their breed are the most suitable ones to breed from. Often, a dog can have a high hip score and yet appear clinically well whereby it can walk for miles, do a day’s work on the shooting field or win a dog show. Hip scores range from 0-106. Each hip is scored separately and are usually reported as two distinct numbers. The lower the score the better the dog’s hips. Most of the commonly scored breeds a have a median score around 12-14. As mentioned above, there are other factors which can influence both a dog’s actual hip score and whether it goes on to develop clinical signs of HD.
Elbow scoring classes a dog’s elbows as normal (0 score), mildly affected (1 score), moderately affected (2 score) and severely affected (3 score). While the dog’s environment can have an effect on the development of ED it is widely accepted that even a mildly affected dog could go on to produce puppies more severely affected than either parent. The fact that dogs with elbow scores of 2 and 3 can appear normal underlines how important elbow xraying is. Without it, severely affected dogs with no clinical signs (known as sub clinical cases) will be bred from unwittingly. Back in the 1980s, there was no elbow scoring scheme. As a result, there were many more cases of dogs crippled with arthritis at a very young age.
There are still many dogs being bred without hip and elbow scoring being done. This can be due to a cost cutting, breeding “on the cheap” approach where no thought is given to the future wellbeing of the puppies. Sometimes, particularly with elbow scoring, a breeder might think ”they have never had any trouble with elbows, so why bother scoring?” These breeders may well be storing up problems for the future if they have subclinical cases in their kennel. It can be devastating to abandon breeding plans due to poor hip or elbow scores. It is so important to do this because failure to act on the scores received could easily result in pain and suffering down the line.
To have a dog’s hips and elbows xrayed requires the dog to be immobilised either by a general anaesthetic or heavy sedation. One view is taken of the hips with the dog lying on its back and its legs extended (see picture) and two views are taken of each elbow. The images are then sent (usually digitally) to a panel of expert veterinary surgeons who examine them and produce a score.
Xrays cannot be taken till a dog is 12 months old.
