The best that we found here in the PNW is to go 75% white clover & 25% Winter Rye. You can turn under when done and get good organic value. this mix produces around 18-22% crude protein and takes a good grazing and bounces right back. Here the rye will grow all year long, but towards the end of the season we will let it fully head out and go to seed. We do this around September or so, giving the young turks some real good forage before harvesting them. Then what they don't get will sprout up and start growing in for the winter time. Here in our mild climate and clay soil it seems to be the best. You could replace the Rye with Alfalfa,timothy,orchard grass,etc. Any kind of grasses that have a good growth rate and high yield amount. Any thing that can take a hard grazing/trampling and bounce right back. The rye and clovers do just that. The turks mowed the rye down over the winter to where you would think nothing at all is planted and now spring here it comes. This year we are experimenting with wheat as well, it doesn't seem to hold up as well as the Rye so far.