HOME > EDICIONES > Año 2007, Volumen 57 - Número 3
Trabajos de Investigación
Effect of flaxseed oil in diet on fatty acid composition in the liver of Nile Tilapia (Oreochromis niloticus)
Ana Carolina Aguiar, Damila Rodrigues Morais, Leandra Pereira Santos, Flavia Braidotti Stevanato,
Jeane Eliete Laguila Visentainer, Nilson Evelázio de Souza and Jesuí Vergilio Visentainer
Universidade Estadual de Maringá. Maringá. Brazil
|
SUMMARY
Effect of flaxseed oil in diet on fatty acid composition in the liver of Nile Tilapia (Oreochromis niloticus)
This study analyzed the effects of different concentrations of flaxseed oil (FO) on the proximate composition and the contents of alpha-linolenic acid (LNA, 18:3n-3), eicosapentaenoic (EPA, 20:5n-3), and docosahexaenoic (DHA, 22:6n-3) fatty acids in the liver of cultured Nile tilapia (Oreochromis niloticus). During the five-month culture period, tilapias were given diets with incremental concentrations of FO (0.00%; 1.25%; 2.50%; 3.75%, and 5.00%) as a replacement of sunflower oil (control). There was no significant difference in moisture and ash content in the liver between treatments. Protein values ranged from 12.1% (treatment II) to 13.9% (treatment V) and total lipids ranged from 5.6% (treatment V) to 7.2% (treatment II). There was no significant difference between most treatments. Fatty acid methyl esters (FAMEs) were quantitatively analyzed by capillary gas chromatography against a C23:0 internal standard. Variations in concentrations (in mg g-1 of total lipids) of fatty acids between treatment I and treatment V ranged from 4.2 to 51.2 (LNA), from 0.2 to 2.3 (EPA), and from 10.6 to 56.2 (DHA), respectively. This experiment demonstrated that increasing amounts of LNA in feed may markedly increase the amounts of LNA, EPA, and DHA in the liver of Nile tilapia.
Key words: Fatty acids, flaxseed oil, composition, liver, Nile tilapia.
RESUMEN
Efecto de la dieta com aceite de linaza sobre la composición de ácidos grasos en el hígado del tilapia de Nilo (Oreochromis niloticus)
Este estudio analiza los efectos de diversas concentraciones del aceite de linaza (AL) en la composición centesimal y el contenido del ácido alfa-linolenico (LNA, 18:3 n-3), eicosapentaenoic (EPA, 20:5 n-3), y (DHA, 22:6 n-3), los ácidos grasos docosahexaenoic en el hígado del tilapia del Nilo (Oreochromis niloticus) criada em cautiverio. Durante un período de cinco meses, a las tilapias le fueron administradas dietas con concentraciones crecientes de AL (0,00%; 1,25%; 2,50%; 3,75%, y 5,00%) como reemplazo del aceite de girasol (control). No se encontró diferencia significativa en el contenido de humedad y de ceniza en el hígado entre los tratamientos. Los valores de la proteina variaron entre 12,1% (tratamiento II) y (al tratamiento 13,9% V) y los lípidos totales entre el 5,6% (tratamiento V) y 7,2% (tratamiento II). No se encontró diferencia significativa entre la mayoría de los tratamientos. Los ésteres metílicos de los ácidos grasos (FAMEs) fueron analizados cuantitativamente por cromatografía de gas capilar contra la CA. 23:0 estándares internos. Las variaciones en concentraciones (en mg g-1 de lípidos totales) de ácidos grasos entre el tratamiento I y el tratamiento V variaron entre 4,2 y 51,2 (LNA), 0,2 y 2,3 (EPA), y 10,6 a 56,2 (DHA), respectivamente. Esto experimento demostró que cantidades crecientes de LNA en la alimentación puede aumentar significativamente las cantidades de LNA, de EPA, y de DHA en el hígado de la tilapia del Nilo.
Palabras clave: Acidos grasos, aceite de la linaza, composición, hígado, tilapia del Nilo.
