The only laws that cannot be violated to preserve a life are those prohibiting murder, idolatry, and sexual immorality. In this regard, it is interesting to note that Chapter 5 of Genesis tells of the very long lives of people in the generations of the vegetarian period from Adam to Noach. Judaism has many beautiful teachings concerning proper treatment of animals. Moses and King David were chosen for leadership, and Rebecca was deemed suitable to be a wife for Isaac, because they were kind to animals. Concern for animals is even expressed in the Ten Commandments.
Many Biblical laws command proper treatment of animals.
Shechitah, Jewish ritual slaughter, insures that when animals are slaughtered for food, it is done in the swiftest and most painless way possible. Obviously, the argument that we must be concerned for animals can be used to argue directly against the killing of animals for meat. Yet, the very allowance of meat challenges such an extension. The modern treatment of livestock in preparation for slaughter, though, may be a further consideration. Animals are raised to ensure the highest return on investment, without sufficient consideration for their personal benefit.