Small Ruminant Research 75 (2008) 24–35

Available online at www.sciencedirect.com

Ewe metabolic performance and lamb carcass traits in pasture andconcentrate-based production systems in Churra Tensina breed

M. Joy ∗, J. Alvarez-Rodriguez, R. Revilla, R. Delfa�, G. RipollCentro de Investigacion y Tecnologıa Agroalimentaria, Gobierno de Aragon, P.O. Box 727, 50080 Zaragoza, Spain

Received 12 February 2007; received in revised form 11 July 2007; accepted 18 July 2007Available online 23 August 2007

Abstract

Thirty-eight adult ewes rearing single male lambs were randomly allocated to two adjacent paddocks (n = 19) grazing permanentPyrenean pastures in spring (0.57 ha/paddock). Treatments were: indoor (IND) in which ewes grazed during 8 h a day (08:00 to16:00 h) without their lambs and thereafter remained indoors with them, receiving a supplement of 0.5 kg of barley meal/day. Lambswere fed concentrate ad libitum and they were weaned at 53 days old; grazing (GR), ewes and lambs were continuously grazing, noconcentrate was available to them and lambs were unweaned. Both management strategies showed a similar pattern of live-weightand BCS during spring grazing, except at day 49 post-lambing, when body reserves of GR ewes were greater than their INDcounterparts (P < 0.05). Milk production of GR ewes was greater on days 13 and 27 of lactation (P < 0.05). Milk composition wasnot affected by the management system (P > 0.05) and fat and protein content increased with advancing lactation (P < 0.001). Milkfatty acid composition was different across treatments during the first month of lactation, with greater contents of short and mediumchain and lower long chain fatty acids in GR treatment (P < 0.05). The stage of lactation had no effect on plasma TRIG, urea andBHB (P > 0.05). Ewes from GR treatment presented greater TRIG and urea, and lower concentrations of BHB than IND (P < 0.01).Concentration of NEFA were greater in IND ewes on days 13 and 27 post-partum (P < 0.05), but not on day 41 of lactation. Thesubjective carcass classification showed that GR treatment presented a slightly inferior conformation score (O+ versus R−) andfatness degree (slight versus average–slight fat cover) to IND (P < 0.01). No differences were detected in redness and yellowness ofmuscle (P > 0.05), whereas IND lambs presented greater lightness values (P < 0.05). Lightness and redness of subcutaneous lumbarfat were not affected by treatment (P > 0.05). However, yellowness was greater in GR lambs (P < 0.001). It is concluded that neitherproductive nor metabolic performance was impaired in continuous grazing ewes in spite of their greater milk and protein production

observed during the first month of lactation. Dietary supplementation of rationed grazing ewes was not sufficient to avoid mobilisingtheir body reserves in early lactation. Carcass classification from grazing lambs was slightly penalised in comparison with indoorlambs, but differences were poorly appreciated in meat and fat colour.© 2007 Elsevier B.V. All rights reserved.

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Keywords: Sheep; Grazing; Management system; Milk fatty acids; B

∗ Corresponding author. Tel.: +34 976 71 64 42;fax: +34 976 71 63 35.

E-mail address: mjoy@aragon.es (M. Joy).� In memory.

0921-4488/$ – see front matter © 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.smallrumres.2007.07.005

tabolites; Carcass

1. Introduction

Traditional lamb meat production in South Euro-

pean countries, especially in Spain, is based on lightlambs (18–24 kg live-weight, younger than 90 daysold, ‘Ternasco’ commercial category), which are fedon a concentrate-based diet and milk until weaning and

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hereafter with only concentrate. As a consequence, ewesre managed under rationated grazing for several hoursaily without their lambs. The rest of the day dams andambs remain indoors and receive supplement. Weanings normally carried out at 45–55 days old, and thereafter,ambs are kept indoors with free access to concen-rate and water until they reach the slaughter weight of2–24 kg. Previous studies concerning Churra Tensinaheep have demonstrated that spring lambing ewes areble to raise lambs on permanent mountain pasturesithout detrimental effects on their performance (Joy

t al., 2004; Alvarez-Rodrıguez et al., 2007). However,ittle documented information is available regardingwe metabolic status in outdoor production systems ofuckling lambs in comparison with the conventionalestricted suckling and grazing management.

In Spain there has been insufficient appreciation forark meat with yellow fat arising from the carcass ofambs raised under extensive systems of managementPriolo et al., 2002). However, the increasing demandor healthy and safe meat products is stimulating thearket interest in extensive systems (Gil et al., 2000).

n addition, supplementary premiums are being takennto account for the preservation of rare breeds andhe promotion of high quality products arising fromhem according to the new Common Agricultural Policyeform of the EU (Canali, 2006).

The first objective of the present study was to com-are the productive and metabolic performance of ewesaising light lambs under two management systems:ontinuous grazing system or restricted grazing systemupplemented with concentrate. The second objectiveas to study the lamb carcass traits in both management

ystems.

. Materials and methods

.1. Experimental site

The experiment was conducted in La Garcipollera Researchtation, in the Pyrenees (North-eastern Spain, 42◦37′N,◦30′W, 945 m a.s.l.), during spring 2003. The average annualainfall is bimodally distributed with peaks in spring andutumn, with dry summers and some precipitation in form ofnow in winter. The mean temperature during March, April,

ay and June 2003 was 7.5, 8.8, 12.2 and 20.2 ◦C, while pre-ipitation in these months was 78.3, 52.5, 48.1 and 59.4 mm,espectively.

