Fish Nutrition & Feed Technology

Unit 9 - Nutritional requirements of cultivable fish and shell fish

9.6.Energy

Energy is not a nutrient and is released during metabolic oxidation of proteins, lipids and carbohydrates. Energy is defined as the capacity to do work, but in biological definition, it refers to muscle activity, energy for chemical reactions in body to enable movement of molecules against a concentration gradient and for other biological as well as physiological functions in the body. Proteins, lipids and carbohydrates contain 5.6, 9.4and 4.1 kcal of GE/g respectively. Fish do have a low energy requirement because no energy expenditure is involved for maintenance of body temperature and due to its neutral buoyancy and less muscle activity to maintain their position and less energy expenditure for excretion of ammonia (85% of metabolic wastes) that are excreted directly through gills into surrounding water. Besides, temperature, size, growth rate species and food are some of the factors that affects energy requirement.