87:4 An animal may not go out wearing a bell even if it's muffled to prevent it from ringing. This is true even in a city that has an eiruv (because it looks as if he's taking the animal out to sell it in the market - Mishnah Brurah 305:43). The animal may wear a (muffled) bell in a courtyard but not one that rings (because it's a noisemaker - MB 305:42).
87:5 One may lead a horse with a rope attached to its bridle so long as he holds the end of the rope in such a way that less than a handbreadth (about 3.5 inches) comes out of his hand (so it shouldn't look like he's carrying a rope - OC 305:16). Also, the rope dangling between his hand and the animal should not come within a handbreadth of the ground (so the horse should not appear to be carrying it as a load - MB 305:51). If the rope is very long, the way to solve this problem is to wrap the surplus rope around the horse's neck.