Training of Trainers - Library - Network of Aquaculture Centres in ...

contribute substantially to maintain this balance. In semi intensive and intensive aquaculture systems, feed is thesingle largest input cost, ranging even up to 80% depending on the quantity and quality of the feed used. Hence, theknowledge of fish nutrition is essential to manage the system effectively and reduce the feed input cost and alsoenhance production.Aquaculture systems;Based on the intensity of cultural techniques adopted, aquaculture systems are classified in to extensive, semiintensiveand intensive systems. In extensive system, excepting stocking, no other management practices areadopted and growth of fish depends on the natural food available in the pond. In the semi-intensive system, inaddition to fertilization to enhance the natural food productivity, supplementary feed is provided to hasten the growthof fish. In intensive aquaculture systems, apart from these management practices, high stocking density of fish,continuous aeration, frequent exchange of water, etc., are resorted to obtain maximum production in limited spaceand time,Feeding habits of fishes:Broadly there are three groups of fishes; herbivores, omnivores and carnivores are recognized. Fishes belonging toherbivore group feed directly on plants, which is the primary source of food energy. These are considered to be themost efficient groups, since there is no loss of energy. Plants use sunlight to convert water, carbon dioxide, air andnutrients dissolved in the water in to organic matter. Phytoplanktons as well as macrophytes are the types of foodresources used by the herbivore group of fishes. The second group of fishes are carnivores: fish and shrimp whichfeed on other smaller animals, insects, frogs, molluscs, fishes and crustaceans, zooplankton are classified ascarnivores fish. They require more protein to eliminate nitrogen from the body. In general terms, carnivores arethose which predate upon other fishes and derive energy required for survival. The third group is omnivores and thefishes belonging to this group feed on plant, animal, detritus etc., without specific preference to any of thesegroups. They are less efficient converters of plant energy than herbivores.Elements contributing to fish / shrimp nutrition:Like in terrestrial farm animals, farmed fish require over nearly 40 different dietary elements for the good growth.All the farmed fish / shrimp require qualitatively all the five major nutrient groups: protein, lipid, carbohydrates,minerals and vitamins. However, the quantitative requirement of these five nutrient groups varies depending on theculture system and age of the fish. In order to gain better understanding on the nutritional studies, it is important toknow the role of each of these nutrient groups (De Silva and Anderson, 1995 ; Tacon 1988)Protein:Proteins are the building blocks of the body and they play an important role in both plants and animals. Proteins aremade up of amino acids and fishes and shrimps have the capacity to synthesize some of the amino acids,However, ten amino acids are not synthesized and these are - Arginine, Histidine, Isoleuicine , Leucine,Metheoinine, Phenylalanine, Threonine, Tryptophan and Valine and they should be supplied through feed.Aminoacids composition of fish varies from species to species and the diets developed based on these aminoacids composition of the muscle are known to provide better growth. Deficiency of these amino acids results indecreased growth. Optimum dietary protein is that which produces maximum growth. Carnivorous fish requirehigher protein as compared to herbivore fishes. Inclusion of non-essential amino acids is also important in the dietfrom the viewpoint of maintaining the palpability of the diet.Lipids:98