Animal performance and fatty acid composition of lambs fed with different vegetable oils

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1 Animl performnce nd ftty cid composition of lmbs fed with different vegetble oils T. Mnso '*, R. Bods b, T. Cstro c, V. Jimeno d, A.R. Mntecón 5 *ETS Ingenierís Agrris, Universidd de Vlldolid, 304 Ptenci, Spin b Instituto de Gnderí de Montñ (CSICULE), Crulleros, León, Spin c Dept. Producción Animl, Univ. Complutense de Mdrid, 280 Mdrid, Spin d Dept. Producción Animl, Univ. Politécnic de Mdrid, 280 Mdrid, Spin ARTICLE INFO ABSTRACT Twentyseven lmbs were used to investigte the effects of the inclusion of 4% hydrogented plm oil () or sunflower oil () in the concentrte on niml performnce, crcss nd met qulity nd ft chrcteristics nd ftty cid composition. Animls (16.2 ±0.27 kg initil weight) were fed concentrte (, or ) nd brley strw d libitum nd slughtered t 25 kg. lmbs tended to et less concentrte thn nimls (P< 0.10). Neither nor ffected ny of the crcss chrcteristics studied, met ph nd met nd ft colour (P> 0.05). decresed proportions of CI 6:0, CI 8:1 Keywords: císj 2 nd clg;3 ( P< 0>05 ) nd i ncre sed C18:l trns (P< 0.001) nd C18:2/C18:3 rtio (P< 0.05). Ath S flow, erogenicity index ws lower (P< 0.05) when ws included in the concentrte. did not ffected Fttening lmbs nc ' ^FO improved ftty cid composition of fttening lmbs without ffecting niml performnce. Ftty cid Atherogenicity 1. Introduction In the Mediterrnen re, intensively rered lmbs re usully fed with brley strw nd concentrte d libitum in order to chieve gret growth rtes. Over the lst decde, ft supplementtion becme common prctice to increse the energy density of the diet for ruminnts (Bumn, Corl, & Peterson, 2003), plm oil supplements being the most used, since they do not hve the negtive effects on rumen fermenttion s unsturted oils (Jenkins, 1993). However, the type of ft in the rtion is known to ffect the composition of body ft (Bs & Mornd Fehr, 2000). Lmb ft is chrcterized by high sturted ftty cid (SFA) content, nd low polyunsturted ftty cid (PUFA) content (Enser, Hllett, Hewitt, Fursey, & Wood, 1996), due to the biohydrogention of unsturted ftty cids by rumen microflor (Doreu & Ferly, 1994). Nevertheless, met from ruminnt nimls (Priz & H, 1990) is within the primry sources of conjugted linoleic cid (CLAs) for humns, which hs been ssocited with wide rnge of positive helth benefits. One of the options of enhncing the beneficil effects of niml products is through diet mnipultion, such s the use of finishing diets supplemented with sunflower oil with high purities of linoleic or oleic ftty cids to improve the concentrtion of CLAs nd thus their helth benefits * Corresponding uthor. Address: Áre de Producción Animl, E.T.S. de Ingenierís Agrris, Universidd de Vlldolid, Avd. Mdrid, s/n, 304 Plenci, Spin. Tel: ; fx: Emil ddress: tmnso@gro.uv.es (T. Mnso). (Kott et l., 2003). On the other hnd, the use of such oil hs been proposed s n lterntive to increse the content of PUFA in lmb tissues (Yu et l., 2008). Studies pper to focus on higher ruminl CI8:1 trns11 production to enhnce endogenous formtion of CLA cis9, trns11 both in beef nd lmb nd to investigte if production of the precursor, or the ctivity of the A9desturse, is the limiting fctor for