Artificial feeding of fish

Artificial feed or feeding is one of the principle methods of increasing production in fish cultivation. Artificial feed is used in intensive culture system where fish/shrimp growth is totally depending upon the complete artificial feed. Artificial feed has a quality diet containing a predetermined nutrient profile. Traditionally it’s a dry or moist pelleted feed consisting of a combination of different feed ingredients.

Importance of artificial feed

Ø    To enhance fish productivity

Ø    To supplied balanced diet for cultured fish

Ø    For the proper growth of species

Ø    For repairing a damaged cells

Ø    To meet up specific requirements of individual items of foodstuff

Ø    To buildup the cell structure

Ø    For maintain physiological functions

Ø    To meet up caloric demand of fish

Forms of artificial feed

Feed types can take numerous forms. However, they basically fall into one of two general forms: dry and non-dry (moist). 

a. Dry feeds: Dry feeds are by far the most commonly used feeds in intensive aquaculture. Dry feeds are generally made from dry ingredients or from mixtures of dry and moist ingredients.  However, even though it may be implied by the name, these feeds are not entirely devoid of moisture, generally containing 6-10% water, depending on the environmental conditions. 

Dry feeds may be subdivided further. Feeds that are simple mixtures of dry ingredients are termed mashes or meals.

Dry feeds that are compacted into a defined shape, generally by a mechanical means, are called pellets. Depending on the formulation  and  compacting  techniques  these  diets  may  be  floating  or  non-floating (sinking) in water.

b. Non-dry feeds: Non-dry feeds can be either wet or moist. Generally, wet feeds

are  those  made  from  wet  ingredients  such  as  trash  fish,  slaughterhouse  waste, undried forage, etc., and contain 45-70% moisture. Moist feeds, on the other hand, are made from mixtures of wet and dry raw materials, or from dry ingredients to which water is added. The moisture content of these feeds ranges from about 18% to 40%. 

Non-dry  feeds,  both moist  and wet, may  be  either  extruded  to  forms  a  pellet  or non-extruded  (non-formed),  resulting  in  balls,  cakes,  etc.  during  the  process  of extrusion, the raw material is forced down a tapering shaft and through a die plate under  pressure  in  an  atmosphere  of  steam.  This  effectively  exposes  the  feed  to controlled  conditions  of  high  temperature,  pressure  and moisture.  The  extrusion process  cooks  the  carbohydrates,  primarily  causing  the  starch  granules  to gelatinize, and increasing the binding quality upon cooling. 

By altering the extrusion process, pellets of variable floating and/ or sinking rates may be produced. This is achieved by trapping air instead of water in the pellet as it leaves the high-pressure chamber. These air pockets are then stabilized by the rapidly cooling gelatinized starch. 

Extruded diets are known to be better utilized.  In certain instances extrusion of ingredients with high starch content, prior to Pelleting, is reported to have had an influence on the utilization of the diet.