The more we learn of the true nature of non-human animals, especially those with complex brains and corresponding complex social behavior, the more ethical concerns are raised regarding their use in the service of man - whether this be in entertainment, as "pets," for food, in research laboratories, or any of the other uses to which we subject them.
"Through a Window: My Thirty Years with the Chimpanzees of Gombe". Book by Jane Goodall, 2000.