.2. Animal management and experimental design

Thirty-eight spring-lambing adult ewes (48.8 ± 0.83 kgive-weight and body condition score 2.79 ± 0.05 at lambing)

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rearing single male lambs (3.6 ± 0.08 kg live-weight at birth)were used. Ewes belong to an experimental flock of 164 ewesof Churra Tensina breed which were bred by natural servicein a 30-day mating period in the autumn (15 October to 15November).

The flock was managed under a year-round grazing systeminvolving the use of supra-forest pastures on high mountainranges in summer (Casasus et al., 1999), forest-shrub pasturesin autumn and winter (Casasus et al., 2007) and permanentvalley pastures in spring and autumn. From mating to 1 weekprevious to lambing, each ewe was supplemented with 250 gof alfalfa pellet/day. One week prior to lambing ewes werehoused and received 1 kg of alfalfa pellet per animal and dayand barley straw ad libitum.

After birth, lambs were provided a complement of sele-nium and remained indoors with their dams for some daysto ensure maternal bonding. After this, ewes were randomlyallocated to two adjacent paddocks (n = 19). Lambing date, par-ity, body condition score and live-weight of ewes and lambswere taken into account to balance groups. The treatmentswere:

1. Indoor (IND): Ewes grazed during 8 h a day (08:00to 16:00 h) without their lambs and thereafter remainedindoors (10 m × 10 m) with them, receiving a supplementof 0.5 kg fresh matter of barley meal/day (119 g/kg CP,248 g/kg NDF, on dry matter basis). The level of supplemen-tation was supplied according to the estimates of herbageintake and milk yield within the same breed and manage-ment (Alvarez-Rodrıguez et al., 2007) and aimed to replythe commonly used systems in that region.

Lambs were fed concentrate ad libitum (182 and 167 g/kgCP; 190 and 212 g/kg NDF, on dry matter basis, thefirst month and subsequently, respectively) and they wereweaned between 50 and 55 days old (52.8 ± 0.86 days).Both dams and lambs had ad libitum barley straw (37 g/kgCP and 807 g/kg NDF, on dry matter basis).

2. Grazing (GR): Ewes and lambs were continuously stockedon a permanent pasture. No concentrate was available todams or lambs. Lambs suckled their mothers and grazeduntil slaughter.

The pasture was composed of 22% legumes (mainly Tri-folium repens), 68% grass (the main species were Festucaarundinacea, Festuca pratensis and Dactylis glomerata) and10% other species (mainly Rumex acetosa and Ranunculus bul-bosus). The stocking rate was 32 ewes/ha (0.57 ha/treatment)and pastures allowed a voluntary intake of forage greater thanthat observed by Valderrabano and Folch (1984) in a grazingstudy with similar conditions to the present experiment. All theewes and lambs were supplied fresh water and mineral vitamin

supplement ad libitum.

Herbage mass and forage quality was measured throughfour samplings at monthly intervals by clipping with an electricmower all plant material to 3 cm of ground level in 10 quadrats(1 m × 0.25 m) per paddock.

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26 M. Joy et al. / Small Rum

Ewes and lambs were weighed on weekly intervals at 8 a.m.,with an electronic balance (0.5 kg precision). Lambs averagedaily gains (ADG) were calculated by the difference betweenfinal and initial weights divided by the total number of days.Three periods were calculated: born to 53 days (weaning datefor IND treatment), from 53 days to slaughter and the wholegrowing period, from born to slaughter. Body condition scoreof ewes (BCS) was measured by two trained people 1 weekbefore lambing, and on days 14, 28, 49, 63 and 91 ± 1.9 post-partum according to Russel et al. (1969).

Milk production was estimated at three different momentsof lactation (13, 27 and 41 ± 0.60 days post-partum) by the oxy-tocin technique proposed by Doney et al. (1979) and machinemilking with hand finishing up (8:00 and 12:00 h) in 10 ewesper treatment chosen randomly, which were sampled through-out the three recordings. Ewes were returned to graze withoutlambs between the two milkings. A final control was carriedout in GR treatment on day 56 of lactation. Individual milksamples (50 ml) were taken and conserved in oxide chromiumand kept refrigerated until analysis.

Blood samples (5 ml) through jugular veins were takenfrom 10 ewes 1 week prior to lambing to assess their generalmetabolic status. During the post-partum period, blood sampleswere taken in the same ewes that were milk recorded. Bloodwas collected into vacuum tubes, centrifuged and plasma wasfrozen.

The sample size for milk and blood sampling was deter-mined according to estimates based on similar data sets withinpublished literature. However, both the level of variability andthe expected difference between treatments for main studyvariables was uncertain in such circumstances because littleknowledge was available regarding this breed. Data collectedin this pilot assay will be used in sample size calculations andverified by additional inferential studies. The 10 ewes wereselected randomly within treatment.

2.3. Slaughter procedure and carcass measurements

When lambs reached 22–24 kg of live-weight they weretransported to the experimental abattoir of the Research Insti-tute in Zaragoza, which is located 180 km away from the farm.They were weighed at arrival and accommodated, until theirslaughter, according to their original treatment. No fastingperiod was carried out. GR lambs received green forage andthose from IND treatment received the same concentrate thanthat offered during the experimental period. Twenty hours aftertheir arrival, lambs were slaughtered according to EU laws.

