The document discusses the use of high-quality wheat proteins, specifically vital and hydrolysed wheat gluten, as alternatives to fishmeal in aquaculture feeds to enhance fish growth performance and nutritional quality. Research indicates these proteins not only maintain good pellet quality during extrusion but also support gut health and immune function without negatively impacting fish health. Wheat proteins exhibit a favorable amino acid profile and have shown promising results in replacing significant portions of fishmeal while ensuring similar growth rates and nutrient retention.

1. Wheat proteins
high quality proteins for aquaculture feeds
by Dr Emmanuelle Apper, MSc Aurélien Feneuil, Dr Frédérique Respondek Tereos, Innovation department
M
any fish feed producers now formulate low fishmeal
diets. To ensure high growth performance, the use of
high quality alternative protein is then required. Both
Vital and Hydrolysed Wheat Gluten are high quality
proteins. While they don’t exhibit the same behaviour at extrusion,
they can both ensure good physical quality of pellets and high level
of growth performance with high nitrogen and energy retention.
Additionally, Vital and Hydrolysed Wheat Gluten may have some
functional health benefits at gut level, especially by stimulating gut
cell proliferation and antioxidative system without damaging gut
structure.
Intensive production of farmed fish fed with compound feeds has
increased greatly, mainly due to the growth of aquaculture production,
but also because it is the most efficient way of production (Olsen
and Hasan, 2012). In such feeds, Fish Meal (FM) used to be the major
source of proteins, especially for marine fish and salmonids (Tacon et
al., 2011). Nevertheless, because of the limited amount of available FM
on the market, its impact on the environment and marine diversity, and
its increasing price, its utilisation has been progressively reduced in the
formulation of diets.
In order to achieve a low FM incorpora-
tion (below 10 percent in formula) with-
out impairing growth performance, active
research was conducted on plant proteins
(PP), which represent an interesting alterna-
tive to FM. In this context, many studies
were undertaken to evaluate the effects
of replacing FM with different types of PP,
tested one by one or in mixture, on fish
growth and health. Among the tested PP
being considered to replace FM, Wheat Proteins (WP), including Vital
Wheat Gluten (VWG) and Hydrolysed Wheat Gluten (HWG) are
easily available PP sources that have given very promising results from
technological, nutritional and health points of view.
Vital and Hydrolysed Wheat Gluten exhibit different behaviour in
extrusion and both proteins allow obtaining pellets of high physical
quality
VWG has already been described elsewhere (Apper-Bossard et al.,
2013) as an effective binder in fish feed, imparting good mechanical
properties (i.e. durability and hardness) to the fish feed pellets as well
as good water stability. Moreover, increased VWG inclusion rate in
replacement of soy protein concentrate results in decreasing extruder
motor load. Indeed, extrusion behaviour of 2 commercial salmon
feed diets has been explored both at small scale (Application Centre,
Tereos, Marckolsheim, France) and at a fish feed Technology Centre
(scale-up; Nofima, Fana, Norway). One diet contained 10 percent
VWG and the other 20 VWG. The two diets were extruded in the
same processing conditions. This resulted in a lower motor load (i.e.
torque) for 20 percent VWG compared to 10 percent VWG (36
percent versus 41 percent motor load). Higher inclusion of VWG
in formulation leads to a decrease in motor load due to the lower
water holding capacity of VWG compared to soy protein concentrate
(Draganovic et al., 2011).
The technological properties of HWG had not yet been reported
in the literature while VWG and HWG have different impacts on
extruder system parameters, especially on motor load and pressure
at the die. Indeed, replacing 25 percent of Crude Protein (CP) of a
FM diet by either VWG or HWG (Voller et al., in preparation) results
in lower motor load with HWG (283 and 376 Nm with HWG and
VWG respectively). The higher effect of VWG on the motor load
can be attributed to the higher water holding capacity (table 1) of this
ingredient (1.5 g of water/g) compared to HWG (0.6 g of water/g).
The reduction in motor load can be seen as a direct process advantage
allowing reduction of energy consumption during extrusion (Specific
Mechanical Energy reduced from 65 to 50 Wh/kg). An alternative is to
run the HWG diet at the same motor load as the VWG diet with the
potential to increase the extrusion capacity.
Wheat Proteins: Amino acid profile
Wheat proteins are a source of functional amino acids, especially
Table 1: Water Holding Capacity (WHC) of different vegetable proteins
Amytex® (VWG) Solpro 508® (HWG)
Soy Protein
Concentrate (Imcosoy
62, Imcopa)
WHC in g of water/g of
commercial product (Mean
+/- Standard Deviation)
1,5 +/- 0,0 0,6 +/- 0,0 3,0 +/- 0,0
14 | INTERNATIONAL AQUAFEED | March-April 2015
FEATURE

2. sulphur amino acids and leucine. They contain rather low levels of
lysine, tryptophan, and arginine meaning that they should be comple-
mented with these amino acids when used at high level in formulae.
