Effects of the flaxseed oil on the fatty acid composition of tilapia heads

Research Article

Effects of the flaxseed oil on the fatty acid composition oftilapia heads

AnaCarolina Aguiar, SolangeMaria Cottica, Marcela Boroski, Sheisa Cyleia Sargi, Ivanor Nunes do

Prado, Elton Guntendorfer Bonafe, Polyana Batoqui Franca, Nilson Evelazio de Souza and Jesuı

Vergılio Visentainer

Department of Chemistry, State University of Maringa, Maringa, Parana State, Brazil

The objective of this study was to evaluate the effects of adding flaxseed oil (FO) to feed on the

incorporation of n-3 PUFA in tilapia heads. Tilapia were given diets with increasing levels of FO

(0.00, 1.25, 2.50, 3.75 and 5.00% for treatments A, B, C, D and E, respectively), as a source of

LNA for 150 days. The proximate composition of the heads indicated high nutritional value and 40 FA

(fatty acids) common to all treatments were identified in total lipids. Intake of LNA caused storage of

LNA and sequential desaturation-elongation to eicosapentaenoic acid (EPA) and DHA.With increasing

levels of FO in the diet, the content of LNA in tilapia heads increased (1.7 and 14.0% for diets A and

E, respectively), as well as the contents of EPA (0.1 and 0.9% for diets A and E, respectively) and DHA

(0.5 and 1.8% for diets A and E, respectively). Adding FO to tilapia feed markedly increased the total

content of n-3 PUFA (3.0 and 21.1% for diets A and E, respectively), decreased the total content of n-6

PUFA (41.3 and 24.9% for diets A and E, respectively), and consequently resulted in a decrease in the n-

6/n-3 ratio (13.8 and 1.2 for diets A and E, respectively). Therefore, feeding tilapia with FO is a good way

of valorizing this part of the fish by creating a valuable nutritional food source.

Keywords: Fatty acids / Flaxseed oil / Tilapia heads / Omega-3

Received: January 30, 2010 / Revised: August 17, 2010 / Accepted: September 13, 2010

DOI: 10.1002/ejlt.201000035

1 Introduction

Tilapia is one of the most cultivated fresh-water fish world-

wide [1, 2]. The importance of fish as a source of PUFA,

particularly n-3 fatty acids (n-3 PUFA) in human nutrition is

well established [3, 4]. The FA composition of fish is clearly

influenced by diet. Captive freshwater fish feeds are charac-

terized by high contents of linoleic acid (LA, 18:2n-6) due to

the high LA contents in the soybean oil used in feeds [5].

Flaxseed oil (FO) is one of the world’s most important

vegetable sources of alpha-linolenic acid (LNA, 18:3n-3) [6],

that is a long chain fatty acid and is a precursor of the n-3

PUFA series, that have more than 18 carbon atoms.

Freshwater fish, which metabolize LNA and LA use the same

sequential desaturation and elongation enzyme systems.

LNA results in the production of n-3 PUFA, such as eico-

sapentaenoic (EPA, 20:5n-3) and docosahexaenoic (DHA,

22:6n-3), and LA results in the production of AA [7].

EPA and DHA fatty acids have been object of innumer-

able studies in the past few decades, being important for their

various benefits to human health, including lowering the risk

of cardiovascular diseases [8, 9], anti-inflammatory and

antithrombotic effects [10], the reduction of blood choles-

terol levels, and anticarcinogenic effects [11]. Western

country diets have a high n-6/n-3 ratio due to the consump-

tion of more n-6 FA than n-3 FA. The large amounts of n-6

FA come from the common use of vegetable oils containing

LA (e.g., soybean oil, sunflower oil). TheWHO/FAO recom-

mends a total daily diet n-6/n-3 ratio of 5:1 [12].

Recent studies have indicated that some fish parts, includ-

ing tilapia heads, are appropriate for human nutrition and

normally discarded in the filleting process [13, 14].

Researchers have also demonstrated significant concen-

trations of n-3 PUFA in viscera [15], fillets [1], heads

[16], and liver [17] of tilapia, and that can be biotransformed

into stable feed ingredients [18].