chieving higher tissue CLA deposition (Res, De Smet, & Demeyer, 2004). However, lthough severl dverse effects of trnsftty cids on humn helth hve been reported, CI8:1 trns11 (typiclly the mjor trnsftty cid in ruminnt ft) cn serve s precursor for endogenous CLA cis9, trns11 synthesis in humn tissues (Ryhánen et l., 2005). Nevertheless, there re no studies compring the effects of the inclusion of fts with different level of sturtion on lmbs performnce nd ftty cid composition. The present work ws conducted to study the effects of 4% hydrogented plm oil () or sunflower oil () supplementtion in the concentrte for fttening lmbs on feed intke, niml performnce, crcss nd met chrcteristics nd met nd subcutneous ftty cid composition. 2. Mterils nd methods 2.1. Animls Twentyseven mle Merino lmbs (initil ge 89 weeks) were llocted by strtified rndomiztion on the bsis of live body

2 weight (LBW, 16.2 ± 0.27 kg) into three equl groups to study the effects of the inclusion of 4% hydrogented plm oil () nd 4% sunflower oil () in the concentrte offered during the fttening period. The lmbs were kept with their mothers until wening, with free ccess to commercil strter concentrte, brley strw nd lflf hy until the commencement of the tril. They were dewormed by dosing with Ivomec (Meril Lbs., Spin) nd vccinted ginst enterotoxemi (Miloxn, Meril Lbs., Spin). Animls were housed individully nd niml hndling followed the recommendtions of Europen Council Directive 86/ 609/EEC for protection of nimls used for experimentl nd other scientific purposes Diets After 5 dys of dpttion to the control diet (brley strw nd concentrte feed without oil dded), lmbs were fed brley strw nd the corresponding experimentl concentrte feed d libitum. The ingredients nd chemicl composition of the concentrtes re given in Tble 1. Hydrogented plm oil nd sunflower oil were dded to nd mixed completely with the concentrte before feeding ech lmb Experimentl procedure Concentrte nd forge (in long form) were supplied in seprte feeding troughs nd fresh drinking wter ws lwys vilble. The mount of feed offered ws djusted dily on the bsis of the previous dy intke, llowing refusls of 20%. The mounts of feeds offered nd of refusls were weighed dily, nd smples were collected for subsequent nlyses. Animls were weighed before morning feeding twice week to bout 24 kg LBW nd then every dy until the slughter LBW (25 kg). Tble 1 Ingredients nd chemicl composition of experimentl concentrtes (g/kg). Brley grin Corn grin Soyben mel Sunflower mel Hydrogented vegetble ft Sunflower oil b Molsses Sodium bicrbonte Vitmin minerl premix c Dry mtter Ash Neutrl detergent fibre Crude protein Ether extrct Ftty cids (% of totl ftty cids) C16:0 C18:0 C18:l C18:2 C18: Hidrogented vegetble ft (NUCLEOVIT99, Lechvit S.A., León, Spin). Anlysis: 990 g ether extrct/kg of DM. Ftty cid composition (g/kg ftty cids): C14:0, 12; C16:0, 625; C18:0, 257, C18:l, 98. Sunflower oil (C.C. Crrefour S.A, Spin). Anlysis: 990 g ether extrct/kg of DM. Ftty cid composition (g/kg ftty cids): C16:0, 60; C18:0, ; C18:l, 288; C18:2, 605. Vitmin minerl premix (NUTEMIX, NUTEGA, Mdrid, Spin) Slughter nd crcss mesurements When n niml reched the intended LBW (pproximtely 25 kg), feed nd wter were withdrwn, nd fter 1 h the lmb ws weighed gin, stunned, bled, skinned