1. health and fitness
2. disease
3. cholesterol

Archiva Zootechnica 15:3, 69-78, 2012
69
The impact of diet on meat quality of common carp
Dragana Ljubojević1†, M. Ćirković1, Nikolina Novakov1, R. Jovanović2,
Snežana Janković2, Vesna Đorđević3, Dejana Trbović3
1
2
Faculty of Agriculture, Novi Sad, Republic of Serbia; Institute for Science Application
3
in Agriculture, Belgrade, Serbia; Institute of hygiene and meat technology, Belgrade,
Republic of Serbia
SUMMARY
The aim of the study was to determine the impact of diet (grains or
formulated feed) on the chemical composition, amount of total cholesterol
and fatty acids profile of common carp. The samples of two-year old carp were
taken from two fishery farms. On the first pond the production was taken
place in the semi-intensive system of production with the addition of corn
(80%) and wheat (20%) and on the second pond the feeding was done with
formulated food. Chemical analysis, fatty acids and total cholesterol
determination were done at the Institute of Hygiene and Meat Technology,
Belgrade. The amount of water, protein and ash was higher (p<0.01) in carp in
which diet was participated formulated food, with the value, expressed as a
percentage, amounted to respectively 78.36±0.04, 17.17±0.05 and 1.03±0.01,
while values of the same parameters in carp fed with corn and wheat were
75.01±0.29; 15.59±0.21 and 0.89±0.04. The percentage of fat in carp fed
formulated fed was 3.19±0.05, and for carp from semi-intensive production it
was 6.85±0.14 (p<0.01). Cholesterol content was higher (p<0.01) in carp fed
grains (57.8±0.11), compared with carp fed pelleted food (51.31±0.12). In two
years-old carp fed formulated feed was observed better ratio UFA/SFA (3.46,
compared with 3.14 in carp fed grain), PUFA/SFA (1.39 compared to 0.45),
n3/n6 (0.26 versus 0.14), higher content of PUFA (31.04 compared with 10.95),
less SFA (22.4 versus 24.23) (p<0.01). Lipids of carp fed formulated food
contained less MUFA (45.12%) compared to carp from the semi-intensive
production (64.34%) (p<0.01).The dependence of content of total cholesterol,
chemical composition and the relative fatty acid content of common carp with
diet was determined in the present work
Keywords: common carp, diet, fatty acids, cholesterol
†
Corresponding author e-mail: [email protected]
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Dragana Ljubojević et al.
INTRODUCTION
Common carp (Cyprinus carpio L.) is the dominant fish species that are
grown on fish farms in Republic of Serbia (Ljubojević et al., 2011). It is
omnivore fish and very effectively uses food. Carp is tolerated to large
variations of quality of ambient conditions. This species is not susceptible to
disease and is tolerated to handling (Ćirković et al., 2002). The opinion about
the culinary quality of common carp in Republic of Serbia, Hungary, Czech
Republic, Romania, Poland, Germany and Italy does not the same with the
belief in Anglo-Saxon states, but there is the fact that there is not a single fish
from which it can make a number of fish specialty (Ćirković et al., 2002).
Results related to meat quality of carp are differ in communications by various
authors, with differences mostly caused due to the analysis of fish of different
age, breeding systems and food, and because of that there are wide ranges of
fat content in carp from 2.3 to 16.8% (Ćirković et al., 2011 a, Ćirković et al.,
2011c) while varying slightly less in case of protein which content is in range
from 14 to 18% (Trbović et al., 2009, Ćirković et al., 2010). According to
Steffens and Wirth (2005) the fatty acid composition reflects, to a large extent,
that of the diet, so the n-3/n-6 ratio varies between 0.8 and 2.4; while Ćirković
et al. (2010) reported that the relationship of these fatty acids it was 0.54.A
similar ratio (0.5) were found by Fajmonova et al. (2003). Common carp fed
exclusively with natural food from fish-pond shows a significant level of total n3 and n-6 fatty acids (Ćirković et al., 2010). Supplementary feeding with grains
leads to reduced amounts of these essential fatty acids and this is due to the
lower proportion of natural food in the diet of the carp which received
additional grain (Ćirković et al., 2011a). The energy value of fish meat is
directly proportional to fat content. Essential fatty acids affect the fluidity,
flexibility, and permeability of membranes. They are precursors of the
eicosanoids and are necessary for maintaining the impermeability barrier of
the skin. They are also involved in cholesterol transport and metabolism
(Steffens et al., 2005). Components of fish are also important in the
development and maintenance of the eyes, skin and nervous system (Vladau
et al., 2008).The most important unsaturated fatty acids are linoleic and
linolenic acid, which are essential and should be ingested in the body by food.
