University of Nebraska - LincolnDigitalCommons@University of Nebraska - Lincoln

Faculty Papers and Publications in Animal Science Animal Science Department

2002

Changes in muscularity with growth and itsrelationship with other carcass traits in threeterminal Sire breeds of sheepH. E. JonesScottish Agriculatural College

R. M. LewisScottish Agriculatural College, ron.lewis@unl.edu

M. J. YoungUniversity of Whales Aberystwyth

C. C. WarkupMeat and Livestock Commission

Follow this and additional works at: http://digitalcommons.unl.edu/animalscifacpub

This Article is brought to you for free and open access by the Animal Science Department at DigitalCommons@University of Nebraska - Lincoln. It hasbeen accepted for inclusion in Faculty Papers and Publications in Animal Science by an authorized administrator of DigitalCommons@University ofNebraska - Lincoln.

Jones, H. E.; Lewis, R. M.; Young, M. J.; and Warkup, C. C., "Changes in muscularity with growth and its relationship with othercarcass traits in three terminal Sire breeds of sheep" (2002). Faculty Papers and Publications in Animal Science. 829.http://digitalcommons.unl.edu/animalscifacpub/829

:\u.tt1hll ~(Ifllt'l' 2002, 74: 2h~\¥~?S

C 2(102 Brili~h ~ocidy of :\1\111\.\1 S,·kncl' 1:157 . 7291l f 02 f IIO(,0265S20\)()

Changes it~ n~uscularity w~th gr?wth and its relationship with othercarcass traits In three terminal SIre breeds of sheep

H. E, [ones'}, K M. Lowis '. M. J. Young l, B. T. Wolf 2 and C. C. Warkup3

t [-mail: h.jol1es@c·d.s.lc.ilc.uk

~:.:.c~t -------:-:---- _

/Jain were {lvailnl)/(' i»: 160 sheep (50 SIlJlilik mates, 50 S/lj]olk femalcs, 40 Texel nmles and 20 C!Iarol/ais males).ollc-jiJih (~rl1l1illl{/(S (/I1/lJl/~c{lch brecr! ant! scx (ocrI' slnug/ilered at each of 14, 18 or 22 weeks of nge and two-flflhsslrlllg!llercd at 26 tvccks. Ajkr sliluglllt'r 11I1mr 1~/('.(lSlln:JI1Cllts were taken 0/1 tlu: carcass. The left side ofeach cnrcl1Ss1uas IhclI 5cpl1mlct1 into clglrl Jomts al/d each JOIIII dissected into lean, bone and fat. Five JIIl/sCl/larity measures

(lltrce jlJr IlIC longissimus tho~'(lcis ~.~ lurnborurn (LTL) muscle, one for the hind leg and one for tile wholecarcass) alld 0111' of the shape (>.f n.I/' U L cross-sect 1011 (depth: widlll) were caicuuued. Wilh the exception of one

measure for lilt, tTL IIl1isculnnl.'lIIlCI'l'(/sed WIlli growth. Rail'S of increase in 11I0st measure» were hiolier ill TexelsIhal1 in eacn (1- fire ollll'r breeds, ()I.ti were not dtjjt'l'Ci!1 bctuieen the ntale am! female Suffolks or betw;;m Ihe Suffolkal/d C!lflroJlai5 laini», Incrcasc5 11/ iIlost niuscularitu measures at 17 constnnt live weight were associated withincreases in 1('(11/ to bone ratio and CI1rcnss lean content. Associations with fat content were either non-significan: orlfegalivc. Rdatio/lships witfl tea» distribution were /lOll-significant or weak. Correlations between the threemeasures of 1iI1J5CII!arity for I!le tTL were high. Correlations between tile whole carcass measure and those unthindiffi~ri'J11 reghJils werc moderate to high ill flit' Texcls bill lower in the Suftolk and Chnrotiai« breeds. The same waslrue for corrclatiolls belweell tile tTL measures and hind leg liIuscularity. If muscularity throughout the carcass is

10 Ill' described effectively, measures iii more /111711 0111' region may be required, particularly in the Suffolk andClwrollais breeds.

Keywords: carcass composition, muscle (('eight, sheep.

