@pinkstars86 Yes. Responsible breeders stop at age 6.
I've seen a good amount of dead and underdeveloped puppies (also dead) because people didn't care.
@jakeyb123 This is also where DNA testing really helps.
Embark gives you the coefficient for every dog you test, they also have a feature for breeders that takes the info of prospective mates and figures it out for you that way.