29/05/2016
Using duckw**d as a feed/supplement
The composition of duckw**d depends on the nutrient content of the water and the prevailing climatic conditions. A range of values for the composition of duckw**d is shown in Table 2. Harvested duckw**d plants contain up to 43% protein on a dry weight and may be used without further processing as a complete feed for fish.
Duckw**d protein has a better array of essential amino acids than most vegetable proteins and more closely resembles animal protein (Hillman and Culley 1978). It is, therefore, a source of high quality protein to be exploited for domestic animal production. Duckw**d grown on nutrient-rich water has a high concentration of trace minerals, K and P and pigments, particularly carotene and xanthophyll, that make duckw**d meal an especially valuable supplement for poultry and other animals, and it provides a rich source of vitamins A and B for humans.
Use of duckw**d in fish nutrition
A major limitation to fish farming is that meals high in protein with high biological value are expensive and often locally unavailable. Duckw**ds grown on water with 10-30 mg NH3-N/litre have a high protein content (around 40%) of high biological value (Hillman and Cully 1978; see Table 2). Fresh duckw**d is highly suited to intensive fish farming systems with relatively rapid water exchange for waste removal (Gaigher et al 1984) and duckw**d is converted efficiently to liveweight by certain fish including carp and tilapia (Hepher and Pruginin 1979; Robinette et al 1980; Van D**e and Sutton 1977; Hassan and Edwards 1992).
A tilapia culture strategy investigated under a World Bank project in Bangladesh was as follows:
A duckw**d lagoon with a standing crop of duckw**d is harvested and placed fresh into a second lagoon containing a mixed size tilapia culture. The pond is harvested twice weekly and the fish sorted into various groups for return to the lagoon or sale. Under these circumstances the average yield of fish per hectare of lagoon is estimated at around 10 tons annually using only duckw**d as the supplement to the naturally available fish feed (Skillicorn et al 1993).
