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1 This rticle ws downloded y: [vhid rnjr] On: 04 Jnury 2013, At: 13:41 Pulisher: Tylor & Frncis Inform Ltd Registered in Englnd nd Wles Registered Numer: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK British Poultry Science Puliction detils, including instructions for uthors nd suscription informtion: Betine: promising ntioxidnt gent for enhncement of roiler met qulity M. Alirezei, H. Rez Gheisri c, V. Rez Rnjr d & A. Hjiemni e Division of Biochemistry, School of Veterinry Medicine-Lorestn University, P.O. Box: 465, Khorrm Ad Rzi Herl Medicines Reserch Center, Lorestn University of Medicl Sciences, Khorrm Ad c Deprtment of Food Hygiene, School of Veterinry Medicine-Shirz University, P.O. Box: 71345, Shirz d Deprtment of Avin Medicine, School of Veterinry Medicine-Shirz University, P.O. Box: 71345, Shirz e Deprtment of Animl Reproduction Science, School of Veterinry Medicine-Shirz University, P.O. Box: 71345, Shirz, Irn Accepted uthor version posted online: 24 Sep 2012.Version of record first pulished: 03 Jn To cite this rticle: M. Alirezei, H. Rez Gheisri, V. Rez Rnjr & A. Hjiemni (2012): Betine: promising ntioxidnt gent for enhncement of roiler met qulity, British Poultry Science, 53:5, To link to this rticle: PLEASE SCROLL DOWN FOR ARTICLE Full terms nd conditions of use: This rticle my e used for reserch, teching, nd privte study purposes. Any sustntil or systemtic reproduction, redistriution, reselling, lon, su-licensing, systemtic supply, or distriution in ny form to nyone is expressly foridden. The pulisher does not give ny wrrnty express or implied or mke ny representtion tht the contents will e complete or ccurte or up to dte. The ccurcy of ny instructions, formule, nd drug doses should e independently verified with primry sources. The pulisher shll not e lile for ny loss, ctions, clims, proceedings, demnd, or costs or dmges whtsoever or howsoever cused rising directly or indirectly in connection with or rising out of the use of this mteril.

2 British Poultry Science Volume 53, Numer 5 (Octoer 2012), pp Betine: promising ntioxidnt gent for enhncement of roiler met qulity M. ALIREZAEI 1,2, H. REZA GHEISARI 3, V. REZA RANJBAR 4 AND A. HAJIBEMANI 5 1 Division of Biochemistry, School of Veterinry Medicine-Lorestn University, P.O. Box: 465, Khorrm Ad, 2 Rzi Herl Medicines Reserch Center, Lorestn University of Medicl Sciences, Khorrm Ad, 3 Deprtment of Food Hygiene, School of Veterinry Medicine-Shirz University, P.O. Box: 71345, Shirz, 4 Deprtment of Avin Medicine, School of Veterinry Medicine-Shirz University, P.O. Box: 71345, Shirz, nd 5 Deprtment of Animl Reproduction Science, School of Veterinry Medicine-Shirz University, P.O. Box: 71345, Shirz, Irn Downloded y [vhid rnjr] t 13:41 04 Jnury 2013 Astrct 1. Antioxidnt nd methyl donor effects of etine in experimentl niml models hve recently een demonstrted. The present study ws therefore designed to exmine the ntioxidnt effects of etine on the ntioxidnt sttus nd met qulity of rest muscles in roilers. 2. Co roilers were rndomly divided into Control, Methionine low, Methionine low plus etine, nd Betine groups. 3. The ctivity of the min ntioxidnt enzyme (glutthione peroxidse) in the Betine nd the Methionine low plus etine groups significntly incresed compred to the Methionine low nd Control groups. Ctlse nd superoxide dismutse ctivities were significntly higher in the Betine group compred to the Methionine low group, nd lipid peroxidtion ws significntly higher in the Control nd the Methionine low groups. 