We have 9 1/2 acres and eight horses. My thrower at home is set up to throw into the pasture. Usually in the summer when I can walk in the pasture I will go out and pick up the wads but not in the winter. Sometimes it takes a few rounds to get the horses to go to the other side of the pasture so they don't distrupt my concentration. But I have not had any of them get sick from the wads or broken targets. An added plus in the spring and summer when the grass is tall. most of the missed targets do n ot break when they hit the ground. I go out pick them up and throw them again. I would not be to concerned about your horses eating hte wads or targets.
Jim Bradbury