Even when you remove the use of physical or emotional pain from the equation, the morality in the interaction between humans and other animals is not clear.

Even "humane" training/domestication of animals (such as horses) still produces creatures that are alienated from their own nature. If you have seen the eyes and demeanors of wild horses, as I have, you will be aware of the life and alertness you see. Compare that to the eyes of horses that have been domesticated for "riding" or for farm work.

Although I eat eggs a lot, I try to buy them from free range chickens. I think it is better for my physical health and for my spirit. The same goes for wild caught fish as compared to farmed fish. And, although I am not sure of the morality of "breaking" horses for riding, I have managed to reconcile myself to the fact that I myself have been domesticated by parents and society and I am thus far from being in the natural state of an uncivilized human. Therefore I forgive myself for riding horses :-)