> Animals know whats okay and not okay to eat, ...
No they don't. Which old wife did you get that gem from?
"Plant poisoning has plagued humans and animals throughout history, especially in North America where many immigrants and their animals were poisoned by unfamiliar plants." "In 1978, a study on the economic impact of poisonous plants on the range livestock industry in 17 western states [of North America] estimated that the problem cost the industry $107 million annually."
In: A Guide to Plant Poisoning of Animals in North America, A. P. Knight and R. G. Walter (Eds.) (2002)