Catalase, SOD and GPx Activities in Triceps brachii Muscle from Aberdeen Angus Steers Finished on Pasture, Pasture and Concentrate, or Concentrate

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1 mericn Journl of Food nd Nutrition, 215, Vol. 3, No. 5, ville online t Science nd Eduction Pulishing DOI: /jfn Ctlse, SOD nd GPx ctivities in Triceps rchii Muscle from erdeen ngus Steers Finished on Psture, Psture nd, or. Terevinto 1, M.C. Crer 1,2,. Sdoun 2, 1 Dpto Producción niml & Psturs, Lortorio Clidd de limentos, Fcultd de gronomí, Universidd de l Repúlic. Grzón 89. Montevideo. Uruguy 2 Fisiologí & Nutrición, Fcultd de Ciencis, Universidd de l Repúlic. Clle Igu Montevideo. Uruguy Corresponding uthor: sdoun@fcien.edu.uy strct Three feeding system were investigted to determine if ny of them is more suitle to ensure etter ntioxidnt protection to met from Triceps rchii muscle of erdeen ngus steers. They were finished on psture, psture + concentrte with corn grin, or concentrte lone. TRS, protein cronyls nd ntioxidnt enzymes ctivities hve een determined in fresh nd ged met (14 dys in vcuum, 1-2 C). The level of TRS rnged etween mg MD/kg met, wheres levels of protein cronyl rnged etween mmoles DNPH/mg protein. The ctivities of ctlse nd superoxide dismutse re higher in fresh met of nimls fed psture, compred to those finished on psture nd concentrte, or on concentrte lone. Glutthione peroxidse (GPx) showed higher ctivities in met of nimls finished on concentrte in comprison those finished on psture nd concentrte, or psture. However, the results of the investigtion do not llow the dvising, for now, for the most suitle feeding system for finishing steers tht help producers to preserve met from lipids nd protein oxidtion. More investigtions re necessry to highlight the feeding conditions, which could influence the ctivities of ntioxidnt enzyme ctlse, SOD nd GPx in met. Keywords: psture, concentrte, trs, cronyls, ctlse, SOD, GPx, erdeen ngus met Cite This rticle:. Terevinto, M.C. Crer, nd. Sdoun, Ctlse, SOD nd GPx ctivities in Triceps rchii Muscle from erdeen ngus Steers Finished on Psture, Psture nd, or. mericn Journl of Food nd Nutrition, vol. 3, no. 5 (215): doi: /jfn Introduction Met is vlule food tht contins importnt nutrients tht re necessry to mintin helth nd well-eing in humn. Met contins high qulity proteins, ftty cids, vitmins nd minerls, like heme iron, zinc, selenium nd copper. However, met is perishle product tht cn e ltered y internl nd externl fctors like storge temperture, oxygen, nd light. Oxidtion induces modifictions of muscle lipids nd proteins nd, therefore, ffects the orgnoleptic nd nutritionl properties of met nd met products [1]. Oxidtion cuse lower industril nd nutritionl vlues of met nd economicl lost for producers. In ddition, consumers generlly reject oxidized met nd met products [1,2]. Oxidnt stressors rise from oth internl nd externl sources nd initite lipid oxidtion in muscle foods. The most importnt stressors re the rective oxygen species (ROS) including free rdicls nd peroxides [1,2]. However, there re different wys to preserve met from oxidtion. One wy is the consumption y the nimls of ntioxidnt components present nturlly in food like vitmins E nd C, phenolic sustnces, ntioxidnt pigments, etc. ll these nturl ntioxidnts ct s chin reking in rdicl production nd re considered s line of protection ginst rdicl ttck [2]. nother wy is tht, physiologiclly, the orgnism uilds different dptive strtegies to protect its own tissues from the rdicl ttck nd oxidtion. This lst wy re represented y n interlinked, complex nd very efficient enzymtic system composed y the ctlse, superoxide dismutse (SOD) nd glutthione peroxidse (GPx) [2]. Tht ntioxidnt enzymtic group constitutes the primry mechnism for protecting cells from oxidtive dmge in vivo [2]. SOD scvenges superoxide nion y forming hydrogen peroxide nd ctlse sfely decomposes hydrogen peroxide to wter nd O 2. GPx cn decompose oth hydrogen peroxide nd lipoperoxides formed during lipid oxidtion. These ntioxidnt enzymes re reltively stle in met during refrigerted storge [2]. Furthermore, current met production opertion implies often the geing process s wy to improve met qulity. The geing process consisted in the storge of met vcuum-pckged t temperture etween 1-2 C in the drk, for 14-6 dys. The geing durtion depends of the mrket conditions, locl or interntionl. The geing is conducted s wy to improve the tenderness of met. In ddition [3], most of the sensoril prmeters lso improved y geing, help to ensure the cceptility of met y consumers. However, geing is nother oxidnt fctor for met.