This study investigated the influence of the incremental

addition of FO as a substitute of sunflower oil in fish feed on

Correspondence: Jesuı Vergılio Visentainer, Chemistry Department,

State University of Maringa, 87020-900, Maringa, PR, Brazil

E-mail: jvvisentainer@uem.br

Fax: þ55 (44) 3011-4389

Abbreviations: FO, flaxseed oil; FA, fatty acids; LA, linoleic acid; SO,

sunflower oil; SFA, saturated fatty acids

Eur. J. Lipid Sci. Technol. 2011, 113, 269–274 269

� 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.ejlst.com

the concentrations of fatty acids, particularly n-3 and n-6, in

heads of Nile tilapias (Oreochromis niloticus) maintained in

captivity for 150 days.

2 Material and methods

The experiments were carried out in the Aquaculture

Laboratory of the Biology Department of the State

University of Maringa, Brazil. Five treatments in five repli-

cates were used with 125 tilapias with initial mean individual

weight of 88 � 6 g distributed in 25 ponds (1000–L each).

The treatments consisted of the addition of flaxseed oil (FO,

A ¼ 0.00%, B ¼ 1.25%, C ¼ 2.50%, D ¼ 3.75%, and

E ¼ 5.00%) as a substitute of sunflower oil (SO, control)

in feeds (Table 1). After 150 days, the tilapia heads were

removed and kept in polyethylene bags with N2 atmosphere

at –188C. At the beginning of each analysis, the samples were

allowed to equilibrate to RT and homogenized.

2.1 Analysis

Moisture, ash, and protein contents of tilapia heads were

determined as described by Cunniff [19], and the total lipids

(TL) were determined by the Bligh and Dyer method [20].

The FAME were prepared by methylation of the TL, as

described by Joseph and Ackman [21]. Methyl esters were

separated by GC using a Varian 3300 (USA) gas chromato-

graph fitted with a FID and a fused-silica DB–WAX capil-

lary column (30 m and 0.25 mm id) (J&W Scientific,

Folsom, CA). The operation parameters were as follows:

detector temperature, 2808C; injection port temperature,

2508C; column temperature, 1708C for 16 min, pro-

grammed to increase at 28C/min up to 2108C, with

final holding time of 25 min; carrier gas, hydrogen at

0.8 mL/min, linear velocity of 38 cm/s, with an oxygen filter

coupled to the feed line; nitrogen was used as the makeup

gas at 30 mL/min; split injection at 1:50 ratio. For identi-

fication of the fatty acids, their retention times were com-

pared to those of standard methyl esters (Sigma, St. Louis,

MO). Equivalent chain-length values (ECL) were used

[22], as well as a Shimadzu QP 5000 coupled gas chromato-

graph–mass spectrometer system and fragmentation by

electron impact, 70 eV. Retention times and percent peak

area were automatically computed by a Varian 4290 inte-

grator. The concentration of fatty acids (g/100 g of tilapia

heads) was calculated by normalization and transformation

of the area percentage to g/100 g of tilapia heads, according

to Eq. 1, using the lipid conversion decimal factor

(F ¼ 0.94) method described by Weihrauch et al. [23]

Table 1. Ingredients and composition of experimental feeds.

