Animal production systems have changed dramatically over the last two decades. Knowledge of energy metabolism and environmental physio logy has increased as appears from many textbooks on these disciplines. The contents of the symposia on energy metabolism of farm animals show this and they have initially focussed on feed evaluation and later on com parative aspects of energy metabolism. They show part of the progress being made. Application of knowledge of energy metabolism for animals has a long history since Lavoisier. In addition to this, studies about the environ mental requirements of...