Here are just a couple examples of dogs displaying altruistic behavior. There are many documented cases of chimpanzees, elephants, dolphins and dogs performing altruistic acts. Many religious people state that altruism only exists in humans and is evidence that we are created by a god, which is simply not true.
Regardless, these are amazing stories. Particularly the second one. The dog tries to pull the injured dog off the highway and instead of using it's teeth, it uses its paws, so as to not further harm the injured dog, to pull it off the highway.