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Gaber, 2001; Soltan, 2005), canola (Slawski et al., 2013; Rajeev and Athithan, 2015), and cottonseed meal
(Andreson et al., 2016; Ananyu et al., 2014), rapseed (Nagel et al., 2012; Slawski et al., 2012), pea meal (Collins
et al., 2013; Fuertz et al., 2013; Gonzalez et al., 2016). However, the utilization of plant based proteins in
aquafeeds resulted in a number of problems. These problems can be summarized as the occurrence of
anti-nutritional factors, reduced digestability and issues of palatability (Hassan et al., 2015). Regardless of their
typically high crude protein content, these fishmeal substituents are usually lacking in one or more essential amino
acids. Theses limiting essential amino acids usually include lysine, isoleucine, and methionine (NRC, 1993).
These imbalances can be overcome to a large extent by mixing complementary protein by-product meals so as to
acquire the required essential amino acid profile (Davies et al., 1989).
Improvement of the nutritive value of these components by processing to increase the bioavailability of nutrients,
diminish or remove anti-nutritional factors. On the other hand, the addition of proper additives could result in
oilseed meals being incorporated at high levels in fish feeds (Wee, 1991). Furthermore, their shortage and
competition from other sectors such as conventional crops for domestic animals and human consumption, as well
as industrial use make their expenses is too high and put them far beyond the reach of fish farmers or producers of
aquaculture feeds (Fasakin et al., 1999).
On the other hand, soybean has become an important source of biodiesel nowadays, thus, raising the world’s
requirements for this crop, consequently, its prices. This results in the presence of anti-nutritional factors and
nutritional profiles that do not fully match the fish requirements, especially with respect to amino acids and fatty
acids (Geurden et al., 2005).
2.6 Terrestrial animal by-products
Terrestrial animal by-products have been extensively used as protein sources for tilapia. It includes blood meal,
poultry by-product meal, hydrolyzed feather meal and meat and bone meal. It has high protein content in addition
to good essential amino acid profiles (Tacon, 1993). Previous studies concluded that animal protein components
can be valuable for fish feed formulation. They are rather much less expensive than fish meal (Hernandez et al.,
2014; Sierra et al., 2014; Kritsanapuntu and Chaitanawisuti, 2015; Yu et al., 2015; Yones and Metwalli, 2015).
Poultry by-product meal is limited most in lysine (Nengas et al., 1999), while methionine was reported as the most
limiting amino acid in meat and bone meal and blood meal. Furthermore, hydrolyzed feather meal is limiting in
both lysine and methionine, while blood meal is also deficient in iso-leucine. However, some suggested way of
overcoming these deficiencies is by supplementing the deficient amino acids or by mixing complementary
alternatives to obtain the desired essential amino acid profile.
2.7 Fishery by-products
The likelihood of substituting fishmeal with fishery byproducts, such as shrimp head meal, fermented fish silage,
squid meal, tuna by-product powder, tuna liver meal, fermented skipjack tuna viscera, and tuna head hydrolyzates
have been tested in various aquaculture feeds (Uyan et al., 2006; Gumus et al., 2009; Iranshahi and Kiaalvandi,
2011; Nguyen et al., 2012; Hernandez et al., 2013; Lee et al., 2014).
2.8 Novel proteins
Finally, novel proteins is another area of active research in the aquaculture feed industry. Novel proteins are
proteins obtained from single cell organisms and invertebrates, but they are often too costly to be considered as an
alternative protein source to fishmeal in aquaculture feed. However, because of the recent increasing cost of
fishmeal, researchers have started evaluating the economic feasibility and optimum usage of these novel proteins
as fishmeal substitutes. Partial fishmeal replacement with algae is also possible (Kiron et al., 2012; Al-Asgah et al.,
2016; Abdel-Warith et al., 2016; Radhakrishnan et al., 2016; Kiron et al., 2016; Kissinger et al., 2016), especially
in tropical areas where they are found in plentiful amounts. Kiron et al. (2016) observed that partial substitution of
fishmeal with defatted biomassof
Desmodesmus
sp. in the feed of Atlantic Salmon does not have any adverse
effects on the specific growth rate, condition factor, protein efficiency ratio and whole body proximate