Treatment £

Ingredients (wt%) A B C D E

Flaxseed oil (FO) 0.00 1.25 2.50 3.75 5.00

Sunflower oil (SO) 5.00 3.75 2.50 1.25 0.00

Corn meal 16.93 16.93 16.93 16.93 16.93

Soybean meal 51.62 51.62 51.62 51.62 51.62

Wheat meal 20.00 20.00 20.00 20.00 20.00

Sugarcane silage 1.28 1.28 1.28 1.28 1.28

Calcium (carbonate) 1.74 1.74 1.74 1.74 1.74

Dicalcium phosphate 2.41 2.41 2.41 2.41 2.41

Premix§

0.50 0.50 0.50 0.50 0.50

Composition #

Total lipids (%) 7.6 � 0.3a 7.7 � 0.4a 8.0 � 0.6a 8.0 � 0.7a 7.8 � 0.3a

Fatty acids p-value

16:0 19.7 � 0.1a 9.6 � 0.1b 9.6 � 0.2ab 9.5 � 0.1c 9.6 � 0.2ab 0.180

18:0 3.7 � 0.1a 3.7 � 0.1b 3.9 � 0.19c 4.1 � 0.1d 4.1 � 0.1d 0.010

18:1n-9 26.6 � 0.3a 25.9 � 0.3b 25.1 � 0.4c 24.4 � 0.3d 23.6 � 0.3e <0.001

18:1n-7 0.8 � 0.0a 0.9 � 0.0b 1.0 � 0.0c 1.1 � 0.0d 1.1 � 0.0e 0.006

18:2n-6 (LA) 54.3 � 1.0a 48.0 � 1.1b 40.4 � 1.5c 33.8 � 1.1d 27.4 � 1.1e <0.001

18:3n-3 (LNA) 1.8 � 0.8a 9.1 � 0.9b 17.5 � 1.6c 24.8 � 1.0d 31.9 � 1.1e <0.001

22:0 0.7 � 0.1a 0.6 � 0.0b 0.4 � 0.1c 0.4 � 0.1d 0.3 � 0.1e 0.008

Other n–3 nd nd nd nd nd

£ Treatments: A (0.00%), B (1.25%), C (2.50%), D (3.75%), and E (5.00%) of flaxseed oil completed up to 5.00% with sunflower oil.§

Mineral and vitamin supplement. #Mean of six repetitions � SDs. Means followed by different letters within a row are significantly different

(p < 0.05) by Tukey’s test.

270 A. C. Aguiar et al. Eur. J. Lipid Sci. Technol. 2011, 113, 269–274

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and Exler [24].

g=100g of tilapia heads ¼ FðdecimalÞ � A�TLðdecimalÞ(1)

Where A means normalized peak area percentages and

TL means total lipids.

2.2 Statistical analysis

Means were statistically compared by Tukey’s test at 5%with

one-way variance analysis (ANOVA). Data were processed

using Statsoft [25].

3 Results and discussion

There were no significant differences (p > 0.05) in TL,

crude protein, and moisture contents of tilapia heads

(Table 2) between B, C, D, and E comparing with the treat-

ment A. The moisture (66.5 to 68.6%) and total lipid (9.6 to

11.4%) contents found in tilapia heads in this experiment

agree with those of 67.2 and 9.6%, respectively, reported by

Stevanato et al. [26] in in natura tilapia heads. The protein

(15.0 to 15.7%) and ash (5.1 to 5.5%) contents also agree

with Stevanato et al. [26], 16.4% (protein) and 5.7% (ash).

Table 1 shows that a total of seven majority fatty acids

were found in the feeds. The only FA in the n-3 and n-6 series

found in the feeds were LNA (18:3n-3) and LA (18:2n-6),

respectively. The FO (an LNA source) and SO (an LA

search) used in the experiment were analyzed separately.

FO contained 45.7% LNA and 15.0% LA, while SO con-

tained 0.4% LNA and 56.0% LA. The increase in feed LNA

content from treatment A (1.8%) to treatment E (31.9%) was

due to the added FO, while the decrease in LA content from

treatment A (54.3%) to treatment E (27.4%) was due to the

substitution of SO. Significant differences in fatty acid com-

position in terms of LNA and LA contents were observed

between the treatments.

Forty fatty acids were identified in tilapia heads from all

treatments. Table 2 shows the fatty acid contents of the

different treatments. The major fatty acids present were

LA, oleic acid (OA, 18:1n-9), and palmitic acid (PA, 16:0).

LA and LNA are essential FA metabolized by the same

sequential desaturation and elongation enzyme systems,

which results in the production of n-3 and n-6 PUFA series.

There is, therefore, a competitive effect by which excess LNA

may interfere with the conversion of LA into arachidonic acid

(AA, 20:4n-6), a highly desirable fatty acid [27]. In this study,

the value of AA ranged from 1.1 (treatment A) to 0.5%

(treatment B).

Most freshwater fish are capable of D–6 desaturation from

LNA to 18:4n-3 and from LA to 18:3n-6, followed by

elongation and D–5 desaturation to EPA and AA, which

finally undergo elongation and D–4 desaturation to produce

DHA and docosapentaenoic acid (22:5n-6) [28]. All n-3 and

n-6 FA found in tilapia heads came from LNA and LA in the

feeds, both desaturation and elongation were observed of FA

on the tilapias heads.

Part of the LNA of feed was converted into 18:4, 20:3,

20:4, EPA, 22:5, and DHA n-3 PUFA, and part was not

converted, but stored in the heads (Table 2). Increases of the

LNA, EPA,DHA, contents, and of all n-3 PUFA in the heads

have been well established, with a significant difference

(p < 0.05) between the treatments for the increasing substi-

tution of SO with FO.

Average values across treatment for saturated FA (SFA),

monounsaturated FA (MUFA), and PUFA were 21.0, 33.0,

and 45.0%, respectively. Additionally, the PUFA/SFA was

approximately 2.1 for all treatments (Table 2).

