No county I'm saying the end result is the same most generally. HYPP is a result of a genetic mutation that can produce muscle tremors and other problems so severe they can result in death, HERDA another genetic disease that although doesn't display itself until the foal is in training usually, shows severe lesions and the separation of skin from the deeper epidermal layers which results in the affected horse not being able to ever be ridden and as a result many are euthanized. LWO another genetic issue while not a disease it does result in the death of a foal.
If you are responsible and do the testing then you know what you can and cannot breed to in order to prevent something like this but not everyone is.
Major conformation issues is just as bad as weefoal said. I personally know of a filly(2yr old) that was bred who had the most deformed front legs she could barely stand let alone walk it took her a good 10 min to walk from one side of a 40ft paddock to the other, the owner a so called reputable breeder here in OK did not think twice about breeding this young girl with no consideration whatsoever that 1. She was entirely too young and 2. Her legs could barely support her weight how much more damage would be done with her being in foal? Why did he do it? Because her lineage was in high demand and it didn't matter to him if she only produced 1 foal that was money in his pocket. I know this because I was there when she was bred. He also has an H/H Stallion that he breeds knowingly and willfully not to mention the horses temperament leaves a lot to be desired the horse is down right nuts.
My point is there are people out there who will do it for the same reason that this guy did they simply don't care. I did not mean to imply that county, weefoal or anyone else here doesn't but I do know that those type of people exist and those people I do have problems with, not the people that will go the extra mile to ensure those problems don't crop up or honestly care about their horses offspring rather than just making a buck.
So if I offended any of you who do go the extra mile I apologize, you are not the people that I was referring to it's the others that simply don't give a crap those are the people that I have had experience with (sighs)