I think it's going to depend on the cognition of the animal. Animals, like humans, can show signs of stress and fear. They can show symptoms from being abused---again like a person. If the animal's disposition doesn't change, I don't see much reason to think it's negative. A dog for instance, will cower when you come close if you've abused it, as they're very revealing of their intentions through body language. They shrink away to show that they are small and cause no problems. They may even urinate.

It's a complicated issue because it's hard to prove from a human standpoint, what another species is thinking. But given what we know, animals avoid pain. Animals avoid things they don't like. An animal's behavior will change when it is impacted by the behaviors of other animals. Another interesting aspect, is that sexually, many animals will avoid sexual contact if they don't want it. Any easy example is ducks who are known for rape. Female ducks actually have developed vaginal canals that are designed to make sure they don't get impregnated by the male ducks that rape them. Female ducks will also do everything they can to avoid amorous male ducks they don't like.

There's also the fact that animals will intentionally seek out human beings sexually without having had that contact before. I think everyone has been humped by some kind of animal in their life.

This makes me think that there's not a whole lot of recognition as to the differences between having sexual relationships with something of the same species versus something that isn't. Some animals appear not to care.