Once it dries outs, the poop weighs the same as what the horse ate. Do the math.
Actually, even less! After all, the horse does get some caloric value out of what he eats, so it must have less dry weight or dry mass when it comes out the other end.
Sorry, the math is just a side track on the real issue, whatever that is here, whether it is manure, grazing, hoofing, or whatever. If it were manure alone, I suppose they could require horses to wear diapers. They do it in the city. For that matter, why not have both horses and politicians wear them?
