Aquaculture is one of the fastest growing industries in food production. However, the future of this growth will depend largely on availability of raw materials and development of new nutrient sources from vegetable or animal origin.

1. May | June 2013
Natural sources of cholesterol,
phospholipids and proteins
The International magazine for the aquaculture feed industry
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3. A
quaculture is one of the fastest
growing industries in food pro-
duction. However, the future of
this growth will depend largely on
availability of raw materials and development
of new nutrient sources from vegetable or
animal origin.
One of the essential nutrients for shrimp is
cholesterol. Driven by the increasing scarcity
of conventional sources of cholesterol, Sonac
recently developed Phosterol. This hydro-
lyzed protein of animal origin is produced in
accordance with all relevant EU regulations
and is readily available from renewable natural
sources. The uniqueness of Phosterol lies in
the natural combination of cholesterol and
phospholipids. Trials on shrimp have shown
a strong synergy between cholesterol and
phospholipids, the two main components of
Phosterol.
Phosterol is a unique protein hydrolysate
with high content of cholesterol and phosphol-
ipids like phosphatidyl choline, phosphatidyl
serine and phosphatidyl inositol. Cholesterol
and phospholipids are essential building blocks
in cellular membranes and are part of several
biological processes. Together with the high
amount of fat, Phosterol is a good ingredient
in aquafeeds, especially shrimp feeds. Shrimps
rely upon a dietary source of cholesterol for
optimal molting.
The origin of Phosterol is porcine tis-
sue which has been collected in dedicated
European slaughterhouses and after enzy-
matic hydrolysis further processed to a beige
brownish and heat stable powder.
Gelko Powder is a new hydrolysed
animal-based product that contains highly
digestible proteins for fish and shrimp. It
hosts a combination of important amino
acids, making aqua feed attractive and
palatable. Naturally present nucleotides,
phospholipids and minerals increase its
nutritional value.
EU Feed law
According to EU Feed law, Phosterol and
Gelko are permitted for use for all animal spe-
cies. No limitations are imposed on produc-
tion facilities, transport systems or use at farm
level. No additional labeling texts are required.
Growth trial with
Phosterol and Gelko
Three diets were formulated to contain
equal amounts of cholesterol. The refer-
ence diet contained crystalline cholesterol.
One diet contained 0.9% Phosterol and
the third diet contained 2% Gelko, a
protein soluble (see Table 2). Feeds were
produced with a pellet mill on a 2 mm die,
using preconditioning with steam (>90°C)
and post-conditioning (>90°C) for 20
minutes.
Shrimp trial
The trial was performed at the AFT-
CreveTec research centre. Forty shrimp of
1-1.4 g were put in 12 nets of 150 litres.
All nets were placed in a bigger tank, so
all nets had the same water quality. Water
quality in the big tanks was maintained with
bioflocs.
Each net was equipped with a feeder. The
feed gift was adjusted daily according to an
expected growth curve and average weight
from initial and last measurement.
Results
Growth (average weight)
We can not observe a statistical difference
in growth between the different feeds. Gelko
seemed to be doing a little better in the mid-
dle of the experiment, but towards the end
the Reference diet was the best.
table 1: Composition of Phosterol and Gelko
Composition Phosterol Gelko
Moisture 4% 4%
Crude Protein 48% 68%
Crude fat 34% 18%
Crude ash 9% 11%
Cholesterol 10% 0.10%
total phospholipids 24% 9%
Phosphatidyl choline 7.80% -
Phosphatidyl inositol 0.90% -
DHa 2.30% -
table 2: experimental diets - Diets were
formulated to contain 38 % proteins and 8 %
lipids.
reF Gelko Phosterol
Corn gluten 5 5 5
Fish meal 26 24 26
Squid meal 2 2 2
Wheat 16.9 16.9 16.9
Wheat flour 25 25 25
Soybean meal 15 15 14.2
Soyalecithin 2 2 2
Fish oil 2 2 2
Wheat Gluten 4 4 4
Premix 2 2 2
Cholesterol 0.1 0.1
Phosterol 0.9
Gelko 2
total 100 100 100
Natural sources of cholesterol,
phospholipids and proteins
by Geert van der Velden, Carine van Vuure and Anke van Doremalen, Sonac BV, The Netherlands
28 | InternatIonal AquAFeed | May-June 2013
FEATURE

