Original Paper Czech J. Anim. Sci., 56, 2011 (3):

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1 Originl Pper Czech J. Anim. Sci., 56, 2011 (3): Effect of different dietry lipid levels on growth performnce, slughter yield, chemicl composition, nd histology of liver nd intestine of pikeperch, Snder lucioperc A. Kowlsk 1, Z. Zkęś 1, B. Jnkowsk 2, K. Demsk-Zkęś 3 1 Deprtment of Aquculture, Stnisłw Skowicz Inlnd Fisheries Institute, Olsztyn, Polnd 2 Deprtment of Met Technology nd Chemistry, Fculty of Food Science, University of Wrmi nd Mzury, Olsztyn, Polnd 3 Deprtment of Ichthyology, University of Wrmi nd Mzury, Olsztyn, Polnd Astrct: In this study, 16-month-old pikeperch, Snder lucioperc, (initil ody weight 280 g) were fed three diets with different lipid levels with the im of determining the impct on the growth performnce, heptic nd intestinl histologicl structure, chemicl composition, nd slughter yield of this species. The fish were fed isoproteinceous feeds (450 g protein/kg feed) contining 60 g lipids/kg feed (group F6), 100 g lipids/kg feed (group F10) nd 180 g lipids/kg feed (group F18). No significnt differences were noted mong the tretment groups in ody weight gin nd in the feeding coefficients of experimentl feeds (P > 0. 05). In the group of fish dministered the diet with the lowest lipid content (group F6), the shre of skinned fillet in the whole ody weight ws the highest (48% vs. 43% in group F18) (P < 0.05). No significnt differences mong groups were confirmed in the reltive vlues of the viscer weight ( %) (P > 0.05). The highest vlues of the size of heptocytes nd their nuclei, intestinl cells, suprnucler vcuoles of enterocytes, nd the degree of vcuoliztion in heptocytes were determined in group F18 (P < 0.05), indicting histopthologicl chnges. The highest ody nd viscer lipid contents were noted in individuls from group F18 (P < 0.05). The high lipid content in the viscer of fish from this group ws linked to the significntly lowest content of protein nd sh. The levels of lipids, protein, nd sh were similr (P > 0.05) in the pikeperch fillets from the three feeding tretments. The levels of n-6 polyunsturted ftty cids (n-6 PUFA) in the whole fish ody, in the viscer nd fillets (P < 0.05) were the significntly highest in group F18. Significnt differences in n-3 polyunsturted ftty cids (n-3 PUFA) mong the groups were confirmed in the whole fish ody nd viscer (P < 0.05), while the vlues in the fillets were similr (P > 0.05). The n 3/n 6 index for the fish fillets rnged from 2.4 (group F18) to 4.7 (group F6) (P < 0.05). The levels of n-3 highly unsturted ftty cids (n-3 HUFA), rchidonic cid (ARA) nd docoshexenoic cid (DHA) in the fillets of fish from the three dietry tretments were similr (P > 0.05). The fillets of fish from group F6, however, hd the lowest levels of linolenic nd linoleic cid (ALA nd LA) nd the highest levels of eicospentenoic cid (EPA) (P < 0.05). Keywords: percid fish; lipid; slughter yield; histology; ody composition The pikeperch, Snder lucioperc L., is populr freshwter fish species mong consumers, especilly in communities tht promote helthy foods (Dil, 2008). The fillets of this species re rich in polyunsturted ftty cids (PUFA), including those tht re vlule to humns: eicospentenoic (C20:5n-3, 136

2 Czech J. Anim. Sci., 56, 2011 (3): Originl Pper EPA) nd docoshexenoic (C22:6n-3, DHA) (Jnkowsk et l., 2003). Ctches of wild pikeperch hve never een significnt, nd even these hve decresed severl-fold over the lst few decdes (FAO, 2007; Dil, 2008). To meet the incresed demnd for pikeperch production in quculture frming, quculture systems re needed (Molnár et l., 2006; Philipsen, 2008). The knowledge of dietry requirements of given species is key fctor in determining the effectiveness of its production in quculture. Slmonid rtificil feed, often with high lipid content, hs generlly een used to dte to rer pikeperch (Zkęś et l., 2001; Schulz et l., 2005). Economic fctors usully motivte the ppliction of this type of feed since it permits more rtionl use of the more expensive protein for somtic growth nd lipids s the less expensive energy source. For intensive culture (fttening) of slmonids, feeds with lipid contents s high s 20 30% produce stisfctory results (Einen nd Roem, 1997). It is understood tht the optiml shres of protein, lipids, nd crohydrtes in diets gurntee pproprite growth rtes, condition nd helth