You should bring the old mule indoors. I’ve seen horses, pigs, and bison in homes. Mules are smart and when he sees dogs and cats going in it must break his heart.
He has a very nice 1200 sq ft covered barn. All the niceties. He sees us in front and back. Loves to come to front door and graze on grass near porch. Have to take him for walks around the farm and he really does not know he is a mule. SRM!