4. The present study indictes tht dding etine (1 g/kg) to diet deficient in methionine cn significntly improve ntioxidnt defences nd met qulity, decresing lipid peroxidtion in the rest muscles of roiler chickens. INTRODUCTION It is well known tht muscles contin vrious endogenous prooxidnt nd ntioxidnt systems nd the lipid peroxidtion process of met results when ntioxidnt defences re overcome y peroxidtion mechnisms (Decker nd Zhimin, 1998; Gheisri nd Motmedi, 2010). The glutthione ntioxidnt system plys fundmentl role in cellulr defence ginst rective oxygen species (ROS). The cellulr tripeptide, GSH (g-glutmyl cysteinyl glycine) reduces peroxidtive dmge y neutrlising free rdicls (Gnesn et l., 2011; Alirezei et l., 2011). Glutthione peroxidse (GPx), superoxide dismutse (SOD), nd ctlse (CAT), which re responsile for the destruction of peroxides, hve specific role in protecting tissues ginst oxidtive dmge (Sun et l., 2008; Gnesn et l., 2011). Reduction of the ctivity of these enzymes in oxidtive stress my led to the formtion of O 2 nd H 2 O 2, which in turn cn form the hydroxyl rdicl ( OH) nd ring out numer of hrmful rections, leding to lipid peroxidtion (Klr et l., 1988). Previous studies in mmmls showed tht ROS generted during metolism were not dequtely removed when the ntioxidnt defences were overcome y oxidtive stress, resulting in lipid peroxidtion (Vogt nd Richie, 1993; Di Simplicio et l., 1997; Roinson et l., 1997; Zhng et l., 2008). Lipid peroxidtion is directly linked to rncidity in Correspondence to: M. Alirezei, Division of Biochemistry, School of Veterinry Medicine, Lorestn University, P.O. Box: 465, Khorrm Ad, Irn. E-mil: lirezei_m54@yhoo.com Accepted for puliction 12th June ISSN (print)/ISSN (online)/12/ ß 2012 British Poultry Science Ltd

3 700 M. ALIREZAEI ET AL. Downloded y [vhid rnjr] t 13:41 04 Jnury 2013 met, which hs considerle negtive effect on met qulity (Ruff et l., 2003; Zhng et l., 2008). Mlondildehyde is metolite derived from lipid peroxidtion nd hs een widely used s n indictor of oxidtive dmge nd met qulity (Hlliwell nd Gutteridge, 1989; Frigg et l., 1990; Winston nd Di Giulio, 1991; Zhng et l., 2008). Antioxidnts dely or prevent lipid peroxidtion y reducing free rdicl ctivities in met (Gheisri nd Motmedi, 2010), nd the ntioxidnt supplementtion of feed is n efficient method for incresing oxidtive stility (Roginsky nd Lissi, 2005; Gheisri nd Motmedi, 2010). Betine is common term for trimethylglycine, sustrte for etine-homocysteine methyl trnsferse (BHMT) in the liver nd kidney (Kettunen et l., 2001; Atti et l., 2009). It is often found in high concentrtions in plnts sujected to drought, which is due to the osmoregultory properties of etine (Kettunen et l., 2001; Atti et l., 2009). Previous studies indicted tht etine my ply importnt roles such s improving growth performnce, ft distriution (Wng et l., 2004; Sun et l., 2008; Atti et l., 2009), immune response, nd ct s coccidiostt enhncer (Swin nd Johri, 2000; Kettunen et l., 2001; Atti et l., 2009) in roilers. The etine in mize nd soyen mel were reported to e elow the detectle level (Chendrimd et l., 2002), nd ws not detected in mize-soyen mel diet (Wldroup nd Fritts, 2005; Atti et l., 2009). Betine nd folic cid re ll considered s methyl donors nd hve een shown to compenste for the prtil deficiency of lile methyl groups in mizesoyen-sed diets (Mtthews nd Southern, 2000; Pilli et l., 2006; Dilger et l., 2007). The formtion of methionine from homocysteine cn occur either vi etine or vi 5-methyl tetrhydrofolte (Crig, 2004; Alirezei et l., 2010; Alirezei et l., 2011, 2012). Previous studies hve shown tht oth pthwys re eqully importnt nd tht etine is vitl methylting gent (Brk nd Tum, 1983; Finkelstein nd Mrtin, 1986; Alirezei et l., 2012). Betine trnsfers methyl group vi the enzyme BHMT to ecome dimethylglycine (Alirezei et l., 2011). Methionine is one of the most limiting mino cids, plying crucil role in ody protein synthesis, nd therefore it would e eneficil to spre its function s methyl donor (Sun et l., 2008). It hs een shown tht choline must first e ctivted nd then converted to etine efore the methyl groups re lierted to methyltion cycles (McKeever et l., 1991; Sun et l., 2008). In contrst, etine contins three methyl groups in its structure nd dontes these in severl metolic rections (Sun et l., 2008; Alirezei et l., 2012), therefore llowing it to e used s n effective compound to spre dietry methionine s methyl donor. Administrtion of etine hs een shown to exert significnt role within tissue s methyl donor, which in