Fishes have adapted to a wide variety of feed. Some of them feed exclusively on plants, others feed on animals while a large number of species are omnivorous, deriving their requirements both from animals and plants sources. A few fishes depend for their nutrition entirely on zooplanktons and phytoplanktons, and are called plankton feeders. (Plankton is an aggregate of passive and free floating micro-organisms of plant and animal kingdom). A wide range of organisms naturally grow in a pond eco-system but are not seen by the naked eye. They are used as feed by the fishes.
Feed of fry and fingerlings is generally different from that of the adult. On a global scale fish farming still largely depends upon natural feed available in the culture pond, supplemented by certain by-products available from agriculture and related industries. In extensive fish farming most of the nutrient requirements of fish are met from natural sources. However, when high density fish culture is undertaken, the artificial feeds are essential to achieve the production target. Formulation of artificial feeds for any fish, requires a knowledge of nutritional requirement at different life stages ranging from larval to juveniles and then to adult phases.
A fish feed manufacturer or a farmer should be aware of a number of factors before he/she can start manufacturing the fish feed. They are briefly highlighted here.
First of all he should decide whether he is producing wet feed, moist feed, or dry feed.
Feeds containing moisture level of in the range of 45-70% are prepared from high moisture ingredients such as trash fish, fishery waste, slaughter house waste etc.
Here the moisture level ranges in between 25-45% and are made from a mixture of high moisture ingredients, as in wet feeds, and dry pulverized ingredients. Wet, moist and semi-moist diets are considered to be more palatable to most species of fish because of the soft consistency, and good growth and feed efficiency are achieved.
They contain moisture in the range of 7-13 per cent. They are relatively easy to manufacture, transport, store and convenient to dispense into the culture systems. Dry feeds also permit production of specialized feeds such as medicated feeds incorporated with specific medicines antibiotics, required to control disease outbreaks. Dry feeds may be either prepared using dry ingredients alone or a mixture of wet and dry ingredients, adequately processed and dried. Dry feeds may be made as meals, pellets, granules, flakes, etc. It can also be made wet with water, cooked rice water etc. The wetness should be such that the feed can be pressed into small balls which will not easily dissolve into pond water.
Selection of ingredients and additives
The choice of feed ingredient and additives play a crucial role in the feed production. The choice also depends on several factors. They are:
Acceptability or palatability of feeds also depends upon the ingredients and additives. Pelletability of the feed and its durability are also affected by the physical characteristic of the ingredients.
The major steps in dry feed manufacturing process are as follows:
-Procurement of quality ingredients and additives,
-Storing in ware-house after proper labeling/marking,
-Preserving ingredients like oils, vitamins, mineral mixtures in preferably low temperature, (or cool places),
-Accurate weighing of the ingredients and additives in proportion required for the selected formula,
-Preparing vitamin and mineral premixes,
-Grinding of underground materials,
-Screening, screening particle segregation,
-Cooling/drying, and storage
Those who would like to set up feed manufacturing units should consult experts in feed manufacturing and companies that install machineries for feed grinding, mixing, bagging, scaling etc.