Meat Science 97 (2014) 480–485

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Fatty acid composition of lamb meat from the autochthonousJezersko–Solčava breed reared in different production systems

Angela Cividini ⁎, Alenka Levart, Silvester Žgur, Drago KompanDepartment of Animal Science, Biotechnical Faculty, University of Ljubljana, Groblje 3, SI-1230 Domžale, Slovenia

⁎ Corresponding author. Tel.: +386 1 320 39 26; fax: +E-mail address: angela.cividini@bf.uni-lj.si (A. Cividini

http://dx.doi.org/10.1016/j.meatsci.2013.12.0120309-1740/© 2014 Elsevier Ltd. All rights reserved.

a b s t r a c t

a r t i c l e i n f o

Article history:Received 28 June 2012Received in revised form 31 July 2013Accepted 18 December 2013Available online 28 March 2014

Keywords:Fatty acidsLamb meatJezersko–Solčava sheepAutochthonous breedPastureProduction system

Thirty two autochthonous Jezersko–Solčava lambs were used to investigate the effect of production (pasture vs.stable) and weaning system (suckling vs. weaned) on fatty acid composition of Longissimus dorsi intramuscularfat in a 2 × 2 factorial design. Pasture lambs had lower intramuscular fat concentration (P b 0.0001) more PUFAand trans C18:1, more ALA (P= 0.0322), ARA (b0.0001) and EPA (0.0149) but less SFA (P b 0.0001) than stablelambs. Weaning system affected PUFA (P = 0.0040) and MUFA (P = 0.0070) but not SFA and trans C18:1 fattyacids. The interaction of production system andweaning systemwas significant mainly for trans C18:1 and transC18:2 fatty acids. Finally, lambmeat from all four treatments which are traditionally used in rearing of Jezersko–Solčava lambs are favourable from the nutritive point of view, due to their low n−6/n−3 ratio.

© 2014 Elsevier Ltd. All rights reserved.

1. Introduction

Manipulating the fatty acid composition of ruminants by changingtheir diet is more difficult than in monogastric animals. Althoughmore than 90% of dietary polyunsaturated fatty acids (PUFA) arehydrogenated in the rumen, some dietary PUFA escape rumenbiohydrogenation. Nevertheless, the results of numerous studies con-firm that fatty acid composition of dietary fats of ruminants can be influ-enced by the production system (Demirel, Ozpinar, Nazli, & Keser, 2006;Díaz et al., 2002; Díaz et al., 2005; Enser et al., 1998). The effects ofdietary supplements rich in conjugated linoleic acid (CLA) ordocosahexaenoic acid (DHA) were investigated in attempts to transferthe long chain PUFA (LCPUFA) from the diet to the meat (Demirelet al., 2006; Doreau & Chilliard, 1997; Mir, Rushfeldt, Mir, Peterson, &Weselake, 2000). A more acceptable way of increasing the n−3 PUFAproportion in meat of ruminants is pasture grazing because of thehigh proportion of α-linolenic acid (ALA, C18:3 n−3) in grass. Manystudies over the last few years have reported differences in fatty acidcomposition of lamb meat between lambs grazing on pasture and fat-tened in dry lots (Bas & Morand-Fehr, 2000; Díaz et al., 2002; Priolo,Micol, Agabriel, Prache, & Dransfield, 2002; Sañudo et al., 2000; Velasco,Cañeque, Lauzurica, Pérez, &Huidobro, 2004). Lambs grazing on pasturegenerally have less fat and more beneficial fatty acid composition

386 1 724 10 05.).

than lambs fattening with grain-based diets (Nuernberg, Fischer,Nuernberg, Ender, & Dannenberger, 2008; Velasco et al., 2004). Meatfrom grazing lambs contains less saturated fatty acids (SFA) and mono-unsaturated fatty acids (MUFA) and more PUFA, especially more ALAand longer chain PUFA i.e. eicosapentaenoic acid (EPA) and DHA andmore n−3 PUFA (Scerra et al., 2007). Pasture lamb meat had a morefavourable n−6/n−3 ratio, due to relatively higher levels of n−3PUFA than lambs fattened with grain-based diets (Nuernberg et al.,2008).

