Cow, sheep, bird and all other widlife poo is an essential part of the recycling of organic matter. Dogs are filthy non-native carnivores, here in their millions, which produce faeces laden with disease organisms all over the place in areas inhabited by people, unlike most wildlife. I really don't know why these things need to be explained. All dogs should always be on leads. Dogs on leads, especially small ones, are sitting ducks for loose dogs who come bounding over out of control.