nd eviscerted. Dressed crcss nd noncrcss components (s defined by ColomerRocher, Delf, & Sierr, 1988) were obtined from the whole body of ech lmb nd weighed seprtely. Crcss ws chilled t 4 C for 24 h nd then weighed gin, so tht chilling losses were clculted s the difference between hot (HCW) nd cold crcss weight (CCW) expressed s proportion of the initil HCW. Killingout percentge ws clculted s CCW expressed s percent of slughter body weight. Thorcic wll thickness (mm), subcutneous ft thickness (mm), ftness score nd consistency of ft were determined s described by ColomerRocher et l. (1988). The left side of ech crcss ws jointed into commercils cuts (shoulder, brestflnk, leg, scrg end, best end, loinrib nd til) ccording to ColomerRocher et l. (1988). Ech cut ws weighed to ssess its proportion in the crcss. Therefter, the shoulder ws dissected into bone, len nd ft depots ccording to the procedure of Fisher nd De Boer (1994) to determine tissulr composition of the crcss Met mesurements At 24h postmortem, loinrib joint (from 6th ribonwrds) ws cut t the level of 13th rib, nd ph nd colour were mesured t the 6th rib site. ph ws lso mesured in m. semimembrnosus nd colour ws lso mesured in m. rectus bdominis nd dorsl subcutneous ft. A Metrohm phmeter (Metrohm, Switzerlnd), equipped with penetrting electrode nd temperture probe ws used for ph determintion. Colour mesurements were performed ccording to the L**b* system (Commission Interntionl de l'eclirge, 1976) using Minolt CM2002 chrommeter (KonicMinolt Sensing, Jpn). Ft colour ws evluted in subcutneous dorsl ft. A smple of m. longissimus thorcis ws tken to determine wter holding cpcity s described by Gru nd Hm (1953) nd modified by Sñudo, Sierr, López, nd Forcd (1986), nd smples of this muscle nd subcutneous ft (ft smple from point situted 4 cm from lst rib nd 4 cm from medium line) were tken nd frozen t 30 C for ftty cid composition determintion. The chemicl composition of the met ws determined on m. longissimus lumborum smples, which were nlyzed for dry mtter (AOAC officil method ), sh (AOAC officil method ), crude protein (AOAC officil method ) nd ft (AOAC officil method ). In situ trnsesterifiction of ftty cids were performed following the method described by Crrpiso, Timón, Petrón, Tejed, nd Grcí (2000), using 300 mg of freeze dried nd minced m. longissimus lumborum. Anhydrous HCl/methnol ws used for the methyltion of the ftty cids nd tridecnoic cid (C13:0) ws used s internl stndrd (4 mg/ml). Methyl esters of ftty cids were quntified by GC (HP 5890 GC, HewlettPckrd, USA) using cpillry column (HP 88,100 m x 0.25 mm, Agilent Technologies, USA). The injector nd detector tempertures were of 200 nd 300 C, respectively, nd the helium flow rtio ws 1 ml/min. An utomtic split/splitless injector s used with rtio 30:1 split nd pressure of 16 psi. After injection (1 u,l), the column temperture ws held t 50 C for 1 min nd then incresed to 180 C t 10 C/min. The temperture ws kept t 180 C for 25 min, followed by n increse of 2 C/min to 220 C nd, finlly, held t 260 C for 5 min. The identifiction of peks ws mde by comprison of retention times with the ones obtined for ftty cid methyl ester (FAME) stndrd mixtures cquired from UnCheckPrep Inc. (Elysin, MN, USA) nd from Supelco Inc. (Bellefonte, PA, USA).