The total n-3 PUFA levels of the treatments were 3.0%

(A), 9.7% (B), 12.4% (C), 15.9% (D), and 21.1% (E), and

the total n-6 PUFA levels of the treatments were 41.3% (A),

37.8% (B), 32.1% (C), 29.4% (D), and 24.9% (E) (Table 2).

The levels of both n-3 and n-6 PUFA showed significant

differences between treatments as the FO contents in feed

were raised. However, while total n-3 PUFA increased, total

n-6 PUFA decreased in all treatments. This occurred owing

to the increase in LNA and the decrease in LA as FO replaced

SO in the feeds.

Some researchers propose that the n-6/n-3 ratio in

Western diets has moved from 20 to 30 in the last few years

[29], a value considered extremely high since the ideal is 5:1

[12]. The n-6/n-3 ratio in tilapia heads in this experiment

decreased significantly with increasing feed FO content in

all treatments (Table 2). Treatment A gave the highest

n-6/n-3 ratio (13.8), the only value higher than the reference

value; the other values were B (3.9), C (2.6), D (1.8).

Treatment E yielded the lowest n-6/n-3 ratio (1.2). The

analysis of the PUFA/SFA ratios revealed no differences

(p > 0.05) between the treatments with medium ratio of

2.1 (Table 2).

The heads of tilapia submitted to treatments B, C, D, and

E in this experiment had n-6/n-3 ratios lower than those

found in other fish species raised in captivity in Brazil,

11.3 in tilapia (O. niloticus) [30], 9.8 in pacu (P. mesopo-

tamicus) [31], 9.1 in matrinxa (B. cephalus) [32].

The Table 3 shows an estimate of the principal PUFA

n–3 and n–6 concentration (g/100 g of head), as well as the

sum of PUFA n–3 and n–6 present in the tilapia heads

submitted to different treatments. It was observed that the

supplementation with linseed oil increased the content of

polyunsaturated n–3 fatty acids, ranging from 0.29 to

2.41 g/100 g of head.

On average, the lipid content of tilapias head observed in

this study was 11.04%, higher than that found by other

researchers in filets of the same species from 0.99 to

2.26% [33, 34]. Weaver et al. [35] evaluated the profile of

fatty acids in commonly consumed fish and found that the

farm-raised tilapias have in their composition less than 0.5 g/

Eur. J. Lipid Sci. Technol. 2011, 113, 269–274 Omega-3 content of tilapia heads fed with flaxseed oil 271

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Table 2. Proximate composition and fatty acid composition (wt% of total fatty acids) of tilapia heads.

Treatment £

Proximate composition A B C D E

Total lipids (%) 9.6 � 0.3a 11.4 � 0.4b 11.4 � 0.2b 11.4 � 0.3b 11.4 � 0.3b

Protein (%) 15.1 � 0.2a 15.7 � 0.3a 15.0 � 0.3a 15.1 � 0.2a 15.6 � 0.2a

Ash (%) 5.3 � 0.2a 5.1 � 0.1a 5.5 � 0.2b 5.5 � 0.1b 5.5 � 0.2b

Moisture (%) 68.6 � 0.2a 66.2 � 0.2b 66.7 � 0.3b 66.6 � 0.3b 66.5 � 0.3b

Saturated fatty acids (SFA) p-value14:0 1.3 � 0.2 1.3 � 0.3 1.3 � 0.2 1.3 � 0.2 1.2 � 0.1 0.180