2 119 mericn Journl of Food nd Nutrition The oxidtive stility of met depends upon lnce etween oxidnt (ROS) nd ntioxidnt from food (vitmins) nd endogenous sources (enzymes). Food offered to the nimls could e good wy to improve the ntioxidnt defense of the niml tissues tht will e trnsferred to met fter slughtering [4]. Then, the proposed investigtion consisted in compring the lipids nd proteins oxidtion nd the ctivities of ctlse, SOD nd GPx in met from nimls fed one of the three feeding systems worldwide used to produce eef met: psture lone, psture nd supplementtion with concentrte nd concentrte lone. 2. Mterils nd Methods 2.1. niml Diets, Smples nd Chemicls erdeen ngus steers with live weight of 479 ± 28 kg (n=3) were fed on psture. Ten of them were rndomly ssigned to remin on this diet (Psture), other ten were ssigned to remin on psture nd received d liitum supplementtion with concentrte (Psture + ). The lst group of ten were finished on feedlot system, without ccess to psture, nd fed concentrte lone. The nimls received the corresponding diet (Psture or Psture + or ) the lst 11 dys until slughter. Psture consisted in tll fescue (Festuc rundince), white clover (Trifolium repens) nd irdsfoot trefoil (Lotus suiflorus). ws composed y roughge of whole plnt sorghum silge nd wet grin sorghum, soyen hulls nd whet rn, minerls nd ure. The nimls were slughtered with 24-3 months of ge in n uthorized ttoir following rules y Ministry of griculture of Uruguy (MGP). fter 36 hours of crcsses chilling, Triceps rchii muscle (T) ws removed from ech crcss. Ech muscle (pproximtely 1 g) ws divided in two pieces, one ws vcuum pckged, ged during 14 dys t 1-2 C nd then frozen t -2 C, nd the other ws directly frozen t -2 C, until further nlysis. ll chemicls used in the investigtion re in nlyticl grde from Sigm chemicls Co (St Louis, US). Ethyl cette (HPLC grde), ethnol (HPLC grde), utnol (HPLC grde), Trichlorocetic cid (nlyticl grde) nd HCl (nlyticl grde), were from Merck Corportion (US) Determintion of Lipid Oxidtion Smples of 1 g frozen met were homogenized in Wring-lender (Fisher Inc. US) with 2 ml of n extrction uffer (.15 M KCl,.2 M EDT nd.3 M HT) t 12, rpm for 1 minute. Prt of the homogente ws frozen overnight t -2 ºC to e used for cronyl nd protein content ssys, nd prt ws used the sme dy for the TRS (thiorituric cid rective species) test. The TRS procedure for the determintion of lipid oxidtion ws followed ccording to [5 nd 2]. riefly, the homogente ws centrifuged t 2 g t 4 C for 1 minutes (Sorvll ST16-R, US) nd 1 ml of the superntnt ws incuted with 1 ml of 2-thiorituric cid (T)-trichlorocetic cid (TC) solution (35 mm T nd 1% TC in 125 mm HCl) in oiling wter th for 3 min. fter cooling in ice for 5 min nd kept t room temperture for 45 min, the pink chromogen ws extrcted with 4 ml of n-utnol nd phse seprtion y centrifugtion t 3 g during 1 min. The sornce of the superntnt ws mesured t 535 nm in Genesys-6 spectrophotometer (Thermo inc.). The concentrtion of mlondildehyde (MD) ws clculted using the molr extinction coefficient of the MD (156, M-1 cm-1). Results were expressed s mg MD/kg of fresh met Determintion of Protein Oxidtion The protein oxidtion level ws determined y the cronyl protein ssy ccording to [6]. The homogente smples, frozen the dy efore, were thwed t room temperture. Two liquots of 2 ml from ech smple were put into two different tues. These tues were centrifuged t 2 g for 1 min (Sorvll ST16-R, US). One ws incuted with 2 ml of 2 M HCl (lnk) nd the other one with 2 ml of.2 M dinitrophenylhydrzine (DNPH) in 2 M HCl, for one hour t room temperture with regulr stirring. Then, 2 ml of 2 % TC ws dded. fter stirring, the mixture ws left t room temperture for 15 min with regulr stirring. The tues were centrifuged t 2 g for 1 min (Sorvll ST16-R, US). The pellets were wshed three times with 4 ml of ethnol:ethyl cette (1:1), centrifuging ech time, to eliminte trces of DNPH. The pellets were dissolved in 6 ml of 6 M gunidine HCl with.2 M KH 2 PO 4 (ph 6.5). The tues were incuted t room temperture for 15 min with regulr stirring. fterwrds, they were centrifuged t 24 g for 1 min (Sorvll ST16-R, US). The sornce of the superntnt ws mesured t 37 nm in Genesys-6 spectrophotometer (Thermo inc.) nd the concentrtion of DNPH ws clculted using the DNPH molr extinction coefficient (22, M-1 cm-1). Results were expressed s nmoles of DNPH/mg of protein. Protein content ws determined t 28 nm in the extrction uffer using ovine serum lumin (S) s protein stndrd [7] Determintion of ntioxidnt Enzyme ctivities 18 g frozen smple ws homogenized in Wring- lender (Fisher Inc. US) with 2 ml of n extrction uffer contining.15 M KCl nd.79 M EDT (ph 7.4) for 1 min t 12, rpm. The homogente ws centrifuged t 9g t 4 C for 1 min (Sorvll ST16-R, US). The superntnt ws used for the determintion of ctlse nd SOD ctivities. The expression of the enzymes ctivities were presented y g of fresh met nd y mg of protein contined in the extrction medi. This exclude ny ised oservtion due to the extrction methods. The ctivity of ctlse ws mesured recording the H 2 O 2 disppernce y the decrese in sornce t 24 nm during 3.5 min using Genesys-6 spectrophotometer (Thermo Inc.), following the method descried y [8]. The incution mixture contined 282 μl of the extrction uffer, 9 μl of the superntnt nd 9 μl of H 2 O 2.2 M. The ctivity ws clculted using the molr extinction coefficient of H 2 O 2 (39.4 M-1 cm-1) nd results were expressed s μmoles of discomposed H 2 O 2 /min/g fresh met nd s nmoles of discomposed H 2 O 2 /min/mg protein. Totl SOD ctivity ws determined s proposed y [9], with the modifictions of [2], y mesuring the inhiition of pyrogllol utoxidtion. The incution mixture contined 285 μl of 5 mm phosphte uffer (ph 8.2),

3 mericn Journl of Food nd Nutrition μl of the superntnt nd 75 μl of 1 mm pyrogllol. The increse in sornce t 34 nm ws recorded during 2 min in Genesys-6 spectrophotometer (Thermo Inc. US). One unit (U) ws tken s the ctivity tht inhiits the rection y 5%, nd results were expressed s U nd U/g fresh met. For the determintion of GPx ctivity, 5 g met smple were homogenized with n Ultr Turrx T18 (IK Co, Germny) with 25 ml of 5 mm KH 2 PO 4 uffer nd.5mm EDT (ph 7.) for 1 min t 18, rpm. The homogente ws centrifuged t 2 g for 2 min t 4 C (Sorvll ST16-R, US). nd then the superntnt ws filtered. The ssy mixture contined 5 mm KH 2 PO 4 uffer,.5 mm EDT, 1 mm reduced glutthione (Sigm G4251),.15 mm NDPH (Sigm N163), 1.5 U glutthione reductse (Sigm G3664),.15 mm H 2 O 2 nd 1 mm NN 3 (Sigm S-22). The incution mixture contined 198 μl of the ssy mixture nd 2 μl of the filtered smple. The ctivity of GPx ws mesured t 22 C recording the oxidtion of NDPH y the decrese in sornce of the incution mixture t 34 nm during 3 min using Genesys-6 spectrophotometer (Thermo Inc. US) [1,11]. n extinction coefficient of 63 M -1 cm -1 ws used to clculte NDPH concentrtion. The GPx ctivity ws expressed s μmoles of oxidized NDPH/min/g of fresh met nd s nmoles of oxidized NDPH/min/mg protein. s for Ctlse nd SOD, the expression of the GPx ctivity ws presented y g of fresh met nd y mg of protein contined in the extrction medi. This exclude ny ised oservtion due to the extrction methods Sttisticl nlysis The effect of feeding system nd geing on