Originl Article Fish Aqut Sci 16(2), 85-92, 2013 Comprison of Mjor Nutrients in Eels Anguill jponic Cultured with Different Formul Feeds or t Different Frms Je-Sung Seo 1, Je-Hee Choi 2, Ji-Hun Seo 2, Te-Ho Ahn 3, Won-Seog Chong 4, Seung-Hoon Kim 4, Hye-Sun Cho 5 * nd Jun-Cheul Ahn 1,4 * 1 Deprtment of Biologicl Sciences, Seonm University, Nmwon 590-711, Kore 2 Deprtment of Aqulife Scinence, Chonnm Ntionl University, Yeosu 550-749, Kore 3 Deprtment of Biochemistry, College of Medicine, Seonm University, Nmwon 590-711, Kore 4 Deprtment of Phrmcology, College of Medicine, Seonm University, Nmwon 590-711, Kore 5 Plnt Systems Engineering Reserch Center, Kore Reserch Institute of Biosciences nd Biotechnology, Dejeon 305-806, Kore Abstrct To determine the reltive importnce of two min fctors, diet or culture environment, tht ffect the proximte composition nd min nutritive ingredients (vitmin A, vitmin E, cholesterol, ftty cid composition) in cultured eels, we nlyzed the composition of eels fed diets of formul feed (FF) produced by four different compnies nd of eels cultured t five different eel frms tht provided only one of the four different FFs. The four commercil eel FFs did not mrkedly differ in proximte composition or mjor nutritive compounds, nd consequently, these vribles did not significntly differ in cultured eels fed the different FFs. The FF imported from Jpn ws mrginlly superior to the two domestic commercil FFs nd the FF imported from Tiwn in terms of the proximte composition nd min nutritive ingredients of both the FF itself nd the eels cultured on it. However, proximte composition nd min nutritive ingredients significntly differed mong eels cultured t the five frms tht used different FF nd mong eels fed the four different FFs t the sme frm. In conclusion, the difference in qulity between domestic nd Jpnese FFs in terms of eel culture ws smll, wheres physicl or chemicl environmentl differences mong frms during eel culture my more strongly ffect the proximte composition nd levels of the min nutritive ingredients in cultured eels. Key words: Anguill jponic, Vitmin A, Vitmin E, Cholesterol, Ftty cids Introduction Anguill includes 19 species of eel distributed worldwide. Among these, the Jpnese eel Anguill jponic nd Europen eel Anguill nguill re populr helth foods in southest Asi (minly Jpn, Kore, Tiwn, nd Chin) nd Europen countries (minly Itly nd Netherlnds), respectively, s these species re rich in protein, ft, minerls, nd vitmins compred to other fish species. In ddition, these eels re common freshwter fish tht hve been cultured for very long time (Lio, 2002). The eel quculture industry in these countries hs been growing every yer; for exmple, in Kore, production incresed from 2,739 tons in 2000 to 6,766 tons in 2009 (Son et l., 2011). Eels re ctdromous species tht htch in the se but migrte s elvers (pre-juveniles) to freshwter to grow to dulthood. Artificil eel-spwning nd even quculture of the complete life cycle hve been conducted, nd some experimentl efforts hve been successful (Oht nd Tnk, 1997; Oht et l., 1997; Kim et l., 2007; Kgw et l., 2009). However, Open Access http://dx.doi.org/10.5657/fas.2013.0085 This is n Open Access rticle distributed under the terms of the Cretive Commons Attribution Non-Commercil License (http://cretivecommons. org/licenses/by-nc/3.0/) which permits unrestricted non-commercil use, distribution, nd reproduction in ny medium, provided the originl work is properly cited. pissn: 2234-1749 eissn: 2234-1757 Copyright The Koren Society of Fisheries nd Aqutic Science 85 Received 5 Februry 2013; Revised 5 Mrch 2013 Accepted 12 Mrch 2013 *Corresponding Author E-mil: secmet2@yhoo.com (J.C. Ahn) hscho@kribb.re.kr (H.S. Cho) http://e-fs.org
