I've been told they love alfalfa but when its balled they will pick through the bale and only eat the leaf thus leaving you a pile of stems. I think those that feed alfalfa use hay racks to feed with to try and eliminate this from happening.
Everything up here eats alfalfa; whitetails, mule deer , antelope and elk. They do the same , eat the leaves and leave the stems. They hit the horse hay as soon as we put it out, doesn't take long at all for them to find it.