Recent research suggests that freshwater fish are capable of producing EPA
and DHA from α­Linolenic n­3 (Bell et al., 2001) and they express all the
desaturase and elongase activities necessary for this biosynthetic pathway
(Sargent et al., 2002). EPA and DHA appear to play a key role in neural
development, functioning of the cardiovascular and immune systems
(Lauritzen et al., 2001), besides the prevention of some types of cancer,
including colon, breast and prostate (Connor, 2000), brain aging and Alzheimer
disease (Kyle, 1999). Beside polyunsaturated fatty acids, fish fats contain
Archiva Zootechnica 15:3, 69-78, 2012
71
cholesterol. Fish meat contains a similar amount of cholesterol (49–92
mg/100g) as pork or beef (45–84 mg/100g), and cholesterol content is not
correlated with fat content (Piironen et al., 2002). Content of cholesterol in
freshwater fish from a free-catch and fish from aquaculture is different and
depends on the species of fish (Moreira et al., 2001). It is necessary to take into
account the nutritional quality of meat because fish is also one of the best
sources of animal protein (Ćirković et al., 2002). Fish proteins contain all the
essential amino acids for the human organism and they can be used as the sole
source of protein in the diet (Vladau et al., 2008).The fish which contains less
fat and cholesterol and has a favourable fatty acid composition could be very
useful in the diet of people whose health conditions have deteriorated, but it
could also serve as a good preventive measure in healthy individuals.
The aim of the present study was to determine the impact of diet on the
chemical composition, amount of total cholesterol and fatty acids profile, of
common carp at same age.
MATERIAL AND METHODS
Samples of two years old of common carp were taken in November from
earthen pond where the production is taken place in the semi-intensive system
of production with the addition of corn (80%) and wheat (20%). Also, the
samples of two-year old carp were taken from another pond where the
feeding was done with complete feed mixture. 12 samples of common carp
were taken from both ponds. Samples of feed were taken from both ponds.
The growing season lasted from April to November in both cases. Fish were
hand-fed twice daily (8:00 and 15:00h). The water temperature was in the
range from 15-26°C during the trial. The amount of natural food and its
influence on chemical and fatty acid profile was not considered.
Until determination the samples were stored ten days at a temperature of
–18ºC. Before examination fish are left at room temperature, in order to
partially defrosted and easily removed skin, taking the head and tail and
remove the viscera. Fish fillets were blended in Braun CombiMax 600 (Spirić et
al., 2009).
The meat from dorsal muscles was used for chemical аnаlysis. Chemical
composition of fish muscle tissue was determined by standard RPS ISO
methods. Protein content was determined by Kjeldahl (N x 6.25) (Kjeltec Auto
1030 Analyzer, Tecator, Sweeden). Water content was determined by drying at
103±2ºC to constant weight. (SRPS ISO methods). For determination of total
fat, sample was hydrolyzed with 4M hydrochloric acid and extracted with
petroleum ether by Soxhlet apparatus. Ash was determined by combustion at
550±25ºC (Trbović et al., 2009). Total lipids for fatty acids determination were
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Dragana Ljubojević et al.
extracted from fish muscle tissues and feed by accelerated solvent extraction
(ASE 200, Dionex, Sunnyvale, CA) (Spirić et al., 2009). The fat extract was
further used for fatty acids determination. Fatty acid methyl esters (FAME)
were prepared by transesterification by using trimethylsulfonium hydroxide,
according to SRPS EN ISO 5509:2007 procedure. The GC instrument Shimadzu
2010 (Kyoto, Japan) used for FAME determination was equipped with a
split/splitless injector, fused silica cianopropyl HP-88 column (J&W Scientific,
USA), and flame ionization detector. The chromatographic peaks in the
samples were identified by comparing relative retention times of FAME peaks
with peaks in a Supelco 37 Component FAME mix standard (Supelco,
Bellefonte, USA) (Spirić et al., 2010). Cholesterol determination in carp fillets
(from direct saponification) was performed by using HPLC/PDA system (Waters
2695 Separation module/Waters photodiode array detector, USA), on a
Phenomenex Luna C18 (2) reverse/phase column, according to Maraschiello et
al. (1996). Quantification of cholesterol was done by external standardization.
Empower Pro software was used to control the HPLC system as well as for data
acquisition and data processing as described (Spirić et al., 2009). The fatty acid
composition of the diets is shown in Table 1.
Statistical analysis was performed with the Student t-test.
Table 1. Fatty acid composition of the experimental diets.