Carcasses were chilled at 4 ◦C during 24 h, cold carcasswas weighed (CCW) and dressing percentage was calculatedas the ratio of cold carcass weight to live weight (dressingpercentage = CCW × 100/slaughter weight). Classification of

conformation and fatness degree was carried out following theCommunity Scale for Classification of Carcasses of Ovine Ani-mals and of Light Lambs (DOCE, 1994). The conformationwas scored with grade values from 18 for S+ (excellent) to 1for P− (poor) of the SEUROP (S superior, E excellent, U very

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good, R good, O fair and P poor), and the classification for fat-ness degree was scored from 12 (4+, very high) to 1 for (1−, verylow) of the scale 1 (low), 2 (slight), 3 (average), 4 (high). Sub-jective fat characteristics (amount, colour and persistence) andmeat colour were determined according to Colomer-Rocher etal. (1988).

Ultimate pH was measured at the fourth vertebral regionwith pH-meter equipped with a Crison 507 penetratingelectrode (Crison Instruments S.A., Barcelona, Spain). Instru-mental colour was measured 24 h post-mortem using aspectrophotometer Minolta CM-2600d in the CIELAB space(Wyszecki and Stiles, 1982) with 8 mm measured area diam-eter, specular component included and 0% UV, standardilluminant D65 that simulates day light (colour temperature6504 K), angle 10◦ and zero and white calibration. The light-ness (L*), redness (a*) and yellowness (b*) were recorded.Subcutaneous lumbar fat colour was determined after the sub-cutaneous muscle was displaced. Each colour values wererecorded at three locations randomly selected avoiding bloodblots, discolorations, and less covered areas. The Rectus abdo-minis muscle colour was measured on two locations of theinternal face of each piece randomly selected to obtain a meanvalue as representative reading of the surface colour.

2.4. Chemical analysis

Herbage dry matter (DM) was determined at 60 ◦C untilconstant weight. Ash content was measured gravimetricallyby igniting samples in a muffle furnace at 550 ◦C for 3 h, andcrude protein was determined by Dumas procedure, accordingto AOAC (1999). Neutral-detergent fibre (NDF) was analysedby the method of Van Soest et al. (1991).

Milk samples were analyzed for protein, fat, lactose andnon-fat solids with infrared (Milkoscan 4000, Foss Elec-tric, Ltd., UK). Milk lipids were extracted from milk withchloroform–methanol and hydrolyzed with alkali. Fatty acids(FA) were converted to methyl esters and quantified using aHP5890 gas chromatograph, with a SP1330 capillary column(30 m × 0.25 mm × 0.2 �m). Fatty acid content was expressedin percentage of the total amount of the fatty acids identi-fied. After individual FA determination, the sum of saturatedfatty acids (SFA), mono-unsaturated FA (MUFA), and poly-unsaturated FA (PUFA), as well as the PUFA/SFA andC18:2/C18:3 ratios were calculated.

Blood samples were analyzed for �-hydroxybutyrate(BHB) (enzymatic method), triglycerides (GPO-PAO method)(TRIG), urea (GlDH method, kinetic UV test) and non-esterified fatty acids (NEFA) (colorimetric method). BHB,TRIG and urea were analysed using an automatic analyser(Vitalab Selectra, Merck, Darmstadt, Germany). Accuracyof all quantification methods was implemented with control

serum from respective manufacturers. Reagent manufactur-ers were: Sigma Diagnostics (St. Louis, MO, USA) for BHBand Diagnostica Merck (Merck KGaA 64271, Darmstadt, Ger-many) for urea and TRIG. NEFA were determined using acommercial kit (Randox Laboratories Ltd., Co., Antrim, UK).

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.5. Statistical analysis

Data from ewe live-weight, BCS, milk yield and milk com-osition were analysed using the MIXED procedure of SASith the following model:

ijk = μ + αi + dj + βk + (αβ)ik + εijk

here yijk is the dependent variable, μ the overall mean, αi thereatment effect, dj the animal effect j, βk the day of lactationffect and εijk is the residual error.

Normal distribution of blood metabolites and subjectivearcass classification traits were tested with the Shapiro–Wilkest before further analysis. On this basis, TRIG, BHB andEFA were log-transformed to achieve normal distribution ofata and analysed using the previous model.

In case of plasma urea and all subjective carcass traits,ormal distribution could not be verified and means were com-ared with non-parametric tests of NPAR1WAY procedure ofAS. To study the temporal pattern of plasma urea through-ut lactation, the sampling point on day 13 post-partum wasompared with the following time points.

Data from lamb performance, carcass weights and dressingercentage were analysed using the GLM procedure of SASccording to the model:

ij = μ + αi + εij

here yij is the dependent variable, μ the overall mean, αi thereatment effect and εij is the residual error.

. Results and discussion

.1. Pastures

Herbage production and chemical composition of theermanent pasture are shown in Table 1. Herbage massanged between 1.2 and 3.2 t DM/ha. Forage availabil-ty was in all samplings greater than 2 kg DM/head/day,nder which the voluntary intake of ewes may have been

imited (Valderrabano and Folch, 1984). The quality ofhe pasture was good, as it provided both a high energy11.3 MJ ME/kg DM, estimated according to Mertens,983), and a high protein diet which surpassed the

able 1erbage mass (kg DM/ha) and chemical composition (g/kg DM) of theermanent pasture

Average Range

erbage mass 1756 1156–3248Ma 205 168–258P 226 205–256DF 467 426–489DF 236 226–239

a DM: dry matter; CP: crude protein; NDF: neutral detergent fibre;DF: acid detergent fibre.

