In my local paper, there has been an ongoing discussion on cleaning up dog poo in the street compared to cleaning horse poo in the street.
Personally I think its ridiculous to compare the two.
First of all, horse poo is at least 20 times bigger that dog poo, so 20 times harder to manage a horse and carry a huge bag of poo. And secondly, horses(well, my horses) do up to 7 poos in 2 hours when out on the street(some horses poo when a little stressed in new surroundings with lots to look at).
And finally, horses eat grass and hay. Dogs eat meat.