Oh my heaven's Jenn. Poor poor Rusty! That looks so bad.
How was he not in pain? It looks as if someone just slit him open

It's too clean a cut to be an animal I would think.
Prayer's coming that Rusty heals and is not really in pain. I have no
idea how he's not.
Buddy and I are sending him a giant hug,
Yes, I remember his story. He has loved your family from the first
time he sat foot on your property and told you so by coming back
everyday.