ABSTRACT
This chapter highlights the partitioning of food energy in animals, as well as the energy systems used in feedstuff evaluation and feeding. Energy metabolism in cells or animals can be defined as biochemical reactions involved in the transformation of various forms of chemical energy. Food energy is partitioned into various fractions on the basis of nutrient digestion and metabolism in animals. Energetic efficiency in the utilization of food energy by animals varies among species, physiological state, the type of production, physical activity, health status, the living environment, and dietary composition. The physiological adaptation of animals to nutrient availability and other environmental factors has important implications for livestock and poultry production in tropical and subtropical regions of the world. In all animals, the efficiency of utilization of dietary Metabolizable energy (ME) for maintenance is greater than that for production, and the efficiencies of the dietary ME from fat or carbohydrates for both maintenance and production are greater than those from protein.
