Don't know about horses & plastic wads but target boxes say not to throw where hogs can get at them (they contain pitch) Cattle will eat small nails & bits of barbed wire etc. that's not good either. Somebody here on TS is sure to have some good knowledge. Ross Puls
i think a horse will eat anything if it will make it sick or kill it. That said i haven't had any problems with my horses and i shoot in their pasture regularly. Just don't keep the grass "scalped" so they aren't grubbing in the dirt when eating.
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.