When do you scratch due to heat?

[Danzig]

not sweating when you're supposed to is a sign of heat stress, or more seriously, heat stroke-which is deadly. i would imagine it would be the same in horses as it is in humans.
i saw them laying whole ice bags on some of the horses backs when they were walking from the track back to the barns.

i just think a combo of things affected big brown, and in total, was way too much for him to overcome. they may never find a reason why-as they're looking for one big thing, and i think it was many little things ( or maybe not so little) combined that kept him from the win.