turn my e used for the synthesis of methionine, crnithine, phosphtidylcholine, nd cretine, sustnces which ply key role in protein nd energy metolism in the cells (Crig, 2004; Alirezei et l., 2012). In this regrd, etine significntly improved the rest met yield nd growth performnce of roilers (Sun et l., 2008; Atti et l., 2009). However, its ntioxidnt effects on rest met qulity hve not yet een explored. We recently demonstrted the methyl donor nd ntioxidnt properties of etine in experimentl niml models (Alirezei et l., 2010; Alirezei et l., 2011). Thus, the present study ws designed to exmine the ntioxidnt nd nutrient effects of etine on met qulity in Co roiler chickens. MATERIALS AND METHODS Mterils Betine (Betfin Õ 96%) ws otined from Biochem Compny (Brinkstrsse 55, D Lohne, Germny). GPx nd SOD kits were otined from Rndox Õ, Antrim, UK). All chemicls used were of nlyticl grde. Animls A totl of 58 5-d-old Co roiler chickens, previously vccinted ginst infectious ronchitis t the htchery, were purchsed from Frs Poultry Compny (Frs Compny, Shirz, Irn). The irds were weighed nd strtified nd 48 rndomly distriuted into 4 equl groups. The control group (C, which received commercil sl diet formulted to meet the nutritionl requirement of the irds ccording to the NRC (1994) recommendtion), Methionine low group (ML, control group diet except methionine content lowered from 51 to 46 g/kg strter nd 42to35g/kg grower diet) (Sun et l., 2008), Methionine low plus etine group (ML þ B, Methionine low group diet plus etine, 1 g/kg of the diet), nd Betine group (B, control group diet plus etine 1 g/kg of the diet) (Atti et l., 2009). The diets were supplemented with commercil vitmin nd minerl premix nd 5000 mg/kg of the diet y choline chloride 50%. The experiment ws conducted into two phses: strter phse (1 21 d) nd grower phse (22 49 d). All irds were fed on mize-soyen mel sl diet (Tle 1 nd 2). All groups were fed for 49 consecutive dys, food nd wter were provided d liitum nd weight gin nd food consumption were determined t weekly

4 BETAINE: A PROMISING ANTIOXIDANT AGENT 701 Downloded y [vhid rnjr] t 13:41 04 Jnury 2013 Tle 1. Ingredient composition nd nutrient content of Strter diet (1 21 d) Ingredients (%) Control Methionine Low (ML) ML þ etine Betine Mize Soyen mel (CP 43%) Mize oil Diclcium phosphte Oyster shell Sodium chloride Vitmin-minerl premix DL-Methionine Betine Totl Clculted nlysis 1 ME (MJ/kg) Crude protein (%) C (%) Aville P (%) N (%) Linoleic cid (%) Lysine (%) Methionine (%) Met þ Cysteine (%) Betine(%) Clculted vlues were ccording to NRC (1994) vlues for feedstuffs. Tle 2. Ingredient composition nd nutrient content of Grower diet (22 46 d) Ingredients (%) Control Methionine Low (ML) ML þ etine Betine Mize Soyen mel (CP 43%) Mize oil Diclcium phosphte Oyster shell Sodium chloride Vitmin-minerl premix DL-Methionine Betine Totl Clculted nlysis 1 ME (MJ/kg) Crude protein (%) C (%) Aville P (%) N (%) Linoleic cid (%) Lysine (%) Methionine (%) Met þ Cysteine (%) Betine (%) Clculted vlues were ccording to NRC (1994) vlues for feedstuffs. intervls (dt not shown). The irds were sujected to continuous lighting progrmme of 23 L:1D nd the temperture ws grdully reduced from 32 Ctd1to20 C y d 21. There ws no coccidiostt included in the diets. The irds were kept in 4 seprted nd clened pens littered with wood shvings. No signs of coccidiosis were pprent nd mortlity ws low (1 out of 48 irds). Hence, the potentil positive effects of etine under coccidiosis chllenge plyed no role in the present experiment. One dy fter the lst tretment the irds were strved for 3 h, slughtered, plucked, led nd weighed. The rest muscles were dissected wy, crefully clened of dhering mterils such s lood nd stored t 70 C for lter (within 2 months) ntioxidnt nlysis. Met proximte composition (crude protein, ft, moisture nd sh) ws nlysed on the fresh met. Muscle preprtion for protein mesurement, TBARS detection nd enzyme ssy Brest muscles were thwed nd mnully homogenised vi liquid nitrogen in cold phosphte uffer (ph 74, 01 M) contining 5 mm EDTA nd