You just bought a farm and missed the fall hay cut the grass is now dry brown and about 8-10 inches high you have a bush hog can you mow the hay even go over it a second time and leave it as mulch?

First, 8-10 inches is some pretty short hay, but I 'spose that's not important. Unless you plan to do something other than hay with the spring crop, cut it tall (about four inches) in one pass and forget about it until spring. Don't bother with a second pass, you're just wasting fuel and time. Let nature break down what get's cut. It'll do the pasture some good.