Scoring of the X-rays will initially be carried out by one of the specialists in Scandinavia to ensure consistency of approach. Dr. Anu Lappalainen has offered to do this for us.
Owners will be informed of the “score”, which will comprise the total number of calcifications, plus their location in the spine. The advice given in Scandinavia is as follows:
IDC 0: no calcifications - low; no restrictions on breeding
IDC 1: 1-2 calcifications - low; no restrictions on breeding
IDC 2: 3-4 calcifications - moderate; aim to breed with a dog with 0 or 1 calcifications
IDC 3: 5+ calcifications - severe; avoid breeding with this dog
Advice for breeders
It is clearly going to take time to screen and report results for UK dogs and it may, therefore, be impossible to adhere rigidly to the advice given above, at least in the short-term. If our UK results are similar to those found in Scandinavia, we might expect 20-30% of dogs to have a score of 5+ calcifications, initially. It would not be sensible from a genetic diversity perspective to remove all these dogs from the gene pool by not breeding from them. A more measured approach will be required.
In the absence of screening data, owners will have to use their best judgment, knowledge of pedigrees and information on family history of IVDD to make informed breeding decisions.
It has been shown that calcifications are highly heritable [Jensen 2000] and dogs with many calcifications are likely to produce puppies with calcifications. In this study, if both parents had calcifications, 91% of their offspring did too; if just one parent had calcifications, only 44% of their puppies had them.
Numerous studies (since the 1960s) have shown that the lower the number of calcifications, the lower the risk of IVDD. In one study, of the dogs which had no calcifications, less than 1 in 10 had IVDD symptoms. In contrast, of the dogs with 5 or more calcifications, two-thirds had symptoms of IVDD. [Lappalainen 2001] Another study showed that dogs with 5 or more calcifications were 18 times more likely to have IVDD symptoms than dogs with no calcifications. [Lappalainen 2014]
If your dog's X-ray score is IDC3 (5+ calcifications), ask yourself these questions before deciding whether the dog should be bred from:
The more of these questions where you answer "Yes", the higher the risk of your proposed litter having back problems.