3 Additionl stndrds of individul CLA isomers (C18:2 cis9, trns11, C18:2 trns10, cis12) were purchsed from Mtrey Inc. (Plesnt Gp, PA, USA). Atherogenicity index ws clculted s described by Ulbricht nd Southgte (1991): (C12 :0 + 4xC14:0 + C16: 0)/(MUFA + PUFA) Sttisticl nlysis Averge dily weight gin (ADG) ws estimted s the regression coefficient (slope) of LBW ginst time using the REG procedure of SAS pckge (SAS Inst. Inc., 1999). Dt were subjected to nlysis of vrince using the GLM procedure of SAS pckge (SAS, 1999). The LSD test ws used to ssess the significnce between tretment mens where the effect ws significnt (P < 0.05). 3. Results Men vlues of feed intke, verge dily gin, feed to gin rtio nd dys to rech 25 kg re shown in Tble 2. lmbs tended to et less concentrte nd totl dry mtter thn nimls (P < 0.10), wheres these showed tendency to lower brley strw intke thn lmbs (P<0.10). On the other hnd, verge dily gin nd feed to gin rtio were not ffected by or diets (P > 0.05) compred to control diet. There were no sttisticlly significnt effects of or s compred to control diet on hot nd cold crcss weight, chilling losses, crcss conformtion, ftness score nd consistency, internl ft depots weight nd thickness of thorcic wll nd subcutneous ft (P > 0.10) (Tble 3). Tble 2 Feed dry mtter intke, verge dily gin, feed to gin rtio nd dys to rech 25 kg LBW. Dry mtter intke (g niml^1 dy~') Concentrte Brley strw Totl Averge dily gin (g nimr 1 dy 1 ) Feed: gin Dys to rech 25 kg RSD: residul stndrd devition. Tble 3 Crcss chrcteristics (1) Group RSD Tble 4 Crcss chrcteristics (2). Thickness (mm) Thorcic wll Subcutneous ft Commercil cuts (%) Shoulder Brestflnk Leg Scrg end Loinrib Best end Til Tissulr composition (%) Muscle Intermusculr ft Subcutneous ft Bone Others RSD: residul stndrd devition RSD Tble 5 Met ph, colour, wter holding cpcity nd chemicl composition, nd ft chrcteristics. Met ph 24h postslughter L. dorsi Semimembrnosus R. bdominis colour l" b" L. dorsi Colour L" b" Wter holding cpcity (%) Chemicl composition Dry mtter (%) Crude protein (%DM) Ether extrct (% DM) Ash (% DM) Fr colour L" b" RSD: residul stndrd devition RSD Hot crcss (kg) Cold crcss (kg) Chilling losses (%) Killingout percentge Crcss conformtion 15 Ftness score c Ft consistency 11 Ft internl depots (g) Omentl Mesenteric Kidney knob nd chnnel ft RSD: residul stndrd devition. Crcss conformtion scle: from 0 (poor) to 5 (excellent). Ftness score scle: from 0 (slim) to 4 (very ft). Ft consistency scle: from 0 (oily) to 3 (firm). RSD Neither nor cused chnges in commercil cuts percentge or tissulr composition (P > 0.10) when compred to control group, s cn be seen in Tble 4. Met ph, colour nd chemicl composition, s well s ft colour prmeters re shown in Tble 5, nd none of them resulted ffected by the oils studied (P> 0.10). Intrmusculr ftty cid composition is recorded in Tble 6. Wheres did not cuse significnt chnges s compred to control group, the ddition of to the concentrte decresed C16:0 (P<0.05). C18:l trns proportion ws sttisticlly greter (P<0.01) nd C18:l cisu lower (P<0.05) for lmbs when compred to either control or nimls. Linolenic cid (C18:3) proportion lowered when 4% ws included in the concentrte, which led to greter C18:2/C18:3 rtio (P<0.05). Sturted (SFA), monounsturted (MUFA) nd longchin

4 Tble 6 Intrmusculr ftty cid composition (% of identified ftty cids). C14:0 C16:0 C16:l C18:0 C18:l trns C18:l cis9 C18:l ris11 Totl C18:l CI 8:2 cis9, cis 12 CI 8:2 cis9, trns11 CI 8:2 trns 10, cisu C18:3 C20:0 C20:4 n6 C20:5 n3 C22:5 n3 C22:6 n3 SFA X MUFA X PUFA X Totl CLA y SFA/(MUFA t PUFA) C18:2/C18:3 Atherogenicity index b b b b b b b RSD W Mens within rows with different superscript differ significntly (P < 0.05). w RSD: residul stndrd devition. x SFA = C14:0 + C16:0 + C18:0 + C20:0; MUFA = C16:1+ C18:1; PUFA = C18:2 cis9, cisu + C18:2 cis9, trns11 +C18:2 trns10, cisu C20:4 n6 + C20:5 n3 + C22:5 n3 + C22:6 n3. y Totl CU\ = C18:2 cis9, trns11 +C18:2 trns10, cisu. z Ulbricht nd Southgte (1991). Tble 7 Subcutneous ftty cid composition (% of identified ftty cids). C14:0 C16:0 