Fatty acids, %
Grains Formulated feed
Myristic, C14:0
Palmitic, C16:0
Palmitoleic, C16:1
Stearic, C18:0
Oleic, C18:1cis-9
Vaccenic, C18:1 cis-11
Linoleic, C18:2n-6
α­Linolenic, C18:3n-3
Arachidic, C20:0
Eicosenoic, C20:1
Behenic, C20:2
Dihomo-gamma-linolenic, C20:3n-6
Eicosatrienoic, C20:3n-3
Arachidonic, C20:4
Lignoceric, C24:0
SFA
MUFA
PUFA
n-6
n-3
n-3/n-6
0.40
10.86
0.16
2.02
27.62
0.16
56.15
0.98
0.38
0.20
0.26
0.61
0.17
13.83
28.14
58
57.02
0.98
0.02
0.47
10.98
0.48
2.74
26.32
0.82
54.15
2.23
0.3
0.34
0.22
0.58
0.32
0.06
0.19
14.55
27.96
57.56
55.01
2.55
0.05
Archiva Zootechnica 15:3, 69-78, 2012
73
RESULTS AND DISCUSSION
Chemical composition and total cholesterol content in the two-years old
carp fillets which was sampled from the pond where the diet is done by adding
a pelleted complete feed, and from a fish farm where the feeding was done by
adding corn and wheat in proportion 80:20 are shown in Table 2.
Table 2. Chemical composition of two-year old carp fed with different food
Parameters
Carp, grains Carp, formulated feed
Moisture content %
75.01±0.29b 78.36±0.04a
Protein content %
15.59±0.21b 17.17±0.05a
Fat content %
6.85±0.14a
3,19±0.05b
Ash content %
Total Cholesterol mg/100g
0.89±0.04b
57.8±0.11a
1.03±0.01a
51.31±0.12b
Values are means ± SD (n=12); Values in the same row with different letter
notation differ significantly statistically at p<0.01
The amount of water, protein and ash was higher in carp in which diet was
participated pelleted food, compared with the values of the same parameters
in carp whose diet were as corn and wheat(p<0.01). The percentage of fat in
carp from intensive production was 3.19±0.05, and for two year olds from
semi-intensive production was 6.85±0.14. Cholesterol content was higher in
carp fed grain, compared with carp fed pelleted food. Determined cholesterol
content in lipids of carp varies considerably in the works of different authors
and is in the range of 47 to 120 mg/100 g, which is consistent with our results
(Bieniarz et al., 2001; Kopica and Vavreinova, 2007), but it must be taken into
account that the tests carried out in different seasons and at different age
categories. Fatty acids in the carp meat are shown in Table 3. In two-year old
carp fed pelleted feed was observed better ratio UFA/SFA, PUFA/SFA, n3/n6,
higher content of PUFA, less SFA. Lipids of carp in intensive production
contained less MUFA compared to carp from the semi-intensive production.
The n-3/n-6 ratio of the fish muscle was higher than that of the consumed
food. The two fatty acids 18:2n-6 and 18:3n-3 are precursors for synthesis of n6 and n-3 PUFAs, respectively (Sargent et al., 2002). Carp that received
extruded formulated feed showed high values of n-6 fatty acids in their
muscle, based on the high content of linoleic acid in the diets. However,
although grain mixture contained slightly higher amount of linoleic acid than
formulated feed, percentage of this fatty acid was lower than in carp fed
formulated feed. In general, in both groups the content of the n-6 fatty acids
was higher than the content of n-3 fatty acids. The fatty acids in the carp meat
were quite affected by that of the diets.
