Food and feeding
Much of the existing information relates to a couple of species and most of it is proprietary and not readily available. It is, however, known that there are considerable differences in dietary requirements between species, particularly with regard to protein levels. Some of the marine shrimps seem to require relatively high protein levels. For example, the protein requirement of P. japonicus is between 48 and 60 per cent. The proteinrequirement of P. monodon is about 35–39 per cent, of P. setiferus 20–32 per cent, of P. aztecus 23–40 per cent, of P. vannamei 30 per cent, of P. stylirostris 35 per cent and of P. indicus 43 percent. Shrimp feeds require sterols and also fatty acids of the linoleic and linolenic series, as denovo syntheses of these do not take place incrustaceans. Dietary lipids are provided mainly by fish oils with high levels of polyunsaturated fatty acids. Very little is known about the requirements of vitamins and minerals, although standard premixes are added in all diet formulations.
In the present state of knowledge on shrimp nutrition, fresh food continues to be important in larval and fry rearing as well as adult grow-out. Commercial feeds are becoming available in many areas, but their acceptance in commercial farming is rather slow. When used, many farmers supplement them with natural food and feedstuffs. Water-stable pellets of different shapes and sizes (worm-like or crumbles) are prepared using finely ground ingredients and different kinds of binders, by cooking-extrusion or dry or wet pelletizing.
As is evident from the description of shrimp hatchery operations, the production of adequate quantities of the required type of live food for larval and post-larval stages is a major problem, and because of this several efforts have been made to develop microparticulate or microencapsulated larval diets. However, these have not so far resulted in products which have wide commercial application. Crustacean wet tissue suspension is reported to be used as larval feed successfully in small-scale hatchery operations in India (Hameed Ali et al., 1982). Mysis and Acetes, blended into a fine particulate suspension and graded by fine-meshed sieves, have been used as the only feed during the entire larval phase, and an average larval survival of 44 per cent has been reported. This type of larval feeding resembles the use of fish flesh suspension in the larval rearing of Macrobrachium.