abundant in plant proteins and cannot be synthesized. In all animal diets, the most
costly and limiting ingredient is animal derived protein, due to its high essential
amino acids content. As a consequence, a challenge in the future will be to
formulate feeds in which animal derived proteins are replaced by plant proteins
or other sources of protein, and to increase the utilization of energy derived from
lipids and carbohydrates in the feeds.
In intensive aquaculture, fish diets must be formulated to meet all requirements,
as the feed provided is the sole source of energy and anabolic units for the fish. In
semi-intensive fish culture systems on the other hand, the supplemental feed used
should be formulated to increase the utilization of the natural food items by
supplying limiting macro- and micro-nutrients. For common carp under semiintensive feeding regimes, energy has been shown to be the first growth limiting
factor (Pucher et al. 2011a, b; De Silva 1995) and must be supplied by supplemental
feed to reduce the utilization of animal derived proteins from natural food resources
(zoobenthos and zooplankton) as an energy source. The second limiting factor is the
quality of protein in the supplement feed.
Artificial fish feeds can be offered in different forms: dough, powder and sinking
or floating pellets (Tacon and De Silva 1997). Dough and powders require less
technical input and are cheap to prepare, but their use is often associated with high
losses of nutrients via leaching and a general loss of feed due to ineffective feed
uptake. In contrast, the preparation of sinking and floating pellets demands a higher
technical input but enables more effective feed uptake by the fish and results in less
nutrient leaching into pond water. The use of pellets also means that all the required
nutrients are delivered at the same time, which is not possible using powders and
dough where single feed ingredients are suspended in the water or float on the
water’s surface. In the study area of Yen Chau district, we tested sinking pellets as
supplemental feed. Production of the pellets required a medium level of technical
input and the pellets sank down to the bottom of the pond, which suited the feeding
behavior of the target species (common carp) and partly prevented other species
from consuming the supplemental feeds.
It is essential for resource-poor farmers in rural upland areas to use feeds for
aquaculture that help give the highest level of profit. The most profitable feed
formulation is not necessarily the one that leads to the highest growth rate, since
more digestible ingredients are often more expensive. Given that fishmeal prices
continue to rise in the rural markets of Vietnam, one study feed with an effective
fish meal replacement (Tuan 2010) was introduced to cooperating farmers in the
research area of Chieng Khoi commune and tested in pond trials. Abdelghany and
Ahmad (2002) evaluated a daily supplemental feeding rate of 2.7 % of total fish
biomass in a polyculture stocked with more than 50 % omnivorous fishes, and at a
stocking density of 2.2 fish per m
2 , which was considered optimal for fish and
income production. In Chieng Khoi commune, Pucher et al. (2010a, b) adjusted the
amount of feed offered to 6 % of the common carp biomass per day each month,
under the assumption that growth of the common carp would be proportional to the
growth of all the species present. Pretests showed that it was not possible to catch a
8 Improved Sustainable Aquaculture Systems for Small-Scale Farmers . . .
299
costly and limiting ingredient is animal derived protein, due to its high essential
amino acids content. As a consequence, a challenge in the future will be to
formulate feeds in which animal derived proteins are replaced by plant proteins
or other sources of protein, and to increase the utilization of energy derived from
lipids and carbohydrates in the feeds.
In intensive aquaculture, fish diets must be formulated to meet all requirements,
as the feed provided is the sole source of energy and anabolic units for the fish. In
semi-intensive fish culture systems on the other hand, the supplemental feed used
should be formulated to increase the utilization of the natural food items by
supplying limiting macro- and micro-nutrients. For common carp under semiintensive feeding regimes, energy has been shown to be the first growth limiting
factor (Pucher et al. 2011a, b; De Silva 1995) and must be supplied by supplemental
feed to reduce the utilization of animal derived proteins from natural food resources
(zoobenthos and zooplankton) as an energy source. The second limiting factor is the
quality of protein in the supplement feed.
Artificial fish feeds can be offered in different forms: dough, powder and sinking
or floating pellets (Tacon and De Silva 1997). Dough and powders require less
technical input and are cheap to prepare, but their use is often associated with high
losses of nutrients via leaching and a general loss of feed due to ineffective feed
uptake. In contrast, the preparation of sinking and floating pellets demands a higher
technical input but enables more effective feed uptake by the fish and results in less
nutrient leaching into pond water. The use of pellets also means that all the required
nutrients are delivered at the same time, which is not possible using powders and
dough where single feed ingredients are suspended in the water or float on the
water’s surface. In the study area of Yen Chau district, we tested sinking pellets as
supplemental feed. Production of the pellets required a medium level of technical
input and the pellets sank down to the bottom of the pond, which suited the feeding
behavior of the target species (common carp) and partly prevented other species
from consuming the supplemental feeds.
It is essential for resource-poor farmers in rural upland areas to use feeds for
aquaculture that help give the highest level of profit. The most profitable feed
formulation is not necessarily the one that leads to the highest growth rate, since
more digestible ingredients are often more expensive. Given that fishmeal prices
continue to rise in the rural markets of Vietnam, one study feed with an effective
fish meal replacement (Tuan 2010) was introduced to cooperating farmers in the
research area of Chieng Khoi commune and tested in pond trials. Abdelghany and
Ahmad (2002) evaluated a daily supplemental feeding rate of 2.7 % of total fish
biomass in a polyculture stocked with more than 50 % omnivorous fishes, and at a
stocking density of 2.2 fish per m
2 , which was considered optimal for fish and
income production. In Chieng Khoi commune, Pucher et al. (2010a, b) adjusted the
amount of feed offered to 6 % of the common carp biomass per day each month,
under the assumption that growth of the common carp would be proportional to the
growth of all the species present. Pretests showed that it was not possible to catch a
8 Improved Sustainable Aquaculture Systems for Small-Scale Farmers . . .
299