Fish Aqut Sci 16(2), 85-92, 2013 the supply of elvers for quculture still depends on nturl resources which is the principl restriction on the volume of eel culture. In ddition, elver rrest, especilly in A. jponic, is not constnt every yer, nd the number of elvers hs been drsticlly reduced due to indiscriminte ctching. As n lterntive, the Atlntic eel A. nguill hs been cultured t severl frms in Jpn, Kore, nd Chin, but the results hve so fr been less thn stisfctory becuse of disese nd nutritionl problems. In ddition to price increses for A. jponic elvers, overll chnges to eel culture, such s increses in the cost of rw mterils for formul feeds (FFs), lbor costs, nd vrious expenses, hve mintined constnt pressure on eel frmers. In response, reserchers hve exmined the use of FFs with no or reduced mounts of fish mel; how to lower the mortlity rte; the development of functionl feed dditives; the ppliction of high-density culture; nd the reltionships between rering tnk size nd stocking density, between body weight nd stocking density, nd between body weight nd dily feeding rte (Be et l., 2008; Choi et l., 2008; Kim et l., 2008; Hwng et l., 2010; Son et l., 2011). We previously reported tht the mjor nutrients (vitmins A nd E, cholesterol, nd ftty cid composition) of A. jponic eels cultured in Kore differ cross frms. We lso suggested tht differences in FFs or in the physiochemicl culture environments used t ech frm my ffect the nutritionl content of eels (Cho et l., 2011). In the present study, we evluted the reltive importnce of these two min fctors (feeding diet nd physiochemicl culture environment) for the ccumultion of mjor nutrients in cultured eels. Mterils nd Methods Eels nd culture conditions Eels A. jponic (bout 300-350 g) were provided by five commercil eel quculture frms locted in Jeollnm-do nd Jeollbuk-do, Kore; ech frm uses n FF from different compny. From ech frm, three eels were rndomly selected, nd only fresh eel met, excluding the hed, bone, nd innrds, ws used for nlysis. Eels for nlysis were collected from ech frm on 20 Jnury 2011. We did not consider differences in elver stocking time, physiochemicl conditions for culture, or culture period. In experiments to compre growth rtes nd specific nutrient contents (proximte composition, vitmins A nd E, cholesterol, nd ftty cids) of eels on diets of vrious commercil FFs (two domesticlly produced brnds, one domestic brnd produced by originl equipment mnufcturing in Jpn, nd one Tiwnese brnd), 1 kg worth of eels (20-30 g ech) were trnsferred to wter tnk (1 ton) instlled t Chenogsn Eel Frm Co. (Yeonggwng, Kore). The eels were fed 1.5-2.0% of their body weight in FF per dy for 5 weeks, nd their weight gin ws mesured. The entire eel body ws used for nlysis. In the feeding experiments to mesure weight gin, feed remining 30 min fter feeding ws recovered nd stored in the freezer; fter it ws dry, the feed ws weighed, nd tht weight ws subtrcted from the totl feed weight. Anlysis of generl compounds The proximte composition of generl compounds (wter content, crude protein, crude lipids, nd sh) contined in cultured eels ws nlyzed using Assocition of Officil Anlyticl Chemists methods (1995). Wter nd ft contents were mesured using CEM utomtic extrctor (Lbwve 9000/ FAS 9001; CEM Corp., Mtthews, NC, USA). Protein ws nlyzed using Kjeltec System (Kjeltec Auto 2400/2460; Foss Tector AB, Högns, Sweden), nd sh ws mesured using n sh nlyzer (Ms 7000; CEM Corp.). In ddition, the proximte composition of vrious dult eel FFs tht were on sle in October 2011 were lso determined using the bove methods. Anlysis of vitmin A nd E For nlyses of vitmins A (V A ) nd E (V E ), 0.5 g freezedried smple, 3 ml 95% ethnol (EtOH), nd 0.5 m 10% pyrogllol/etoh were dded to test tube nd mixed well. Then 1 ml 50% KOH solution ws dded to the tube, nd the smple ws sponified in 95 C wter bth for 30 min nd cooled rpidly on ice. Then we mixed in 3 ml distilled wter nd