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

type of ingredients used, since some ingredients containing toxic materials require cooking at highertemperature. However, it should be noted that over cooking results in the loss of nutrients.5. Pellets: Cooked dough should be allowed to cool and mixed with the vitamin and mineral mixtures. Thecooled dough is allowed to pass through the pelletizer and pellets are dried. Pellets of 1-2 mm are fed in theinitial stage and with the increase in growth, pellets size is increased to 2-3 mm diameter. Noodle makinginstruments could be made use of for preparing the pellets,6. Drying: could be done in the sum or oven depending on the availability. Feed should be dried to contain lessthan 10% moisture.As indicated already, there are a number of ingredients available in different countries and these could be screenedthrough on-farm trials and used as fish feed.While the dry sinking pellet feed production is possible on the farm, production of floating extruded pellets is yet tobecome reality because of the high investment needed in the processing machinaries and their unsuitability forsmall scale production units at present. With the improvements in feed production technology, this situation maychange soon.Feed presentation, feeding rate, frequency and feed acceptance:From the compounded feed, the loss of nutrients will be rapid and hence it is necessary that fish and shrimp aretrained well to accept the artificial feed soon they are presented in to the water. Loss of nutrients will also depend onthe quality of the binders used and quality of the feed ingredients used. In order to avoid wastage of feed, feed isrecommended to be presented in feeding trays or plastic / fertilizers bags. Feed is provided generally at 2-3% in thegrow-out systems, however, in the early phase, when the fish/ shrimp are smaller, feed could be provided up to10% and the gradual reduction in the feed could be adopted, feeding twice a day has been found to be more useful.In the case of shrimps, feeding more than twice a day appears to influence better growth. However, shrimp beingnocturnal, evening feeding should be considered as a potential way to increase shrimp growth. Poor water qualitydecreases the feed acceptance by both fish and shrimps. Decreased dissolved oxygen, higher ammonia and othertoxic gases, low water temperature are reported to decrease the feed acceptance.Assessing the efficiency of formulated feedsThe most important factor to be considered in all feeding experiments is the food conversion ratio. It helps inunderstanding the efficiency of the feed in inducing the growth. It is the ratio between the amount of feed consumedon dry weight basis to produce one unit of biomass on wet weight basis. In tropical acculturate system, as there isproduction of plankton in the water, which is also consumed by the fish, measurement provides only apparentfood conversion ratio and not the true food conversion ratio.Potential ways to increase fish yield from small-scale aquaculture systems:(A) Use of non-conventional feed resources as feed:Fish require higher amount of protein compared to poultry and cattle. Fishmeal has consistently shown to be thebest source of feed ingredient for inclusion in the feed. However, this ingredient is not only too expensive for use insmall-scale aquaculture, but is becoming increasingly scarce. Use of low value fish for fish for fish meal productionmay no longer be acceptable and there is an urgent need to look for other alternatives, besides reducing the usageof fish to lowest level where it is absolutely essential (Naylor, et.al., 2000). A number of experiments conducted toevaluate the various plant sources of proteins have shown that the growth induced by these ingredients is notcomparable to fish meal based diets (New, et.al., 1993). This is reported to be largely due to the lower protein102