Conversely, no data on the fatty acid composition in lamb meat ofautochthonous sheep breeds in Slovenia have been reported in the liter-ature. The Jezersko–Solčava sheep is one of four autochthonous sheepbreeds in Slovenia. The main characteristics of the Jezersko–Solčavasheep breed have been described elsewhere (Feldman, Bietzker, &Mendel, 2005). It is mainly suited for lamb production in the Alpineand pre-alpine region where it stays on Alpine pastures in summer.The production system of winter born lambs (30–35 kg slaughterweight) in most areas in Slovenia normally involves a suckling periodof approximately 60 days and a subsequent fattening period on hayand grain based diet. Late spring or early summer born lambs are graz-ing with their dams on the pasture till they reach 30 to 35 kg of slaugh-ter weight. However, the chance of usingmountain pastures in additionto suckling until slaughtermay enable a similar productive performanceto grain-fed lambs with a reduction in feeding costs and an improve-ment in meat quality. Moreover, by using grazing systems, especiallyin mountains, we can conserve cultivated agricultural land, preventovergrowing and stimulate sustainable farming. The aim of this study

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was to investigate the effects of different production systems (pasturevs. stable), and including or excluding of weaning conducted in thetraditional way, on fatty acid composition of the intramuscular fat(M. longissimus dorsi) of Jezersko–Solčava lambs.

2. Materials and methods

2.1. Animals and production systems

Our experiment was conducted in nature under the usual conditionsfor rearing and management of the flock. Thirty-two Jezersko–Solčavalambswere assigned to one of four treatments in a 2× 2 factorial design.The factors were production system (grazing vs. grain-fed indoors) andweaning system (weaning vs. no weaning). All lambs were born on thesame location. Because of year-round lambing system there were win-ter born lambs and late spring or early summer born lambs. Sixteenwinter born lambs were kept with their dams in the stable (S) (8males and 8 females). From 10 days of age stable lambs had ad libitumaccess to a hay and grain-based diet (47% barley, 52% pressed beetpulp). At around 120 days of age (or at target live weight 30 kg), halfof the stable lambs were slaughtered (no weaning or suckling lambsin the stable) (S1). The remaining half of the stable lambs were weaned(on the same day as slaughtering S1 group) and continued with fatten-ing period on hay and grain-based diet till they reached 38 kg live bodyweight (S2). Late summer born lambs (another 16 lambs; 8 males, 8 fe-males) were grazing with their dams on the mountain pasture (P) at1200 m above sea level. Pasture lambs were only grazing, and receivedno feed supplementation. Half of the pasture lambswere slaughtered attarget live weight 30 kg (no weaning or suckling lambs on the pasture)(P1). The remaining half of the pasture lambs were weaned (on thesame day as slaughtering P1 group) and continued with grazing tillthey reached 38 kg live weight. Lambs remained at pasture throughoutthe study. The mean botanical composition of pasture was the averageof surveys on several 10 m2 parcels. Relative cover of a species was cal-culated as the ratio of the recorded presence for a given species to thesum of the presences of all species and expressed as a percentage. ThePoaceaewas the dominant family (50%) present in the pasture followedby Fabaceae (20%), Ranunculaceae (13%), Plantaginaceae (6%), Apiaceae(5%), Lamiaceae (3%) and 3% other plant families. Herbage was abun-dant and did not present a limiting factor. The chemical and fatty acidcomposition of mountain pasture is presented in Table 1.

Individual lamb weights were recorded weekly. When lambsreached target slaughterweight of 30 and 38 kg, theywere slaughtered.At slaughter, lambs were weighed on the farm before transportationto the experimental abattoir at the Zootechnical Department at

Table 1Chemical and fatty acid compositions of mountain pasture in Slovenia.