petroleum ether (v/v), fter which only the petroleum ether lyer ws collected. This step ws repeted three times. The resulting solution ws filtered using nhydrous N 2 SO 4 to remove moisture nd then evported using rotry evportor. The concentrte ws dissolved in 1 ml isopropyl lcohol for V A nlysis or in 1 ml hexne for V E. After filtrtion through 0.2 μm membrne filter, the solution underwent HPLC nlysis for vitmin content using n HPLC column (μ-porsil, 4.6 250 nm; Wters, Milford, MA, USA) nd n- hexne:isopropnol (99.92:0.08, v/v, isocrtic mode) s the mobile phse. The flow rte ws 1 ml/min. Detection ws conducted t 336 nm for V A nd t 280 nm for V E, using UV/ VIS detector (Model 2489; Wters). Anlysis of cholesterol One grm of freeze-dried smple nd 3 ml 95% EtOH were dded to test tube nd extrcted using soniction for 30 min. Subsequently, 1 ml 50% KOHA ws dded to the tube, nd the solution ws incubted in 50 C wter bth for 1 h nd then cooled rpidly on ice. Next, 5 ml hexne ws dded to the solution, nd fter mixing for 5 min, 1 ml of the upper lyer (orgnic lyer) ws removed nd evported to dryness using N 2 gs. Then we dded 3 ml Liebermnn-Burchrd regent, nd the smple ws vortexed nd plced t room temperture for 30 min. Then the bsorbnce ws mesured t http://dx.doi.org/10.5657/fas.2013.0085 86
Seo et l. (2013) Comprison of Mjor Nutrients in Frmed Eels 640 nm. Anlysis of ftty cids Extrctions for ftty cid nlysis followed the procedure of Folch et l. (1957), nd the extrct ws methylted ccording to Morrison nd Smith s method (1964). The superntnt of methylted extrct ws removed nd stored t -80 C. The nlysis ws conducted using gs chromtogrph equipped with n utoinjector (Vrin 3400; Vrin, Oshw, ON, Cnd). The instrumentl conditions re described in Cho et l. (2011). types of FFs (Tbles 1 nd 2). The proximte composition of dult eel FFs ws lso determined (Tble 1). Moisture content rnged from 5.92% (K Co. FF) to 7.43% (C Co. FF). Crude protein levels, min fctor determining both eel growth nd the feed efficiency of n FF, did not significntly differ cross the four FFs, rnging from 45.5% (T Co. FF) to 49.47% (C Co. FF). The protein requirements of eels depend on size nd species, but protein content must be pproximtely 45-50% (Ari et l., 1971; Nose nd Ari, 1973; Degni et l., 1985; Hn et l., 2005). Crude lipids, which contin essentil ftty cids needed for the norml growth nd survivl of fish, rnged from 5.5% (C Co. FF) to Sttisticl nlysis All mesurements were performed in triplicte. The results of ll mesurements re expressed s mens ± SD. If necessry, results were nlyzed using one-wy ANOVA with 95% confidence level. Results nd Discussion We reported previously tht the mjor nutritionl ingredients in cultured eels significntly vried cross eel frms (Cho et l., 2011). To determine the mechnism driving this result, we must first exmine the extent to which differences in FFs or in physicl/chemicl conditions mong frms ffect the min nutritionl content of eels. Five different eel frms, ech using just one of four FFs from different compnies to feed mture eels, were selected for nlyzing the levels of V A, V E, cholesterol, nd ftty cids in mture eels (bout 300-350 g) t ech frm. In ddition, for comprtive evlution mong FFs under the sme environmentl conditions, 15 1-ton tnks were instlled t Frm A (in Yeonggwng-gun, Jeollnm-do, Kore), nd the bove ingredients were nlyzed fter feeding eels (25-30 g) ech FF for 6 weeks. The proximte composition of nutrients (i.e., wter content, crude protein, crude lipids, sh, clcium, phosphorous, nd crude fiber) must be determined to register FFs for fish in Kore (Sttute Book for Feed Mngement, 2002). The contents of severl min nutritionl ingredients ((VA, VE, nd ftty cids) of eels were determined for eels fed the four different Tble 2. The comprison of ftty cids compositions between four