Article in today's Guardian with views from the excellent Dr Clare Rusbridge, a longtime friend of CavalierTalk and the cavalier breed. Outcrossing used to be very common before breed standards started to be fixed in the Victorian era and gene pools thus gradually narrowed and breed-related health issues began to arise. FWIW the cavalier is itself a reconstructed breed, which results from a 1920s competition to breed a longer nosed toy spaniel of the sort seen in paintings of King Charles II's era (hence the breed name). Several breeds supposedly went into the reconstruction. So it isn't as if there's some cavalier-only lineage that stretches back into the mists of time; the breed was only recognised in the UK from 1945, not even 80 years yet.
But bringing in other genes remains controversial with some breeders. What do you think?
www.theguardian.com
But bringing in other genes remains controversial with some breeders. What do you think?

Dog breeds must be ‘rebooted’ to halt health problems, says expert
Exclusive: Prof Clare Rusbridge calls for careful cross-breeding to introduce new genetic material