But do put a decent amount of protein in the mix.I don't bother with peas/vetches now, they don't bulk and aren't in the ground long enough to produce a useful amount of N.
If you are baling and wrapping it you may have a big problem with rats attacking the bales. I baled some grass a few years back with self set wheat in it; rats wrecked a lot of the bales. It was good silage though!