the deris removed y centrifugtion t 5000 g for 10 min (Centrifuge 5415 R; Rotofix 32 A, Germny) (Kherdmnd et l., 2010). Superntnts were recovered nd used for protein mesurement, ntioxidnt enzyme ctivities, nd TBARS concentrtion. With respect to the different moisture contents of the muscle tissues in the control nd tretment groups (due to the osmoregultory effect of etine), we decided to express ctivity of the ntioxidnt enzymes in order of unit/mg protein. Protein content of tissue homogentes ws determined using the colorimetric method of Lowry with ovine serum lumin s stndrd (Lowry et l., 1951) Mesurement of GPx ctivity The ctivity of glutthione peroxidse (GPx) ws evluted with Rndox Õ GPx detection kit ccording to the mnufcturer s instructions. GPx ctlyse the oxidtion of glutthione (GSH) y cumene hydroperoxide. In the presence of glutthione reductse (GR) nd NADPH, the oxidised glutthione (GSSG) is immeditely converted to the reduced form with concomitnt oxidtion of NADPH to NADP þ. The decrese in sornce ws mesured spectrophotometriclly (Vrin Austrli, Pty Ltd) ginst lnk t 340 nm. One unit (U) of GPx ws defined s l mmol of oxidised NADPH per min. The GPx specific ctivity ws expressed s milliunit per milligrm of tissue protein (mu/mg protein). Mesurement of SOD ctivity The ctivity of superoxide dismutse (SOD) ws evluted with the Rndox Õ SOD detection kit ccording to the mnufcturer s instructions. The role of SOD is to ccelerte the dismuttion

5 702 M. ALIREZAEI ET AL. Tle 3. Brest muscle proximte composition (men SEM) in the control, methionine low, methionine low þ etine, nd etine group of Co roiler chickens Groups Ft (%) Crude protein (%) Ash (%) Moisture (%) Control Methionine Low (ML) M.L þ etine Betine Downloded y [vhid rnjr] t 13:41 04 Jnury 2013 of the toxic superoxide (O 2 ), produced during oxidtive energy processes, to hydrogen peroxide nd moleculr oxygen. This method employs xnthine nd xnthine oxidse to generte superoxide rdicls which rect with 2-(4-iodophenyl)-3-(4-nitrophenol)-5-phenyltetrzolium chloride (I.N.T.) to form red formzn dye. The SOD ctivity is then mesured y the degree of inhiition of this rection. One unit of SOD is tht which cuses 50% inhiition in the rte of reduction of INT under the conditions of the ssy. The SOD specific ctivity ws recorded t 505 nm nd through stndrd curve, nd expressed s unit per milligrm of tissue protein (U/mg protein). Mesurement of CAT ctivity Tissue ctlse ctivity ws ssyed using the method descried y Cliorne (1986). The rection mixture (1 ml) consisted of 50 mm potssium phosphte (ph 70), 19 mm H 2 O 2, nd20 50 l smple. The rection ws initited y the ddition of H 2 O 2 nd sornce chnges were mesured t 240 nm (25 C) for 30 s. The molr extinction coefficient for H 2 O 2 is 436M 1 cm 1. The CAT specific ctivity ws expressed s the unit defined s 1 m mol of H 2 O 2 consumed per min per milligrm of tissue protein (U/mg protein). Mesurement of TBARS content The 2-thiorituric cid (TBA) ssy ws crried out ccording to the extrction method descried y Vyncke (1975), with some modifictions: the met smple (150 g) ws homogenised (Ultr Turrx T-25, Stufen, Germny) with 6 ml of 75% trichlorocetic cid solution including 01% propylgllte nd 01% EDTA for 45 sec t RPM nd the homogente filtered through filter pper, The extrct (2 ml) ws mixed with 002 M thiorituric cid (2 ml), heted nd cooled s descried y Vyncke (1975). The sornce ws mesured t 532 nd 600 nm using CARY 3 UV-visile spectrophotometer (Vrin Austrli, Pty Ltd), nd the sornce difference, A 532 nm A 600 nm, ws clculted with A 600 nm correcting for smple turidity. TBARS ws clculted using 1,1,3,3-tetrethoxypropne (TEP)/mlonic ldehyde s stndrd nd expressed s nmol/mg protein of muscle tissue. Anlysis of met The ground met ws nlysed for crude protein, ft, moisture, nd sh contents ccording to the methods of AOAC Interntionl (AOAC, 1984) (Tle 3). Sttisticl nlysis All results re presented s Men stndrd error of men (S.E.M.). Dt were compred y one-wy nlysis of vrince (ANOVA) with Tukey s post hoc nlysis. A clculted P vlue of less