Hi and welcome. You are absolutely on the right track in looking for breeders who test and are open and honest about results and their breeding programme and I always am delighted to find puppy seekers who value this, as they are the ones who will help ensure the breed has a viable, healthier future. Those of us who have campaigned for cavalier health for many years, and talked to and supported the key CM/SM (and other health issue) researchers, would all say that MRI testing is an absolute must. If anything, it's needed now more than ever and recent published papers have once again indicated that puppies from tested parents with good MRI results are considerably less likely to have SM or symptomatic SM, whereas puppies from unscanned parents have a high chance of being affected. Sadly, many cavalier breeders still claim that testing doesn't show improvements but this simply is not supported by the evidence in several studies. While it is true that puppies from parents with good test results can still develop SM, and pretty much all will have CM, the chances are far lower, and such an argument is like saying there's no point in hip scoring for hip dysplasia, or doing eye tests or testing hearts because some dogs will still be affected. I've always said, it's sure funny how insistent breeders are about carefully choosing dogs that will produce, say, the headshape or bone structure or movement they desire in a show dog, they don't randomly breed any pair of cavaliers because genetics is a 'crap shoot' (a favourite phrase used by those who don't wish to test). This is patently untrue, and genetics isn't a 'crap shoot', as Mendel proved with his experiments centuries ago. Even with a condition with complex inheritance such as mitral valve disease or CM/SM, studies show that proper testing and using breeding guidelines reduces incidence and severity.
I think any breeder who was MRI testing and doesn't any more for any reason, was never in the category of 'best breeder' and is now not even bothering to hide the fact. I know they may have well known show names or even be involved in the national or local breed club, but a study of puppy registrations in the UK club has shown that even people who are on the club committees have bred puppies from dogs far younger than is recommended (because heart and MRI tests have little meaning in most young dogs, who will test clear). Some dogs used were only a year old
.
Cavalier Matters has a very good guide for finding a breeder and what tests to expect a good breeder to be doing, with a UK focus:
From talking with people around the breed, I have the sense now that the UK Club has grown increasingly isolated internationally due to the attitudes of many club breeders towards health testing. It's frustrating because they could be leaders in working towards the breed's future. It can be more challenging to find a good, testing breeder, but they are there. And yes: unfortunately, that does as you say, massively reduce the number of breeders for consideration. That says a lot about where the UK is right now. Health testing including MRIs for CM/SM is far more widespread in other clubs such as in most of Scandinavia and the Netherlands and in some cases, is a legal requirement (in the Netherlands since 2011). The Irish club has become very health focused in recent years, too. When some UK breeders state that MRIing makes no difference this is likely because even when they did MRI, they didn't follow recommended breeding advice from researchers and thus, those breeders saw no change.
Here's a FAQ for breeders produced by the leading researcher on CM/SM, Dr Clare Rusbridge, which explains why MRI testing remains important:
https://veterinary-neurologist.co.u...-during-talks-and-symposia-and-online-forums/
She notes (about one early study on using breeding guidelines):
The outcome of using these guidelines was reported
here. It was found that offspring without SM were more common when the parents were both clear of SM (SM-free; Cavalier King Charles spaniels (CKCS) 70%, Griffon Bruxellois (GB) 73%). Conversely, offspring with SM were more likely when both parents had SM (SM-affected; CKCS 92%, GB 100 %). A mating of one SM-free parent with an SM-affected parent was risky for SM affectedness with 77 % of CKCS and 46 % of GB offspring being SM-affected. The breeding guidelines became more restricted (
here) because it became impossible to recommend a breeding when there was a greater of 1 in 2 chance of offspring being affected. Meanwhile it was hoped that breeders would comprehensively screen to create an
estimated breeding value scheme which would be more accurate and allow greater retention of genetic material. Unfortunately the number of breeders MRI screening their breeding dogs diminished and the disease remains prevalent.
The most recent study found:
our study demonstrates that if breeders use only unaffected older CKCS, the risk of getting affected offspring clearly decreases. Over time, the prevalence of SM dropped from 38% (period 2010–2014) to 27% (period 2015–2019). It is commendable to see this decrease in SM, but the effect is less than expected as in the second period, the number of younger CKCS used has increased significantly. The result could have been better if other choices had been made.
In other words, because breeders started using younger dogs for breeding, they increased the chances of affected offspring. Breeding dogs should be at least 2.5 years old and re-MRI'd ideally as they get older. However, Dr Rusbridge has pointed out that there's no longer enough genetic diversity in cavaliers to use only unaffected dogs, especially when there are so many additional health issues. That raises other issues of course!
it seems a lot easier!