My daughter and SIL feed their horses a little alfalfa hay too. Something the SIL's dad does with his horses.
My son on the other hand wouldn't feed alfalfa at all, it worries him that Jenny does. I guess it just all in who you talk too.
Becky
We can't put a bale out for horses of course, and pay attention to the amount that they get, but they do very well on it.
I think we mostly think, alfalfa has protein in it, and is cheaper than grass hay with is just basically filler (the grass hay we get here).