Buddhism represents the doctrine that killing is wrong as a principle. It is forbidden to kill an animal, or even kill an insect. I believe that life is not only existing in living organisms such as animals, but even the profane tomato, in any vegetables, fruits and even in every blade of grass.
Life comes from the universe, it is part of it and it it not understood at all what it really is yet. We just guess and assume, make decisions they suit us or believe what others tell us.. Why should it be wrong to kill an animal to eat it? However, to cut the grain and threshing is any better? I mean in the eyes of the universe all are the same. Humans, animals and plants. The sea, the clouds, the heat and the cold. It is all the same.