IntroductionThe shape of a lamb carcass is considered importantcommercially, as is its weight and fatness. Inabattoirs, carcass shape is evaluated subjectively asconformation and assessed using a scale such as thelinear EUROP score. Shorter more blockv carcassesarc considered of better shape and are g(ven higherconformation scores. Trad i tiona IIy. these carcasseswere perceived to have a higher lean to bone ratio,higher proportions of lean in the high value jointsand greater thickness of muscle at the same carcassweight, each attribute l"laving commercial value(lackson and Mansour, 1974; Kempster d al., 1981;Harrington and Kempster. 1989; Purchas and Wilkin,1995). In practice the positive associations betweenhigher conformation and Jean to bone ratio and

265

increased muscle thickness have been shown butfound to be weak. Moreover, higher conformationhas been shown to have an undesirable positiveassociation with fatness (jackson and Mansour, 1974;Kempster el al., 1981; Abdullah 1'1 al., 1993; Purchasand Wilkin, 1995; Lewis et al., 1996; Jones el I1f., 1999).

Since fatness and conformation are confounded, anassessment of muscularity has been proposed as apreferable alternative for quantifying carcass shape(Kirton e! al., 1983; Purchas ei al., 1991; Purchas andWilkin, 1995). Muscularity is a term used to describe,usually subjectively, the appearance/shape ofmuscles on a carcass. But, as vet, no standardobjective methods for measuring the muscularity of acarcass are available.

Jones, Lewis, Young, Wolf & Warkup in Animal Science (2002) 74. Copyright 2002, British Society of Animal Science. Used by permission.

266Jones, Lewis, Young, Wolf and Warkup

De Boer ct al, (1974) defined mllsculari~y as ,'th~thickness of muscle relative to a skeletal dImensIOn.:Despite this clear definition, early developnlcl,'t. 01useful objective measures was slem'. an~ lIkelyhindered by problems obtaining. measures 01 nlw~cl.~thickness in most regions of the carcass. 1 hIS,

roblem WLlS largely overcome with the pro~osal 01Pp I . f a! (1091) that averaze muscle thicknessurClasc " '7, "0 ,.,! '.,can be approximated by \f(WII LIl ) , W;'l:le \1\/ ',5. theweight of a muscle or gn:up of muscle 5 ~n~ ~~J IS t~~~length of ~ closely a~soc'<lted bone. A. dllm"nslOl~lc~~measure at muscularity WLlS then obtained by fui th~tdividing this estimated thickness b~ t~le bone slength. This dimensionless property IS .lm}-~ortan.tsince, by being independent at scale effects thesemeasures of muscularity can be cOl11par:d,justifiably, between animals of different sizes,. 1 hePurchas et at. (1991) approach has been used III allsubsequent studies of muscularity.

Most subsequent studies have focused. on therelationship bet\Neen I11USCUIMity and con!or.m(ltlonscores and it positive, but not strong association hasbeen shown (Abdullah cI al., 1993; Purchas (In<.~

Wilkin, 1995). Although of interest, the strength otassociations with the conformation score should notbe the main determinant of the most appropriatemuscularity measures for a lamb carcass. The aimshould be' to develop a single or relatively fevvmeasures (to be practical), that are stronglyassociated with the carcass lean to bone ratio, theshape of different commercial cuts and if possible,with the distribution of carcass lean, both within andacross breeds. The focus should therefore be onestablishing the relationships between muscularityand these other measures and between muscularityin different parts of the carcass. Obtaining a goodunderstanding of how muscularity throughout thecarcass changes as lambs from different breeds growwould greatly aid these investigations.

Some of these questions have been addressed inprevious studies but much remains unknown.Abdullah et al, (1998) showed that measures ofmuscularity in the hind leg and shoulder increasedas Southdown lambs grew, but no information isavailable for measures in other regions of the carcassor in different breeds. Waldron et al. (1992)investigated the relationship between muscularityand composition, but only measures in the loin wereused and their relationships with lean distributionwere not investigated. No previous study hasinvestigated the relationship between measuresbased in different parts of the carcass.

This study had three main objectives: (i) toinvestigate how different muscularity measures

c.l:ange in l~ifferent bre?ds and sexes as lambs grOlv;(1I) to describe the re!~tlOnshlpsbetween I1lUScU!<lritvand carcass composinon and lean distribution; i'llld(iii) to determine the relationships betweenmuscularity measures located in different parts of thecarcass.

