Hay is alfalfa once it has been harvested. It is high in fiber, and cows are great at digesting fiber, but they also need sugars to convert into milk. Oats provide protein and fiber. Corn provides sugars and iirc, fiber(maybe protein? its getting late here). There has been quite a bit of research about optimum ratios. I could look for some if you are interested, I get most of my info from my dad's dead tree magazines.

And I hear you about ethanol production. I for one can't wait for our new renewable energy sources.

"Corn is a particularly water thirsty crop, which while delicious is over produced"

Sweet corn, which we eat; and field corn are different things. According to the washington post article I posted earlier, there isn't that much sweet corn produced.

"Calories per acre is important but for the Ogalalla Aquifer calories per gallon-water is more important"

Yeah, but people want food today... Desalination, and other water related technologies can't come soon enough :(