The question presented in this discussion is definitely one that has no easy answer. I will start by saying, a obligation is defined by what a person is bound to from either tradition or law. If I took a relative approach I would say that morals and ethical obligation are subjective. I personally believe that to a extent humans do have a obligation to animals. To go out of your way to depict cruelty to any creature illustrates a flaw in your own character. However, humans don't have to have a diet that includes meat but most do. Even in these cases the way that the livestock is going to be treated does not have to be treated cruelly, or put in discomfort. I remember watching a show in which the farmer said, that his cows tasted so good because they lived a happy life. In many ways he treated the cows akin to a pet, by feeding them properly, making sure their living quarters are clean, and showing them affection. His belief was that by doing this his cow's meat was more tender, then if he hadn't done these practices. Do I believe this maybe, maybe not. However, this does illustrate that the livestock that we consume does not have to be treated in a cruel manner. Yet, in theory in our society animals do not perform any function but companionship and food, which means humans really don't have a obligation to them. However, I feel it is boorish to depict cruelty to any creature or anyone.