I think horse manure will be the easiest to get by in my area in big quantities.
The horses are not from organic farms, so there will be deworming given to them. I suppose this will come out the other end and therefore end up in the manure.
How bad is this for your soil?
Would it make any difference when the dung is fresh or after some time composting? I think about leaching out or concentrating or reacting away or maybe something else?