Several experiments showed WP can successfully replace a large part
of FM when diets are supplemented with free lysine in salmonids
(Davies et al., 1997).
WPs contain a relatively high concentration of sulphur-containing
amino acids, due to the numerous di-sulphur bonds (1.8 percent CP
of methionine and 2.6 percent CP of cysteine), whereas PP sources
are generally low in sulphur-containing amino acids. For instance, soy-
bean meal and soy protein concentrate respectively contain 1.4 and
1.3 g/100 g CP of methionine and 1.3 and 1.4 g/100 g CP of cysteine.
Furthermore, WPs are high in leucine, with about 7.9 g/100 g CP.
Leucine is considered as the main amino acid triggering muscle protein
synthesis and inhibiting proteolysis in mammals (Li et al., 2009) and
probably in fish. Indeed, in different species, amino acids regulate the
TOR signalling pathway (Seilliez et al., 2008). Furthermore, supple-
menting media containing 0.6 mM leucine with an additional 2.5 mM
leucine reduced rates of protein degradation in rainbow trout primary
myocytes by 8 percent (Cleveland, 2010).
WPs are also rich in glutamine: from 35 to 40 percent CP.
Glutamine is a major substrate for all rapidly proliferating cells and
plays an important role in maintaining intestinal trophicity (Verlhac-
Trichet, 2010). In addition, glutamine is one of the most important
energy substrates of enterocytes. Free glutamine significantly increases
enterocyte and microvilli length in catfish gut (Pohlenz et al., 2012),
hybrid striped bass (Cheng et al., 2012), and juvenile hybrid sturgeon
(Zhu et al., 2011). Glutamine also constitutes a major substrate for
immune cells, thus modulating immune response (Verlhac-Trichet,
2010; Zhu et al., 2011; Cheng et al., 2012). Moreover, glutamine
plays a role in eliminating free radicals as it acts as a precursor for glu-
tathione synthesis (Wu, 1998). Such effects are reported for juvenile
hybrid sturgeon (Zhu et al., 2011) and hybrid striped bass (Cheng et
al., 2012). Glutamine has proven to stimulate muscle synthesis in ter-
restrial vertebrates but such results are not available for fish. However,
dietary glutamine supplementation increases growth performance in
juvenile hybrid sturgeon (Qiyou et al., 2011) and in hybrid striped bass
(Cheng et al., 2012).
Effects of wheat proteins on growth performance
Because of its high digestibility and its absence of anti-nutritional
factors, replacement of a large proportion of FM with VWG results
in similar growth performance and fish composition whatever the
species are. The apparent CP digestibility of VWG is high, between
March-April 2015 | INTERNATIONAL AQUAFEED | 15
FEATURE
Figure 1: Nitrogen apparent digestibility of a fish-meal based
diet where fish meal is replaced from 0 to 75% by hydrolysed
wheat gluten (HWG), on a Crude Protein basis. Nitrogen
apparent digestibility curvilinearly increases with increasing
HWG in diet.
SIZE 10
MAXUM
80
1600
NORGREN
52.19
[1325]
DCC
Inlet
BIN
Inlet
102.13 [2594]
111.12 [2822]
18.00 [457]
1.93 [49]
256T
060
1545
30
195.72 [4971]
F085SHIMPO
108.59
[2759]
15.00
[381]
36.91
[937]
Ă12.00
[305]
1.00
NPT
2.00 NPT
3/4 NPT
101.44
[2577]
30.38
[772]
88.00
[2236]
108.28
[2750]
278.03
[7062]
67.28
[1709]
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3. 92 and 98.5 percent (Apper-Bossard et al., 2013). In rainbow trout,
VWG successfully substitutes more than 50 percent FM providing
diets supplemented with lysine without affecting protein and lipid
composition of the carcasses (Davies et al., 1997). Furthermore, the
inclusion of 14.5 percent VWG in diets does not adversely affect
the flavour of fillets (Skonberg et al., 1998). In Atlantic salmon, the
replacement of 35 percent FM with VWG without supplementing by
lysine results in similar final body weight and growth (Storebakken
et al., 2000). These authors estimate the replacement of FM with
VWG without amino acid supplementation can go up to 50 percent
based on the amount and the availability of lysine in VWG and on
the requirement of fish.