Fig. 1. Evolution of live-weight and body condition score (BCS) ofChurra Tensina lactating ewes grazing between 08:00 and 16:00 h andsupplemented with barley meal indoors (�) or stocked continuouslyon pastures (�).

minimum content suggested by Avondo et al. (2002)to compromise dry matter intake of lactating ewes inMediterranean conditions.

3.2. Ewes performance

Both management strategies showed similar patternof live-weights and BCS during spring grazing (Fig. 1),except at day 49 post-lambing, when body reserves of GRewes were greater than their IND counterparts (P < 0.05).Ewes lost between 14% (GR) and 20% (IND) of theirinitial live-weight until the end of the experiment. Thegreater losses were registered during following 2 weeksafter lambing, being greater in IND ewes (8.9% versus16.7% in GR versus IND, respectively). As the subse-quent live-weight losses until day 91 post-partum wereopposite (5.2% versus 2.0% in GR versus IND, respec-tively), the slight differences across treatments might bedue to the higher live-weight loss during the 2 weeksafter lambing in IND rather than to a difference in theperformance on the whole period. This results could bepartially explained by the restricted feeding managementand the loss of digestive content at turnout due to thechange from a dry to a green diet (6% of live-weight;

INRA, 1978).

Similar results were obtained in lactating Latxa andGallega ewes, two breeds with similar body size toChurra Tensina, during spring grazing on other Spanish

28 M. Joy et al. / Small Ruminant Research 75 (2008) 24–35

Table 2Milk production (g/day) and composition (g/kg) of Churra Tensina ewes managed under continuous stocking (GR) and rationed grazing withsupplementation (IND) during spring, according to day of lactation†

Days of lactation S.E.

13 27 41 56

GR IND GR IND GR IND GR

Production (g/day)Milk 1616 a 1183 b 1322 a 955 b 1073 1205 713 117.5Fat 94.9 a 66.3 b 57.9 46.8 58.0 62.8 53.6 6.6Protein 72.2 a 55.4 b 70.0 a 44.2 b 49.0 57.8 36.1 5.3

Milk composition (g/kg)Crude fat 63.4 56.3 43.7 48.5 53.7 52.2 80.6 4.2Crude protein 45.3 46.3 46.6 46.4 45.4 47.7 52.5 1.3Lactose 54.3 54.3 56.5 55.9 54.3 54.9 51.9 0.8

ers are

Non-fat solids 108.0 108.1 110.8

† Least square means in the same row and control with different lett

permanent mountain pastures with non-limiting swardherbage heights (Osoro et al., 2002) as well as in thesame breed as the present managing identical treatments(Alvarez-Rodrıguez et al., 2007). These results wouldconfirm the observations of Revilla et al. (1991), whosuggested an average recovery of body reserves in com-mercial sheep flocks on this area during spring grazingon permanent pastures, as a consequence of the highherbage availability and quality in comparison with thepreceding seasons.

Ewes from GR treatment had greater milk produc-tion on days 13 and 27 of lactation (P < 0.05), whereasthis superiority disappeared on day 41 of lactation(P > 0.05; Table 2). In this sense, Cardellino and Benson(2002) concluded that greatest differences among groupsoccurred in ewes milk yield throughout early lactation.

The differences in fat yield were only significanton day 13 post-partum (P < 0.05) whereas protein yieldremained higher in GR than in IND during the first monthof lactation (P < 0.05). Alvarez-Rodrıguez et al. (2007)observed a greater milk production in continuous stockedewes with lambs supplemented at pasture in ChurraTensina breed. However, no differences were detectedbetween continuous stocked ewes unsupplemented andrestricted grazing ewes supplemented indoors. The con-tinuous presence of lambs close to mothers in GRtreatment could have a positive effect on milk produc-tion in the first month of lactation (Fuertes et al., 1998).Likewise, the high quality of the pasture in early springincreased the dietary protein:energy ratio of GR ewes

(Robinson, 1980) and therefore milk yield improved.Afterwards, barley supplementation of IND ewes mayhave produced a positive effect on the persistence of thelactation curve (Bocquier and Caja, 2001), although milk

109.5 107.1 110.0 111.6 1.5

different (P < 0.05).

yield difference on day 41 of lactation was not significant(P > 0.05). Lambs reared on pasture, which ought to ini-tiate grazing activity at 3 weeks old (Alvarez-Rodrıguezet al., 2007), should increase the time spent grazing reg-ularly, as milk yield of dams decreased.

Milk composition was not affected by the manage-ment system (P > 0.05). Fat and protein content increasedwith advancing lactation (P < 0.001).

If we take into account the requirements proposed byBocquier et al. (1987), the recommendations of Bocquierand Caja (2001) and the estimates of herbage intakewithin this breed and managements (Alvarez-Rodrıguezet al., 2007), it can be drawn that feed would have met onaverage the total energy demands for maintenance andlactation in a similar way in both treatments whereasprotein contributions would have covered at least twicethe requirements of GR ewes but not of IND ewes. Thisdifference in the energy/protein ratio in the diets mighthave promoted milk yield in GR ewes whereas produceda slight mobilization of body reserves in their IND coun-terparts.