Chemical composition (g/kg)

Dry matter 224.71Crude protein 29.07Crude lipid 3.05Crude fibre 47.81Ash 18.45

Fatty acid composition (g/100 g total fatty acids)

C16:0 14.88C18:0 1.30ΣC18:1 3.67C18:2 n−6, LN 20.43C18:3 n−3, ALA 49.41SFA 22.53MUFA 7.39PUFA 70.08n−3 PUFA 49.54n−6 PUFA 20.55n−6/n−3 PUFA 0.42

Biotechnical Faculty (50 km) according to welfare codes of practice.All lambs were slaughtered at four consecutive dates by exsanguina-tions after stunning by the same procedures. Carcasses were suspendedby theAchilles tendon and chilled at 4 °C for 24 h in conventional chiller.Longissimus dorsi (LD) muscle samples (ca. 100 g) were carefully dis-sected from the hindpart of the loin of each carcass. Samples were vac-uum packed and immediately stored at −20 °C until lipid extractionand assessment of fatty acid composition.

2.2. Total fat and fatty acid composition of meat samples

Prior to chemical analyses meat samples were homogenised using alaboratory homogeniser (Grindomix). Total intramuscular fat was de-termined using SoyCap™ 2047 in combination with a Soxtec extractionsystem according to the manufacturer's procedure (Foss Analytical AB,2005). Briefly, homogenised meat samples were hydrolysed in 4 MHCl, filtered, washed with deionised water, and extracted with petro-leumether. After solvent evaporation, extracts were dried andweighed.

Fatty acid methyl esters (FAME) from meat samples were preparedusing the in situ trans-esterification method of Park and Goins (1994).For separation of FAME an Agilent 6890 series GC instrument equippedwith anAgilent 7683 Automatic Liquid Sampler, a split injector, a flame-ionization detector (GC-FID) and a WCOT fused silica capillary columnCP-Select CB for FAME (Varian, 100m× 0.25mm i.d.) was used. AgilentGC ChemStation was used for data acquisition and processing. Separat-ed FAMEwere identified by retention time comparison and resultswerecalculated using response factors derived from chromatographic stan-dards of known composition (Nu Chek Prep).

2.3. Statistical analysis

All data obtained were analysed by SAS/STAT software (SAS/STAT,User's Guide, 2001). All fatty acids with the value above 0.01 wt.% oftotal fatty acidswere included in the data processing.We studied the ef-fects of production systems on the fatty acid composition in LD by thefollowing model:

yij ¼ μ þ Pi þWj þ PWij þ eijk

where:

yij fatty acid, wt.%μ meanPi production system, i = pasture, stableWj weaning system, j = suckling lambs, weaned lambsPWij interaction between production system and weaning system,

ij = pasture suckling lambs, pasture weaned lambs, stablesuckling lambs, stable weaned lambs

eijk residual.

The model included fixed effects ascribed to production system,weaning system and production system × weaning system interaction.A pre-analysis showed that gender and all other interactions were notsignificant, so they were excluded from the model.

3. Results and discussion

3.1. Fat content, saturated and monounsaturated fatty acids

The level of intramuscular fat (g/100 g muscle) and fatty acid com-position (expressed as % of total fatty acids) in LD muscle of Jezersko–Solčava lambs reared under different production (pasture, stable) andweaning (suckling, weaned) systems is presented in Table 2. The sumsof fatty acids in LDmuscle are presented in Table 3. As expected, the pro-duction system affected intramuscular fat concentration. LD muscle oflambs fattening in stable contained higher levels of total intramuscular

Table 2Effect of production system (P), weaning system (W) and P × W interaction on total fat (g/100 gmuscle) and fatty acid composition (g/100 g total fatty acids) of Longissimus dorsimusclefrom Jezersko–Solčava lambs.