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Table 3. Fatty acid composition of two-years old carp fed with different food
Fatty acids, %
Grains
Formulated feed
Lauric, C12:0
0.14±0.01a
0.10±0.00b
Myristic, C14:0
0.72±0.01a
0.73±0.01a
Pentadecylic, C15:0
0.01±0.01b
0.23±0.01a
Palmitic, C16:0
17.33±0.06a 16.89±0.03b
Palmitoleic, C16:1
6.23±0.01a
5.20±0.04b
Margaric, C17:0
0.12±0.01b
0.18±0.01a
Stearic, C18:0
5.79±0.02a
4.16±0.01b
Oleic, C18:1cis-9
51.35±0.04a 34.45±0.01b
Vaccenic,C18:1cis-11
4.54±0.04a
2.93±0.01b
Linoleic, C18:2, n-6
8.75±0.06b
22.56±0.01a
Linolenic(GLA)C18:3,n-6
0.12±0.01b
0.25±0.01a
α-Linolenic, C18:3, n-3
0.64±0.00b
2.12±0.01a
Arachidic, C20:0
0.12±0.01a
0.10±0.01b
Eicosenoic, C20:1
2.22±0.01b
2.54±0.01a
Behenic, C20:2
0.3±0.04b
0.73±0.01a
Dihomo-γ-linolenic,C20:3,n-6
0.46±0.02b
1.02±0.01a
Eicosatrienoic, C20:3, n-3
0.06±0.00b
0.71±0.01a
Erucic+Arachidonic, C22:1+C20:4
0.74±0.01b
1.43±0.01a
Eicosapentaenoic, C20:5, n-3
0.19±0.02b
0.93±0.01a
Docosapentaenoic, C22:5, n-3
0.18±0.01b
0.85±0.02a
Docosahexaenoic C22:6, n-3
0.25±0.01b
1.86±0.04a
SFA
24.23±0.06a 22.40±0.03b
MUFA
64.34±0.06a 45.12±0.03b
PUFA
10.95±0.09b 31.04±0.03a
n-6
9.63±0.08b
24.57±0.03a
n-3
1.32±0.02b
6.48±0.04a
n-3/n-6
0.14±0.00b
0.26±0.00a
n-6/n-3
7.28±0.08a
3.79±0.02b
PUFA/SFA
0.45±0.00b
1.39±0.00a
UFA/SFA
3.14±0.01b
3.46±0.01a
SFA- saturated fatty acids, MUFA- monounsaturated fatty acids, UFA -unsaturated fatty acids, PUFApolyunsaturated fatty acids from the n-3 (n-3 PUFA) and n-6 (n-6 PUFA) families Values are means ± SD
(n=12); Values in the same row with different letter notation differ significantly statistically at p<0,01.
In the present study, feeds did not contain highly UFAs. Freshwater fish
possess the bioconversion capacity to elongate and desaturate C18 PUFA to n3 and n-6 fatty acids such as arachidonic acid (20:4n-6), EPA (20:5n-3) and DHA
(22:6n-3) (Bell et al., 2001). Wood et al (2008) have suggested that ratio of
PUFA/SFA should be above 0.4 and according that examined fish in the both
group meet this suggestion. Scollan et al., (2006) have advised that ω-6/ω-3
Archiva Zootechnica 15:3, 69-78, 2012
75
ratio should not exceed 4. Fish fed corn and wheat did not meet this
requirement.
The content of n-3 in two years old carp in this study was lower than in the
two-years carp fed only natural food from the pond, which was noted by
Ćirković et al. (2010) and the amount of n-3 in naturally fed common carp was
9.85%, as much as more compared to the two years old fed pelleted feed
(6.48%), and in relation to two years old carp in which the dominant feed was
corn and the content of n-3 was 1.32%. In carp fed pelleted food was
established a higher content of n-6 fatty acids, compared to the data
presented in the paper Ćirković et al. (2011b) for carp fed only natural food
(24.57% versus 17.63%), so that the total content of PUFA was higher in carp
fed with pelleted food. According to research conducted by Buchtová et al.
(2010) and Ćirković et al. (2010) common carp grown-based on natural food
had a high content of both n-6 and n-3 fatty acids, while the carp fed grains
which are characterized by low levels of n-3 PUFA (Buchtová et al., 2010;
Ćirković et al., 2011), contained lower concentrations of these acids, a higher
concentration of oleic acid (Steffens et al., 1998). The above statements are in
agreement with the present results, because a higher content of oleic acid
(51.35%),while the carp fed pelleted food of the same age contained 34.45%
oleic acid. It is known that the application of formulated feed impact the values
of many zootechnical coefficients, including, among others, the slaughter yield,
proximate composition, and fatty acids profile (Jobling, 2001). The dependence
of n-3/n-6 relationship with diet was established in the present study.
According to Steffens et al. (2005) the n-3/n-6 ratio in common carp varies to a
large extent, between 0.8 and 2.4 and is most influenced by diet.
CONCLUSIONS
The chemical composition of fish varies greatly depending on feed,
environment and season. The lipid content of farmed common carp can vary
widely depending on the feed used. Quantity of N-3 fatty acids varies largely in
dependence on the origin of diets (formulated food or cereal supplement) and
its composition (rich primarily in PUFA n-3or saccharides). The dependence of
n-3/n-6 relationship with diet was established in our work. Nutritive value of
examined common carp is high since its fatty acid composition is characterized
by satisfactory proportion of n-3 polyunsaturated fatty acids and by high
proportion of n-6 polyunsaturated fatty acids, especially linoleic and
arachidonic acids and favourable content of total cholesterol.
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ACKNOWLEDGEMENTS
This research is part of a project of the Ministry of Science and
Technological Development, Republic of Serbia:"The influence of the quality of
the components of food for cyprinid fish species on the quality of meat, losses
and the profitability of production ", No. 31011
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