The mistake people often make, and really, this is quite natural, is in thinking that somehow (let's name it) "Mr. Steer" lives in the steer that is grazing, or has been rounded up, or has been butchered, or has been cut up for sale. So, they say "I won't eat that meat because the animal ("Mr. Steer") suffered. But we have to really examine the nature of what is going on, and 'who" actually felt the pain.
"Mr. Steer" is really no different from you or me or any other creature insofar as
associating the experience of its seemingly continuous existence with the component parts of what we call its body, or its carcass, depending on where it is, either chewing cud on the meadow or dangling from a meat hook.
He suffers from the pains of the body as we all do, not because the body itself experiences pain, or because the brain experiences the severing of the nerves as
pain, even though this is what occurs. The primary reason for experiencing pain, and this is the same reason why I also experienced pain today when I sliced open my finger, is because of the association of the experience of 'self' or of 'me' with the events of the body.
But we know from studying the dharma, that no self or 'me' ( "Mr. Steer" )can be found to reside anywhere inside (or outside) of the body, despite the fact that this is precisely the experience we have. We put the two (body and "me") together and experience them as inseparable. They are like two traveling companions, riding side by side through life.
But what happens when that "life" ends? It is the belief of at least some schools of Buddhism that what we could call the mind of the animal (or human) is still attached to the components of the body. Not in a conscious way as we know it, but in a very subtle way, due to a lifetime of clinging (habits are very hard to break!) You can think of it much the same way a survivor of a leg amputation experiences a 'phantom limb' although this has physiological causes.
In some instances, it is said that after death there is even attachment to objects, especially sentimental objects or items of great value that one has become "very attached to" during one's life. I have a friend who had a very elaborate, Tibetan style shrine with expensive offering bowls and such. Her teacher told her to get rid of all that stuff, and just to get cheap bowls, so that she wouldn't be attached to it when the time came to die.
So, even though "Mr. Steer" doesn't consciously think "oh, how sad, part of me is now a hamburger" there are still traces of attachment, the same very subtle attachment that we all experience as "my body". This is why you can do practices that benefit the deceased, whether it is a person in a coffin or a chicken in the fryer. Not because the "being" is there, but because from the habitual point of view, that illusory sense of "being" is still experiencing attachment to the body, in a very subtle way. Beings suffer from attachment to the body, both in life and in death.
It is very interesting, because we do not feel the same attachment to the body of someone else. And we do not feel that attachment to animals, even though we can become very attached emotionally to animals. We can feel empathy for their suffering, but every person (except perhaps for conjoined twins) only feels their own bodily suffering.
If you donate a kidney or something, or maybe donate your long hair to a charity that makes wigs for cancer survivors, you do not feel any confusion about where that part of your body is. You don't sense, "hmmmm, it feels like part of me is being combed right now, someplace far away" because consciously you still identify your sense of, your experience of
"me" as being in this body. But at death, when the elements begin to separate, that is a different situation.
What happened to the rest of my body??