3.3. Milk fatty acids

The most prevalent milk FA were oleic (C18:1),palmitic (C16), stearic (C18), caprinic (C10) and miris-tic (C14), that accounted for around 754 and 776 g/kg ofthe total fatty acids in GR and IND milk fat, respectively(Table 3). These results are similar to those reported inSicilo-Sarde dairy ewes (748 and 771 g/kg for grass and

concentrate-fed Atti et al., 2006). However, in the presentstudy oleic acid was the most abundant milk FA in bothtreatments whereas in the study of Atti et al. (2006) itwas palmitic acid. As oleic acid is the most important

M. Joy et al. / Small Ruminant Research 75 (2008) 24–35 29

Table 3Fatty acid composition of milk fat (g/kg) of Churra Tensina ewes managed under continuous stocking (GR) and rationed grazing with supplementation(IND) during spring, according to day of lactation†

Days of lactation S.E.

13 27 41 56

GR IND GR IND GR IND GR

C4 43.0 42.2 38.3 37.2 36.7 36.5 36.8 1.1C6 37.5 a 26.9 b 34.4 a 23.4 b 29.2 30.2 24.8 1.1C8 36.5 a 21.5 b 35.6 a 19.9 b 26.9 27.9 21.2 1.4C10 93.0 a 47.6 b 91.8 a 45.4 b 72.0 76.7 55.2 3.9C12 47.8 a 23.5 b 46.5 a 22.6 b 36.4 39.1 30.0 1.9C14 87.5 a 50.2 b 74.8 a 50.1 b 75.1 76.3 74.7 3.1C15 9.8 a 7.7 b 9.5 a 8.4 b 12.6 a 11.6 b 12.5 0.4C16 171.3 172.8 163.0 171.0 177.6 190.8 196.3 4.7C16:1 5.1 b 9.8 a 6.3 b 10.3 a 8.3 9.1 9.9 0.5C17 6.2 b 10.1 a 6.3 b 10.3 a 7.7 7.4 9.4 0.4C18 123.7 b 156.8 a 133.7 b 161.9 a 164.7 149.5 155.3 6.1C18:1 255.4 b 347.7 a 280.2 b 360.6 a 277.0 270.6 291.5 7.6C18:2 17.9 b 21.3 a 11.9 b 18.4 a 12.6 b 17.0 a 16.4 1.0C18:3 13.5 a 10.3 b 15.5 a 11.3 b 11.7 10.6 10.2 0.8C4–C10 210 a 138 b 200 a 126 b 165 171 138 6.5C12–C16:1 322 a 264 b 300 a 262 b 310 327 323 8.2C17–C18:3 417 b 546 a 448 b 563 a 474 455 483 11.4SFAa 656 a 559 b 634 a 550 b 639 646 616 9.2MUFA 260 b 358 a 287 b 371 a 285 278 301 7.7PUFA 31.4 31.7 27.4 29.8 24.3 27.6 26.5 1.3PUFA/SFA 0.49 b 0.57 a 0.43 b 0.54 a 0.38 b 0.43 a 0.43 0.03C18:2/C18:3 13.9 b 21.5 a 8.0 b 17.2 a 11.2 b 16.4 a 16.6 1.4

a SFA: saturated fatty acids, MUFA: monounsaturated fatty acid, PUFA: polyunsaturated fatty acids, and relations between SFA/PUFA andC

ers are

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18:2/C18:3.† Least square means in the same row and control with different lett

lasma non-esterified fatty acid (Ponter et al., 2000), theigh amount of this acid is a reflection of a greater adi-ose tissue mobilization in our dams in comparison withhe milked ewes in late lactation reported by the studyf Atti et al. (2006).

Milk fat from continuously stocked ewes (GR) pre-ented greater contents of short (C4–C10) and mediumhain fatty acids (C12–C16:1) (P < 0.05) than milk fromationed grazing ewes supplemented indoors (IND)uring the first month of lactation (days 13 and 27 post-ambing). In contrast, GR ewes had lower long chain FAC17–C18:3) (P < 0.05) than IND ewes during the sameeriod. On day 41 post-partum, differences across man-gement systems in all chain FA classes disappearedP > 0.05) (Table 3). In general, decreased short andedium chain FA are due to a lack of precursors (acetate

nd �-hydroxybutyrate) for the synthesis of FA in the

ammary gland and increased long chain FA are due

o the mobilization of FA from adipose tissue, whichre directly incorporated into milk fat (Luick and Smith,963).

different (P < 0.05).

No significant (P > 0.05) differences were observedacross treatments in C4 and C16 acids. The content ofC15 was higher in GR than in IND (P < 0.01). On thecontrary, linoleic acid (C18:2) was greater in IND than inGR ewes (P < 0.001). The rich content of linoleic acidof concentrates (Valvo et al., 2005) may have enhancedthe milk content of this fatty acid in rationed grazingewes supplemented with barley meal indoors. The stageof lactation affected the content of C4, C15, C16, C18:2acids (P < 0.001).

Contrary to expectation, milk from GR ewes con-tained higher contents of SFA (P < 0.05) and lower ofMUFA (P < 0.05) than IND treatment during the first andsecond milk recordings. However, the content of PUFAwere similar in both management systems (P > 0.05) andthey decreased with advancing lactation (P < 0.001). Thepresent study did not support the results of Valvo et al.