C16:l C18:0 C18:l trns C18:l cis9 C18:l ris11 Totl CI 8:1 CI 8:2 cis9, cis 12 CI 8:2 cis9, trns11 C18:2 trns 10, cisu C18:3 C20:0 C20:4 n6 C20:5 n3 C22:5 n3 C22:6 n3 SFA X MUFA X PUFA X Totl CLA y SFA/(MUFA t PUFA) C18:2/C18:3 Atherogenicity index b b b b b b 0.71 b b 1.18" b b RSD W < < < Mens within rows with different superscript differ significntly (P < 0.05). w RSD: residul stndrd devition. x SFA = C14:0 + C16:0 + C18:0 + C20:0; MUFA = C16:1+ C18:1; PUFA = C18:2 cis9, cisu + C18:2 cis9, trns11 +C18:2 trns10, cisu C20:4 n6 + C20:5 n3 + C22:5 n3 + C22:6 n3. y Totl CU\ = C18:2 cis9, trns11 +C18:2 trns10, cisu. z Ulbricht nd Southgte (1991). polyunsturted (PUFA) ftty cids s well s therogenicity index were not ffected by either or. Ftty cid composition of subcutneous ft is shown in Tble 7. cused significnt decreses in the proportion of C16:0 nd C16:l (P<0.05) s compred to nd control lmbs. C18:l trns proportion incresed significntly in lmbs (P< 0.001), wheres C18:l sj J tended to decrese when nimls were compred to lmbs (P<0.10). C18:2 trns10, cisu proportion incresed in lmbs (P< 0.001). C18:3 proportion decresed significntly when ws dded to the concentrte (P<0.01), C18:2 to C18:3 rtio incresing for lmbs (P < 0.001). significntly decresed the therogenicity index when compred to control diet (P<0.05). However, longchin PUFA were not ffected by tretments studied (P> 0.1). 4. Discussion The effects of dding ft to the diets for ruminnts depend not only on the type of ft (Doreu & Chillird, 1997) but lso on the mount dded. Likewise, it hs been proposed tht the digestive processes in the hindgut compensted for the possible reduction in digestion in the rumen resulting in limited effect on whole trct digestion (Sutton, Knight, McAlln, & Smith, 1983). In our experiment, nimls receiving ft in the diet did not show reduced totl dry mtter intke, even though group te less concentrte thn lmbs. Nevertheless, niml performnce ws not ffected, since no differences were observed in growth rte nd feed to gin rtio. Hddd nd Younis (2004) nd Bess, Portugl, Mendes, nd SntosSilv (2005) recorded reduced feed intke when ruminlly protected ft (5%) nd soyben oil (10%), were included in the rtion for lmbs. Despite these chnges, verge dily gin ws not modified in ny cse. Notwithstnding, Dutt, Agnihotri, nd Ro (2008) suggested tht including plm oil in the diet could improve verge dily gin nd niml performnce. It should be pointed out tht their tril lsted double time thn current experiment, their nimls being lso hevier thn ours t the beginning or the experiment. None of the crcss chrcteristics studied in this experiment were ffected by the ddition of either or to the concentrte. Previous works hve shown tht dding fts to the diet for fttening lmbs does not cuse modifictions in niml performnce or crcss chrcteristics (Hddd & Younis, 2004). Our results gree with Cstro, Mnso, Mntecón, Guiro, nd Jimeno (2005) who found no differences for these prmeters when lmbs received up to 6% of supplementing ft. Likewise, Kott et l. (2003) did not observe differences in kidney knob nd chnnel ft weight in n experiment crried out with lmbs, whose diet ws supplemented with 6% sunflower oil. On the other hnd some studies hve shown chnges relted to ft deposition. Thus, Bess et l. (2005) observed greter proportion of intrmusculr ft nd less proportion of muscle when lmbs were fed with 10% soyben oil. Moreover, Brndt nd Anderson (1990) nd Zinn (1992) suggested tht supplementing ruminnt rtions with oil would increse crcss ftness. Nevertheless, the ltter studies were performed in cttle nd lsted more thn our experiment, nd the level of ft included ws lso greter (6% vs. 4%). The lck of effects on commercil cuts percentge nd tissulr composition is ccording with the lcking differences in growth rte nd crcss ftness, the men vlues being within the rnge found in the bibliogrphy for lmbs rered under similr systems (CnoExpósito et l., 2006; Rodriguez et l., 2008). It must be pointed out tht chnges in these prmeters re usully relted to chnges in growth rtes, ge nd mturity (Huidobro & Cñeque, 1994).