different formul feeds for mture eel culture Ftty cids Formul feed compnies * (crbon No. : double bond) K P T C Sturtes 38.79 35.93 35.43 34.68 Myristic cid (C14:0) 06.72 05.83 05.50 05.32 Plmitic cid (C16:0) 24.81 23.29 22.87 21.78 Steric cid (C18:0) 07.26 06.81 07.06 07.58 Monoenes 28.21 30.52 31.06 29.10 Plmitoleic cid (C16:1n7) 07.13 06.77 06.70 05.89 Vccenic cid (C18:1n7) 03.45 04.08 03.34 03.69 Oleic cid (C18:1n9) 15.08 16.31 18.46 16.39 Eicosenoic cid (C20:1n9) 02.55 03.36 02.56 03.13 Highly unsturtes (n-6) 04.13 02.26 07.93 01.83 Linoleic cid (C18:2n6) 01.98 00.67 05.39 00.31 Docostetrenoic cid (C22:4n6) Archidonic cid (C20:4n6) 00.23 00.21 00.37 00.20 01.92 01.38 02.17 01.32 Highly unsturtes (n-3) 28.48 28.96 25.28 32.60 Linolenic cid (C18:3n3) 00.57 00.67 01.13 00.60 Eicospentenoic cid (C20:5n3) Docoshexenoiccid (C22:6n3) 09.85 11.53 08.42 11.14 18.06 16.76 15.73 20.86 * K nd P compnies produce their own formul feed-products nd T nd C compnies produce products with the rw formul feed-mterils imported from Jpn nd Tiwn, respectively. Vlues re men of pplicble % ftty cid contents. Tble 1. The comprison of proximte compositions between four different formul feeds for mture eel culture Formul feed compnies * Moisture Crude protein Crude lipid Ash Crude fiber Clorie (cl/g) Clcium Phosphorus K 5.92 46.24 6.51 14.05 0.08 4,393 3.67 2.30 P 5.98 47.09 4.67 14.37 0.10 4,393 3.94 2.11 T 6.03 45.50 4.65 14.16 0.06 4,379 3.63 2.26 C 7.42 49.47 5.50 12.18 0.11 4,495 2.82 2.09 * K nd P compnies produce their own formul feed-products nd T nd C compnies produce products with the rw formul feed-mterils imported from Jpn nd Tiwn, respectively. 87 http://e-fs.org
Fish Aqut Sci 16(2), 85-92, 2013 6.51% (K Co. FF). Ash nd crude fiber contents rnged from 0.11% (C Co. FF) to 14.37% (P Co. FF) nd from 0.08% (K Co. FF) to 12.18% (C Co. FF), respectively, nd these vribles did not significntly differ mong the tested FFs. Clories rnged from 4,379 cl/g (T Co. FF) to 4495 cl/g (C Co. FF), clcium content rnged from 2.82% (C Co. FF) to 3.67% (K Co. FF), nd phosphorous content rnged from 2.11% (C Co. FF) to 2.3% (K Co. FF). Becuse the ftty cid composition of FFs hs been shown to ffect the growth nd ftty cid composition of cultured eels (Tkeuchi et l., 1980; Be et l., 2004), the ftty cid composition of the four FFs ws lso nlyzed. Sturted ftty cids (SFA) nd monounsturted ftty cids (MUFA) did not differ mong the four FFs. In contrst, the highly unsturted ftty cid (HUFA) ω-6 HUFA rnged from 1.83% (C Co. FF) to 7.93% (T Co. FF), nd ω-3 HUFA levels were highest in C Co. FF (32.6%) nd lowest in T Co. FF (25.28%). These differences my hve been cused by differences in the type of fish mel or oil used s feed dditives. For the eels fed the four different FFs t the sme eel frm, the proximte composition nlysis reveled no significnt differences in moisture (67.5 ± 1.0% to 68.7 ± 0.8%), crude protein (16.7 ± 0.5% to 17.2 ± 0.1%), crude lipids (10.9 ± 0.6% to 11.5 ± 0.8%), or sh (1.1 ± 0.1% to 1.2 ± 0.1%), suggesting tht lthough the proximte composition did vry somewht mong FFs nd between domestic nd imported FFs, these differences were not lrge enough to ffect the qulity or proximte composition of cultured eels. In contrst, the results from eels cultured t the five different frms were mrkedly different. Across the five frms, moisture content of the eels rnged from 62.8 ± 3.2% (Frm B, K Co. FF) to 67.8 ± 2.0% (Frm C, P Co. FF), but vlues did not significntly differ mong frms. Crude protein levels were lower in eels from Frm B (16.6 ± 0.7%), but the vlues from the other frms were similr (bout 17.5%). Crude lipids in cultured eels significntly differed cross frms; eels from Frm B hd the highest crude lipid content (K Co. FF, 19.4 ± 0.7%), where- s those from Frm C hd the lowest crude lipid content (P Co. FF, 14.0 ± 0.5%). Ash content did not significntly differ cross either the four FFs or the five frms (Tble 3). Becuse the difference between domestic FF brnds ws not significnt, the effect on the proximte composition of eels ws not expected to be significnt. However, becuse the proximte compositions of eels from frms tht used different FF brnds did significntly differ, differences in the physicl or chemicl environments of ech frm likely strongly ffected the mjor proximte composition of cultured eels. The V A content of wild mture eels is typiclly 1 mg/100 g dry weight (wt; bout 3,500 IU), lthough vlues vry depending on the species nd tissue nlyzed. In ddition, V A levels tend to increse with the ge nd size of fish (Edisbury et l., 1937; Cho et l., 2006). V A content differed mong the four FFs, but vlues were very low compred to those in eels (dt not shown). V A content differed mong eels fed the four different FFs; vlues were highest in those fed C Co. FF (1.76 ± 0.3 mg/100 g dry wt) nd lowest in those fed P Co. FF (0.92 ± 0.25 mg/100 g dry wt), indicting tht V A content my be somewht correlted with the content in FFs. Across the five frms tht used different FFs, differences in V A content were more remrkble, being highest (1.3 ± 0.25 mg/100 g dry wt) in eels from Frm C (P Co. FF) nd lowest (0.42 ± 0.2 mg/100 g dry wt) in those from Frm E (T Co. FF) (Fig. 1). The differences in eel V A content mong FFs nd mong frms were not significnt, suggesting tht differences in culture techniques or culture environments more strongly ffect the V A content of eels compred to vrition in V A content of different FFs. V E (α-tocopherol) content ws compred in the sme smples s described bove for V A (Fig. 2). Tocopherol in cultured eels is composed of primrily the α-type nd smll mounts of the β- nd γ-types (Cho et l. 2011). V E levels in wild eels re 4-7 mg/100 g dry wt, nd the content of cultured eel muscle in Jpn is 21-37 mg/100 g dry wt, which serves s n indictor of the qulity of cultured eel (Furuit et l., 2009). Compred Tble 3. The comprison of proximte compositions between eels fed with four different formul feeds for mture eels nd between eels cultured t 5 different eel frms where eels fed with one of the four different formul feeds Eel frms * Formul feed Moisture Crude protein Crude lipid Ash compnies A K 64.75 ± 1.22 17.52 ± 0.70 16.49 ± 0.89 1.12 ± 0.07 B K 62.83 ± 3.15 16.60 ± 0.66 19.44 ± 0.72 1.22 ± 0.04 C P 67.76 ± 2.01 17.70 ± 0.47 14.00 ± 0.54 1.26 ± 0.04 D T 65.29 ± 3.24 17.65 ± 0.96 16.23 ± 0.72 1.03 ± 0.06 E C 63.30 ± 1.42 17.44 ± 0.29 18.61 ± 0.89 1.24 ± 0.14 A K 68.68 ± 0.79 16.73 ± 0.46 11.24 ± 1.39 1.14 ± 0.06 A P 68.04 ± 0.47 17.24 ± 0.08 11.42 ± 0.60 1.23 ± 0.05 A T 68.63 ± 0.50 17.14 ± 0.19 10.85 ± 0.55 1.17 ± 0.10 A C 67.54 ± 0.97 17.10 ± 0.46 11.45 ± 0.80 1.20 ± 0.07 * Five different eel frms where eels were cultured using different formul feeds. Loctions of ech frm re s follows. A, Jeollnm-do, Yeongm-gun; B-D, Jeollbuk-do, Gochng-gun; E nd F, Jeollnm-do, Yeonggwng-gun, Four different formul foods which re produced from different compnies, K nd P compnies re produced domesticlly nd T nd C compnies supply the formul feeds imported from Jpn nd Twin, respectively. http://dx.doi.org/10.5657/fas.2013.0085 88
