The trouble is, at the moment it's just so wet everywhere, so under all that long grass will be a nice wet'n'warm environment where nasty footrot bacteria will lie. So yes, you will get scald, but it is more likely to turn into footrot. So...
If you can get it topped do so.
Or
Strip graze it with some electric fence. This will minimise them walking through the long grass. Also, they will graze it more efficiently and less will get wasted due to "trampling". Move the fence a little twice a day, the more often you move it the less likely they will try to jump the fence.