of the fish, nd tht these prmeters re specific to ech species (Joling, 1994; Hlver nd Hrdy, 2002). Fish fed diets tht re not tilored to their nutritionl requirements exhiit, mong other symptoms, hlted growth rtes nd/or ntomicl pthology nd histopthologicl chnges in the limentry trct (Prpour nd Alexis, 2001; Ostszewsk et l., 2006). Percid fish of the genus Perc (yellow perch, P. flvescens Mitchill, nd Europen perch, P. fluvitilis L.) fed diets with high lipid contents exhiit unstisfctory rering results, nd these fish cn exhiit viscerl ft deposits nd internl orgn dysfunction (especilly in the liver) (Brown et l., 1996; Kestemont et l., 2003). Additionlly, diets high in lipid content led to the deposition of lrge mounts of ft in the viscer effectively lowering slughter yield. Therefore, the chemicl composition of feed is determining fctor in the mrket vlue of rered fish nd cn impct the yield of the edile prts nd the chemicl composition of the ody, including the fillets (Joling, 2001). Nutritionl experiments conducted on juvenile pikeperch to dte hve focused on feeding regime; levels of dietry protein, lipids nd crohydrtes; dietry lipid content nd type on growth; ody composition; nd the histologicl structure of some orgns (Zkęś et l., 2001, 2003; Nyn-Wmwiz et l., 2005; Ostszewsk et l., 2005; Molnár et l., 2006; Kowlsk et l., 2010). The results of these studies hve not lwys een unequivocl, nd the knowledge of nutritionl requirements of this species remins unstisfctory nd fr from complete. Some of the spects of nutrition tht hve yet to e investigted, included the impct the chemicl composition of feed on the vlues of such significnt indexes of pikeperch rering s slughter yield nd dietry qulity of fillets or the histologicl structure of the liver nd intestines. The lipid quntity nd qulity in feeds cn e linked to growth, lipid metolism, ftty cid content in the tissues, histologicl chnges in the liver, intestine, nd resistnce of fish (Klogeropoulos et l., 1992; Rennert et l., 2005; Piedecus et l., 2007). The lipid level nd deficiency of some ftty cids in fish feed hve n effect on the degree of heptocyte vcuoliztion, suprnucler zone of enterocytes, ccumultion of lipid droplets in enterocytes nd consequently they impct the size of these cells (Olsen et l., 2000; Cllero et l., 2002; Ostszewsk et l., 2005, Kowlsk et l., 2010). Anomlies in heptocyte nd intestine structure cn distur dietry ft metolism which my ffect the immune system nd led to poor fish helth (Wtne et l., 1989; Tcon, 1992; Prpour nd Alexis, 2001; Cllero et l., 2002; Hlver nd Hrdy, 2002). The im of the present study ws to investigte the impct the dministrtion of feeds with different lipid contents to pikeperch [rered in recirculting quculture system (RAS)] on growth performnce, slughter yield, pthologicl chnges in liver nd intestine nd in the chemicl composition of the fish. Mteril nd methods Fish nd rering The fish were otined from induced spwning t the Inlnd Fisheries Institute in Olsztyn, Polnd (IFI Olsztyn; Zkęś nd Szczepkowski, 2004). The lrve were rered in n RAS nd received initilly mixed feed (Artemi sp. + formulted feed) nd then exclusively commercil trout feed (Szkudlrek nd Zkęś, 2007). Juvenile pikeperch of the men ody weight 55 g were plced in three rering tnks of 0.8 m 3 in volume ech nd fed experimentl diets with different lipid contents (60, 100, 180 g/kg feed; Tle 1). After 6 months of initil rering, the proper experiment egn. Fish of the men initil ody weight pproximtely 280 g nd totl 137

3 Originl Pper Czech J. Anim. Sci., 56, 2011 (3): Tle 1. Chemicl (g/kg dry weight) nd selected ftty cid (FA) composition (g FA/kg of totl FA) of experimentl diets Diets F6 F10 F18 Crude protein Crude ft NFE Crude sh Gross energy (MJ/kg feed) Ftty cid composition C14: C16: C18:1cis C18:2n C18:3n C20:4n C20:5n C22:6n Totl n Totl n Totl n n 3/n F6 60 g lipid/kg feed, F g lipid/kg feed, F g lipid/kg feed NFE nitrogen free extrct, clculted s 1000 (protein + lipid + sh + fire) ft/kg feed Gross energy clculted s: 24 MJ/kg protein, 39 MJ/kg ft, 17 MJ/kg NFE (Joling, 1994) Totl n-3 C18:3n-3, C20:3n-3, C20:4n-3, C20:5n-3, C22:5n-3, C22:6n-3 Totl n-6 C18:2n-6, C20:3n-6, C20:4n-6, C22:5n-6 Totl n-9 C18:1cis9, C20:1n-9, C22:1n-9 length (TL) 31 cm (ged 16 months) were plced in 12 rering tnks (of 0.2 m 3 in volume ech) in n RAS. Forty-five individuls were chosen from ech group receiving feeds with