5. Conclusion
Phosterol is a valuable alternative source of
cholesterol and gives similar results in growth
and lower FCR than the pure source. It also
shows lower mortality.
Gelko can replace high quality fish meal
with a minimum of 2% with no growth loss,
and results in a lower mortality.
Due to the composition, Phosterol has
many benefits in aquafeeds:
• Fat and protein mixture
• Rich in cholesterol (10%)
• Rich in phospholipids (24%)
• Good suspension
• Good emulsifier
• Attractant and palatant in shrimp diets
• Improved growth rates, molting fre-
quency and survival in farmed shrimp
• Cholesterol is heat stable (3 hours
133°C)
The advantages of Gelko:
• Fat and protein mixture
• Rich in phospholipids (9%)
• Good suspension
• Attractant and palatant in shrimp diets
• Soluble proteins with extreme high
digestibility
table 3: Growth of shrimp (g/week) on diets containing Phosterol and Gelko
Week 1 2 3 4 5 6 average
reference 0.89 0.41 1.16 2.00 2.65 2.39 1.58
Phosterol 0.83 0.43 1.41 1.63 2.62 2.15 1.51
Gelko 0.82 0.52 1.55 1.75 2.22 2.44 1.55
overall, the observed growth was good, given the fact that shrimp were relatively small at the
start of the experiment. once they reached 3-4 g, they grow above 2g/week.
table 4: FCr of shrimp on diets containing Phosterol and Gelko
Week 1 2 3 4 5 6 total
reF 0.81 2.02 1.18 1.39 0.99 1.36 1.18 b
Phosterol 1.09 1.81 0.69 0.87 0.86 1.41 0.99 a
Gelko 0.70 1.71 0.76 0.98 1.61 1.17 1.07 b
The feed with Phosterol showed the best FCR, and was statistically better than the other diets
table 5: Summary of results
Initial
weight
Final
weight
Growth
(g/week)
% Growth Mortality FCr
reference 1.31 10.81 a 1.58 826 % 9.53 % 1.18 b
Phosterol 1.17 10.25 a 1.51 872 % 5.94 % 0.99 a
Gelko 1.26 10.56 a 1.55 838 % 6.41 % 1.07 b
More InforMatIon:
Website: www.sonac.biz
May-June 2013 | InternatIonal AquAFeed | 29
FEATURE
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Limitations of formulated feeds
for live feed production
Formulated feeds offer low cost and con-
venience, but they have fundamental short-
comings. Zooplankton, including rotifers and
Artemia, can feed only on micro particles of
appropriate size (from bacteria to 10 µm for
Brachionus [Baer et al. 2008, Vadstein et al.
1993], and from bacteria to 28 µm, with the
optimum about 8-16 µm for Artemia [Makridis
and Vadstein 1999, Fernández 2001]). It is
difficult to produce dry feeds that provide
uniform particle sizes, and even when uniform
dry particles can be produced they can be
subject to clumping when dispersed into
water for feeding. But probably the most criti-
cal shortcoming of dry feeds is rapid leaching
of water-soluble nutrients; the smaller the par-
ticle, the faster nutrients are leached out. Not
only are leached nutrients unavailable to the
live feeds, they can cause fouling of the water.
Rotifer Brachionus
plicatilis
Algae concentrate (Reed
Mariculture Tetraselmis 3600)
May-June 2013 | InternatIonal AquAFeed | 13

6. www.aquafeed.co.uk
LINKS
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They are what they eat
Enhancing the nutritional value of live feeds
with microalgae
Controlling mycotoxins with
binders
Ultraviolet
water disinfection for fish
farms and hatcheries
Niacin
– one of the key B vitamins for sustaining
healthy fish growth and production
Volume 16 Issue 3 2013 - mAY | Ju Ne
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fIsh fARmING TeChNOlOGy
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