Pasture Stable Production system (P) Weaning system (W) P × W

Sucklingn = 8

Weanedn = 8

Sucklingn = 8

Weanedn = 8

Sig. Sig. Sig. SE

Total fat 2.08 2.43 2.91 4.00 *** ** ns 0.28Fatty acid nsC12:0 0.50 0.29 0.36 0.23 ns * ns 0.07C14:0 3.87 3.21 3.79 3.46 ns ns ns 0.38C14:1 n−5 0.27 0.26 0.32 0.32 * ns ns 0.02C15:0 0.57 0.49 0.61 0.55 ns ns ns 0.04C16:0 17.87 18.91 22.77 23.47 *** ns ns 0.70C16:0 iso 0.20 0.18 0.27 0.25 *** ns ns 0.01C16:1 t9 0.28 0.26 0.11 0.09 *** ns ns 0.02C16:1 n−7 1.24 1.32 1.67 1.70 *** ns ns 0.08C17:0 0.95 1.14 1.33 1.38 *** * ns 0.05C17:0 iso 0.47 0.44 0.47 0.50 ns ns ns 0.02C17:0 aiso 0.46 0.51 0.59 0.66 *** * ns 0.02C18:0 14.69 16.93 15.00 15.08 ns ns ns 0.68C18:1 t6 0.22a 0.25a 0.17a 0.06b *** ** *** 0.01C18:1 t9 0.28ab 0.30a 0.22bc 0.17c *** ns * 0.01C18:1 t11 2.78 2.70 1.35 1.29 *** ns ns 0.15C18:1 n−9 25.87 29.80 30.66 34.21 ** ** ns 1.31C18:1 n−7 1.26 1.20 1.14 1.02 ** ns ns 0.05C18:1 n−6 0.20 0.23 0.17 0.17 *** ns ns 0.01C18:2 t9t12 0.14a 0.23b 0.15a 0.15a ** ** *** 0.01C18:2 c9t12 0.10a 0.12b 0.09c 0.08dc *** ns ** 0.00C18:2 n−6, LN 10.67 7.80 6.83 5.73 *** ** ns 0.63C18:2 c9t11, CLA 1.12 1.01 0.63 0.61 *** ns ns 0.08C18:2 t10c12 0.03 0.04 0.02 0.03 ns ns ns 0.00C18:3 n−6 0.13 0.12 0.11 0.09 ** * ns 0.01C18:3 n−3, ALA 3.06abc 3.48c 3.04abc 2.71ab * ns * 0.17C20:0 0.14 0.13 0.14 0.12 ns * ns 0.01C20:2 n−6 0.10 0.08 0.08 0.07 * ** ns 0.00C20:3 n−6 0.45 0.28 0.26 0.21 *** ** ns 0.03C20:4 n−6, ARA 5.03 3.00 2.47 1.37 *** *** ns 0.37C20:5 n−3, EPA 1.74 1.23 1.24 0.92 * * ns 0.16C21:0 0.16 0.11 0.03 0.00 *** *** ns 0.01C22:4 n−6 0.16 0.10 0.12 0.07 ** *** ns 0.01C22:5 n−3, DPA 2.18 1.36 1.48 1.01 ** *** ns 0.17C22:6 n−3, DHA 0.70 0.44 0.57 0.38 ns *** ns 0.05

The production systems were as follows: pasture grazing (P) and fattening in stable (S). The weaning systems were as follows: suckling lambs (1) and weaned lambs (2).Sig.: significance; ns; P N 0.05; *P ≤ 0.05; **P b 0.01; ***P b 0.001; SE, standard error of mean.a,b,c,dMeans in the same row, within P×W effect , having different superscripts are significant different.

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fat than lambs grazing on the pasture (P b 0.001). From the view ofmedical recommendation a reduction in total fat intake in order tocurb the potentially adverse effects of fats on obesity and coronaryheart disease, the leaner meat of pasture lambs can be recommendable(Webb & O'Neill, 2008). The predominant saturated fatty acids in intra-muscular fat were palmitic (C16:0) and stearic (C18:0) acids. The pro-portions of C12:0 (lauric acid) and C14:0 (myristic acid) were notaffected by the production system (P N 0.05). The LD from pasturelambs contained lower concentrations of C16:0 in comparison to stable

Table 3Effects of production system (P), weaning system (W) and P × W on sums of fatty acid (g/100

Sums of fatty acid Pasture Stable

Suckling (P1)n = 8

Weaned (P2)n = 8

Suckling (S1)n = 8

Weanedn = 8

SFA 40.50 42.87 46.06 46.26MUFA 33.26 37.08 36.43 39.63PUFA 26.24 20.05 17.52 14.12n−3 PUFA 7.79 6.62 6.42 5.57n−6 PUFA 17.51 12.61 10.61 8.08LC PUFA 10.48 6.63 6.35 4.55LC n−3 PUFA 4.69 3.10 3.35 2.77LC n−6 PUFA 0.76 0.53 0.54 0.41trans C18:1 3.56 3.55 1.93 1.73n−6/n−3 2.23 1.92 1.67 1.47