different lipid levels. These were stocked into 3 rering tnks (n = 3) where they continued to receive the experimentl feeds. The stocking density ws 15 individuls per tnk, nd the iomss ws pproximtely 20 kg/m 3. The wter flow rte ws mintined t 4 l/min. Wter temperture, oxygen content, totl mmoni nitrogen (TAN = NH 3 -N + NH 4 + -N) nd wter ph t the rering tnk outflow were: 22.2 ± 0.1 C; 5.6 ± 0.3 mg O 2 /l; 0.08 ± 0.02 mg TAN/l; , respectively. A constnt LD 24:0 photoperiod ws used. Light intensity mesured t the wter surfce of rering tnks ws lux. The experiment ws three months long, which permitted the pikeperch to grow to the size tht produced consumer-sized fillets (Summerfelt, 1996). Feed nd feeding The se feed dministered to the fish ws Aller Sfir (Aller-Aqu, Golu-Dorzyń, Polnd), which is commercil feed product without the ddition of lipids. The min sources of protein in this feed re fish nd soy mels. The lipid quntity in the se feed ws 60 g/kg feed, nd ws derived minly from fish mel. The fish received the se feed (group 138

4 Czech J. Anim. Sci., 56, 2011 (3): Originl Pper F6) or se feed with the ddition of fish oil (Peter Möller, Möller s Trn, Oslo, Norwy) nd soy oil (ZPT Olvit, Gdńsk, Polnd) in quntities of 12 nd 28 g/kg feed (group F10) or 36 nd 84 g/kg feed (group F18). The oils were dded to the se feed using vcuum pump (AGA Lor, Lulin, Polnd). Feed ws prepred every seven dys nd stored in refrigerted unit (+4 C). The chemicl composition of the feed is presented in Tle 1. The fish were fed continuously (19 h/dy) with nd feeder (4305 FIAP, Fishtechnic GmH, Germny). For the first three weeks of rering the dily feed rtion ws 0.8% of the stock iomss, nd in the lst nine weeks of rering it ws 0.5% of the stock iomss. The experiment ws crried out during three-month period (from 280 g to the finl smpling). No mortlity ws oserved during the experiment. Experimentl procedure nd clcultion On the first nd on the lst dy of the experiment, ll fish were weighed (W ± 0.01 g), mesured (TL ± 0.1 cm), nd smples were tken for the sic nlyses of the chemicl composition of the odies. The fish were nesthetised with dose of 1.0 ml/l of etomidte (Propiscin, IFI Olsztyn, Kzuń nd Siwicki, 2001) efore weighing nd mesuring. The individuls used to determine the ody chemicl composition nd for histologicl nlyses were nesthetized with dose of 4 ml/l nd then decpitted. The following formuls were used to determine the vlues of the chosen rering indexes: Specific growth rte, SGR (%/dy) = 100 [(ln W f lnw i )/T]; Dily growth rte, DGR (g/dy) = (W f W i )/T; Condition fctor, CF = 100 (W/TL 3 ); Feed conversion rtio, FCR = TFI/(FB IB); Protein efficiency rtio, PER = (FB IB)/TFP; Weight of ft in given ody prts (whole fish, viscer, fillets), WF x (g/fish) = (W x LP x )/100; Reltive ft content, FC (%) = (WF x 100)/Wf t. Ten individuls were chosen from ech dietry tretment to determine slughter yield. The fish were nesthetized in solution of Propiscin (4 ml/l) nd then decpitted. They were weighed (± 0.01 g), gutted, filleted, nd skinned. All ody prts were weighed nd their shres in the totl ody weight were determined s follows: WR x (%) = (W x 100)/W The vlues of the heptosomtic index (HSI, %) were lso determined s follows: HSI = 100 (LW/W) The nottion used in the preceding formuls ws s follows: W f nd W i were the finl nd initil ody weight (g); T time of rering (dys); TL totl length (cm); FB nd IB finl nd initil fish iomss (g); TFI totl feed intke (g); FBP finl ody protein content (%); W x weight of given fish ody prt (g); WF x weight of ft in given ody prt (g); LP x shre of ft in given fish ody prt (%); WF t weight of ft in whole fish (g); LW liver weight (g). Histologicl nlysis of liver nd intestines On the lst dy of the experiment, the liver nd nterior sections of the intestines were excised from 7 individuls from ech group (2 3 individuls from ech tnk). The tissues were fixed in Bouin s fluid, dehydrted in ethnol, clered in xylene, emedded in prffin locks, nd then sliced with rotting microtome (Leic, Bensheim, Germny) into 5 μm sections nd stined with H&E. Anlyses nd histologicl mesurements were performed with light microscope (Nikon E600, Jpn), the MultiScnBse v computer progrmme (Computer Scnning System Ltd., Wrsw, Polnd), nd the NIS-Elements F2.30 v progrmme (Nikon, Jpn). The following nlyses were performed: 50 heptocytes nd their nuclei; 50 enterocytes nd