Ethics on Eating Animals 101

Michael Pollan's seventeenth chaper in "Omnivore's Dilemma" titled, "The Ethics of Eating Animals," sheds some light on the morality of the soncumption of meat in a society like our own, where animals are slaughtered daily. Pollan makes the first point (made before in the book) that people would not eat meat if they had originally known where it came from and how it was obtained. That would explain why the way meat is packaged usually does not in any way resemble the animal from which it was taken, and thus those who buy it dont care to think about its origin. Pollan later quotes the famous Australian philosopher, Peter Singer, who relates animal exploitation to slavery and oppression of women. Singer and Pollan both believe that the main issue when it comes to animal's rights is their ability to feel suffering and pleasure. Since the animals that are slaughtered tend to spend the majority of their lives in suffering, he concluded that the raising and slaughtering of animals for meat was unethical, and thus he became a vegetarian. Yet, he later goes on to point out that the problem is not solved just by avoiding meat altogether, and that there is a necessary level of maintainence for certain species so as to avoid issues with overpopulation.
Personally i agree whole-heartedly with Pollan here. I think for example that it is absolutely terrible the way that baby calves are kept in small containers so that they cant even turn around, solely for the purpose of eating their tender meat when they are slaughtered. This makes me extremely sad. On the other hand, i think that the way the slaughterhouses handle their cattle is humane enough...the cattle are allowed to live and graze for a good amount of their life, and the way that they are killed is by no means a painful process. (Pollan even notes at the end of this chapter that after visiting a slaughterhouse he decided that animal killing is ok as long as it is humane). So my question is, where and when do we draw the line on what we consider humane treatment of animals?