The production systems were as follows: pasture grazing (P) and fattening in stable (S). The wSig.: significance; ns; P N 0.05; *P ≤ 0.05; **P b 0.01; ***P b 0.001; SE, standard error of mean.

lambs (P b 0.001). Aurousseau et al. (2007) observed a decrease of con-centration of C16:0 after grazing but a rapid increase after feeding lambswith concentrate for less than 20 days. When feed contains more ener-gy, the intake of energy is then higher and consequently de novo syn-thesis of C12–C16 is higher too (Aurousseau et al., 2007). The effect ofgrazing on the C16:0 concentration in intramuscular fat has been re-ported in some studies (Aurousseau, Bauchart, Calichon, Micol, &Priolo, 2004; Santos-Silva, Mendes, & Bessa, 2002), but not in others(Nuernberg et al., 2008; Velasco et al., 2001). There were no differences

g total fatty acids) of Longissimus dorsimuscle from Jezersko–Solčava lambs.

Production system (P) Weaning system (W) P × W

(S2) Sig. Sig. Sig. SE

*** ns ns 0.72* ** ns 1.21*** ** ns 1.53* ns ns 0.54*** ** ns 1.03*** ** ns 0.80* * ns 0.41** ** ns 0.05*** ns ns 0.17*** *** ns 0.05

eaning systems were as follows: suckling lambs (1) and weaned lambs (2).

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in concentrations of C18:0 between the observed production systems(P N 0.05). In their studies, Scerra et al. (2007) and Nuernberg et al.(2008) did not report any difference in C18:0 concentration of lambmeat. Contrary to these results, Velasco et al. (2001) observed differ-ences with a greater value of C18:0 in intramuscular fat of concentratefed lambs compared with pasture lambs. The meat from pasturelambs had also lower proportion of some other SFA such as C16:0 iso,C17:0, and C17:0 aiso which was concordant with the results ofSantos-Silva et al. (2002) and Velasco et al. (2001).

In our study the proportion of C18:1 n−9 (oleic) acid was higher instable than in pasture lambs (P b 0.01). Concentrate diets were expect-ed to increase the absorption of oleic and linolenic acids, which are themajor fatty acids in cereal grains (Jenkins, 1994). The difference in con-centration of oleic acid between pasture and stable lambs also could berelated to the greater intramuscular fat content of meat of stable lambscompared to pasture lambs (Scerra et al., 2007; Velasco et al., 2001).Usually, the concentration of oleic acid increases with fatness due toan increase in the activity of the enzyme of Δ9 desaturase, whichsynthesises oleic acid from stearic acid (Bauman, Baumgard, Corl, &Griinari, 2000). Lower concentration of oleic acid in meat of grazinglambs in comparison to those fed cereal-based (concentrate) dietswere also observed by several authors (Aurousseau et al., 2004, 2007;Nuernberg et al., 2008; Santos-Silva et al., 2002; Velasco et al., 2001).Greater concentrations of oleic acid in intramuscular fat of lambs fedcereal-based (concentrate) diets could be valuable because of thegood oxidative stability of oleic acid in comparison to PUFA like linoleicand linolenic acids. Consequently, due to higher values of some majorsaturated and monounsaturated fatty acids in meat of stable lambs,the overall proportion of SFA (P b 0.001) and MUFA (P ≤ 0.05) washigher in intramuscular fat of stable lambs (Table 3).

The weaning system affected fatness; weaned lambs displayedhigher proportion of total intramuscular fat of the LD than sucklinglambs (P b 0.01), probably due to longer fattening period and conse-quently higher weight at slaughter (38 kg vs. 30 kg). Velasco et al.(2004) found higher proportion of intramuscular fat in weaned lambsthan in those which remained with ewes until slaughter. With regardto the effect of weaning system only the proportion of C12:0, C17:0,C17:0 aiso, C20:0, and C21:0 differs significantly with higher proportionof C12:0, C20:0 and C21:0 and lower proportion of C17:0 and C17:0 aisoin intramuscular fat of suckling lambs (P ≤ 0.05). Oleic acid was themost abundant fatty acid in IMF of LD muscle. Meat from weanedlambs contained higher proportion of oleic acid in comparison to meatof suckling lambs (P b 0.01). This findingwas in agreementwithfindingof Velasco et al. (2004). The main reason for higher content of oleic acidin muscles of weaned lambs was probably due to extensive hydrogena-tion of C18 unsaturated fatty acids in the rumen, caused by greater for-age intake in weaned lambs (grass or hay) (Velasco et al., 2004).

