Page 48 - New additives and ingredients in the formulation of aquafeeds

Traditionally, animal protein supplements were and are the main source of
the aquaculture feed formulation. Thus, the diet provided in larval stages is
based on live rotifer and artemia (micricrustaceans). Rotifers can be raised
in ponds with algae, but is cumbersome, and the farmer has to have time,
labour and place to grow them. More difficult is the case of Artemia due
to the lack of an efficient culture system, because the artemia cysts are
collected and commercialized in cans. A priori, the farmer only has to put
those eggs to hatch. The problem is that there are few places worldwide
where Artemia cysts can be harvested industrially, and subsequently, it is not
only a scarce and expensive product but also this culture system has a high
risk of overexploitation. Given the limited global supply and the increasing
in prices of these products, aquaculture nutritionists are considering other
protein resources. Moreover, these problems will beset in the future as
aquaculture will take a greater role occurring a more competition for the
same substrates and therefore less profits margins.
At the same time, other considerations, not just the lack and the price of
animal protein foods in the future, are taken into account when alternative
protein sources for aquaculture are looked for. One of themain current factors
is the accumulation of contaminants in animal diets. Protein supplements
based on fish meal are composed mostly of nitrogen. Those that are not
eaten or digested are introduced into the environment and the production
facilities, increasing nitrogen and phosphorus concentrations unnecessarily,
causing eutrophication problems and excessive growth of algae.
On the other hand, the wild fishes would eat also contaminants that have
been accumulated in different prey in the food chain. Currently, in this case,
the aquaculture fishes have the same peculiarity because it is fed by fishmeal
and fish oil mainly. For these reasons and because it is not possible to control
the diet in wild fish, the only option is to control the diet of farmed fish.
The contribution of alternative protein sources in aquaculture feed instead
of the current animal protein, would decrease the wild fish catches, would
improve water quality and would reduce pollutants in the diet derived
from fish food. It is an urgent need that protein resources do not interfere
with food safety in humans. Recent disease outbreaks or epidemics such
as bovine spongiform encephalopathy transmitted through animal feed
including animal protein, have led to a cascade of questions about if it is
convenient to feed vegetarian species with animal protein sources. One
of the alternatives could be found in plant protein sources as these are
available in greater quantity and the cost is lower than the fish meal or
animal protein. In fact, protein supplements derived from plant sources
as protein resource are being incorporated into diets for aquaculture as a
supplement of the animal protein, although this has been done in low rates
of substitution. Some of the causes of its total replacement has not been
industrial scale. Thus, commercial enzymes, like Alcalase and Flavourzyme,
were used in a sequentially way in order to get protein hydrolysates with a
high degree of hydrolysis.
Development
46 Plant protein isolates and hydrolysates as alternative to the animal protein in aquaculture diets