Material and methodsData were collected in 1997 at the ScottishAgricultural College (SAC) on 50 Suffolk male and50 Suffolk female lambs, 40 male Texel lambs and 20male Charollais lambs. Suffolk lambs were obtainedfrom the SAC Suffolk flock and consisted of equi'llnumbers within sex from the lean growth selectlonand control lines. Further details of the SAC Suffolkflock are given by Lewis ct al. (1996) and Sirnm ct ai,(2002). Texel lambs were obtained from the ANTURHock at the Institute of Rural Studies (IRS),Aberystwyth and consisted of equal numbers fromthe lean growth and leg conformation selection lines.Further details of the ANTUR flock are given bv Wolfct al. (2001). Charollais lambs were obtained fromtwo commercial pedigree flocks. The Suffolk, Texeland Charollais lambs were the progeny of 14, eightand eight sires respectively,

Mal/agclIIcl/ f

Suffolk lambs were weaned at approximately 8weeks of age. From 1 to 2 weeks prior to weaningthev were offered free access to a performance testdiet (12-4 MJ metabolizable energy and 178 g crudeprotein per kg dry matter). Texel and Charollaislambs were purchased at approximately 8 weeks of(lge, These lambs were gradually introduced to thisSame diet while providing ad libitum access to hayduring an adjustment period. All lambs were grouppenned according to breed and sex, with ad libitl//IJaccess to the diet for at least 6~vecks prior toslaughter.

SIal/slifer measurementsOne fifth of lambs wi thin each genotype wereslaughtered at each of 14, 18, and 22 weeks of age.The remaining two fifths were slaughtered at 26weeks of age. All lambs were assigned at randomwithin sire families to a slaughter age. Live weightsprior to slaughter were recorded. After slaughtercarcasses were chilled for 24 h and then weighed.The carcass was then split and side length wasmeasured as the distance from the cranial end of thesymphysis pubis to the cranial dorsal edge of thefirst thoracic vertebra. The left side of the carcass wassubsequently frozen and retained for dissection.

After thawing the width (A) and depth (B) of thelongissimus thoracis et lumborum (LTL) muscle weremeasured on the caudal surface when the side was

Breed, muscularity and carcass traits in growing lambs

'l:lble .) 1'/lhn'l Jill l ioIlSillId calm/a/iolls IIS/'d Ie) derive Ihe dif!f'J'l'1I11111'17SWCS jiJr til<' carcrrss side

267

=--- --Trail

CompositionTissue contentLean to bOIll' r"ltio

Lean dislribution

Ml'an ll1uscle thickness

Ll'UThreedissected ll'g muscles'[(lui carcass muscle

Muscu[ilrilyiJ'L

Hind kgWholl' side

Shapel.l'L Cl'OSSsection

Abhrcviat ion

Lean, ratL:B

Leg, loin, best end,shoulder

AIUh3M_thTivUh

ASLB5L

ABSL3MFLTMSL

13 : A

Calculationst

weight of tissue (gl/side weight (kg)weight of lean/weight of bone

weight of lean in the joint (g)/totalweight of lean in the side (kg)

\/(A X 13 X 0·8)~\)TM/5L

(A/SL) X 10(13/SL) X 1()

(NA X 13 X 0-8)/5L) X 10(,,!3M/FLJ) X 10

(,,!TM/SI}) X 1000

(B/A)Xl0

t Aand 1$ are the wid th and depth of the Itmgissim liS titoracis ct 11/I1I/JOfllll! (LTL) muscle respectively (rnrn): SL, FL are the length(ern) of the.carcass side and fern u I' respect!~'el)~; 3M is lhe cOt):binec! weight of the semitendinosus, si'llJimcm/JraflosIiS andgIlIlrobicepsmuscles chssecled from the hind leg (g); I M IS the total weight of lean III the left SIde of the carcass (kg),

cut between the last and second to last thoracicvertebrae (Palsson, 1939). The area of the tTL surfacewas not directly measured but approximated byAX 13 X (J·8 as done by Hopkins et al. (1993).

The left side of the carcass WZIS separated into theeight joints as described by Cuthbertson ei al. (1972).Each joint was weighed and then dissected into lean,bone, fat (subcutaneous and inter-muscular) andwaste. Three muscles from the hind leg(scllli/Clldillosl/s, semimembranosus and glutcobiceps)were individually separated and their weightsrecorded. Length of the femur was measured.Further details of measurements recorded are givenin Table 1.

MllsclIlarity and tTL cross-section s!Iape I/}('(/SlirCSThree measures of muscularity for the LTL werederived based on cross-sectional dimensions of theLl'L muscle and side length. These were the ratio oftTL width (A) to side length (ASL), the ratio of LTLdepth (B) to side length (BSL) and the ratio of'average thickness' of the muscle at the point ofmeasurement (square root of its area) to side length(ABS1.). A measure of muscularity in the hind legand one for the whole carcass were derived using theapproach of Purchas ct al. (1991). The hind legmeasure was based on the length of the femur andthe combined weight of the three dissected muscles(3MFL), and the whole carcass measure was derivedusing the total weight of lean in the side and sidelength (TMSL).

A measure of the shape of the LTL cross-section wasdefined as the ratio of muscle depth to width (B : A).Details of each of the muscularity and B: A measuresarc given in Table 1.

