personally, I wonder why it's always horselover who starts threads like this...
And why in horse breeds?
Everything can be bad for horses- water, hay, minerals. It's the human factors that cause the issue.
Racing- If they were started later, no issue
Dressage- no hyperflexion and proper training, no issue
and so on.
The key to everything is time. I'd like to see special races for older or rescue horses of unknown breed. Then they could pick up adult horses at auctions to race. Slower, but safer