I've been wondering about this too. A reputable breeder near me that does all health testing (24 holter, echo, ARVC test, OFA hip, and thyroid levels posted on website) and breeds show boxers. The only thing I noticed is the results of DM seemed a bit off.
Is it OK to breed a dog that is a "carrier" to one that is "at risk" for DM?
Owned by a floppy fawn boxer boy: Johann's Rubber Biscuit, CGC, TT, RL1X (DOB 3/6/08)