Fish Nutrition & Feed Technology

Unit 8 - Energy

8.4.Forms of energy partitioning

• Gross energy (E) is the energy that is released as heat when a substance is completely oxized to carbon dioxide, nitrous oxide or water.
• Intake energy (IE) is gross energy consumed by an animal in its food. The majority of intake energy is in the form carbohydrate, protein or lipid.
• Faecal energy (FE) is the gross energy of the faeces. Faeces consists of undigested food and metabolic products, which may include sloughed gut epithelial cells, digestive enzymes and secretory products.
• Digeted energy (DE) refers to apparently digested energy with in a food and is determined as the energy in food minus the energy in faeces (DE=IE-FE).
• Urinary energy (UE) is gross total energy in urinary products.
• Gill excretion energy (ZE) is the gross energy of the compounds excreted through the gills.
• Surface energy (SE) is the energy lost from the surface of fish i.e. mucus or scales sloughed off from the fish.
• Metabolizable energy (ME) is the energy in the food minus the energy lost in faeces, urine and through gill excretion {ME=IE-(FE+UE+ZE)}. It is energy available for the conduct of the metabolic processes.
• Total heat production energy (HE) is the energy lost from the animal in the form of heat. The heat is produced as a result of metabolism and so HE is a measure of metabolic rate in fish.