Seo et l. (2013) Comprison of Mjor Nutrients in Frmed Eels 2,400 250 Vitmin A (μg/100g, dry wt) 2,000 1,600 1,200 800 400 cd cd cd cd c c c b Cholesterole (mg/100g, dry wt) 200 150 100 50 b b 0 A(K) B(K) C(P) D(T) E(K+C) (K) (P) (T) (C) 0 A(K) B(K) C(P) D(T) E(K+C) (K) (P) (T) (C) A A Fig. 1. The comprison of vitmin A contents between eels tht cultured t severl eel frms where different formul feeds were fed, nd between eels tht cultured t sme eel frm where different formul feeds were fed. Letters outside brckets men eel frms nd letters inside brckets men formul feed. Loctions of ech frm re s follows. A, Jeollnm-do, Yeongm-gun; B-D, Jeollbuk-do, Gochng-gun; E nd F, Jeollnm-do, Yeonggwng-gun. K nd P re goods produced domesticlly nd T nd C re formul feed imported from Jpn nd Tiwn compny, respectively. All dt re expressed s men ± SE. Different letters indictes significnt differences (P < 0.05) between the groups. Fig. 3. The comprison cholestrol contents between eels tht cultured t severl eel frms where different formul feeds were fed, nd between eels tht cultured t sme eel frm where different formul feeds were fed. Letters outside brckets men eel frms nd letters inside brckets men formul feed. Loctions of ech frm re s follows. A, Jeollnm-do, Yeongm-gun; B-D, Jeollbuk-do, Gochng-gun; E nd F, Jeollnm-do, Yeonggwng-gun. K nd P re goods produced domesticlly nd T nd C re formul feed imported from Jpn nd Tiwn compny, respectively. All dt re expressed s men ± SE. Different letters indictes significnt differences (P < 0.05) between the groups. 8 Vitmin E (mg/100g, dry wt) 7 6 5 4 3 2 1 0 c b to eels fed ech of the four FFs, those fed the C Co. product hd the highest V E levels (1.47 ± 0.5 mg/100 g dry wt), wheres those fed the P Co. product hd the lowest (0.15 ± 0.1 mg/100 g dry wt); however, overll vlues were not high compred to the content in cultured eels. In eels cultured t the five different frms, those from Frm C hd the highest content (5.5 ± 2.3 mg/100 g dry wt), while eels from the other frms rnged from 1.6 ± 1.0 to 0.42 ± 0.2 mg/100 g dry wt. Bsed on A(K) B(K) C(P) D(T) E(K+C) (K) (P) (T) (C) Fig. 2. The comprison of vitmin E (tocopherol) contents between eels tht cultured t severl eel frms where different formul feeds were fed, nd between eels tht cultured t sme eel frm where different formul feeds were fed. Letters outside brckets men eel frms nd letters inside brckets men formul feed. Loctions of ech frm re s follows. A, Jeollnm-do, Yeongm-gun; B-D, Jeollbuk-do, Gochng-gun; E nd F, Jeollnm-do, Yeonggwng-gun. K nd P re goods produced domesticlly nd T nd C re formul feed imported from Jpn nd Tiwn compny, respectively. All dt re expressed s men ± SE. Different letters indictes significnt differences (P < 0.05) between the groups. b A b b these results, differences in V E levels mong commercil FFs ppered to ffect the V E content of cultured eels. Moreover, the environmentl differences in cultures cross frms lso ffected V E content. In summry, the ft-soluble V A nd V E contents in fresh eel vried depending on the commercil FF used. Vitmin levels were much more strongly ffected by the culture environment, including differences in wter purity, the types of microorgnisms present, nd whether vitmin supplements were dministered. In n experimentl system, Burgos et l. (1990) demonstrted tht cholesterol, mjor nutritive component of eels, constituted nerly 7.5% of totl lipids in the liver nd bout 1% in the muscle of control eels. Cholesterol content in fish ws proportionl to the mount of lipids, nd lipid content ws ffected by vrious environmentl (diet, seson, wter temperture) nd biologicl fctors (ge, sex, size). However, these fctors do not necessrily led to significnt chnges in protein nd sh contents (Jeong et l., 1998). Thus, we determined whether cholesterol content vried cross cultured eels fed different FFs nd mong eels cultured t different eel frms. For eels fed one of the four FFs under the sme culture conditions (i.e., t the sme frm), cholesterol content rnged from 172 ± 10 mg/100 g dry wt to 159 ± 3 mg/100 g dry wt nd did not significntly differ mong FF types, which ws consistent with the lck of significnt difference in the crude lipid content of eels fed the different FFs (Tble 2). However, similr to the results for V A nd V E contents, cholesterol content significntly differed for eels cultured t the five different frms; the highest content ws 198.6 ± 3.4 mg/100 g dry wt t Frm A (K Co. FF), nd the lowest content ws 131.4 ± 6.8 mg/100 g dry wt t Frm C (P Co. FF) (Fig. 3). However, 89 http://e-fs.org