their nuclei; suprnucler vcuole (±0.01 μm) (Ostszewsk et l., 2005). Heptocyte vcuoliztion ws rted on scle of 0 to 4, which incresed s the cell cytoplsm ecmed incresingly filled with the lipid vcuole (no lipid vcuoliztion 0, low vcuoliztion 1, moderte 2, high 3, mximum vcuoliztion 4; Figueiredo-Silv et l., 2005). The degree of vcuoliztion in the cells ws determined in field with surfce re of 2500 μm 2 (50 50 μm). Twenty such fields were mesured for ech individul, nd vcuoliztion on the five-degree scle ws determined for ech heptocyte. Feed nd fish chemicl nlysis Wter content, totl protein, crude ft nd crude sh (wet weight) nd individul ftty cids [g/kg of 139

5 Originl Pper Czech J. Anim. Sci., 56, 2011 (3): totl ftty cid (tfa)] were determined in 5 whole fishes, in skinned fillets from 6 fishes, nd in the viscer from 10 fishes tht were chosen from 2 tnks of ech dietry tretment. The fish nd ody prts of the individuls from given tnk were comined nd nlysed together (n = 2, for ech feeding tretment). Protein content ws determined y the Kjeldhl method. Ft content ws determined y the Soxhlet method (AOAC, 1975), nd the ftty cids were nlyzed ccording to the method of Folch et l. (1957). The ftty cids were methylted y dding mixture of chloroform, non-queous methnol nd sulphuric cid (100:100:1) (Peisker, 1964). Chromtogrphic seprtion ws performed on n Agilent Technologies 6890 N gs chromtogrph with flme ionistion detector (FID). The detector signl ws registered y Philips recorder with 1 mv full-scle sensitivity t tpe speed of 10 mm/min. The ftty cids were identified using stndrds y Supelco (Bellefonte, PA, USA). Results Growth performnce, feed utiliztion, slughter yield The feeds tested did not hve significnt impct either on pikeperch growth rte nd condition or on the vlues of the coefficients FCR or PER (P > 0.05, Tle 2), ut the feeds with different lipid contents influenced the slughter yields of fish (P < 0.05, Tle 3). The highest reltive vlue for skinned fillets, expressed s the per cent of totl ody weight, ws otined in the group receiving feed with the lowest lipid content (48.1% group F6 vs % groups F10 nd F18). Among the ody prts nlyzed, significnt differences mong groups were noted in the reltive vlues of the weight of the hed nd fins (P < 0.05), ut it did not pply to the weight of the viscer (P > 0.05, Tle 3). Sttisticl nlysis All dt were sujected to one-wy ANOVA nd Tukey s test (for the nlysis of rering indexes, cell size structure, fish chemicl composition nd slughter yield) or Kruskl-Wllis test (to nlyse the degree of vcuoliztion) using the GrphPd Prism progrmme (Soft. Inc., USA). Differences were considered significnt t P All vlues expressed s percentges were trnsformed with rcsin efore sttisticl processing. Histologicl oservtions Significnt differences were determined in the size of heptocytes nd their nuclei, nd in the degree of heptocyte vcuoliztion in the liver of fish receiving feeds with different lipid contents (Tle 4). The lrgest heptocytes occurred in individuls dministered feed with the highest lipid content (group F18) (P < 0.05, Tle 4). The degree of heptocyte vcuoliztion incresed proportionlly to the dietry lipid content (P < 0.05). Smll Tle 2. Weight, length nd production prmeters of pikeperch fed experimentl diets (men ± SD; n = 3) 140 Dietry tretments F6 F10 F18 Body weight (g) ± ± ± Totl length (cm) ± ± ± 0.73 Dily growth rte DGR (g/dy) 1.90 ± ± ± 0.01 Specific growth rte SGR (%/dy) 0.57 ± ± ± 0.01 Condition fctor CF 0.96 ± ± ± 0.06 Feed conversion rtio FCR 1.28 ± ± ± 0.02 Protein efficiency rtio PER 1.74 ± ± ± 0.04 Asence of superscripts letters indictes no significnt differences etween tretments (P > 0.05) F6 group fed feed with 60 g lipid/kg feed, F10 group fed feed with 100 g lipid/kg feed, F18 group fed feed with 180 g lipid/kg feed

