You have answered your own question but fail to realize it.
Animals are not humans. Our legal system recognizes humans as legal entities with rights derived from a long legal evolution based upon a Judaeo Christian Greco Roman tradition.
In fact Ms Schiavo had legal living relatives who wanted to care for her. If I had a dog who was brain dead and I wanted to take care of my dog, I cannot imagine any judge coming in and forcing me to kill it.
"If I had a dog who was brain dead and I wanted to take care of my dog, I cannot imagine any judge coming in and forcing me to kill it."
He wouldn't have to. The animal would start to smell pretty bad in short order. What would you be doing as it defecates and urinates 2 or 3 times a day? How long before you would take it to the pound to be euthanized. But you'll come up with some cock and bull response, I'm sure.
Animals are not humans, you say. Yet you also said that animals are treated better than humans. If an animal was in the same state as Terri was, it would be euthanized at the pound. That's a fact. There is no better treatment; it would be worse, and the animal would be put away immediately.