INTRODUCTION
A freshwater fish, Nile tilapia is widely
distributed and is one of the most commercially cultured species, being the
sixth most cultured finfish species in the world. It is well known for its fast
growth, ability to grow in a wide range of culturing conditions, and its high
consumer acceptability (1).
Recent studies have indicated that some parts of fish not used as food are
appropriate for human nutrition (2) and may be used in oil extraction. Research
has shown the existence of significant concentrations of n-3 polyunsaturated
fatty acids (n-3 PUFA) in viscera (3), heads (4), and liver (5).
The importance of fish as a source of omega-3 polyunsaturated fatty acids (n-3
PUFA) in human nutrition is widely recognized (6, 7). Among these acids, mainly
eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3), as
well as its precursor, alpha linolenic acid (LNA, 18:3n-3) stand out. These
acids are associated to numberless benefits to human health. DHA plays an
important role in the formation, development, and working of the brain and
retina (8). EPA has anti-inflammatory properties (7), and in general contributes
to the prevention of heart diseases and to the reduction of biochemical factors
associated to cancer (9).
Flaxseed oil is one of the word’s most important vegetable sources of LNA
(10), a precursor of the n-3 PUFA series in freshwater fish (11). In a recent
study, n-3 PUFA composition of feeds at supply directly reflected in the
fatty acid composition in Nile tilapia given flaxseed oil, presenting the
highest content of n-3 PUFA in muscle tissue (12).
Considering the few studies related with fatty acid manipulation in fish liver
and alternative sources of n-3 PUFA, this work investigated the incremental
addition of flaxseed oil in substitution of sunflower oil in feed and its
influence on the concentrations of LNA, EPA, and DHA (in mg/g of total lipids)
in liver of Nile tilapia (Oreochromis niloticus) maintained in captivity
for five months.
MATERIALS AND METHODS
Animal and diets
The experiments were carried out in the Aquaculture Laboratory of the
Biology Department of Universidade Estadual de Maringá, Brazil. It utilized 125
Nile tilapia (Oreochromis niloticus) with initial mean individual weights
of 88 ± 6 g distributed in 25 ponds (1000-L water capacity) in five treatments
and five duplications. The treatments consisted of the addition of flaxseed oil
(0%, 1.25%, 2.50%, 3.75%, and 5.00%) in substitution for sunflower oil (control)
in feeds (Table 1). After five months, the fish were slaughtered and the liver
was removed and kept in polyethylene packing (in N2 atmosphere) at -18 °C. At
the beginning of each analysis, the samples were allowed to equilibrate to room
temperature and homogenized.
Proximate composition
Proximate composition of liver and feeds were determined as described by
Cunniff (13). Total lipids (TL) were determined by Bligh & Dyer (14).
Fatty acid composition
Fatty acid methyl esters (FAME) were prepared by methylation of total lipids
by Joseph & Ackman (15). Methyl esters were separated by gas chromatography
using a Varian 3300 (USA) gas chromatographer fitted with a flame ionization
detector (FID) and a fused-silica DB-WAX capillary column
(30 m x 0.25 mm i.d.) (J&W Scientific, Folsom, CA).
The operation parameters were as follows: detector temperature, 280oC; injection
port temperature, 250oC; column temperature, 170oC for 16 min at 2oC/min up
to 210oC with final holding time of 25 min; carrier gas, hydrogen at
0.8 mL/min with linear velocity of 38 cm/s and oxygen filter coupled to the
feed line; make-up gas, nitrogen at 30 mL/min; split injection, 1:50 ratio
(injection in duplicate). For the identification of fatty acids, fatty acid
retention times were compared to those of standard methyl esters (Sigma, St.
Louis, MO). Equivalent chain-length values (ECL) were used (16, 17), as well as
coupled system gas chromatograph-mass spectrometer Shimadzu QP 5000 and electron
impact fragmentation at 70 eV. Retention times and peak area percentages
were automatically computed in a Varian 4290 integrator.
