I think you are right to err on the side of caution if you are not sure. I would have no problem feeding my goat horse feed, but not the other way around. I have winessed goats eat terrible things and be none the worse for wear.
Years ago when I worked at a trail riding establishment there was a goat there that would eat anything. One day a guy dropped a pack of cigs and they all scattered on the ground, and the goat ran over and ate as many as he could before the guy could pick them up! Filters and all!