(2005), who found that grass-fed Comisana ewes pro-duced lower levels of SFA and greater MUFA and PUFAthan dams which were given concentrates in early lacta-tion.

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30 M. Joy et al. / Small Rum

Linolenic acid (C18:3) content was higher in milk fatof GR ewes than in their IND counterparts through-out the first month of lactation (P < 0.05), resulting ina lower C18:2/C18:3 relation in GR than in IND treat-ment (P < 0.05). This is in agreement with Chilliard etal. (2001), who reported a reduction of n6:n3 relation inmilk fat when rich green forage diets were offered. Thistrait might be linked to fatty acid composition of adiposetissue in the group of lambs which suckled until slaugh-ter (GR), as its profile generally reflected milk fatty acidcomposition (Bas and Morand-Fehr, 2000).

3.4. Ewe blood metabolites

The mean plasma concentrations the weekprior to lambing were 0.39 ± 0.07 mmol/l TRIG,1.14 ± 0.15 mmol/l NEFA, 7.63 ± 0.55 mmol/l urea and0.48 ± 0.11 mmol/l BHB. On that moment, even thoughewes had been housed and fed 1 kg of pelleted dehy-drated alfalfa, feeding requirements were unlikely metand according to NEFA concentrations, fat mobilizationwas occurring (Russel, 1984) in response to the highnutrient demands of late gestation. In spite of that, eweslambed with a good BCS, which did not compromisetheir performance during the spring season.

During the post-partum period, concentrations of

TRIG were higher in GR than in IND ewes (P < 0.01;Fig. 2) but followed the same pattern with advancinglactation (P > 0.05). The greater plasma concentration ofTRIG registered in GR ewes was likely due to a greater

Fig. 2. Blood metabolites in Churra Tensina lactating ewes grazing betweenstocked continuously on pastures (�) (TRIG, NEFA and BHB concentrationsof log values. Urea concentrations are means).

esearch 75 (2008) 24–35

adipose tissue hydrolysis to cover the energy require-ments for milk synthesis, which is in accordance withthe higher milk production observed in this treatment.

The evolution of NEFA plasma concentrations didnot follow the same trend of TRIG. Ewes from INDtreatment had higher values of NEFA than GR oneson days 13 and 27 post-partum (P < 0.05), but not onday 41 of lactation. Ewes IND peaked on day 27 post-partum whereas their GR counterparts peaked smoothlyon day 56 post-partum, when the IND lambs werealready weaned. It is known that concentrate supple-mentation produces a depressive effect on circulatingplasma NEFA (Gonda and Lindberg, 1993). However,the level of supplementation of IND ewes and the highnutrient requirements during early lactation did not allowthe expression of this effect in our experiment.

As plasma NEFA are the major source of long chainmilk fatty acids, IND ewes showed a greater concentra-tion of them during the first month of lactation (P < 0.05),which produced, according to live-weight and BCS, aloss of body reserves in this treatment in the short term(day 49 post-partum, P < 0.05). The low concentrationsof plasma NEFA in GR ewes, in contrast to the high TRIGconcentrations, can be due to the high rate use of NEFAby mammary gland, which allows a greater expressionof the adipose tissue lipolytic potential without major

increases in plasma NEFA concentrations (Chilliard etal., 1998).

Another possible explanation for the greater NEFAconcentrations in rationed grazing ewes (IND) could be

08:00 and 16:00 h and supplemented with barley meal indoors (�) orare back transformed values of least square means from the analysis

inant R

ttfitTapN

tipPtssop

Iomtst

TP

L

C

M. Joy et al. / Small Rum

heir lower dietary protein in comparison with the con-inuous stocked ewes (GR), which may have achievedrom pasture during the remaining time outdoors a sim-lar energy intake (Alvarez-Rodrıguez et al., 2007) tohe supplementation of IND (0.5 kg/head barley meal).hat would have led to enhanced gluconeogenesis fromminoacids and therefore, a less important hydrolysis oflasma triglycerides, which did not elevate circulatingEFA in GR treatment.This hypothesis is in agreement with the concentra-

ions of plasma urea, which were higher in GR thann IND (P < 0.001) and remained constant during theost-partum period (P > 0.05). In this sense, Jaime andurroy (1995) found that diets with a great crude pro-

ein content produced increases in plasma urea anduggested that high ammonia concentrations were con-equently present in the rumen and significant amountsf urea were synthesized and liberated into the bodyool.

The BHB concentrations were lower in GR than inND (P < 0.01) and they were not affected by the stagef lactation (P > 0.05). The supplementation of barley

eal could be responsible for the greater BHB concen-

ration observed in IND ewes, since concentrate-basedystems favour the availability of gluconeogenic ratherhan acetogenic nutrients (Majdoub et al., 2003).

able 4erformance and carcass characteristics of lambs reared on pasture (GR) or c