Regarding the interaction of production and weaning system, therewere no differences in proportion of any SFA.

3.2. Trans and conjugated fatty acids

The major isomer of trans C18:1 acids in lambmeat was C18:1 trans11 (vaccenic acid), with higher values in meat from pasture lambs(P b 0.001). Consequently, the proportion of overall trans C18:1(Table 3) was higher in pasture lambs than in lambs raised in stable(P b 0.001). These results were in concordance with other previousexperiments (Aurousseau et al., 2004, 2007; Nuernberg et al., 2008;Scerra et al., 2007, 2011). Moreover, vaccenic acid is a precursor ofrumenic acid (CLA, cis-9, trans-11 C18:2), the major acid of beneficialCLA isomers (Griinari et al., 2000). Consequently, the proportion ofcis-9, trans-11 CLA was also greater in intramuscular fat of pasturelambs (P b 0.001). For vaccenic acid and cis-9, trans-11 CLA reportedan anti-carcinogenic effect (Pariza & Hargraves, 1985; Pariza, Park, &Cook, 2001). Vaccenic acid in ruminant meat can play a positive rolefor the endogenous synthesis of CLA.

A greater proportion of CLA in the meat of pasture lambs could bealso due to botanical composition and altitude of the pasture(Collomb, Bütikofer, Sieber, Jeangros, and Bosset, 2002). Collomb et al.(2002) found greater CLA levels in milk of cows grazing on mountainandhighland pastures than inmilk of cows grazing on lowland pastures.In our experiment lambs were grazing on the mountain pastures withheterogeneous botanical structure over 1200 m about see level.

With regard to the effect of weaning systemonly C18:1 t6 and C18:2t9t12 were affected. Suckling lambs reached a higher proportion ofC18:1 t6 (P b 0.01) but lower proportion of C18:2 t9t12 (P b 0.001)thanweaned lambs. In concordancewith Juárez et al. (2008) the resultsindicate an influence of weaning on C18:2 n−6 trans fatty acids. Someauthors reported the increasing CLA found in intramuscular fat of lambscorrelated with the time of weaning (Juárez et al., 2008; Lanza et al.,2006). The proportion of MUFAwas higher (P b 0.01) in weaned lambs.

The interaction of production and weaning system was significantfor C18:1 trans and C18:2 trans fatty acids, except trans vaccenic acid(Table 2). The group of weaned lambs grazing on the pasture reachedthe highest proportion of C18:1 t6 (0.22%) and C18:1 t9 (0.28%) anddid not differ to the proportions of these fatty acids in pasture sucklinglambs. But both groups of pasture lambs had significant difference in theproportion of these fatty acids when compared to the stable weanedlambs (P b 0.001). The lowest proportion of these fatty acids was ob-served in the intramuscular fat of stable weaned lambs.

3.3. Polyunsaturated fatty acids

The production system had effects on almost all polyunsaturatedfatty acids (Table 2) and on all overall fatty acids (Table 3). As expected,the proportion of the essential ALA was higher (P ≤ 0.05) in IMF ofpasture lambs than in stable lambs. The proportion of LN was alsohigher (P b 0.001) in IMF of pasture in comparison to stable lambs.Higher concentration of ALA in intramuscular fat of pasture lambs wasmost probably the consequence of high concentration of ALA in pasturegrass (49.41%). Because of high values of ALA in grass, especially in freshgrass (Chilliard, Ferlay, &Doreau, 2000) and in grass frommountain andhighland pastures (Collomb et al., 2002), the intake of ALA is greater andconsequently the content of ALA in grazing lamb meat is greater(Aurousseau et al., 2007; Nuernberg et al., 2008; Scerra et al., 2007;Velasco et al., 2001). Consequently, due to higher intake of ALA, thepolyunsaturated acids EPA (P ≤ 0.05) and DPA (P b 0.01) that arederived from ALA were greater in the intramuscular fat of pasturelambs. In addition, the sumof n−3 PUFA and LC n−3 PUFAwas greater(P≤ 0.05) in pasture lambs than in stable lambs. Mostly LC n−3 PUFAhave a lot of biological effects and have a beneficial influence on humanhealth.