Fish Aqut Sci 16(2), 85-92, 2013 these differences did not pper to be correlted with the type of FF nd were likely relted to the frm itself, i.e., the eel culture environment. Although the cholesterol content nd ftty cid content of eels differed cross the five different frms, the lower levels of cholesterol nd ftty cids in Frm C eels re likely relted to ech other. The SFA, MUFA, nd HUFA of cultured eel flesh/whole body eel were compred (Tble 4). SFA nd MUFA did not significntly differ cross eels fed different FFs, wheres ω-6 HUFA did significntly vry mong FFs. Vlues of ω-6 HUFA in eels fed K Co., P Co., C Co., nd T Co. FFs were 1.60 ± 0.1%, 1.41 ± 0.2%, 1.13 ± 0.2%, nd 1.08 ± 0.1%, respectively, wheres the vlues of ω-3 HUFA in eels t the sme frms/ FFs were 8.38 ± 0.6%, 8.0 ± 0.52%, 8.27 ± 0.29%, nd 7.81 ± 0.55%; however, ω-3 HUFA did not significntly differ cross frms (P > 0.05). Of the ω-3 HUFAs tht hve nutritionl implictions, eicospentenoic cid (EPA) did not significntly differ mong eels fed different FFs, except for slightly lower levels (1.48 ± 0.1%) in those fed T Co. FF. Docoshexenoic cid (DHA) levels rnged from 6.48% to 6.02% nd did not significntly vry mong eels fed different FFs. Be et l. (2004) reported tht the dietry ddition of EPA or DHA in young eel cultures did not ffect the growth of eels or the EPA or DHA content, lthough the rtio of linoleic cid (n-6) to linolenic cid (n-3) in eel food did ffect the composition of ftty cids. However, s shown in the present study (Tbles 2 nd 4), the differences in HUFA content mong FFs did not significntly ffect the composition of ftty cids in mid-sized eel cultures. In fct, previous studies hve reported tht the composition of ftty cids is lso ffected by lck of food or non-nutritionl fctors including wter temperture (Wtnbe et l., 1983; Stoh et l., 1984; Bell et l., 1986). Similr to V A, V E, nd cholesterol, the levels of some ftty cids significntly vried cross eels cultured t different frms. SFA rnged from 32.7 ± 1.6% (Frm C, P Co. FF) nd 32.6 ± 1.2% (Frm D, S Co. FF) to 29.0 ± 1.4% (Frm A, K Co. FF) nd 28.0 ± 0.6% (Frm B, K Co. FF). MUFA ws highest t Frm B (63.2 ± 1.8%) nd lowest t Frm C (52 ± 5.0%) nd significntly differed cross eels cultured t different frms. ω-6 HUFA nd ω-3 HUFA lso significntly vried mong frms, with the highest vlues t Frm C (4.77 ± 4.3% nd 10.1 ± 2.9%, respectively) nd the lowest vlues t Frm B (1.5 ± 0.1% nd 7.31 ± 0.6%, respectively). Of the ω-3 HUFAs, EPA rnged from highest to lowest t Frm A (2.11 ± 0.2%), Frm D (2.03 ± 0.1%), Frm B (1.71 ± 0.2%), nd Frm C (1.55 ± 1.1%), wheres DHA exhibited vlues in the following order: Frm C (8.26 ± 1.7%), Frm D (6.43 ± 0.4%), Frm A (6.25 ± 0.3%), nd Frm B (5.45 ± 0.4%). Tble 4. The ftty cids compositions in totl lipids of eels fed with four different formul feeds for mture eels nd between eels cultured t the five different eel frms where eels fed with one of the four different formul feeds Ftty cids (crbon No. : double bond) Eel frms * (formul food compnies) A(K) B(K) C(P) D(T) B(C+K) A(K) A(P) A(T) A(C) Sturtes 29.0 ± 1.4 28.0 ± 0.6 32.69 ± 1.6 32.6 ± 1.2 32.8 ± 0.9 31.7 ± 0.6 32.5 ± 1.4 32.0 ± 1.2 32.7 ± 1.6 Myristic cid (C14:0) 3.16 ± 0.0 3.31 ± 0.1 3.96 ± 0.3 3.34 ± 0.2 3.36 ± 0.3 4.24 ± 0.1 3.97 ± 0.0 4.03 ± 0.2 3.7 ± 0.3 Plmitic cid (C16:0) 20.6 ± 0.9 20.4 ± 0.2 22.8 ± 0.5 23.4 ± 0.5 23.5 ± 0.4 23.3 ± 0.2 24.4 ± 0.9 24.1 ± 0.5 24.4 ± 0.5 Steric cid (C18:0) 5.22 ± 0.5 4.30 ± 0.3 5.92 ± 0.8 5.78 ± 0.5 5.95 ± 0.2 4.20 ± 0.3 4.13 ± 0.5 4.00 ± 0.5 4.55 ± 0.8 Monoenes 61.0 ± 1.7 63.2 ± 1.8 52.2 ± 5.0 57.2 ± 2.6 52.3 ± 1.2 58.2 ± 1.8 58.0 ± 1.7 57.8 ± 2.6 53.7 ± 5.0 Plmitoleic cid (C16:1n7) 