Quantification of LNA, EPA and DHA
The concentration of n-3 series fatty acids, LNA, EPA, and DHA in mg g-1 of
total lipids, in liver was measured against tricosanoic acid methyl ester (23:0)
from Sigma (USA) as an internal standard as described by (15). Theoretical FID
(flame ionization detector) correction factor values (15, 18, 19) were used to
obtain fatty acid concentration values. The following formula was used to
calculate the concentrations:
where LT = total lipid, AX is the peak
area (LNA, EPA, and DHA), AIS is the peak area of the internal standard (IS)
tricosanoic acid methyl ester (23:0), WIS is the weight (mg) of IS added to the
sample (in mg), WX is the sample weight (in mg), CFX is the theoretical
correction factor, and 1.04 is conversion factor necessary to express results as
mg of fatty acids rather than as methyl esters.
Statistics
The values of the means were statistically compared by Tukey test at 5% with
one-way ANOVA. Data were processed using the Statistica software (20).
RESULTS
The experimental FID correction factor values for the LNA
(0.97 ± 0.02), EPA (0.99 ± 0.01), and DHA
(0.98 ± 0.02) were determined experimentally. As the experimental
values were close to the calculated ones, the theoretical corrections factors
(CFX) of LNA (1.01), EPA (0.99), and DHA (0.97) were used to determine
concentrations as recommended by (15, 18).
According (Table 1), there were no significant differences (P > 0.05) in
either total lipids or moisture contents of feeds among the treatments. The
increase in the concentration of LNA acid was well established; values ranged
between 13.6 and 272.4 mg/100 g of feed with a significant difference (P <
0.05) between treatments with flaxseed oil. EPA and DHA were not detected in
feeds. Fatty acids profiles of commercial feeds used in treatment of cultured
species in Brazil presented low values of LNA (3.3%) and high values of LA
-18:2n-6 (38.8%) (21).
TABLE 1
Composition of experimental feeds |
 |
| ATreatments: I (0.00%); II (1.25%); III (2.50%); IV (3.75%) and V (5.00%) of flaxseed oil completed up to 5.00% with sunflower oil. BData are presented as mean (n=9) ± SD. Different letters in the same line are significantly different (P<0.05) by Tukey test. Abbreviations: LNA = alpha linolenic acid. EPA = eicosapentaenoic acid. DHA = docosahexaenoic acid. BHT = butylated hydroxytoluene. Premix = mineral and vitamin supplement. nd = not detected. |
The liver of Nile tilapia (Table 2) did not present any
significant difference between treatments I, III, IV, and V for total lipids and
protein contents. However, treatment II (1.25% flaxseed oil) presented the
largest lipid content (7.2%) and the lowest protein content (12.1%), differing
significantly from other treatments. The values of total lipids and protein in
this experiment were lower than those found by researchers (22), who studied the
liver of juvenile Nile tilapia, with mean values of 10.2% (total lipids) and
14.3% (protein), while total lipid content was higher than those found in the
liver of Atlantic salmon (23). Moisture and ash contents did not vary
significantly (P > 0.05) between treatments, with mean values of 72.5%
(moisture) and 1.1% (ash). These values are close to those determined by (5) in
Nile tilapia, moisture (72.7%) and ash (1.0%).
TABLE 2
Proximate composition (g/100g) and LNA, EPA,
and DHA concentrations (mg g-1LT) in liver |
 |
| ATreatments: I (0.00%); II (1.25%); III (2.50%); IV (3.75%) and V (5.00%) of flaxseed oil completed up to 5.00% with sunflower oil. Data are presented as mean (n=30) ± SD. Different letters in the same line are significantly different (P < 0.05) by Tukey test. Abbreviations: LT = total lipids. LNA = alpha linolenic acid. EPA = eicosapentaenoic acid. DHA = docosahexaenoic acid. |
DISCUSSION
It was observed differences in the protein
concentration and the total lipids between treatments I and II, with an increase
in the lipid concentration and a decrease in the protein concentration. After
these treatments, the concentrations were stabilized.Total lipids (Table 2)
average of 7.8% was larger than 1.1% in fillets (24) and protein average of
13.2% was smaller than 18.0% (25) in fillets of Nile tilapia.