i15:0 0.2 � 0.1 0.2 � 0.1 0.2 � 0.1 0.2 � 0.1 0.2 � 0.1 <0.001

15:0 0.3 � 0.1 0.3 � 0.1 0.3 � 0.1 0.3 � 0.1 0.3 � 0.1 <0.001

i16:0 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 <0.001

16:0 14.4 � 0.7 14.3 � 0.6 14.1 � 0.5 14.0 � 0.7 13.8 � 0.5 <0.001

i17:0 0.3 � 0.1 0.3 � 0.1 0.3 � 0.1 0.3 � 0.1 0.3 � 0.1 <0.001

ai17:0 0.3 � 0.1 0.3 � 0.1 0.3 � 0.1 0.3 � 0.1 0.3 � 0.1 <0.001

17:0 0.3 � 0.1 0.3 � 0.1 0.3 � 0.1 0.2 � 0.1 0.2 � 0.1 0.050

18:0 3.7 � 0.3a 3.7 � 0.4b 4.0 � 0.3b 4.0 � 0.4b 4.0 � 0.3b 0.050

20:0 0.2 � 0.1 0.2 � 0.1 0.2 � 0.1 0.2 � 0.1 0.2 � 0.1 <0.001

22:0 0.2 � 0.1 0.2 � 0.1 0.1 � 0.1 0.1 � 0.1 0.0 � 0.1 0.010

24:0 0.1 � 0.1 0.1 � 0.1 Tr Tr Tr <0.001

MUFA

14:1n-7 0.1 � 0.1 0.1 � 0.1 Tr Tr Tr <0.001

15:1n-7 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 Tr <0.001

16:1n-9 0.6 � 0.1 0.6 � 0.2 0.5 � 0.2 0.5 � 0.1 0.50 � 0.1 0.050

16:1n-7 2.2 � 0.2 2.3 � 0.3 2.3 � 0.2 2.2 � 0.2 2.30 � 0.3 0.600

16:1n-5 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 0.10 � 0.1 <0.001

17:1n-9 0.2 � 0.1 0.2 � 0.1 0.2 � 0.1 0.2 � 0.1 0.2 � 0.1 <0.001

18:1n-11 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 <0.001

18:1n-9 26.7 � 1.5a 26.6 � 1.7a 26.4 � 1.5a 26.4 � 1.4a 26.0 � 1.5b 0.016

18:1n-7 2.7 � 0.3 2.6 � 0.2 2.9 � 0.3 3.0 � 0.3 2.7 � 0.2 0.500

20:1n-11 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 <0.001

20:1n-9 1.0 � 0.2 0.8 � 0.2 0.9 � 0.1 0.8 � 0.1 0.9 � 0.1 0.500

22:1n-9 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 0.1 � 0.1 <0.001

n–6 PUFA

18:2n-6 34.9 � 2.5a 32.3 � 3.0b 27.5 � 2.9c 25.8 � 3.5d 22.6 � 2.9e 0.009

18:3n-6 1.6 � 0.1a 1.4 � 0.1b 1.2 � 0.2c 1.0 � 0.2d 0.7 � 0.2e <0.001

20:2n-6 1.4 � 0.2a 1.2 � 0.3b 1.1 � 0.2c 0.8 � 0.3d 0.5 � 0.2e 0.002

20:3n-6 0.8 � 0.2a 0.8 � 0.2a 0.6 � 0.1a 0.5 � 0.1b 0.3 � 0.1c 0.006

20:4n-6 (AA) 1.1 � 0.2a 0.9 � 0.1b 0.8 � 0.1c 0.7 � 0.1c 0.5 � 0.1e 0.001

22:2n-6 0.1 � 0.1 Tr Tr Tr Tr <0.001

22:3n-6 0.1 � 0.1 0.1 � 0.1 Tr Tr Tr <0.001

22:4n-6 0.5 � 0.2a 0.5 � 0.2a 0.4 � 0.1a 0.2 � 0.1b 0.1 � 0.1b 0.010

22:5n-6 0.8 � 0.2a 0.6 � 0.1bc 0.5 � 0.1c 0.4 � 0.1c 0.2 � 0.1d 0.001

n–3 PUFA

18:3n-3 (LNA) 1.7 � 0.3a 4.2 � 0.4b 8.8 � 0.5c 10.7 � 0.5d 14.0 � 0.7e <0.001

18:4n-3 0.1 � 0.1a 0.3 � 0.1b 0.5 � 0.1c 0.7 � 0.2d 1.1 � 0.2e 0.001

20:3n-3 0.3 � 0.1a 0.7 � 0.1b 1.1 � 0.1c 1.4 � 0.2d 1.7 � 0.2e <0.001

20:4n-3 0.1 � 0.1a 0.2 � 0.1b 0.3 � 0.1c 0.5 � 0.1d 0.7 � 0.1e 0.002

20:5n-3 (EPA) 0.1 � 0.1a 0.3 � 0.1b 0.4 � 0.1c 0.5 � 0.1d 0.9 � 0.1e 0.009

22:5n-3 0.2 � 0.1a 0.3 � 0.1b 0.4 � 0.1c 0.7 � 0.1d 0.9 � 0.2e 0.004

22:6n-3 (DHA) 0.5 � 0.1a 0.7 � 0.1b 0.9 � 0.2c 1.4 � 0.2d 1.8 � 0.3e 0.003

Sum and ratios p-valuePSFA 21.4 � 0.8 21.3 � 0.8 21.2 � 0.7 21.0 � 0.9 20.6 � 0.7 0.013PMUFA 34.0 � 1.58 33.7 � 1.81 33.7 � 1.58 33.6 � 1.47 33.0 � 1.56 0.035PPUFA 44.3 � 3.2 44.5 � 3.4 44.5 � 3.2 45.3 � 3.2 46.0 � 3.6 0.022PPUFA n-6 41.3 � 3.2a 37.8 � 3.4ab 32.1 � 3.2bc 29.4 � 3.1bc 24.9 � 3.4c <0.001PPUFA n-3 3.0 � 0.4a 6.7 � 0.4b 12.4 � 0.5c 15.9 � 0.9d 21.1 � 1.2e 0.001