6 Czech J. Anim. Sci., 56, 2011 (3): Originl Pper Tle 3. Fish ody weight (g) nd slughter yield (% sed on the whole fish ody weight) of pikeperch from three dietry tretments (men ± SD; n = 10) Prmeter Dietry tretments F6 F10 F18 Totl fish ody weight (g) ± ± ± Viscer 4.8 ± ± ± 1.1 Gutted fish 94.9 ± ± ± 7.5 Crcss (without hed nd viscer) 71.3 c ± ± ± 1.4 Fillet with skin 58.1 ± ± ± 1.0 Skinned fillet 48.1 ± ± ± 2.1 Skin 9.8 ± ± ± 1.6 Fins 2.6 ± ± ± 0.3 Hed 23.4 ± ± ± 1.3 Spine 9.7 ± ± ± 0.8 Dt on the sme line with different superscript letters re significntly different (P > 0.05) F6 group fed feed with 60 g lipid/kg feed, F10 group fed feed with 100 g lipid/kg feed, F18 group fed feed with 180 g lipid/kg feed lipid vcuoles were oserved in the fish from group F6, while fish from groups F10 nd F18 hd lipid droplets of vrious sizes (Figure 1). In group F18, the lipid droplets tended to drin nd to form lrge ftty cysts. The smllest epithelil cells nd enterocyte suprnucler vcuoles were confirmed in the fish from group F6, while the lrgest were in group F18 (P < 0.05, Tle 4). Smll lipid vcuoles were oserved in the individuls from group F6 (Figure 2). Lrger nd more numerous lipid vcuoles nd lipid droplets in the enterocyte suprnucler vcuoles were confirmed in group F18. In this instnce, lrge lipid droplets distorted the enterocyte cell structure on the surfce in some plces. Chemicl nlysis The pikeperch receiving feed with 180 g lipids per kg feed hd the highest content of ft in the whole fish ody nd viscer nd the lowest levels of Tle 4. Comprison of heptocyte nd enterocyte morphometric chrcteristics (n = 7) nd heptosomtic index (n = 10) of pikeperch fed experimentl diets (men ± SD) Dietry tretments F6 F10 F18 Heptosomtic index HSI (%) 0.95 ± ± ± 0.24 Size of heptocyte (μm) 11.1 ± ± ± 1.3 Size of nuclei (μm) 3.6 ± ± ± 0.1 Vcuoliztion degree 0.7 ± ± ± 0.7 Height of enterocyte (μm) 22.9 ± ± ± 2.2 Size of nuclei (μm) 5.1 ± ± ± 0.7 Height of suprnucler zone (μm) 12.5 ± ± ± 1.7 Asence of superscripts letters indictes no significnt differences etween tretments (P > 0.05) F6 group fed feed with 60 g lipid/kg feed, F10 group fed feed with 100 g lipid/kg feed, F18 group fed feed with 180 g lipid/kg feed 141

7 Originl Pper Czech J. Anim. Sci., 56, 2011 (3): Figure 1. Histologicl picture of the livers of pikeperch fed feed with 60 g lipid/kg feed (F6), 100 g lipid/kg feed (F10), 180 g lipid/kg feed (F18); rrows indictes heptocyte lipid droplets (H & E) protein nd sh in the viscer in comprison with fish dministered feed with lower lipid contents (P < 0.05, Tles 5 nd 7). The contents of protein, ft nd sh in the fillets of fish from the 3 dietry tretment groups were similr (P > 0.05, Tle 6). The higher lipid content in the pikeperch feed ws lso linked to higher content of ft in the whole fish odies nd viscer (Figure 3). Although it did not influence the mount of ft in the fillets, the reltive ft content (FC) in the fillets of fish from group F6 ws the highest, while in group F18 it ws the lowest. The vlues of the FC index for the viscer were significntly the highest in the group of fish receiving feed with the highest ft (P < 0.05, Figure 3). The content of polyenic cids (PUFA) from the n-3 series (totl n-3) in the odies of fish from group F18 ws lower thn in group F6 (P < 0.05, Tle 5), while the fish from group F6 were chrcterized y the significntly lowest quntity of monoenoic ftty cids (MUFA) of the n-9 series (totl n-9) nd PUFA from the n-6 series (totl n-6) in the whole ody s compred to group F18. Significnt differences were noted in the quntities of myristic (C14:0), linoleic (C18:2n-6, LA), linolenic (C18:3n-3, ALA), rchidonic (C20:4n-6, ARA), EPA, nd DHA cids in the whole odies of fish from the different dietry tretments (P < 0.05, Tle 5). The content of n-6 PUFA ws significntly the lowest in the fillets of fish receiving feed F6 in comprison with those of fish from the other dietry tretments (P < 0.05, Tle 6). The met of fish from group F6 ws chrcterized y the highest contents of EPA (P < 0.05), ut the contents of DHA in the fillets of fish from groups F6, F10, nd F18 were similr (P > 0.05). The vlues of the n3/n6 index were the most dvntgeous in the fillets of fish from group F6 (4.72 vs groups F10 nd F18) (P < 0.05, Tle 6). The quntities of n-3 PUFA in the viscer of fish from group F18 were significntly lower thn those in groups F6 nd F10 (P < 0.05, Tle 7). In turn, the content of n-6 PUFA in group F18 ws significntly higher (P < 0.05). The dministrtion of feeds with the highest lipid content (group F18) lso resulted in the significntly lowest quntities of plmitic 142

