i read your essay - i may have missed the answer within the text - regarding the animal pictures; were they specifically killed for the peices or aquired after their death and used as art? theres obviously a large difference, but in essence, that difference should not be taken into consideration when discussing the content in and of itself.
The animals were killed specifically for the pieces. In talking about the cow being killed, you really do a good job of highlighting the moral quandry of this sort of art. Everything you say is precisely on point, especially about context and intent; but I think there's key word that people may miss is in your last sentence, when you say that it "shouldn't and doesn't discredit their initial response to that work." The keyword is initial.
For example, I think the photograph of the dead woman is a beautiful work of art. I have an understanding that the woman died of natural causes, and the artist posed and photographed her with permission from her family after the autopsy. However, if I were to learn tomorrow that this explanation was a ruse, that the artist had actually killed the woman, my perception of the image would chance, and I would not be able to appreciate it. However, my initial reaction - that it is of aesthetic value - would not be changed or diminished; it would serve to contrast the subsequent feeling of disgust. Is it still art at that point? Yes. Unfortunately, perhaps, but yes.
Compare this to the mice or the sheep; we already know
they were killed for the sake of the art. Animals are not on the same level of humans, of course, but nonetheless, a life has been extinguished for the sole purpose of aesthetics.
To contrast my own opinion, I'd invite Pozer and Meatball to qualify their brief reponses.