5 Regrding met chrcteristics, no chnges were found ttributble to ddition nd type of oil dded. Some uthors hve found chnges in ph decline, relting them to the diet, but these reltionships re bsed on the crcss ftness nd chilling rte (Ahlus, Jnz, Tong, Jones, & Robertson, 2001). As for met colour, chnges were not expected, since they re usully ssocited to differences in ft content, crcss ftness or ultimte ph (Priolo, Micol, & Agbriel, 2001), nd no differences were observed for these prmeters. Likewise, no differences were observed in ft colour. Chnges in it re linked to differences in pigments deposition or ftty cid composition, the ltter being ssocited to lipid oxidtion processes, which re still not pprent for 24 h fter slughter (Wood et l., 2004). Nevertheless, in our study, modifictions observed in ftty cid composition, did not led to gret chnges in PUFA or MUFA proportions, which my hve bigger influence in lipid oxidtion thn only rumenic or vccenic cid. Vlues of ftty cid composition gree with those found in the bibliogrphy (Cstro et l., 2005), the most bundnt ftty cid being oleic (C18:l cis9), followed by plmitic (C16:0) nd steric (C18:0). Regrding the effects of in ftty cid composition, these re lmost negligible in the current experiment when compred to control group. In this sense, previous works hve shown tht the effects of plm oil supplements on ftty cid composition re more likely to be evident in internl depots such s omentl nd mesenteric ft (Cstro et l., 2005). Moreover, group hd to be included in the experimentl design in order to clrify whether the effects observed were due to the ddition of ft, to the type of ft dded or both. In the current study, the ddition of to the concentrte cused significnt decrese in the proportion of plmitic cid (C16:0) in both intrmusculr nd subcutneous ft, which is probbly due to its lower proportion in the thn in the other two diets. This grees with previous works suggesting tht the content of this ftty cid reflect its dietry concentrtion (Cooper et l., 2004; Scolln et l., 2001). Highconcentrte diets re ssocited with high levels of C18:l trns10 (Bess et l., 2005). Although in the current experiment the chromtogrphic peks corresponding to trns10 nd trns 11 C18:l isomers could not be differentited, the pek hs been interpreted s C18:l trns, ccording to Bess et l. (2005). It hs been suggested tht this ftty cid could be formed by reduction of trns10 CLA or by isomeriztion of oleic cid (Griinri & Bumn, 1999). Sunflower oil, dded t rte of 6%, hs been reported to increse CLA content in the intrmusculr ft of lmbs (Mir, Rushfeldt, Mir, Pterson, & Weselke, 2000). In the current study, CLA trns10, cis12 s well s CI8:1 trns incresed in subcutneous ft of nimls receiving diet. However, none of both chnged in response to or in intrmusculr ft. In this sense, previous works hve shown greter chnges in subcutneous thn in intrmusculr ft (Cstro et l., 2005; Lourenco, Vn Rnst, De Smet, Res, & Fievez, 2007). This lck of significnt chnges in intrmusculr ft could be due to the fct tht during the finishing period subcutneous dipose tissue increses t greter rte thn other dipose depots, such s intrmusculr (Demeyer & Doreu, 1999). On the other hnd, subcutneous ft seems to be more responsive to chnges in the dietry ftty cid supply or chnges in rumen metbolism thn intrmusculr ft (Demirel et l., 2004; Wchir et