I just found this, it is interesting:
"Cows aren't really designed to eat any grain, it is too acidic for them. However, cows are strictly grain fed. It makes them fatten up fast (does that to humans too). To counteract all the terrible things that happen to grain fed cow's rumen (stomachs) they give them loads of antibiotics to keep them alive. This highly acidic environment in their rumen has lead to the evolution of a new type of E. Coli bacteria that is able to endure the high acid environment of a normally ph neutral cow stomach (and the human intestinal tract). And that's the form of E. Coli that is causing problems for us now. "
"Cows are ruminants, they ferment the food. It doesnt "heat up their insides" , they pig out, they bloat and can die.
Yes, if they over eat any grain - wheat or barley - it is "hot" (high energy) and creates rumen acidosis - commonly known as grain overload.
Feedlots feed a lot of grain and on the verge of acidosis all the time the way they are fed . They are fed this way to fatten them for slaughter."