Besides the genetic predisposition and the dietary supply of nutrients, environmental factors affect the performance of the pig. Environment can affect the nutrient composition and availability of the feed. It can also influence appetite and therefore the feed intake. Furthermore, nutrient and energy utilization on the level of digestion and intermediate metabolism can depend on environmental factors. Especially the energy requirements of the pig are determined by such factors like physical activity or climate. Finally, stress or disease are interacting with the environment, nutrient and energy utilization as well as performance of the pigs.