How to keep sheep from eating cows grain?

[edukeusa]

I have 2 cows that go up to a shed and eat grain that I put out every morning, and I also have 5 sheep in the same pasture, that want to eat the grain, so they usually push the cows out of the way, and eat the grain that they dont need. Is there anyway to keeep the sheeps from eating cows grain out of their trough? I've tried raising the trough, but the sheep sut jump up to it and eat.