7.01 ± 0.2 8.13 ± 0.5 7.26 ± 0.7 7.25 ± 0.8 5.95 ± 0.2 8.97 ± 0.5 9.42 ± 0.2 9.66 ± 0.8 9.12 ± 0.7 Vccenic cid (C18:1n7) 2.24 ± 0.0 2.14 ± 0.1 2.52 ± 0.1 2.20 ± 0.1 2.01 ± 0.2 2.33 ± 0.1 2.37 ± 0.0 2.26 ± 0.1 2.26 ± 0.1 Oleic cid (C18:1n9) 49.6 ± 1.3 50.8 ± 1.0 40.1 ± 3.9 45.5 ± 1.5 42.8 ± 0.7 44.5 ± 1.0 43.9 ± 1.3 43.6 ± 1.5 40.1 ± 3.9 Eicosenoic cid (C20:1n9) 2.07 ± 0.1 2.20 ± 0.2 2.29 ± 0.3 2.22 ± 0.1 4.47 ± 0.1 2.41 ± 0.2 2.29 ± 0.1 2.27 ± 0.1 2.20 ± 0.3 Highly unsturtes (n-6) 1.59 ± 0.2 1.50 ± 0.1 4.77 ± 4.3 1.68 ± 0.1 2.05 ± 0.1 1.60 ± 0.1 1.41 ± 0.2 1.08 ± 0.1 1.13 ± 0.2 Linoleic cid (C18:2n6) 0.73 ± 0.1 0.63 ± 0.1 1.48 ± 0.1 1.01 ± 0.0 1.41 ± 0.0 0.74 ± 0.1 0.73 ± 0.1 0.12 ± 0.0 0.58 ± 0.1 Docostetrenoic cid (C22:4n6) 0.19 ± 0.1 0.22 ± 0.0 2.59 ± 4.1 0.17 ± 0.0 0.25 ± 0.0 0.18 ± 0.0 0.16 ± 0.1 0.22 ± 0.0 0.11 ± 0.0 Archidonic cid (C20:4n6) 0.58 ± 0.0 0.55 ± 0.0 0.60 ± 0.0 0.44 ± 0.0 0.39 ± 0.0 0.68 ± 0.0 0.52 ± 0.0 0.74 ± 0.0 0.44 ± 0.0 Highly unsturtes (n-3) 8.50 ± 0.5 7.31 ± 0.6 10.1 ± 2.9 8.66 ± 0.6 9.89 ± 0.6 8.38 ± 0.6 8.00 ± 0.50 7.81 ± 0.60 8.27 ± 0.30 Linolenic cid (C18:3n3) 0.15 ± 0.0 0.15 ± 0.0 0.24 ± 0.0 0.20 ± 0.0 0.32 ± 0.0 0.18 ± 0.0 0.17 ± 0.0 0.23 ± 0.0 0.15 ± 0.0 Eicospentenoic cid (C20:5n3) 2.11 ± 0.2 1.71 ± 0.2 1.55 ± 1.1 2.03 ± 0.1 1.63 ± 0.1 1.72 ± 2.2 1.81 ± 0.2 1.48 ± 0.1 1.75 ± 1.1 Docoshexenoiccid (C22:6n3) 6.25 ± 0.3 5.45 ± 0.4 8.26 ± 1.7 6.43 ± 0.4 7.94 ± 0.5 6.48 ± 0.4 6.02 ± 0.3 6.10 ± 0.4 6.37 ± 1.7 * Letters outside brckets men eel frms nd letters inside brckets men formul feed. Five different eel frms where eels were cultured using different formul feeds. Loctions of ech frm re s follows. A, Chonrnm-do, Yeongm-gun; B-D, Chonrbuk-do, Gochng-gun; E nd F, Chonrnm-do, Yeonggwng-gun. K nd P compnies re produced domesticlly nd T nd C compnies supply the formul feeds imported from Jpn nd Twin, respectively, Vlues re men of pplicble % ftty cid contents nd stndrd devitions. http://dx.doi.org/10.5657/fas.2013.0085 90
Seo et l. (2013) Comprison of Mjor Nutrients in Frmed Eels The composition of ftty cids in cultured eels did not significntly differ cross frms, in contrst to previous reports by Choi et l. (1985) (SFA, 30.5%; MUFA, 53.6%; HUFA, 8.0%) nd Cho et l. (2011) (SFA, 30.5 ± 1.3% to 33.0 ± 0.5%; MUFA, 59.9 ± 2.0 to 55.8 ± 0.5%; HUFA, 8.0 ± 0.5% to 9.2 ± 0.7%). The difference in the composition of ftty cids mong FFs ws not s high s expected, which my ccount for the smll difference in qulity between domestic nd imported FFs. On the other hnd, becuse ftty cid composition differs somewht between eels cultured in still-wter system nd wter-recircultion system (Cho et l., 2011), our results lso suggest tht environmentl differences experienced by cultured eels t different frms could more strongly ffect the ftty cid composition thn differences mong eels fed different FFs. In prticulr, Frm C exhibited higher vlues of ω-6 nd ω-3 HUFA compred to the other eel frms, suggesting tht the culture conditions t Frm C hve certin dvntges. An opertor of Frm C mentioned tht they use specil methods bsed on their experiences, but these methods hve not been empiriclly proven nd thus require more detiled experimentl study. In conclusion, eel-culture techniques still must be stndrdized nd systemtized to produce high-qulity eels. In prticulr, while eel qulity did not significntly differ between eels fed domestic or imported FFs nd becuse domestic FFs cnnot be considered superior to Jpnese eel FFs, domestic FFs must be improved. In ddition, becuse significnt differences in eel qulity were observed mong eel frms, it is necessry to determine the specific environmentl fctors tht ffect eel qulity. Further studies focused on identifying these fctors nd pplying culture techniques for high-qulity eel culture re needed. 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