What kind of animals specifically? Most of them don't like getting gritty feeling ash on their feet, but if the lure of fresh juicy plants is strong enough, that will outweigh their dislike of the ash.
The only animal that ashes will reliably deter are slugs and snails which will dry out in contact with ashes, but not other animals. Some insects might not like it, but if there is another mode of movement (jumping, leaping, flying) then ashes won't make any difference.
Let me know in the comments what kind of animal you're trying to deter, and I'll make some suggestions that have worked for me.