TRS nd cronyl content on ctlse, SOD nd GPx ctivities were nlyzed y NOV using the Generl Liner Model (GLM) procedure (NCSS softwre relese 26, 329 North 1 Est, Kysville, UT 8437) for fixed effect model with three feeding systems nd two processes. Only when significnt feeding system x process interction ws noted for ech prmeter studied, NOV one- wy or T-test were used to determine differences etween feeding systems within the sme processing nd etween processing (fresh nd ged met) for ech feeding system. When tretment effects were significnt (P <.5 ) mens were compred with Tukey-Krmer test (NCSS softwre relese 26, 329 North 1 Est, Kysville, UT 8437). 3. Results nd Discussion 3.1. Lipid Oxidtion There is no min effect of feeding system (P>.5) on lipids oxidtion (TRS) of fresh met from T (Figure 1). However, when only fresh met is considered, feeding psture nd concentrte seems to cuse more lipids oxidtion (P<.5) thn feeding concentrte (Figure 1). This oservtion is in ccord with previous oservtion from our lortory, using the iceps femoris muscle from steers of the sme reed (unpulished dt). oth results re, however, not in ccord to other two investigtions. In first study, using Longissimus dorsi muscle from Chrolis reed steers, the tril showed tht feeding with concentrte cused more lipids oxidtion in fresh met [12]. The sme conclusion ws reched in the second investigtion, using Psos mjor muscle, from crossreed nimls fed exclusively psture or concentrte [13]. However, this sme lst group, reported recently [14], using Longissimus dorsi muscle, tht they do not detected different lipids oxidtion in met from erdeen ngus steers, the sme reed used in the present investigtion. TRS (mg MD/kg met) 1,,8,6,4,2 s Figure 1. Lipid oxidtion (TRS, mg MD/kg met) in fresh nd ged Tricep rchii muscle of steers from psture, psture + concentrte nd concentrte sed feeding systems. Dt re men ±SEM (n=1). Different lowercse letters mens significnt differences mong feeding systems in fresh met (P<.5). Min effects: s No significnt. geing No significnt The reed of nimls nd the type of muscles used in ech investigtion could explin the different results reported etween the descried investigtions nd our own work. For exmple, muscles re not identicl, nd show individul chrcteristics in their iochemicl prmeters, like their different oxidtive nd glycolytic metolism [15]. s well s in their nutritionl composition [16,17]. More comprtive studies should e conducted to highlight the importnce of the feeding system on the oxidtive stility of met nd met products. When geing process is considered, there is no min effect of the feeding system on the lipids oxidtion when met is sumitted to 14 dys of geing tht include vcuum pckging nd chilling t 1-2 C (Figure 1). However, in previous work from our lortory using iceps femoris muscle (unpulished dt), the geing cused more lipids oxidtion, in spite of the vcuum pckging nd the chilling. This difference etween our experiments with different muscles reinforces our hypothesis tht in oxidtion studies, the type of muscle used in the investigtion could determine the kind of responses. Interesting dt ttrcted our ttention in the present experiment. In Tle 1 the totl lipids content of T ws presented, nd the steers fed concentrte showed level twice compred to nimls fed psture nd lmost twice compred to the nimls fed psture nd concentrte. This oservtion is in ccord with other report not only for eef met [13], ut lso for lm [18]. Thus, it seems tht higher level of lipids in T muscle is not necessrily ssocited with higher lipids oxidtion sttus. This point should e considered in future investigtion.