In European sea bass, substituting more than 50 percent FM with
VWG does not impair palatability, growth performance, and nitrogen-
energy retention (Tibaldi et al., 2003). In gilthead sea bream, the
use of 88 percent CP from VWG not only successfully replaced FM
but also produced better growth and feed conversion ratio, prob-
ably related to higher protein and energy intake of fish (Allan et al.,
2000). In Nile tilapia fed with diets differing in their protein sources,
the highest growth is reported for VWG, FM, and soybean extract
diet. In shrimp, results are scarce but the replacement of up to 20
percent marine protein with VWG does not significantly affect feed
efficiency and growth performance (Molina-Povida et al., 2004; Tereos i
nternal data).
HWG also seems promising in aquaculture feeds as it results in high
growth performance. CP digestibility of HWG has recently been meas-
ured. It is very high and further increases with higher HWG inclusion
rate in FM-diet for rainbow trout (figure 1; Apper et al., 2014). Recent
studies on juvenile hybrid sturgeon show that the replacement of 1 to
5 percent of soy protein concentrate by 1 to 5 percent of HWG in a
diet containing animal and plant proteins significantly increases growth
performance (Qiyou, 2011). The use of 12.5 to 50 percent CP of
HWG to replace high quality FM does not modify growth performance
and feed efficiency in rainbow trout (Apper et al., 2014). In the same
experiment, authors compared energy and nitrogen retention obtained
with either VWG or HWG. Nitrogen retention was similar for the 2
protein sources, with very low metabolic losses of nitrogen (35.1 and
43.4 kg/ton of fish produced for HWG and VWG respectively). Energy
retention was higher with HWG than with VWG.
Effects of wheat proteins on gut
health and microbiota
Compared to a fishmeal-based diet, the use of Wheat Proteins
does not damage gut morphology and microbiota. In Rainbow trout,
the replacement of up to 50 percent high quality FM by either VWG
or HWG results in no modification of gut structure (figures 2 and
3; Apper et al., 2014). Indeed, no areas of necrosis were observed
in enterocytes, all appearing uniform, regular, and healthy. Microvilli
observations confirmed such results, all microvilli being packed and
showing the same density. Similarly, in the same study, microbiota was
not significantly different between FM, HWG and VWG diets, with a
predominance of Firmicutes. Richness, OTUs, and diversity of micro-
biota were not different across treatments, suggesting that replacing up
to 50 percent of high quality FM by WP is without consequence for
gut health. Such results are typical of wheat proteins as soy-proteins
or pea proteins have been demonstrated to impair gut morphology or
microbiota at high inclusion rates (Mc Kellep Bakke et al., 2007; Penn
et al., 2011).
In soy-based diets, the inclusion of hydrolysed wheat proteins mod-
ulates gut function and morphology, the anti-oxidative system, and the
non-specific immune system. The replacement from 1 to 5 percent of
soy protein concentrate in a diet based on 20 percent FM, 20 percent
soybean meal, eight percent corn gluten meal and 10 percent blood
meal increased digestive enzyme activities and fold heights, modulated
non-specific immune response and stimulated anti-oxidative status
(Qiyou et al., 2011; Zhu et al., 2011). Interestingly, in these studies,
the results of 3 percent of HWG inclusion were equivalent to results
obtained when authors added one percent free glutamine in the soy
protein concentrate diet. Such results suggest that HWG may have a
bioactive role, by acting on highly proliferative cells or by saving energy
as a glucose precursor.
Due to their technological and nutritional properties, Vital and
Hydrolysed Wheat Gluten already appear as high value protein sources
for fish feeds. Furthermore, new insights on gut morphology, micro-
biota and health highlight a potential functional role of these proteins
on the antioxidative system and on digestive enzyme activity and reveal
that wheat proteins do not disturb carnivorous fish microbiota signifi-
cantly. Further research is needed to confirm these functional benefits
and to fully understand the underlying mechanisms.
16 | INTERNATIONAL AQUAFEED | March-April 2015
FEATURE
Figure 2. Posterior intestine of rainbow trout fed with a
diet containing only fish meal (FMC), 50% hydrolysed
wheat gluten, 50% vital wheat gluten, or a blend of
hydrolysed and vital wheat gluten, on a crude protein
basis (electronic microscopy, × 900). No large areas of
necrosis whatever the treatment. Enterocytes appear
uniform, regular and healthy.
Figure 3. Microvilli of posterior intestine of
rainbow trout fed with a diet containing only fish
meal (FMC), 50% hydrolysed wheat gluteTable
1Formulation and compositions of experimental
diets (%).tein basis (electronic microscopy, × 20
000). Microvilli are uniform and densely packed for
all treatments.

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