The space applications are very interesting. If bone density can be maintained just by strapping several cats to an astronaut, I say we go for it. Besides, we can't bring dogs on deep space missions because they can't go outside to poop.
Dogs can be trained to use a litter box. The animal crap, along with the human feces, could be bagged up and used to line the ship interior walls against interstellar radiation. Everybody wins!