4 121 mericn Journl of Food nd Nutrition Tle 1. Lipids content (%) in Triceps rchii muscle of erdeen ngus steers from psture, psture nd concentrte or concentrte sed feeding systems Lipids(%) Psture Psture ± ± ± 1.28 Significtion P<.1 Dt re men ± SEM. Different lowercse letters mens significnt differences mong feeding systems y NOV nd Tukey test (P<.5) Protein Oxidtion To the contrry to the results for lipids oxidtion, protein oxidtion showed significnt min effect (P<.3) of the feeding system. The met from nimls fed psture presented lower protein oxidtion compred to oth, nimls fed psture nd concentrte, nd nimls fed concentrte (Figure 2). fter geing, there is significnt min effect (P<.1) showing tht the ged met hve higher protein oxidtion when compred to the unged met (Figure 2). Like for lipids, protein oxidtion is ssocited with the rdicl ttck of met in presence of oxygen through chin rection [19]. Tht rection could occurs with reduced forms of trnsition metls like iron nd copper present in met [2]. The oxidtion of protein of muscle result of denturtion nd proteolysis-induces chnges in met qulity, which include colour, rom, flvour, wter-holding cpcity. Protein oxidtion lso induces multiple physico-chemicl chnges nd nutritionl vlue in met proteins including decrese in the iovilility of mino cid nd impired digestiility of protein [19]. Our results presented differences with the investigtions of Mercier [6], when fresh met is considered. However, in tht experiment, the muscles, the reed nd the sex were different, Longissimus dorsi versus Triceps rchii, Chrolis cows versus erdeen ngus steers, respectively Limited informtion on tht point is ville in the scientific literture. The reltion etween protein oxidtion nd met qulity received little ttention from met scientist, thus more investigtion re needed. nmoles DNPH/mg protein,5,4,3,2,1 Psture Psture + s Figure 2. Cronyl proteins (nmoles DNPH/mg protein) in fresh nd ged Triceps rchii muscles of steers from psture, psture + concentrte, nd concentrte. Dt re men ±SEM (n=1). Min effects: s P<.3 Psture < Psture + concentrte, concentrte; geing P<.1 > 3.3. ntioxidnt Enzyme ctivities Ctlse There is significnt min effect (P<.5) of ctlse, when ctivity is expressed y g of met. Indeed, met from nimls fed psture presented more ctivity thn nimls fed psture nd concentrte or concentrte lone (Figure 3). However, this significnt effect turn not significnt when the ctivity of the enzyme ws expressed y mg of protein. This opposed results mke difficult to conclude out the effect of feeding system on the ctivity of ctlse. In previous investigtion showed no differences etween nimls fed psture nd other one fed concentrte using Longissimus dorsi [2], nd Psos mjor [21]. In oth experiments, the expression of ctlse ctivity ws y mg of protein. Furthermore, in previous experiment for our lortory, the ctlse ctivity of iceps femori muscle from erdeen ngus steers (unpulished dt) showed no min effect of the feeding system similr to the present experiment. In tht experiment, the ctivity of ctlse ws lso expressed y mg of protein. Together, the four experiments seems to shows tht ctlse proly did not respond differently to feeding systems when psture nd concentrte were compred. Ctlse (umoles/min/g met) Figure 3. Ctlse ctivity (μmoles/min/g crne) in fresh nd ged Triceps rchii muscle of steers from psture, psture + concentrte nd concentrte. Dt re men ±SEM (n=1). Different uppercse letters mens significnt differences mong feeding systems in ged met (P<.5). shows difference etween fresh nd ged met (P<.5). Min effects: P<.5 Psture > Psture + concentrte nd. geing P<.5 > Ctlse (nmoles/min/mg protein) Figure 4. Ctlse ctivity (nmoles/min/mg protein) in fresh nd ged Triceps rchii muscle of steers from psture, psture + concentrte nd concentrte. Dt re men ± SEM (n=1). shows difference etween fresh nd ged met (P<.5). Min effects: No significnt; geing P<.1 >

