There are? Humans are animals. Other animals kill animals. Cougars kill deers. Bears kill bugs. Cheetahs kill impalas. What ethics?
Free range animals is one area of 'meat ethics'. Also, shipping guidelines and slaughter issues. Some slaughterhouses ship animals long distances, in intense heat or cold with no food or water, just to run them through a slaughter house that doesn't kill them efficiently or humanely. Animals raised free range, and slaughtered in areas that don't require such duress, tend to actually taste better.