thn 005 ws considered sttisticlly significnt. Sttisticl nlysis ws performed using the Grphpd PRISM version 5 (Grphpd Softwre Inc., Sn Diego, CA). All vriles were previously tested for norml distriution nd homogeneous vrinces y Leven s sttistic test. RESULTS The men vlues (S.E.M.) of the glutthione peroxidse (GPx), superoxide dismutse (SOD) nd ctlse (CAT) ctivity of the rest muscles re presented in Figures 1 3, respectively. GPx ctivity ws significntly higher in the B group thn in the C nd ML groups. The ML þ B group hd GPx levels similr to the B tretment nd significntly higher thn ML tretment. SOD ctivity ws significntly lower in ML tretment compred to the other tretments (P <005). Although SOD ctivity in the C nd ML þ B tretments ws lower thn in the B tretment, this reduction ws not sttisticlly significnt (P >005). CAT ctivity in the B group ws significntly higher thn in the other groups; thus it ws indicted tht etine is not le to increse CAT ctivity in the ML þ B group ner to tht of the B group. Lipid peroxidtion concentrtion (TBARS content) ws significntly higher in the ML group thn in those receiving the B nd ML þ B tretments (P <005). However, significnt decreses were oserved in lipid peroxidtion for oth groups tht received the B nd ML þ B tretments

6 BETAINE: A PROMISING ANTIOXIDANT AGENT 703 GPx ctivity mu/mg protein CAT ctivity U/mg protein Downloded y [vhid rnjr] t 13:41 04 Jnury 2013 Control Meth. low M.L.+ etine Betine Figure 1. Glutthione peroxidse (GPx) ctivity (men þ SEM) in rest muscle tissue in the control, methionine low, methionine low þ etine, nd etine groups., Mens with different superscripts differ significntly (P < 005). SOD ctivity U/mg protein Control Meth. low M.L.+ etine Betine Control Meth. low M.L.+ etine Betine Figure 3. Ctlse ctivity (men þ SEM) in rest muscle tissue in the control, methionine low, methionine low þ etine, nd etine groups., Mens with different superscripts differ significntly (P < 005). Figure 2. Superoxide dismutse (SOD) ctivity (men þ SEM) in rest muscle tissue in the control, methionine low, 0 methionine low þ etine, nd etine groups., Mens with different superscripts differ significntly (P < 005). Control Meth. low M.L.+ etine Betine TBARS nmol/mg protein compred to controls (P <005), nd the C group indicted slightly lower TBARS content compred to the ML group lso (Figure 4). Tle 3 shows the effects of etine nd methionine on iochemicl indictors of muscle composition. Overll, the tretment with etine improved ll of the rest indictors, lthough the effects were not significnt (P > 005). Betine hd no significnt effect (P >005) on the sh nd moisture of the rest muscles in ny of the groups. There ws no significnt difference in muscle composition mong the tretments. There ws tendency for the etine-treted irds to hve lower ft content (P ¼ 0072) nd for ML group to hve lower crude protein Figure 4. Thiorituric cid rective sustnces (TBARS) concentrtion in rest muscle tissue in the control, methionine low, methionine low þ etine, nd etine groups., Mens with different superscripts differ significntly (P < 005). content (P ¼ 0065). One possile reson for the lck of sttisticl significnce in effects on met composition my e the smll smple size (n ¼ 48) of roilers. The reduction in methionine in the diet significntly decresed the weight gin of the roilers in the ML group (P <005). In contrst, the ddition of etine to the C nd ML diet significntly incresed the weight gin (P <005). The weights of the roilers in the groups tht received etine were higher thn those in of the

