Animals survived perfectly well before we domesticated them, seeking out the most appropriate food stuffs at certain times of the year (like sheep who will search out wild garlic). However, man has intensified their production, confined them and increased their stocking density, thus throwing a spanner in the works. Hence the need for chemical solutions.
I'm sure there are plant & mineral based solutions that work but you also have to factor in stocking densities and pasture rotation etc. In the wild it might be that an animal will only visit a particular grazing area once a year?