Back in the eighties, I went along with a friend to help load hay that he had bought. He asked me what I thought and if he should buy enough for the year. I told him I thought it was to rich, and that I wouldn't use it. Well, he bought enough to last a year.
A few weeks later his wife is telling me that they have a sick horse, and the vet is trying to figure out what is wrong.
I suggested the hay was the problem, and asked if she wanted me to bring some hay over. This suggestion and offer was refused. Three months later they decided that the hay was to rich and put the horse on grass hay. They had racked up $3000 in vet bills and almost lost the horse.
The rich hay of Wisconsin is designed to keep a milk cow producing at a high volume, and completely unnecessary for horses.