The fatty acid LNA is a precursor of the n-3 PUFA series and only LNA was
present and in increasing amounts in the different feeds of this experiment
(Table 1). In the elongation and desaturation conversions of the series, EPA and
DHA in the liver of Nile tilapia (Table 2) and some LNA were rather stored in
the liver rather than converted. Similar results were obtained in muscular
tissue (26) and visceras (27) of Nile tilapias.
Increases in the concentrations of LNA, EPA, and DHA (in mg g-1 total lipids)
were well established in liver, with a significant difference (P<0.05)
between all the treatments with the incremental substitution of sunflower oil by
flaxseed oil. Therefore, increasing the amounts of LNA in feed can markedly
increase the amounts of EPA and DHA in Nile tilapia liver.
CONCLUSION
There was no significant alteration in the proximate composition, except in
treatments I and II. The increase in the concentration of alpha-linolenic acid
(LNA) in feeds resulted in a gradual increase in fatty acids alpha-linolenic
(LNA), eicosapentaenoic (EPA), and docosahexaenoic (DHA) in all treatments. The
largest concentration of these fatty acids in Nile tilapia liver was obtained
with treatment V (largest level of flaxseed oil).
REFERENCES
- Yasmin A, Takeuchi T, Hayashi M, Hirota T, Ishizuka W, Ishida S. Effect of conjugated linolenic and docosahexaenoic acids on growth of juvenile tilapia Oreochromis niloticus. Fish Sci 2004; 70: 473-481.
- Pessatti ML. Aproveitamento de subprodutos do pescado. Meta 11. Relatório final de ações prioritárias ao desenvolvimento de pesca e aqüicultura no Sul do Brasil, Convênio Ministério da agricultura, pecuária e abastecimento (MAPA), Universidade do Vale do Itajaí, 2001.
- Souza NE, Matsushita M, Franco MRB, Prado IN, Visentainer JV. Composition química, perfil de ácidos graxos e quantificação dos ácidos alpha-linolênico, eicosapentaenóico e docosahexaenóico em vísceras de tilápias (Oreochromis niloticus). Acta Sci Technol 2005; 27: 73-76.
- Moreira AB, Souza NE, Visentainer JV, Matsushita M. Composição de ácidos graxos e teor de lipídios em cabeças de peixes: Matrinxã (B. Cephalus), Piraputanga (B. Microlepis) e Pracanjuba (B. Orbignyanus) criados em diferentes ambientes. Ciênc Tecnol Aliment 2003; 23: 179-183.
- Carapelli R, Matsushita M, Souza NE, Visentainer JV. Fígados de tilápia: composição centesimal e de ácidos graxos. Rev. Nac Carne 2004; 4: 160-161.
- Simopoulos AP, Leaf A, Salem N. Essentiality andrecommended dietary intakes for omega-6 and omega-3 fatty acids. Ann. Nutr Metabol 1999; 43: 127-130.
- Simopoulos AP. Omega-6/omega-3 essential fatty acid ratio and chronic diseases. Food Rev Int 2004; 20: 77-90.
- Sangiovanni JP, Chew EY. The role of omega-3 long chain polyunsaturated fatty acids in heath and disease of the retina. Progr Retin Eye Res 2005; 24: 87-138.
- Kimura Y, Takaku T, Nakajima S, Okuda H. Effects of carp and tuna oils on 5-fluorouracil-induced antitumor activity and side effects in sarcoma 180-bearing mice. Lipids 2001; 36: 353-359.
- Wanasundara JPD, Shahidi F. Alkanol-amonia-water/hexane extraction of flaxseed. Food Chem 1994; 49: 39-44.
- Hendersom RJ, Tocher DR. Fatty acid metabolism in freshwater fish with particular reference to polyunsaturated fatty acids. Arch. Anim. Nutr 1996; 49: 5-22.
- Justi KC, Hayashi C, Visentainer JV, Souza NE, Matsushita M. The influence of feed supply time on the fatty acid profile of Nile tilapia (Oreochromis niloticus) fed on a diet enriched with n-3 fatty acids. Food Chem 2003; 80: 480-493.
- Cunniff PA. (Ed.). Official Methods of Analysis of AOAC International. 16th ed. Arlington: Association of Official Analytical Chemists. 1998.
