I've never bothered with horse manure. (It's too heavy to lift, I have no car.) I didn't tell my plants and they've not noticed that they don't get it.
PS. I use garden compost as an improver and comfrey tea as a liquid feed. Comfrey is more nutritious than pony poo anyway: TeacherNet, A to Z of School Leadership temp - Individual Education Plan (IEP)

__________________
~ What do I think of Western civilisation? I think it would be a very good idea ~ Gandhi