7 704 M. ALIREZAEI ET AL. Downloded y [vhid rnjr] t 13:41 04 Jnury 2013 Weight of roiler chickens (Kg) Control Meth. low M.L.+ etine Betine Figure 5. Weight gin (men þ SEM) in the control, methionine low, methionine low þ etine, nd etine groups., Mens with different superscripts differ significntly (P < 005). controls, however, the enhnced weights were not sttisticlly significnt (P >005). Indeed, the ddition of etine to the control diet hd no significnt effect on weight gin in roilers (Figure 5). DISCUSSION The present study demonstrted for the first time tht etine cn ct s n ntioxidnt gent in low-methionine diet-induced oxidtive stress for roilers, nd it is suggested tht it does so y promoting the min ntioxidnt enzyme ctivities including GPx, CAT, nd SOD, susequently decresing lipid peroxidtion in rest muscles. Our oservtion for ntioxidnt enzymes, TBARS concentrtion nd weight gin in the etine-treted roilers supports the ide tht etine is ssocited with ntioxidnt nd methyl donor properties through its involvement in cell memrne stilistion nd homocysteine remethyltion (Zhng et l., 2008; Alirezei et l., 2011). This experiment reveled tht supplementtion of etine (1 g/kg of diet) to the diet of 10% methionine deficiency incresed growth performnce in roilers. Thus, it ppers tht etine in mrginlly methionine deficient diet could led to n equivlent growth response in roilers, nd tht etine could spre smll portion of methionine (Sun et l., 2008). To evlute the effects of etine on ntioxidnt sttus in Co roiler chickens, the rest muscle ctivity of some ntioxidnt enzymes nd the concentrtion of TBARS s lipid peroxidtion mrker were evluted. The result of oxygen rdicl formtion is well-known to dmge DNA, RNA, protein nd lipids, susequently dmging vrious cellulr comprtments (Gheisri nd Motmedi, 2010; Alirezei et l., 2011). Memrne-ssocited polyunsturted ftty cids re redily ttched y the hydroxyl rdicl in process tht leds to the peroxidtion of lipids, which cn ffect met qulity (Ruff et l., 2003). It hs een clerly indicted tht lipid peroxidtion significntly increses y ccumultion of H 2 O 2 in concentrtion-dependent mnner (Grci et l., 2005). Cells re le to defend themselves ginst the dmging effects of oxygen rdicls y wy of their own ntioxidnt mechnisms, including enzymtic nd nonenzymtic ntioxidnt systems (Ross, 1988; Sehirli et l., 2008). GPx nd CAT re two key ntioxidnt enzymes tht cn decompose hydrogen peroxide to wter (Turner nd Lysik, 2008; Kherdmnd et l., 2010). SOD, nother ntioxidnt enzyme in cells, rpidly converts the superoxide nion (O 2 ) to less dngerous hydrogen peroxide (H 2 O 2 ). GPx nd CAT cn then decompose H 2 O 2 to wter (Kherdmnd et l., 2009; Kherdmnd et l., 2010). Although H 2 O 2 is not prticulrly rective product, it cn e reduced to highly rective metolite hydroxyl rdicl (Peltol et l., 1994). With respect to ntioxidnt enzyme ctivities, our dt showed significnt increse in ntioxidnt defencse sttus in the rest muscle of the etine-treted roilers, which suggests decrese in the ROS genertion rte (Alirezei et l., 2011). In the present study, etine cused significnt increses in the GPx ctivity for oth groups tht received etine compred to the C nd ML groups. Betine supplementtion lso significntly reduced TBARS concentrtions, suggesting etine cted s n ntioxidnt, possily y scvenging ROS free rdicls. On the other hnd, the muscle TBARS content decresed in the etine-treted roilers, suggesting etine possessed ntioxidnt effects nd preserved the cellulr ntioxidnt stores. In ccordnce with GPx ctivity, other ntioxidnt enzymes incresed in the B group compred to the ML group. In this setting, ntioxidnt properties of etine decresed tissue dmge rising from lipid peroxidtion in het stress of roilers (Atti et l., 2009). Further, we recently demonstrted tht homocysteine decreses the ctivity of ntioxidnt enzymes (Alirezei et l., 2011). Therefore, hyperhomocysteinemi tht ws induced vi methionine low diet might potentite the toxic effects of ROS. In ddition, the utooxidtion of homocysteine is known to generte ROS (Alirezei et l., 2011). The increse in CAT nd SOD ctivity in our study for etine-treted roilers correltes well with the decrese in TBARS content s lipid peroxidtion mrker in the rest muscle tissue. Mlondildehyde is one of the mjor ldehyde derivtives of lipid peroxidtion nd it is