5 mericn Journl of Food nd Nutrition 122 Independently of the unit of expression of the ctivity of the enzyme, geing cused higher ctivity of ctlse (Figure 3 nd Figure 4). ctivities of ctlse, s ntioxidnt enzyme in vcuum pckging met is poorly documented nd this mke difficult to conclude out the results otined here. There is not n explntion out the higher level of ctlse fter geing. More investigtions re required to understnd this point Superoxide Dismutse significnt min feeding system effect ws found in SOD ctivity (P<.5), met from psture fed nimls showed higher SOD ctivity independently of the unit of expression of the ctivity (Figure 5 nd Figure 6). These ctivities re in ccord to the results reported in erly studies in fresh met from Longissimus dorsi nd Psos mjor muscles [2,6,21]. SOD nd ctlse re coupled s ntioxidnt enzymes. Then, it would e expected tht the two enzymes cooperte to fight ginst oxidnt fctor nd could e influenced similrly y the feeding system. However, in the present experiment nd previously pulished reports, the two enzymes seem to hve different responses to feeding system, [2,21]. The ctivity of SOD cn e ffected y the content of copper nd zinc in met [2]. In previous investigtion from our lortory, it hs een found tht met from erdeen ngus steers fed psture contin more Zinc thn ones fed concentrte. This oservtion could explin the higher ctivity of SOD in nimls fed psture in comprison to other fed concentrte [22]. Other nturlly occurring ntioxidnt, like vitmins present in psture, cn complete the enzymtic ction [2]. SOD (UI/g met) Figure 5. SOD ctivity (UI/g met) in fresh nd ged Triceps rchii muscle of steers from psture, psture + concentrte nd concentrte. Dt re men ± SEM (n=1). Different uppercse letters mens significnt differences mong systems in ged met (p<.5). NS: no significnt. Min effects: : P<.5 Psture >, Psture + concentrte = Psture, ; geing P <.5 > fter geing, SOD showed min effect of geing (P<.5) independently to the expression of enzymtic ctivity (Figure 5 nd Figure 6). These responses could e explined y the responses to the ROS ttck occurring in met during refrigerted geing in vcuum. There re very few reports, which studied the effect of geing on the ctivity of ntioxidnt enzymes in met. ntioxidnt enzymes continue to e ctive in met, even fter vrious dys post mortem. Enzymes nd ntioxidnt nutrients (minly vitmins nd peptides) continue to fight ginst ROS vrious dys fter ded of nimls [2]. This effect, more pronounced in met produced on psture, help to extend the shelf life of the met during commercil disply. This point need to e considered in future investigtion. SOD (UI) 1,6 1,4 1,2 1,,8,6,4,2 Figure 6. SOD ctivity (UI) in fresh nd ged Triceps rchii muscle of steers from psture, psture + concentrte nd concentrte. Dt re men ± SEM (n=1). Different uppercse letters mens significnt differences mong systems in ged met (P<.5). Min effects: Feeding system P<.5 Psture >, Psture + concentrte = Psture, ; geing P<.5 > Glutthion Peroxidse For GPx ctivities, significnt min feeding effect (P<.1) ws found independently of the unit of expression of the ctivity, showing tht nimls receiving psture nd concentrte or concentrte lone hve higher ctivities of the enzyme (Figure 7 nd Figure 8). The nimls fed psture seems hve lower ctivity of GPx. This is in ccord with results reported previously in nimls produced in Europe nd fed psture or grin [2,6]. It hs een hypothesized tht