I am not sure why there is all this debate about the breeding guidelines. Surely the intention is that CKCS breeders use the EBV system developed by the AHT (at huge expense). This is this the most effective way of decreasing disease and increasing genetic variability and information about MVD and other diseases can be added.
It was my understanding the the new guidelines were revised based on the recently published paper here http://www.veterinary-neurologist.co...myelia/page54/ . A worrying finding from this paper that in a D x A mating 75% of offspring were SM affected. Part of the reason for this was that many of the "A " dogs were not truly A - 30% of the grade C dogs became D and 43% of the A dogs became D
This said "In conclusion, the results from this study suggest that it is appropriate to continue using the breeding guidelines for both the CKCS and GB until a more robust system based on EBV or genetic testing is available. The following modifications are suggested .....To increase the number of SM-free offspring, at least one parent should be ascertained to be SM-free by MRI as a young adult. In ideal circumstances, both parents would be SM-free. According to the studyby Parker and others (2011), the optimum age for this early MRI screening is 36 months. If an SM-affected dog is used, for example, to preserve desirable traits or to increase genetic diversity then ideally the chosen mate would either be selected on the basis of its EBV and/or would be an older SM-free dog (five years or older). The offspring of the proposed
mating should also be MRI scanned and ideally bred to older SM-free dogs. The SM status of the dog when at least five years old should be established. SM has a complex inheritance and an EBV mate select programme should allow breeders to select safer breeding combinations.To ensure success, the programme requires a substantial collection of accurate population wide data. Consequently, all breeding dogs from breeds susceptible to CM and SM should be MRI screened and these results should be submitted to a central source. Pedigree and clinical history from dogs presenting with clinical signs of CM and/or SM should also be submitted to this central system. D status (or equivalent) will only be appropriate if the dog was first proved to be SM-free before 36 months of age. Future breeding recommendations should also take
account of dogs with CCD less than 2 mm.....