In Australia, Labradors - both sire and dam - must be screened for hereditary hip and elbow dysplaysia in order for the state controlling bodies (Dogs NSW, ACT Canine Association, etc) to accept the registration of their progeny. There is some talk of making testing for Progressive Retinal Atrophy (PRA or PRCD), a hereditary eye condition that can lead to blindness, also compulsory.
DO NOTE that no amount of screening and testing can ever wholly guarantee that puppies will be free of hereditary diseases. However, breeding from sound parents demonstrably increases the likelihood that their offspring will be sound.
Hip Dysplaysia: This is probably the most well-known hereditary disorder that affects many large dogs across a range of breeds.
What is it? A hip joint is a ball-and-socket type joint (something fairly intuitive to any of us with hips!), and in healthy mammals the ball of the femur fits neatly into the acetabulum socket in the pelvis. In a dog with hip dysplaysia, however, the socket is not a neat fit for the ball, and this causes uneven wear and tear on the joint which in turn can cause arthritis - the dog experiences stiffness, pain, and possibly the eventual loss of mobility in the affected joint.
What does screening involve? A dog screened for hip dysplaysia has a series of x-rays taken at twelve or more months of age (to allow for the bones to fully develop). These are then scored by a professionally accredited facility (usually the AVA in Sydney or Wyburn Institute in WA). Each hip is given a score in nine categories leading to a possible total of 53. The lower the number, the sounder the hip. The scores are then totalled (maximum possible = 106) and compared to national averages.
What does this mean? Dog's hip scores are shown as a ratio of one hip to the other, eg 2:3, which means that one hip received a score of 2 and the other a score of 3. The 'perfect' hip score is 0:0, which means in essence that no faults were found (or were too negligible to recieve a score). However, this is not the only factor to consider; hips which are even are also preferable, so a dog with 5:5 hips is going to have a better time of it than a dog with 3:7 hips, even though both of their combined scores are 10.
At present, the median score for Labradors is around 14. Note that this is a median, not an average, because it's assumed that not all x-rays are submitted for scoring. It has been suggested that an actual average for the breed would be closer to 18 or 19. In terms of what this means for breeding, Dr Wyburn, a leading expert in the field, recommends not to breed from dogs with:
a) any one hip score greater than half the breed average (which would be 7 at present); or
b) a score of three or more in any of the nine individual categories (you can check this on the hip certificate).
Naturally, as more people abide by this the average hip score should decrease, so in ten years' time dogs might have to have hips no worse than 3! Wouldn't that be nice?
Elbow Dysplaysia: Elbow dysplaysia is also a joint condition that can result in arthritis and eventual lameness. It's a bit different from hip dysplaysia, though.
What is it? The elbow joint is composed of three separate bones which have to grow in sync with one another in order to produce a healthy adult joint. In a healthy elbow, the surface of the ulna should merge smoothly with the surface of the radius. In a dog with elbow dysplaysia, the two surfaces don't meet smoothly and instead form a step.
What does screening involve? As for hip dysplaysia, elbows are x-rayed and the films scored. The scoring, however, is different and is based on the degree of 'step' between the ulna and the radius. Scores range from 0 to 3.
What does this mean? Elbow scores are also shown as a ratio, eg 1:0. The 0-3 grading is international, unlike the hip scores, and it is generally accepted that a dog with 3:3 elbows will be severely affected and should never, under any circumstances, be bred from. 2s are also considered high risk and should not be bred from. 0s are, of course, ideal.
For more detailed information, see Dr Wyburn's article, hosted on the Southbank Labradors website.