8 Czech J. Anim. Sci., 56, 2011 (3): Originl Pper Figure 2. Interior intestine epithelium of fish fed feed supplemented with 60 g lipid/kg feed (F6), 100 g lipid/kg feed (F10), 180 g lipid/kg feed (F18); rrows indicte enterocyte lipid vcuoles (H & E) cid (C16:0). The viscer of fish from groups F10 nd F18 contined more oleic cid (C18:1cis9) nd LA, nd less ALA, ARA, EPA, nd DHA in comprison with the vlues recorded in group F6 (P < 0.05, Tle 7). Discussion Growth performnce nd slughter yield The isoproteinceous diets with different lipid contents did not influence the men finl ody weight of t pikeperch. Nyin-Wmwiz et l. (2005) confirmed tht when protein supply is pproprite ( g protein/kg feed for percid fish), different lipid contents in feeds do not hve n impct on the rering results of pikeperch. As reported y Zkęś et l. (2004), Nyin-Wmwiz et l. (2005), Molnár et l. (2006) nd Schulz et l. (2007), no protein spring effect ws demonstrted. However, Schulz et l. (2007) confirmed significntly fster growth rtes in pikeperch dministered feeds with higher lipid contents (170 in comprison with 90 nd 130 g lipids/kg feed; protein contents 470 to 530 g/kg feed). The vlue of the FCR coefficient ws dvntgeous (pprox. 1.3) in ll feeds tested in the present study, nd ws similr to those reported for the impct of the diets on slughter yield ecmed especilly evident when wild nd rered individuls of the sme species were compred (Joling, 2001). Lowered slughter yield vlues in fish receiving formulted feeds, which resulted minly from n increse in the weight of the viscer, were confirmed for exmple in rinow trout, Oncorhynchus mykiss (Wl.) (Joling et l., 1998), Europen se ss, Dicentrrchus lrx (L.) (Boujrd et l., 2004) nd Europen perch (Mthis et l., 2003). However, it ws not oserved in pikeperch (Jnkowsk et l., 2003). In the present study, feeds with different lipid contents, nd thus energy concentrtions, hd significnt impct on the slughter yield of pikeperch. The fillet yield, expressed s the percentge of the totl ody weight, of individuls fed more 143

9 Originl Pper Czech J. Anim. Sci., 56, 2011 (3): Tle 5. Chemicl (g/kg of wet weight) nd min ftty cid (FA) composition (g FA/kg totl FA) of whole odies of pikeperch fed diets with different lipid contents (men ± SD; n = 2) Components Dietry tretments F6 F10 F18 Crude protein ± ± ± 3.6 Crude ft 40.9 ± ± ± 0.4 Crude sh 40.2 ± ± ± 2.4 Gross energy (MJ/kg) 6.6 ± ± ± 0.1 Ftty cid composition C14: ± ± ± 2.6 C16: ± ± ± 5.6 C18:1cis ± ± ± 1.8 C18:2n ± ± c ± 1.3 C18:3n ± ± c ± 1.1 C20:4n ± ± ± 0.4 C20:5n ± ± ± 4.2 C22:6n ± ± ± 3.2 Totl n ± ± ± 3.5 Totl n ± ± c ± 2.0 Totl n ± ± ± 3.5 n-3/n c ± ± ± 0.01 Different letter within line denotes significnt differences (P < 0.05) F6 group fed feed with 60 g lipid/kg feed, F10 group fed feed with 100 g lipid/kg feed, F18 group fed feed with 180 g lipid/kg feed; for explntion of gross energy clcultion nd ftty cids groups see Tle 1 energetic feeds ws significntly lower. It is symptomtic tht the reltive viscer weight in the experimentl groups of fish ws comprle nd tht the reltive hed nd fin weights differed. By comprison, in perch it ws confirmed tht the lowered slughter yield of individuls receiving formulted feed with higher energy nd lipid contents resulted from the higher viscer weight (VSI) (Mthis et l., WF WF (g/fish) c c group F6 group F10 group F18 group F6 group F10 group F18 Whole fish Fillet Viscer Whole fish Fillet Viscer FC (%) FC (%) c c group F6 group F10 group F18 group F6 group F10 group F18 Fillet Fillet Viscer Viscer Figure 3. Weight of lipid (WF; g/fish) nd reltive lipid content (FC; %) in the odies of pikeperch fed feed with 60 g lipid/kg feed (group F6), 100 g lipid/kg feed (group F10), 180 g lipid/kg feed (group F18) 144

10 Czech J. Anim. Sci., 56, 2011 (3): Originl Pper Tle 6. Chemicl (g/kg of wet weight) nd min ftty cid (FA) composition (g FA/kg totl FA) of fillets from pikeperch fed diets with different lipid contents (men ± SD; n = 2) Dietry tretments F6 F10 F18 Components Crude protein ± ± ± 3.4 Crude ft 9.7 ± ± ± 3.5 Crude sh 11.9 ± ± ± 0.3 Gross energy (MJ/kg) 5.6 ± ± ± 0.1 Ftty cid composition C14: ± ± ± 0.1 C16: ± ± ± 9.0 C18:1cis ± ± ± 4.4 C18:2n ± ± ± 7.1 C18:3n ± ± ± 0.3 C20:4n ± ± ± 0.4 C20:5n ± ± ± 0.3 C22:6n ± ± ± 2.0 Totl n ± ± ± 0.2 Totl n ± ± ± 6.9 Totl n ± ± ± 4.0 n-3/n ± ± ± 0.11 Different letter within line denotes significnt differences (P < 0.05) F6 group fed feed with 60 g lipid/kg feed, F10 group fed feed with 100 g lipid/kg feed, F18 group fed feed with 180 g lipid/kg feed; for explntion of gross energy clcultion nd ftty cids groups see Tle ). It ws lso confirmed tht differences in the filleting yield nd VSI were typicl not only of wild nd rered perch ut lso of fish rered in