8 BETAINE: A PROMISING ANTIOXIDANT AGENT 705 Downloded y [vhid rnjr] t 13:41 04 Jnury 2013 y-product of the lipid peroxidtion process (Smith et l., 2005; Alirezei et l., 2011). To this extent, oxidtive stress nd lipid peroxidtion ws decresed in roilers receiving etine supplementtion. It is widely ccepted tht CAT nd SOD, which re responsile for the destruction of peroxides, hve very specific role in protecting tissues ginst oxidtive dmge (Gnesn et l., 2007; Alirezei et l., 2011). In the present experiment, the unpired electron present in the hydroxyl free rdicl my hve een trpped nd susequently dismuted y etine (Srvnn nd Prksh, 2004; Alirezei et l., 2011). However, the protective effect of etine ginst methionine low-induced oxidtive stress oserved in this study my lso e ssocited with the restortion of S-denosyl methionine (SAM), which contriutes to n increse in the supply of sustrte needed for the synthesis of glutthione tht protects the cell from rective metolites nd ROS (Gnesn et l., 2007; Alirezei et l., 2011). The positive influence of 1 g etine/kg diet on met qulity oserved in the present study my lso e due to the incresing percentge of crude protein, while the percentge of ft nd sh decresed. The exct mechnism ffected y etine on crcse composition is not cler. One report did indicte tht etine improved rest met yield (McDevitt et l., 2000). In contrst, dominl ft yield s well s the ft content in the liver ws reduced, wheres ft content in the rest ws incresed y the supplementtion of etine, (Zhn et l., 2006; Sun et l., 2008). In the present study, with respect to rest composition, there ws decrese in the ft content of the rest met, lthough it ws not significnt. The ility of etine to spre some of the methionine needs in roiler diets is suject to considerle controversy. Esteve-Grci nd Mck (2000) evluted the potentil replcement vlue of methionine y etine in methioninedeficient diet. There were no significnt interctions etween etine nd methionine; methionine supplementtion significntly improved ody weight nd feed to gin t 21 nd 41 d, nd significntly incresed rest yield t d 41. However, the ddition of etine significntly improved crcse yield with no significnt chnge in other crcse prmeters such s rest yield or dominl ft (Esteve- Grci nd Mck, 2000; Sun et l., 2008). It ws concluded tht etine could not e sustitute for methionine deficiency, ut it my improve crcse composition, especilly rest met yield (Esteve-Grci nd Mck, 2000). The present study showed tht up to 10% of dietry totl methionine could e replced y etine without negtively ffecting the growth performnce of the roilers. As previously mentioned, this is the first in vivo study to show tht replcement of 10% methionine y etine in roiler diets results in n increse in the min ntioxidnt enzyme ctivities nd decresed lipid peroxidtion in rest muscle, susequently improving met qulity. Betine is methylting gent like SAM nd it lso spres methionine vi the BHMT pthwy (Wldroup et l., 2006; Alirezei et l., 2011). Therefore, etine my hve ntioxidnt nd nutrient effects ginst oxidtive dmge in roiler diets. In ddition, etine my hve some dvntges compred to the methionine ppliction, s numerous methyltion rections involve methionine, which is then converted to SAM, the methyl group donor, nd then to homocysteine (Esteve-Grci nd Mck, 2000; Wldroup et l., 2006; Alirezei et l., 2011). Both methionine nd homocysteine re potentilly toxic to cells, nd oth my ccumulte if methyl donors or methyl cceptors re deficient (Wldroup et l., 2006). Alterntive methyl donors such s etine or choline my llevite the dietry needs of methionine y tking the plce of methionine s methyl donor or y providing the methyl group necessry for the conversion of homocysteine to methionine (Wldroup et l., 2006; Alirezei et l., 2011). Although, etine ws demonstrted in the present pper s potentil ntioxidnt gent for the prevention of methionine lowinduced oxidtive stress in the roiler diet nd improved ntioxidnt defence s well s met qulity, further studies should e performed to evlute the nutrient effects of etine principlly on met qulity with lrger smple size of roilers. ACKNOWLEDGEMENTS This reserch ws finncilly supported y project numer 751-MKR, School of Veterinry Medicine- Shirz University, Shirz, Irn. 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