It looks like the dog found his buddy....it would be ideal if you could get the dog to eat closer (a little at a time) to the house....he may not have had rabies shots. It takes patience to get him use to you. You could also try throwing him some treats when he's with the bull... Its funny how some animals bond with others. The dog has found his soul mate....:O)
We laughed ourselfs silly watching a horse follow 2 ducks around....when they left the arena the horse would wait for them to come back....It was an outdoor arena. The horse was stabled at night, but the barn cats kept her company then....
The other horse had been her stable mate for years. She sure was happy when the other horse came back home...
The dog won't come within 300 feet of a human and no one actually lives on the ranch. My husband goes down there 3 or 4 times a week and he has a man go and check his cows when he can't go down. We put worm medicine in it's food but a rabies vaccination is out of the question. This creature might as well be a coyote.