the difference etween nimls fed psture or concentrte could e ssocited with the fct tht concentrte re richer in selenium in comprison with psture [2]. GPx (umoles/min/g met) 2, 1,5 1,,5 s Figure 7. GPx ctivity (µmoles/min/g met) in fresh nd ged Triceps rchii muscle of steers from psture, psture + concentrte nd concentrte. Dt re men ± SEM (n=1). Different lowercse nd uppercse letters mens significnt differences mong feeding systems in fresh nd ged met, respectively (P<.5). Min effects: Feeding system P<.1, Psture + concentrte, concentrte > Psture; geing: No significnt This is linked to the geogrphicl difference of the selenium content in plnt [22,23]. This explntion could

6 123 mericn Journl of Food nd Nutrition e cceptle for nimls produced in Europe, ut no for those produced in South meric. Indeed, psture produced in South meric is rich in selenium when compred those psture produced in Europe [22,23]. However, two investigtions relized in South meric (rgentin) showed opposed results using crossreed steers. ritish X indicus in one report nd crossreed without more detils in the other one [1,21]. The reed effect in the responses to selenium in GPx ctivity cnnot e ruled-out. No effect of geing hs een oserved in the GPx ctivities, independently of the unit of expression of the ctivity (Figure 7 nd Figure 8). GPx (nmoles/min/mg protein) s Figure 8. GPx ctivity (nmoles/min/mg protein) in fresh nd ged Triceps rchii muscle of steers from psture, psture nd concentrte nd concentrte. Dt re men ±SEM (n=1). Different lowercse nd uppercse letters mens significnt differences mong feeding systems in fresh nd ged met, respectively (P<.5). shows difference etween fresh nd ged met (p<.5). Min effects: s P<.1 > Psture, Psture + concentrte; geing P<.1 > 4. Conclusion The investigtion results point towrds tht the feeding system seems not to hve direct effect on the resistnce to lipids oxidtion, of met from Triceps rchii muscle of erdeen ngus steers. However, in the cse of protein oxidtion, psture lone protect more efficiently met compred to psture nd concentrte, nd concentrte lone. These results could e proly ssocited, glolly, to the ction of ctlse nd SOD, which present higher ctivities in nimls fed psture. It is well known tht these two ntioxidnt enzymes work ssocitively to fight ginst ROS. s expected nd previously descried in other report, GPx present more ctivity in nimls fed concentrte in comprison to ones fed psture. This ehvior of the GPx remin uncler nd cnnot e explined only y the fct tht the concentrte is richest in selenium thn psture. This is true for Europen psture, ut not for South mericn one, like in the present investigtion. This point hs to e deeply studied in future investigtion. Of course, no-enzymtic ntioxidnt present in food, like vitmins, proly completed the ntioxidnt ction of enzymes in reducing the oxidtion. However, the enzymtic ction of ctlse, SOD nd Gpx ginst ROS, remin the first line of defense. Future studies hve to highlight precisely the ntioxidnt ction of those enzymes in the protection of met from lipids nd protein oxidtion. For now, nd in regrd to the results oserved here, it s not possile to dvice wht kind of feeding system is the most suitle to preserve met from lipids nd protein oxidtion. cknowledgement To lejndro Sns (Frigorifico Solis) nd Ricrdo Plm (Uruguyn Society of erdeen ngus reeders) for their help. Conflict of Interest The uthors declre tht there is no conflict of interest. References [1] Insni, E. M, Eyheride,, Grigioni, G, Sncho,. M, Pensel, N., nd Desclzo,. M, Oxidtive stility nd its reltionship with nturl ntioxidnts during refrigerted disply of eef produced in rgentin, Met Science, 28, 