This is an extremely difficult area, even for a libertarian -- perhaps moreso. In the end, I believe the conflict boils down to the individual rights and responsibilities of the owners vs the rights of any free assembly of people to decide and codify what is right or wrong. The evidence is overwhelming that people, in their various governmental schemes, will make cruelty against the law. As long as there is wisdom in implementation, the libertarian has no quarrel with any law given that he can choose to live in or out of its jurisdiction. This does overlook the idea that one onerous law within a collection of good laws may be preferable to a good law among deplorable ones. I think this has more to do with why 1 person will live in l.a. while another lives in kansas than with the distribution of natural and economic resources. See the red states and the blue states.
This is the classic issue where local decisions are best, and the more local the better. This is within bounds, however, as 1 man cannot make himself a governmental unit. So the decision should be pushed down to the level at which the process most closely matches group desires with the consensus of individual sentiment. Then birds of a feather can flock together.
I don't know enough about the michael vick case to say whether he is being held up to local law or to federal strictures. If the former, I am ok with it and its outcome.
As a farmer, I tend toward being the animal lover. My farm is posted, and abounds with turkey, deer, hawks, geese, raccoons, and songbirds by the throngs. I will not kill a deer to save a tomato. As long as I have forage for my horses, the wildlife can eat all they wish. Most of my neighbors are practicing hunters, so when the wildlife overflourishes it is usually taken care of in the vicinity.