There is nothing unethical about killing animals for food.
That depends on the moral system in question. A psychopath’s ethical code would allow such killing without question.
You did not specify the circumstances. In the Western World, where I am located and I expect most here are, unless we are lost at sea, lost in the mountains, or in some other sort of 'survival' situation, then there is no justification for killing anything for food (anything sentient and with a central nervous system, that is). And even in a survival situation, would it not be the kindest act, an act of utmost altruism and selflessness to just fade away instead of causing great pain and death to others, and most likely many others?
My code of ethics is very straightforward. Simply put it is to cause least harm.
They are not "barbaric
They are very barbaric. In fact I doubt very much that they could be any more barbaric than they are now (any more barbarity and production could be threatened).
Perhaps you wrote that because you know very little about what actually goes on in animal agriculture? Or maybe you are guilty of indifference toward our fellow earthlings and you have commodified them, in which case it would be hard to consider anything done to a truck full of limestone as barbaric.