GR

amb performanceBirth weight (kg) 3.6Weight at 53 days old (kg) 17.0ADG birth to 53 days old (g) 253Final live-weight (kg) 23.0ADG 53 days old to slaughter (g) 217ADG from birth to slaughter (g) 242Age at slaughter 85.5Slaughter weight (kg) 22.1

arcass classificationCold carcass weight (kg) 10.0Dressing percentage 45.3Conformation scorea 5.5 (O+)Fatness degreeb 4.6 (slight)Fat persistencec 2.0Amount of pelvic and renal fatd 3.3Fat coloure 2.9Meat colourf 5.7

a From 18 for S+ (excellent) to 1 for P− (poor) of the SEUROP (S superior,b From 12 for 4+ (very high) to 1 for 1− (very low) of grade 1 low, 2 slight,c From 1 (very hard) to 9 (very oily), of a classification for hard, soft and od From 1 (very low fat) to 9 (very high fat) of the classification of low, norme From 1 (very white) to 9 (intensive yellow) of white, cream or yellow clasf From 1 (very clear pink) to 9 (very dark) of clear pink, pink, other colour

esearch 75 (2008) 24–35 31

3.5. Lambs performance

Lamb birth weight, live-weight on day 53 of lactation(weaning of IND treatment) and slaughter weight weresimilar across managements (Table 4). The ADG frombirth to 53 days was similar in both treatments (P > 0.05).However, when ADG considered the period from birth toslaughter, gains were significantly higher in IND than inGR lambs (P < 0.01). As expected, IND lambs presenteda higher growth rate after 53 days old than their GRcounterparts due to concentrate intake. A similar growthpattern was found in identical spring managements onmountain pastures in the same breed (Alvarez-Rodrıguezet al., 2007) but slightly different to that observed in RasaAragonesa sheep grazing alfalfa during spring, sincethe continuous stocked treatment could achieve a simi-lar ADG to lambs fed in drylot (Joy et al., 2005). Oneof the reasons for this great performance could be thehigher mean protein content of alfalfa crop in compari-son with the present permanent pastures (average around260 g CP/kg DM versus 220 g CP/kg DM), as well as thedifferent breed compared.

Most of the comparative trials between pasture versusconcentrate-based systems have concluded that ADG oflambs is lower when they are raised under a grazingsystem (Prache et al., 1990; Notter et al., 1991; McClure

oncentrate-based (IND) systems

IND S.E. Significance

3.6 0.1217.9 0.63

273 8.723.3 0.22

292 15.6 **281 8.0 **74.2 2.6 **22.9 0.26

10.8 0.17 **47.1 0.49 *7.1 (R−) 0.37 *6.6 (average–slight) 0.34 ***2.0 0.004.6 0.28 **2.0 0.245.2 0.17 *

E excellent, U very good, R good, O fair and P poor) (DOCE, 1994).3 average, and 4 high (DOCE, 1994).

ily (Colomer-Rocher et al., 1988).al and high (Colomer-Rocher et al., 1988).sification (Colomer-Rocher et al., 1988).classification (Colomer-Rocher et al., 1988).

inant R

carcasses showed slight differences, with greater chromavalue in carcasses from grazing.

There were no significant differences in muscle pH(P > 0.05; Table 5), rejecting stress effect on muscle

Table 5pH of muscle Longissimus dorsi and instrumental colour of muscleRectus abdominis and subcutaneous lumbar fat from lambs reared onpasture (GR) or concentrate-based (IND) systems

GR IND S.E. Significance

pH 5.64 5.65 0.11

Muscle Rectus abdominis instrumental colourLightness (L*) 48.88 52.57 0.95 *Redness (a*) 7.26 7.80 0.46Yellowness (b*) 3.91 4.98 0.87

32 M. Joy et al. / Small Rum

et al., 1994; Zervas et al., 1999), but they have dealt withweaned lambs that were slaughtered at heavy weights.However, in our conditions we may practice a productionsystem in which lambs graze and suckle their mothersuntil slaughter without a major biological set-back inlamb performance.

The differences in ADG had a significant effect onthe time needed to reach slaughter weight, being higherin GR than in IND lambs (P < 0.01). In spite of this, theextensive raising system constitutes one of the most eco-nomic ways of producing meat and GR lambs were ableto reach 22–24 kg live-weight in less than 90 days, whichis the target rearing duration for light lambs demanded byMediterranean consumers (Joy et al., 2007). Therefore,grass-based systems can be a good alternative to indoorlamb production systems in order to rear herbivoresunder extensive conditions and use natural resources toprovide the meat required by new tendency of consumers(Grunet et al., 2004).

3.6. Carcass characteristics

The slaughter weight was lower than the final live-weight obtained at farm. As abattoir was 180 km faraway from the Garcipollera Research Station transportlosses were registered in both treatments (4.2% for GRand 2.6% for IND, P > 0.05). The CCW and the dressingpercentage were lower in GR lambs than in IND lambs(P < 0.05; Table 4), because forage-fed systems increasedigestive tract size (Fluharty et al., 1999; McClure et al.,2000), resulting in lower dressing percentages (Bortonet al., 2005; Dıaz et al., 2002). Nevertheless, differencesacross grazing and indoor lambs regarding digestive tractwere promoted by a major importance of the small intes-tine in the former, rather than by a greater forestomach(Delfa et al., 2005).

