Page 49 - New additives and ingredients in the formulation of aquafeeds

carried out may be the presence of antinutritional factors in vegetablemeals,
his low digestibility especially in the larval stage of fish, because they have
not developed an efficient digestive system yet, and its lower contribution
to energy intake and some minerals such as phosphorous. While this last
point is easily solved by an optimal formulation of the final product, the first
two reasons are attractive targets for further and deeper research.
Therefore, the biotechnology has much to say in this regard and could be a
suitable instrument for solving these problems. Plant seeds and meals have
a very heterogeneous composition, thus it is not easy to include them in the
aquaculture formulation. The replacement of fish meal with plant protein
concentrates is associated with antinutritional compounds in plant proteins
presenting a mixed picture on antinutrient (Francis et al., 2001). Generally,
these protein concentrates produced from oilseed contain antinutrients
that affect the aquaculture nutrition more than those that come from the
cereal process.
Some of these antinutritional factors are destroyed or inactivated (with or
during the processing of vegetal material) by the pelletization and extrusion
process. Others, however, remain unchanged and should be removed or
reduced to eliminate the detrimental factor for the optimum growth of the
fish. Among the antinutritional factors are the phytic acid, glucosinolates,
saponins, tannins, carbohydrates or polysaccharides insoluble, gossypol and
phytoestrogens. Therefore, a purification of the proteins in these seeds and
meals not only would solve the problem derived from the formulation but
also the removal of different compounds that could have antinutritional
factors. Thus, the plant protein isolates obtained by alkaline solubility and
subsequent precipitation of solubilized proteins at his isoelectric point, is a
process of great performance and very feasible economically, where the final
result is a product with a high protein content, more than the 70 - 80% in
dry matter, and therefore with a great decreased of antinutritional factors
that may be included in the starting vegetable meal (Pedroche et al., 2004,
Rodríguez-Ambriz et al., 2005; Taherian et al., 2011 ; Rodrigues et al. 2012).
Nowadays, there are a number of experimental assays carried out with plant
proteins, trying to achieve ​a possible substitution of the animal protein
and many of them have a high digestible plant protein similar to the levels
found in animal protein (Tibbetts et al., 2006; Hardy, 2010, Cabral et al., 2011,
Enterria et al., 2011, Richard et al., 2011). Most of these tests were made ​from
plant protein meals or concentrates where the percentage of antinutritional
factors may be excessive for efficient growth of fish (Francis et al., 2001).
Furthermore, recent studies have shown that the essential amino acid
content and the source from which these amino acids come from are an
essential requirement when we need to optimize the percentage of fish
meal replaced by plant protein (Larsen et al., 2012). Thus, corn gluten meal
is usually found as a high digestible protein source in Teleosts as tilapia (Wu
et al., 1995), rainbow trout (Gaylord et al., 2010), Atlantic cod (Tibbetts et al.
, 2006) or sargo/white seabream.
Plant protein isolates and hydrolysates as alternative to the animal protein in aquaculture diets 47