OK, it's been a loooong time since OT (or Old Testament) times. Back then, people had different ideas about what was "right" or "wrong". They believed that God required physical sacrifices as a sign of respect and observance. You gotta understand, back then animals were a sign of wealth... the more of them you had, the wealthier you usually were. They didn't get money until much later. So it was really giving of your wealth to show God that even though you might be getting sucessful, you knew that he was still the Boss Man and in control, and that he had given you this bounty (in the form of animals) and that you appreciated it, so he wouldn't take it away.. . also, the old testament (and the whole Bible, for that matter) was written by many different people many years ago, based largely on oral tradition and second-third-fouth etc.-hand accounts. Because in the time of Genisis, there wasn't much in the way of a written language yet and people were largely nomads.. . Christians today largely do not follow every law in the Old Testament... they are, to say the least, outdated. They were largely formed because the Children of Israel (Abraham's descendants) needed a system of order and structure in their lives, and these laws provided it. Today, some Christians mainly follow the teachings of Jesus and largely use the OT for backup to verify and supplement this. Jewish people do not always observe all the laws either, except for Ultra-Orthodox ones, and even they aren't seen burning cattle everyday.. . So, no, you do not have to take that stuff literally. IT's the idea of communicating with God and having a good relationship with Him that is considered important, not killing animals.