The subjective classification for carcass conformationshowed that GR treatment presented a slightly inferiorclassification (O+) to IND lambs (R−) (P < 0.01). AllGR carcasses were classified between P+ (11.1%) and R(22.2%), being most of carcasses O− and O+ (61.1%).The carcasses of IND lambs were classified betweenO− (5.2%) and R+ (15.8%) and most of them were R−(31.6%) and R (26.3%). These results agree with severalworks that observed that lambs raised under a grazingsystem without any supplementation presented a slightlyinferior conformation (Ely et al., 1979; Olleta et al.,1992; Murphy et al., 1994; McClure et al., 1995; Priolo et

al., 2002). Lambs from IND treatment presented a fatnessdegree of 3− (average–slight fat cover), while GR treat-ment presented an average fatness degree of 2 (slight fatcover) (P < 0.001). Most of carcasses from GR treatment

esearch 75 (2008) 24–35

were classified within the category 2−/2+ (66.6%) andIND carcasses between 2+/3− (68.4%). Pena et al. (2005)reported that the majority of carcasses of Segurena lambsslaughtered at 19–25 kg live-weight were classified asmedium fat with 2/3−, which is one requirement of theSpanish light lamb market. All carcasses were includedwithin B and C classes of the European carcass clas-sification system for light lambs (9–12.5 kg, Ternascocommercial category).

The visual muscle colour of GR lambs graded aspink+ and IND lambs as pink (P < 0.05). There weredifferences (P < 0.01) in the amount of pelvic and renalfat as expected according to the fatness degree. All thecarcasses had hard fat (2), being a suitable fat firmnessfor the Spanish market. Fat colour was not affected bytreatment (P > 0.05), with a subjective classification ofwhite-cream and white for GR and IND, respectively,in keeping with Ripoll et al. (2005), when comparingtwo grazing and two indoor systems. Carcasses fromIND treatment presented a more uniform fat colour (allwhite fat) than GR (20% very white, 32% white, 32%white-cream and 16% cream fat).

The colour characteristics of muscle Rectus abdomi-nis and lumbar fat colour from GR and IND carcassesare shown in Table 5. No differences were detected inredness and yellowness of muscle (P > 0.05), whereaslightness of IND lambs muscle was significantly greaterthan GR (P < 0.05). That is in agreement with the dif-ferences (P < 0.01) in subjective classification (Table 4),being the muscle of GR lambs graded as pink+ and INDlambs as pink. Ripoll et al. (2005) in the above citedexperiment concluded that muscle colour of lamb light

Subcutaneous lumbar fat colourLightness (L*) 79.42 79.15 0.70Redness (a*) 0.87 0.29 0.24Yellowness (b*) 10.40 6.26 0.38 ***

inant R

coieaatobesocallmwy

tfusoTrtaPttw

4

mritepDnemfut

t

M. Joy et al. / Small Rum

olour, via lower glycolytic potential or different activityf muscle enzymes (Hopkins et al., 1998). As this muscles not affected by the physical exercise (Colomer-Rochert al., 1988), these differences must be due to the diet,lthough Hopkins et al. (1998) in lambs and Young etl. (1997) in cattle reported that there was no consis-ent diet effect on meat colour. Ripoll et al. (2005) alsobserved that colour display of meat was no affectedy the management system (P > 0.05). The small differ-nces across treatments had no commercial constraintince all carcasses meet Spanish market requirementsf medium–high conformation, average–low fatness andlear meats. In relation to that, Panea et al. (2006) insensorial meat evaluation of suckling lambs, heavy

ambs, grazing light lambs and concentrate-fed lightambs concluded that grazing light lambs presented the

ost tender meat, in keeping with Ripoll et al. (2005),ho found similar results in an instrumental texture anal-sis using Warner–Bratzler.

There was no significant effect of management sys-em on lightness and redness of subcutaneous lumbarat (P > 0.05) while fat of GR lambs had higher val-es of yellowness (P < 0.001; Table 5). The managementystem affects fat colour due to carotenoids (yellow torange) arisen from pastures and stored in fat depots.hese results are consistent with Ripoll et al. (2005), who

eported values of yellowness of 10.8 and 6.0 in two iden-ical managements to GR and IND. Similar differencescross grass and concentrate-fed lambs were indicated byriolo et al. (2002), but yellowness values were greater

han those observed in the present experiment becausehey studied older weaned lambs with greater slaughtereight.

. Conclusions

It is concluded that milk and protein yield of ewesanaged under continuous grazing was higher than in

ationed grazing ewes supplemented with barley mealndoors during the first month of lactation, probably dueo the high crude protein content of permanent pasture inarly spring. However, neither productive nor metabolicerformance was penalised in continuous grazing ewes.ietary supplementation of rationed grazing ewes wasot sufficient to avoid mobilising their body reserves inarly lactation, being their metabolic status reflected inilk fatty acids composition and blood non-esterified

atty acids. The high crude protein intake increased blood

rea in continuous stocked ewes and thus it might alterheir energy catabolic pathways.

Lambs suckling their mothers and grazing untilhe slaughter presented a lower performance than

esearch 75 (2008) 24–35 33

concentrate-fed lambs but this difference was not bio-logically significant. Carcass classification from grazinglambs was slightly penalised in comparison with indoorlambs, but differences were poorly appreciated in meatand fat colour. Grazing system can be a good alternativein order to maintain local sheep breeds, which are ableto offer labelled products to consumers.

Acknowledgements

The authors wish to thank S. Tort, G. Bleriot, thestaff of La Garcipollera Research Station and of theCITA de Aragon. Special thanks to Soledad Gracia ofthe Departamento de Grasas y Productos Lacteos delLaboratorio Agroambiental del Gobierno de Aragon formilk fatty acids analysis. We would like to dedicatethe present study to Angel Bergua (in memory) for allefforts done. The study was funded by the Ministryof Education and Science of Spain and the EuropeanUnion Regional Development funds (INIA RTA-03-031). J. Alvarez-Rodriguez is granted by the INIA-DGA(Spain).

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