l., 2002). Similrly to the results observed in the current experiment using, in tril with cttle, Beulieu, Drckley, nd Merchen (2002) reported n increse in CLA trns10, cis12 when supplementing highconcentrte finishing diets with soyben oil, but not n increse in CLA cis9, trns11. Therefore, s they did, it cn be suggested tht supplementing highconcentrte diets with n oil source of linoleic cid is not n efficcious method for incresing the proportion of the ltter ftty cid. Indeed, in study crried out with lmbs, Bess et l. (2005) observed n increse in CLA trns10, cis12 nd C18:l trns10, while CLA cis9, trns11 nd CI8:1 trns11 were not sttisticlly ffected in response to soyben oil supplementtion to highconcentrte diets. On the other hnd, in response to the ddition of other oils such s soyben oil, Bess et l. (2005) reported n increse in C18:3 proportions. As in the current experiment insted of soyben oil ws used, which is known to hve smller concentrtions of C18:3 thn the ltter, our results show decrese in C18:3 in response to, s Mir et l. (2000) reported previously. Although these uthors did not provide suitble explntion for this fct, it could be relted to biohydrogention process within the rumen, which is extensive nd my be enhnced when nimls receive high unsturted lipid supplements (Wchir et l., 2001). Ft with high therogenicity index vlue is ssumed to be more detrimentl to the humn helth (Ulbricht & Southgte, 1991). Conversely, some unsturted ftty cids hve protective effect ginst the risk of crdiovsculr disese (Willims, 2000). In the present study, significnt decrese in the therogenicity index ws found in response to supplementtion in subcutneous ft. Intrmusculr ft showed only tendency to hve lower therogenicity index, which could probbly be relted to the numeric chnges in sturted nd monounsturted ftty cids, which did not rech the required significnce level to be sttisticlly different. It is not yet cler whether the effects on helth of trnsftty cids from ruminnt products re opposite sitution to the possible dverse of trns ftty cid isomers from prtilly hydrogented plnt oils. However, lthough CI8:1 trns11 seems to ply more importnt role thn the trns10 isomer in modulting plsm lipid nd lipoprotein metbolism (Roy et l., 2007), CLA cis9, trns11 nd CLA trns10, cis12 hve potentil beneficil effects for humn helth, since both hve be found to exert significnt but different biologicl effects (Prk, 2008). It cn be concluded tht wheres 4% does not hve gret effects, the inclusion of 4% in the concentrte for young fttening lmbs improves intrmusculr nd subcutneous ftty cid composition without ffecting feed intke, niml performnce nd crcss nd met chrcteristics. Acknowledgements The uthors wish to cknowledge the finncil support received from the Junt de Cstill y León (Project VA084/04). References Ahlus, J. L, Jnz, J. A. M., Tong, A. K. W., Jones, S. D. M., & Robertson, W. M. (2001). 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T., & Anderson, S. J. (1990). Supplementl ft source ffects feedlot performnce nd crcss trits of finishing yerling steers nd estimted diet net energy vlue. Journl of Animl Science, 68, CnoExpósito, T., Peñ, F., Mrtos, J., Domenech, V., Alclde, M. J., Grci, A., et l. (2006). Clidd de l cnl y de l crne en corderos ligeros de rz Segureñ. Archivos de Zootecni, 52,

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