- Bligh FG, Dyer WJ. A rapid method of total lipid extraction and purification. Can. J. Bioch and Physiol 1959; 37: 911-917.
- Joseph JD, Ackman RG. Capillary column gas chromatography method for analysis of encapsulated fish oil and fish oil ethyl esters: collaborative study. J AOAC Intern 1992; 75: 488-506.
- Thompson RH. A simplified fatty acid analyses in multicomponent foods with a standard set of isothermal GLC conditions couplet with ECL determinations. J. Chrom Sci 1996; 34: 495-504.
- Strànsky K, Jursík T, Vitek A. Standard equivalent chain length values of monoenic and polyenic (methylene interrupted) fatty acids. J. High Res Chrom 1997; 20: 143-158.
- Bannon CD, Craske JD, Hilliker AE. Analysis of fatty acid methyl ester with high accuracy and reliability. Validation of theoretical relative response factors of unsaturated ester in the flame ionization detector. J. Am Oil Chem Soc 1986; 63: 105-110.
- Visentainer JV, Franco MRB. Ácidos Graxos em óleos e gorduras: Identificação e Quantificação, 1 ed. Varela: São Paulo, Brasil, 2006.
- Statsoft. Statistica 5.1 Software. Tucksa: Statsoft. 1996.
- Moreira AB, Souza NE, Visentainer JV, Matsushita M. Fatty acids profile and cholesterol of three Brazilian brycon freswater fish. J Food Comp Anal 2001; 14: 565-574.
- Visentainer JV, Gomes STM, Silva ABM, Santos-Junior OO, Justi KC, Souza NE, Hayashi C, Matsushita M. Composição físico-química e perfil de ácidos graxos em fígados de tilápias (Oreochromis niloticus) submetidas ao fornecimento de rações diferenciadas à base de óleos de girassol e linhaça. Ann Ass Bras Quim 2003; 51: 18-21.
- Jordal AEO, Lie O. Torstensen BE. Complete replacement of dietary fish oil with a vegetable oil blend affect liverlipid and plasma lipoprotein levels in Atlantic salmon (Salmo salar L.). Aquaculture Nutr 2007; 13: 114-130.
- Visentainer, JV, Souza, NE, Matsushita, M, Hayashi, C, Franco, MRB. Infuence of diets enriched with flaxseed oil on the alfa-linolenic (LNA), eicospentaenoic (EPA) and docosahexaenoic (DHA) fatty acids in Nile tilapia (Oreochromis niloticus). Food Chem 2005, 90:557-560.
- Justi, KC, Padre, RG, Hayashi, C, Soares, CM, Visentainer, JV, Souza, NE, Matsushita, M. Efeito da temperatura da água sobre desempenho e perfil de ácidos graxos de tilapia do Nilo (Oreochomis niloticus. Acta Scientiarium 2005, 24:529-534.
- Souza, ES, Matsushita, M, Oliveira, CC, Franco, MRB, Visentainer, JV. Manipulation of fatty acid composition Nile tilapia (Oreochromis niloticus) fillets with flaxseed oil. J Sci Food Agri 2007, 87:1677-1681.
- Visentainer, JV, Matsushita, M, Souza, NE, Prado, IN, Franco, MRB. Composiçao química de ácidos graxos e quantificação dos ácidos alfa-linolenico, eicosapentaenoico e docosahexaenoico em vísceras de tilapias (Oreochromis niloticus. Acta Scientiarium 2005, 27:73-76.
Recibido: 31/08/2007
Aceptado: 04/10/2007
 |
PRIVACIDAD | ACCESIBILIDAD
ALAN-VE ISSN 0004-0622 - Depósito Legal: pp 199602DF83
Sociedad Latinoamericana de Nutrición
Producción editorial en Venezuela: Capítulo Venezolano - RIF: J-30843129-0
Urbanización Santa María, primera transversal, No. 417-214, Planta Alta
Tele-Fax: (+58-212) 283.8618
E-mail info@alanrevista.org
Código Postal: 1070
Caracas - Venezuela |
|
|
Ir al principio