different rering quculture systems (extensive, semi-intensive, nd intensive rering). More intensive rering conditions resulted in lowered slughter yield nd increses in the vlues of the VSI, with the highest viscer weight recorded in perch rered in recirculting systems (Miresse et l., 2005). Histologicl exmintion Differences in the histologicl structures of liver nd intestines were noted mong groups of pikeperch rered on feeds with different lipid contents. Similrly like in Europen perch dministered feed contining 60, 120, or 180 g lipids/kg feed (Kestemont et l., 2001), the lrgest lipid vcuoles nd the most pronounced histopthology were oserved in the heptocytes of fish receiving feed with the highest lipid content. The occurrence of lrge ftty cysts in the pikeperch from group F18 indicted the eginning of orgn degenertion tht leds to necrosis nd structurl distortions in enterocyte memrnes which resulted from the high lipid content, including soy oil in quntities of 120 g/kg feed. Bc et l. (1983) nd Prpour nd Alexis (2001) lso reported necrosis nd the degenertion of heptocyte cell memrnes in Europen sess nd gilthed serem, Sprus urt L., which received feeds supplemented with soy oil. The lowest quntities of myristic nd plmitic cids (169.0 g/kg tfa) nd the highest quntity of LA (313.1 g/kg tfa) in the feed given to group F18 could hve led to the cesstion of phospholipid synthesis nd the ccumultion of lipids in the liver of these fish, which concurs with results reported y Klogeropoulos et l. (1992), Rennert et l. (2005), nd Piedecus et l. (2007). Both Wtne et l. 145

11 Originl Pper Czech J. Anim. Sci., 56, 2011 (3): Tle 7. Chemicl (g/kg of wet weight) nd min ftty cid (FA) composition (g FA/kg totl FA) of viscer from pikeperch fed diets with different lipid contents (men ± SD; n = 2) Components Dietry tretments F6 F10 F18 Crude protein 67.2 ± ± ± 6.6 Crude ft ± ± ± 35.4 Crude sh 5.8 ± ± ± 0.6 Gross energy (MJ/kg) 24.3 ± ± ± 1.2 Ftty cid composition C14: ± ± ± 2.8 C16: ± ± ± 2.1 C18:1cis ± ± ± 1.6 C18:2n ± ± ± 19.5 C18:3n ± ± ± 1.8 C20:4n ± ± ± 0.4 C20:5n ± ± ± 3.8 C22:6n ± ± ± 5.7 Totl n ± ± ± 3.2 Totl n ± ± ± 18.9 Totl n ± ± ± 0.4 n-3/n ± ± ± 0.10 Different letter within line denotes significnt differences (P < 0.05) F6 group fed feed with 60 g lipid/kg feed, F10 group fed feed with 100 g lipid/kg feed, F18 group fed feed with 180 g lipid/kg feed; for explntion of gross energy clcultion nd ftty cids groups see Tle 1 (1989) nd Tcon (1992) confirmed the lipid degenertion of heptic tissues in mrine fish species dministered diets with low levels of n-3 PUFA. Although pikeperch is cple of ioconverting n-3 HUFA precursors, the level of 8.9 g ALA/kg tfa in the fish diets might e insufficient, especilly in the individuls in which pthologicl chnges in the liver re evident. Additionlly, the comined content of EPA nd DHA in the diet fed to group F18 ws just 87.5 g/kg tfa. Liver pthology ws noted in Europen sess when their diet contined similrly low contents of these cids (69.0 g/kg tfa) (Prpour nd Alexis, 2001). The results ove indicte tht SFA nd PUFA influence significntly heptic nd intestinl pthologicl chnges in percid fish, including the pikeperch. In the present study, no pthologicl chnges were oserved in the orgns exmined t miniml comined quntities of C14:0 nd C16:0, EPA nd DHA, nd ALA of 193.8, nd 23.8 g/kg tfa, respectively. Body chemicl composition The shre of ody ft in pikeperch incresed long with increses in the lipid content of feeds, which ws lso shown in other studies (Zkęś et l., 2004; Nyin-Wmwiz et l., 2005; Schulz et l., 2007). Percid fish store energy reserves minly in the viscer (intestinl ft), nd the chemicl composition of the fillets is quite stle (Xu et l., 2001; Zkęś et l., 2004). In the present study, it ws estimted tht s much s 84% of the ft in the whole odies of the individuls from group F18 ws stored in the viscer. The ft content in the pikeperch fillets in the present study ws 8.7 to 11.1 g/kg, in comprison with previously presen-ted < 20 g/kg (Jnkowsk et l., 2003). The chemicl composition of the pikeperch viscer ws the most lile (Zkęś et l., 2004; Kowlsk et l., 2010; this study). In the present study, significnt differences were noted not only in the quntity of ft ut lso in tht of 146

