Founder trap.
  This is "free choise" the wrong way. "Free choise" should be in time not in volume. Free to it when ever not limitless.
 
  It also gives a lot of wasted hay.
 
  All horses must have "free choise" of straw. Free choice to eat when ever they feel like it.
  3of my Islandic customers ate them selves to founder on hay in this kind of arrangement last vinter.