79, [2] Gtellier, P, Mercier, Y, nd Renerre, M, Effect of diet finishing mode (psture or mixed diet) on ntioxidnt sttus of Chrolis ovine met, Met Science, 24, 67: [3] Ouli,, Herrer-Mendez, C. H, Coulis, G, ecil, S, oudjelll,, ury, L, nd Sentndreu, M., Revisiting the conversion of muscle into met nd the underlying mechnisms, Met Science, 26, 74, [4] Dley, D., ott,, Doyle, P.S, Nder, G., nd Lrson, S, review of ftty cid profiles nd ntioxidnt content in grss-fed nd grinfed eef. Nutrition Journl, 21, [5] Lynch, S. M, nd Frei,, Mechnisms of copper- nd irondependent oxidtive modifiction of humn low-density lipoprotein, Journl of Lipid Reserch, 1993, 34, [6] Mercier, Y, Gtellier, P, nd Renerre, M, Lipid nd protein oxidtion in vitro, nd ntioxidnt potentil in met from Chrolis cows finished on psture or mixed diet, Met Science, 24, 66, [7] Stoscheck, C. M, Quntittion of Protein, Method of Enzymology, 199, 182, [8] ei, H, Ctlse in vitro. In L. Pcker (Ed), Oxygen rdicls in iologicl systems, Method of Enzymology, 1984, 15, [9] Mrklund, S, nd Mrklund, G, Involvement of the superoxide nion rdicl in the utoxidtion of pyrogllol nd convenient ssy for superoxide dismutse, Europen Journl of iochemistry, 1974, 47, [1] DeVore, V. R. nd Greene,. E, Glutthione peroxidse in postrigor ovine semitendinosus muscle, Journl of Food Science, 1982, 47, [11] Günzler,, nd Flohé, L, Glutthione peroxidse. In R.. Greenwld (Ed), CRC Hndook of methods for oxygen rdicl reserch, 1985, 1, [12] Gtellier, P, Mercier, Y, Juin, H, nd Renerre, M, Effect of finishing mode (psture- or mixed diet) on lipid composition, colour stility nd lipid oxidtion in met from Chrolis cttle, Met Science, 25, 69, [13] Desclzo,. M, Insni, E. M, ioltto,, Sncho,. M, Grcí, P. T, Pensel, N., nd Josifovich, J., Influence of psture or grin-sed diets supplemented with vitmin E on ntioxidnt/oxidtive lnce of rgentine eef, Met Science, 25, 7: [14] Pouzo, L., Desclzo,.M, Zritzky, N.E, Rossetti, N, Pvn, E, ntioxidnt sttus, lipid nd color stility of ged eef from grzing steers supplemented with corn grin nd incresing levels of flxseed, Met Science, 216,111, 1-8. [15] Tlmnt,, Monin, G, rind, M, Ddet, M, nd rind, Y, ctivities of metolic nd contrctile enzymes in 18 ovine muscles, Met Science, 1986,18, [16] Crer, M. C, Rmos,, Sdoun,, nd rito, G, Selenium, copper, zinc, iron nd mngnese content of seven met cuts from

7 mericn Journl of Food nd Nutrition 124 Hereford nd rford steers fed psture in Uruguy. Met Science, 21, 84, [17] Rmos,, Crer, M.C, nd Sdoun,, ioccessiility of Se, Cu, Zn, Mn nd Fe, nd hem iron content in unged nd ged met of Hereford nd rford steers fed, Met Science, 212, 91, [18] Popov, T, Effect of rering system on the ftty cid composition nd oxidtive stility of the M. Longissimus lumorum nd M. semimemrnosus in lms, Smll Ruminnts Reserch, 27, [19] Lund, M. N., Heinonen, M., ron, C. P., & Estevez, M. (211). Protein oxidtion in muscle foods: review. Moleculr, Nutrition nd Food Reserch, 55, [2] Flowo,., Fyemi, P.O, nd Muchenje, V, Nturl ntioxidnts ginst lipid protein oxidtive deteriortion in met nd met : review, Food Reserch Interntionl, 214, 64, [21] Desclzo,.M, Rossetti, L, Grigioni, G, Iruruet, M, Sncho,.M, Crrete, J, nd Pensel, N., ntioxidnt sttus nd odour profile in fresh eef from psture or grin-fed cttle, Met Science, 27, 75, [22] Crer MC, Rmos nd Sdoun, Selenium, zinc, copper nd mngnese in fresh ngus steers met from pstures to concentrted-sed feeding systems in Uruguy. IUNS 2th. Interntionl Congress of Nutrition. Grnd. Espñ. nnls of Nutrition & Metolism, 64:1531. [23] Crer, M.C, nd Sdoun,, n overview of the nutritionl vlue of eef nd lm met from South meric, Met Science, 214, 98,3,