I am not an expert on grazing down corn at all but gthere are so many potential pitfalls to this I would not even consider it for cows near calving.  If put in ahead of calving they will gorge themselves on the ears and put weight on themselves and the calves they are carrying. You are almost guaranteed to have calving problems.

If allowed to graze after calving you have a high probability of nitrate poisoning especially likely since the stalks are broken and maybe more palatable.  If you could wait until after a killing frost then maybe ok to graze but by then the aflatoxin may be in the danger range.

My advice: take the insurance check, work the corn under, reseed something ASAP for late fall grazing while you still have time to get a stand. This will provide some useful income/grazing with no danger.

You don't want to add a second disaster onto the hail damage. Good luck.

Jim at Dawn