n-6/n-3 13.8 � 0.7a 5.6 � 0.6b 2.6 � 0.4c 1.8 � 0.3cd 1.2 � 0.3d 0.048

PUFA/SFA 2.1 � 0.3 2.1 � 0.2 2.1 � 0.3 2.2 � 0.3 2.2 � 0.3 0.057

£ Treatments: A (0.00%), B (1.25%), C (2.50%), D (3.75%), and E (5.00%) of flaxseed oil completed up to 5.00%with sunflower oil. Values

are mean � SD of six replicates. Different letters in the same line are significantly different (p < 0.05) by Tukey’s test. Tr: trace (%

area < 0.1).

272 A. C. Aguiar et al. Eur. J. Lipid Sci. Technol. 2011, 113, 269–274

� 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.ejlst.com

100 g of fish n–3 PUFA, a value lower than that observed for

tilapia’s head subjected to treatment E (2.41 g/100 g) in this

study.

The daily ingestion (EPA þ DHA) of 0.65 g [36] has

been recommended for the prevention of cardiovascular

and inflammatory diseases. The consumption of 100 g of

heads submitted to the treatment E, supplies approximately

50% of the daily ingestion recommended for those fatty acids.

The ingestion of 0.8 to 1.1 g of LNA, a precursor of the

other acids of the family n–3, has also been recommended by

some researchers [37], and this recommendation is achieved

when are consumed of 100 g of heads of the treatments A-E.

4 Conclusion

Feed supplementation with FO improved the nutritive value

of the TL composition of Nile tilapia heads by providing

higher LNA, EPA, and DHA contents, increasing all n–3

fatty acids and decreasing n–6 fatty acid levels. In addition,

the information presented in this study may be used to help

balance n–6/n–3 ratios in dietary supplements, create a val-

uable alternative food source for the human diet and valorize

this part of fish.

The authors have declared no conflict of interest.

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Table 3. Concentration (g/100 g head) of n-3 and n-6 fatty acids for different treatments.

Treatment £

Fatty acids A B C D E p-value

20:4n-6 (AA) 0.10 � 0.02a 0.10 � 0.01ab 0.09 � 0.01ab 0.07 � 0.01bc 0.05 � 0.01c 0.014

18:3n-3 (LNA) 0.15 � 0.03a 0.45 � 0.04b 0.94 � 0.05c 1.15 � 0.05d 1.50 � 0.07e <0.001

20:5n-3 (EPA) 0.01 � 0.01a 0.03 � 0.0ab 0.05 � 0.01cb 0.06 � 0.01c 0.10 � 0.01d 0.003

22:6n-3 (DHA) 0.05 � 0.01a 0.08 � 0.01ab 0.10 � 0.02b 0.16 � 0.02c 0.21 � 0.03d 0.003

S PUFA n-6 4.31 � 0.07a 3.96 � 0.04b 3.66 � 0.05c 3.35 � 0.08d 2.84 � 0.05e 0.030

S PUFA n-3 0.29 � 0.07a 0.76 � 0.1b 1.41 � 0.15c 1.81 � 0.14d 2.41 � 0.2e <0.001

£ Treatments: A (0.00%), B (1.25%), C (2.50%), D (3.75%), and E (5.00%) of flaxseed oil completed up to 5.00%with sunflower oil. Values

are mean � SD of six replicates. Different letters in the same line are significantly different (p < 0.05) by Tukey’s test.

Eur. J. Lipid Sci. Technol. 2011, 113, 269–274 Omega-3 content of tilapia heads fed with flaxseed oil 273

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