Updated on July 30, 2019.

DM Testing is Important but how about not producing a DM At Risk Puppy?
When looking around for a pup please make sure your puppy's parents are health tested for DM (Degenerative Myelopathy) if that is applicable for your breed. But testing alone is not enough, the right combination needs to be chosen to prevent a potential health problem.
The breeds most commonly affected include the German Shepherd, Pembroke Welsh Corgi, Cardigan Welsh Corgi, Boxer, Borzoi, Rhodesian Ridgeback, American Eskimo Dog, Bernese Mountain Dog, Golden Retriever, Great Pyrenees, Kerry Blue Terrier, Poodle, Pug, Shetland Sheepdog, Soft Coated Wheaten Terrier, Wire Fox Terrier, and Chesapeake Bay Retriever. And thus any cross from these breeds also (which I DO NOT condone).
Think golden doodle, bernedoodle, golden pyrs etc etc.
In my opinion: If one of the parents is tested At-risk or Carrier, the other parent HAS to be clear. Don't let them tell you otherwise. There is no need for these combo's.
2 parents testing carrier should not be done. There is a 25% chance the pups will become At Risk.
Your pup could come down with DM down the road. For BOTH gene's (DM-BMD and SOD1 gene) that can be tested. If the breeder doesn't test or takes high risks. RUN!
11 years ago I bought Heidi from a breeder when no test were available. Heidi now a year and a half into symptomatic DM, is starting to decline.
Let me tell you. This is the saddest thing you as an owner and she the dog can go through. I am trying to keep her as happy as I can.
We went out for just over 4 hrs last Sunday and came back to a very distressed pup who cried and cried and cried. She is not in pain really but has problems now with her front (pins and needles while her strength is going). She is feeling helpless and needs us for everything. She is getting frustrated at times. She can not be left alone at all!.
Her wheels are not working for her anymore as her back is not strong enough now and she sags through it. She walks with very tiny steps in her front end. She doesn't want to go in her regular cart anymore. She also does not want to walk far supported by us. Just out to pee and that's it.
As off beginning of July, she is now in a quad cart and has a wagon to keep her involved.
She is mentally all there and otherwise reasonably healthy (the mastcell cancer breakout under her chin is again under control). Her body failing her and having accidents in the house (which we totally praise and don't care about but she feels bad, its ingrained in them NOT to do this). It's so so so sad.
Bottomline is if Heidi wouldn't have DM at this moment in time would testing have been available back then. She would be running around with the others right now.
I am home all day and can care for her, a lot of dogs would have been put down at this point already.
Her moments of happiness are plentiful still and as long as she doesn't give up, we will endure her accidents in the house (even though she is manually helped with defecation and urinating), we will break our backs because she lost ALL control over her hind feet, she is catered to her every whim. She is groomed almost daily to relieve the itch she cannot itch herself and gets another god scratch by one of use at night, water is brought to her 4-5 times a day, she pees over our shoes when going out but we don't care. We are her legs.
She is carried upstairs at night as that is where she slept all her life, (she weighs 100 lb) before sleeping we massage her shoulders and neck to relief her pins and needles. We do everything we can for her.
Breeders who think "-DM is not that bad, -only for old dogs, - the dogs usually die before they get DM anyway,
- they may not even get it or even,or - it's a cross so therefore it is healthier", have never gone through it or don't mind their dogs mental health. (Yes I am generalizing but these are my feelings at this moment.)
Sure good breeders do not exclude any Dogs from the gene pool, I get that. But in my opinion Having an at-risk dog in future lines should be frowned upon!! There is no reason whatsoever!!!
All DM status dogs can be bred But a carrier or at Risk dog should be bred to a CLEAR dog ONLY!