The title of this thread attracted my attention, as 2 days ago I had 30 rubble sacks filled to the brim with horses poo in my "other vehicle" (campervan). However, I wouldn't dream of putting one single lump of dog poo in it - so I'm afraid I can't quite agree with your assertion.
As far as I'm concerned, there's poo and - - - there's poo.
Poo is poo ~ if it comes out of a rectum, ...regardless of creature, beast or man then it is poo I'm afraid.