In our experiment, greater proportion of PUFA (P b 0.001) in themeat fat of pasture lambs was mainly due to the greater level of n−6PUFA (P b 0.001) and n−3 PUFA (P b 0.0336) in the meat of pasturecompared to stable lambs. Popova (2007) found that the rearing regimeinfluenced mainly the concentrations of PUFA in phospholipids withgreater concentration of PUFA in pasture-raised animals. Greater con-centration of PUFA in meat of grazing lambs was also reported byAurousseau et al. (2007).

Themost abundant n−6 PUFA in intramuscular fat was C18:2 n−6(LN) (from 5.73% to 10.67%), with greater proportions (P b 0.001) inpasture lambs. In meat of pasture lambs there were also observedhigher proportions of LC n−6 PUFA as C20:3 n−6, C20:4 n−6 andC22:4 n−6. It is a fact that concentrate or grain based diet containsmore n−6 PUFA, especially linoleic acid (LN), than forage based diet.Consequently, feeding animals with concentrate or grain-based dietsshould produce meat with a greater amount of LN compared to grazinganimals. In our study, we found opposite results. Nevertheless, severalstudies have found no differences in proportions of LN between grazingand concentrate fed lambs (Scerra et al., 2007, 2011) or between con-centrate and barley fed lambs (Velasco et al., 2004). The resulting

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proportion of LN in IMF of lamb muscle was probably the reflection ofthe diet. Pasture grass (Table 2) contained higher concentration of LN(20.43%) than hay produced from comparable areas in Slovenia(14.92%), but lower than the commercial pressed beet pulp (49.49%)(Kompan, 2003). The study ofWarren et al. (2008) found a negative cor-relationbetween totalmuscle fat and LNproportion in longissimusmuscleof steers given a concentrate or grass silage diet. This curvilinear patternwas explained by the high proportion of LN in phospholipid and a declin-ingproportionof phospholipid in totalmuscle fat as total fat increased. In-deed, in our study there was a negative linear regression between totalintramuscular fat and LN (data not shown). Furthermore, IMF in musclesof pasture lambs was lower (P b 0.001) than that of stable lambs.

In addition, Collomb et al. (2002) reported correlations betweenfatty acids in cow milk fat produced in the lowlands, mountains andhighlands and the botanical composition of the fodder. The pasturesfrom the highlands (1275 m–2120 m) and mountains (900 m–

1210m)were characterized by a much greater number of plant speciesthan the pastures from the lowlands. Some plant species were encoun-tered only in themountains and highlands andmany of those plant spe-cies were positively correlated with the concentration of total PUFA incow milk. They concluded that the intake of different plant familiescould be related to the fatty acid composition of milk fat. Even thoughthe conclusions of Collomb et al. (2002) are for cow milk fat, they givea plausible reason for the greater proportion of LN in the intramuscularfat of pasture lambs. Pasture lambs were grazing on mountain pasturecontaining many different plant species.

Another possible explanation is given by Lourenço, Van Ranst, DeSmet, Raes, and Fievez (2007). As in their study, intramuscular fat oflambs grazing on pastures with botanically diverse compositioncontained higher proportions of PUFA, particularly LC PUFA (C20:4n−6, C20:5 n−3, C22:5 n−3). We can also confirm lower IMF andoleic acid content in meat of pasture lambs in comparison to stablelambs, which Lourenço et al. (2007) explained with higher phospholip-id/triacylglycerol ratios in leaner meat of grazing animals.