12 Czech J. Anim. Sci., 56, 2011 (3): Originl Pper protein. In effect, the energy vlue of the viscer of fish from group F18 ws significntly higher thn tht in the individuls from groups F6 nd F10 while this ws not s distinctly pprent with regrd to VSI. The resons for the lck of significnt differences mong the groups should include, mong others, the high individul vrition of this index (individul susceptiility to ft deposition). The high individul vrition in the VSI vlues ws lso reported in perch (Mthis et l., 2003). The lower levels of C14:0 nd C16:0 in the fish odies most proly resulted from supplementing soy oil to the experimentl feeds. It ws demonstrted tht supplementing lipids of vegetle origin to diets leds, mong other effects, to lower levels of SFA in pikeperch nd in the tissues of other species (Joling et l., 2001; Cllero et l., 2002; Schulz et l., 2005). The F6 nd F10 diets contined lower quntities of monoenoic cids thn did the F18 diet. Nonetheless, the content of MUFA (nd oleic cid) in the ody of pikeperch might e linked to the tendency of fish to store these cids s n energy source nd/or to the synthesis of monoenoic cids in the fish tissues (Krpngiotidis et l., 2007). However, the pprent selection ginst metolism of some ftty cids might lso e due to MUFA content in fish tissue (Bell et l., 2003). The met of percid fish is usully rich in HUFA (Jnkowsk et l., 2003; Kowlsk et l., 2010). The lipids in pikeperch fillets re minly phospholipids tht re rich in EPA nd DHA (Jnkowsk et l., 2003). Although the quntities of EPA were significntly the highest in group F6, the comined quntity of n-3 HUFA in pikeperch fillets ws similr in ll dietry tretments. This resulted from the high content of docospentenoic cid (C22:5n-3, DPA) nd DHA in the fish met. No differences in the content of DHA in the fish fillets indicte tht the mount of DHA nd EPA is stisfctory to fulfil the needs for mintining the phospholipid profile. To summrize, the results of the present study indicted tht the ppliction of low-ft feed is eneficil in the rering of pikeperch. Although no significnt differences were noted in the growth rtes of fish or in the feed conversion rtio of diets contining 60, 100, nd 180 g lipids/kg feed, the slughter yield (skinned filet) nd the ftty cid profile (n-3/n-6 rtio) were the most dvntgeous in the pikeperch rered on the diet with the lowest lipid level. It could e connected with lower LA nd higher EPA, DHA content in this feed compred to the others experimentl diets, with the higher level of lipids prtilly originting from the vegetle source (high LA nd low EPA, DHA content). Additionlly, no pthologicl chnges were oserved in the heptic nd intestinl histologicl pictures of the fish in groups F6 or F10, in contrst to those of individuls from group F18. Acknowledgments The uthors would like to thnk the feed mnufcturer Aller-Aqu of Golu-Dorzyń for their dontion of the se feed used in this study. REFERENCES AOAC (1975): Officil Methods of Anlysis. Assocition of Officil Anlyticl Chemists, Wshington,. Bc N., Biginti S., Brusle J. (1983): Etude cytologique ultrstructurle des nomlies heptiques du Loup, de l Durde et de I Anguille, induites pr une limenttion rtificielle. Bses iologiques de l quculture. In: Actes de Colloque, No. 1. Ifremer, Montpellier, Frnce, Bell J.G., Tocher D.R., Henderson R.J., Dick J.R., Crmpton V.O. (2003): Altered ftty cid compositions in tlntic slmon (Slmo slr) fed diets contining linseed nd rpeseed oils cn e prtilly restored y susequent fish oil finishing diet. Journl of Nutrition, 133, Boujrd T., Gèlineu A., Covès D., Corrze G., Dutto G., Gsset E., Kushik S. (2004): Regultion of feed intke, growth, nutrient nd energy utiliztion in Europen se ss (Dicentrrchus lrx) fed high ft diets. Aquculture, 231, Brown P.B., Dąrowski K., Grling D.L. (1996): Nutrition nd feeding of yellow perch (Perc flvescens). Journl of Applied Ichthyology, 12, Cllero M.J., Och A., Rosenlund G., Montero D., Gisvold M., Izquierdo M.S. (2002): Impct of different dietry lipid sources on growth, lipid digestiility, tissue ftty cid composition nd histology of rinow trout, Oncorhynchus mykiss. Aquculture, 214, Dil H. (2008): The Europen mrket of the pikeperch for humn consumption. In: Fontine P., Kestemont P., Teletche F., Wng N. (eds): Percid fish culture, from reserch to production. Presses Universitires de Nmour, Belgium, Einen O., Roem A.J. (1997): Dietry protein/energy rtios for Atlntic slmon in reltion to fish size: growth, 147

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