The intramuscular fat from the pasture lambs was richer in bothn−6 and n−3 PUFA compared to that from stable lambs. The differ-ence was greater in proportion of n−6 PUFA, consequently the n−6/n−3 ratio (Table 3) was higher (P b 0.001) in intramuscular fat of pas-ture lambs than in stable lambs. The ratio n−6/n−3was widely used toevaluate the nutritional value of fat for human consumption (Wood et al.,2003). Dietary recommendations for n−6 PUFA are from 2.5 to 9%, andfor n−3 from 0.5 to 2% of total fat energy (Elmadfa & Kornsteiner,2009). However, the increase in n−3 fatty acids and the low ratio ofn−6/n−3 fatty acids (1.92–2.23) in intramuscular fat of pasture lambsare beneficial for human nutrition. But even in intramuscular fat of stablelambs the ratio n−6/n−3 was low, even lower than in pasture lambs(1.67–1.47). When compared to the recommended n−6/n−3 ratio5:1, our results indicate that using both traditional production systemsled to the very low n−6/n−3 fatty acid ratio in lamb meat.

With regard to the effect of weaning system, the proportion of PUFA,n−6 PUFA, LC PUFA, and LC n−6 PUFAwas lower (P b 0.01) inweanedlambs compared to suckling lambs. Consequently, the n−6/n−3 fattyacid ratio was lower in weaned lambs.

The interaction of production system and weaning system affectedonly ALA and C18:4 n−3. Significant differences in the proportion ofALA in LD were observed only between pasture weaned lambs (3.48%)and stable weaned lambs (2.71%) (P≤ 0.05). There were no significantdifferences between P × W groups in any sums of fatty acids.

4. Conclusions

The prevailing fatty acids of the intramuscular fat of lambs grazingmountain pasturewere oleic, palmitic, stearic and linoleic acids. In addi-tion, the meat of pasture lambs contained significantly less total intra-muscular fat than the meat of lambs fattened with hay, barley andbeet-pulp (2.25% vs. 3.45%). Also, the meat of pasture lambs contained

significantly more n−3 PUFA (7.21% vs. 5.60%) as well as significantlymore n−6 PUFA (15.06% vs. 9.34%), more n−3 long chain PUFA(3.89% vs. 3.06%) and more n−6 long chain PUFA than the meat fromstable lambs. Meat of pasture lambs was considered to be morefavourable from the nutritive point of view because of significantlygreater concentration of ALA, ARA, EPA and DHA compared to themeat of stable lambs. As recommended by WHO, lamb meat fromboth production systems (pasture and stable) which are traditionallyused in rearing of Jezersko–Solčava lambs in Slovenia are favourablefrom the nutritive point of view, because of its low n−6/n−3 ratio.

Regarding weaning system there were some effects on fatty acidcomposition. Weaned lambs displayed higher proportions of MUFAand lower proportions of PUFA, n−6 PUFA, LC PUFA, LC n−6 PUFAand lower n−6/n−3 fatty acid ratio than suckling lambs. The interac-tion of production and weaning system was exposed as having notsuch an important impact regarding fatty acid composition in IMF ofJezersko–Solčava lambs. When weaned lambs on the pasture (groupP2) continued to graze, the IMF of those lambs had higher proportionof ALA when compared to the weaned lambs in the stable (S2).

In conclusion, this study with Jezersko–Solčava lambs showed thatmountain pasture grazing presents some advantages over feeding ahay and grain-based diet regarding lipid content and fatty acid compo-sition. Thus, grazing pasture increased the concentration of n−3 PUFA,especially ALA, EPA andDHA,which is beneficial for human health. Con-versely, under the current experimental conditions of this study, therearing of lambs in the stable and fattening them with hay, barley andbeet pulp could produce good quality lamb meat regarding fatty acidcomposition. Described production systems could be recommendedfor the production of quality lambmeatwith a beneficial fatty acid com-position throughout the year, and not just during the pasture season. Inthis study, grazing lambs on the pasture especially mountain pastureswith combination of weaning at around 120 days of age displayed a rec-ommendable production system regarding fatty acid composition inbenefit of PUFA.

Acknowledgements

The authors wish to thank the breeder Klemen Matk for his helpin managing the flock in mountain rearing conditions. This work wasfinancially supported by the Ministry of Agriculture and Environmentof the Republic of Slovenia through contract 2311-05-000062.

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