Statisiicn! (/)Jl1lysisData for tVI'O Suffolk males and three Suffolk femaleswere removed. Their live weights were greater thantwo standard deviations below the mean for theirrespective slaughter age groups (within breed-sex)causing the distribution to be highly skewed(P < 0·05).

The distribution of live weight across slaughter agegroups was continuous in each breed-sex withconsiderable overlap between contiguous agegroups. This allowed a linear regression on liveweight to be fitted across age groups. Within eachbreed-sex, for each muscularity measure, once alinear recression on live weizht was fitted ace (Troup.Db' b oand a quadratic regression on live weight did notexplain additional variation (P > 0·05). The same wastrue for each composition and lean distributionmeasure considered. The effect of age group and aquadratic regression on live weight were thereforenot included in any of the subsequent models fitted.

Regression 011 live weightValues for each of the muscularity and B: Ameasures were regressed individually on Jive weightwithin each breed-sex to investigate how thesemeasures change with growth. Prior to analysis each

268 Jones, Lewis, Young, Wolf and Warkup

lamb's live weight was expressed as a deviation fromthe mean live weight for the 14 week slaughtergroup in their respective breed-sex. ~rhe itl~er~ept forthe regression on adjusted live weight within eachbreed-sex was then used to assess whether breedsand sexes differed in their muscularity values at thestart of the study. Mean weights for the 14 weekslauuhtcr groups"Nere 41·7, 36·7, 38·1 and 3()·O kg forthe 'Suffol'k males, Suffolk females, Charollais andTexcls. respectively.

In order to facilitate comparisons between breed­sexes, all data were combined and breed-sex fitted asan effect in the model. In preliminary investigations,slopes for the regression of each mu~c~lIi1rity and13 : A measure on live \veight did not differ betweenthe Suffolk males, Suffolk females and Charollaismales, but were frequently different from thatestimated for the Texel males (P < 0·05). A singlecommon slope was therefore fitted for data from theSuffolk males, Suffolk females and Charollais lambsin the analysis, whilst a separate slope WZlS fitted forthe Texel larnbs.

Allol11C1njChanges in muscularity with growth occur as aconsequence of differences in the relative grovvth rateof the measure's components. These relative grO\vthrates Gill be investigated in more detail usingallometry (Huxley, 1932). Allometric coefficients (f3)were derived (rm;1 the slooe of a 10" flew rezressionr b c» b

of each muscle thickness (included in the measures)on its associated skeletal dimension.

Relationship with composit ion and lean distributionRelationships between the muscularity measures andcarcass composition and lean distribution afteraccounting for the effect of live weight wereinvestigated using multiple regression (Constat.1994). The models fitted included the effect of breed­sex, live weight and one of the muscularity or B: A

measures as linear co-variates. The intera f. . ~ ,.Clonbetween breed-sex and both co-variates was' I-f i · I' - I . ,I soittcc 1I1 pr~' Imll1ary .In..-I Y~l'S, however, slopes for

the I-egression on live ~:'elght were nut diiferenl(P > 0-05) between the Suffolk males 'lnd fennk's') -j. _ ''-. ,Ihthe C.hilroll?IS and therefore a single common slo)(~

:VilS lilled lor t1~ese breed-sexes. This was also IT~letor the regression on the muscularitv and 13: i\measures and therefore ,1 common 51011e was ~I'-

• • V< <I. "sofitted for this regression for the Suffolk andCharollais lambs.

Corrctatiou« bcnoccn 1111' musculI/rill/ and B : 1\ 1//('11'111'". . - (~

Correlations between residuals (hom the regressionof each measure on live weight), for each of the fivemuscularity measures and L-fL shape were estimatedwithin each breed-sex scparatclv (Genstat,1994).These estimates were then compared bytransforming them to Z values using the Fishertransformation and testing the difference betweenthese values (Zar, 1996). Comparisons wereconducted initially ,KrOSS all four estimates using il

multiple sample test (experiment wise error rate of5%,), and subsequently between pairs wheredifferences had been detected (comparison wise errorra te of 5'1.,).

Correlation estimates for the Suffolk male. Suffolkfemale and Charollais lambs did not differ (P > ()·()S).A common correlation coefficient was thereforecalculated for these breed-sexes. The commoncoefficient was subsequently compared with thatestimated for the Texcls.

ResultsMuscularity measures were consistently hizher in. . nthe selection than in the control line in both Suffolksexes. Hind leg muscularity was also higher in theleg conformation line than in the lean growth line inthe Texels (results not shown). However, differences

Table 2 Intercepts (a) for each breed-sexfrom tileregression of itu: muscuiarits, and 13 : A mcasun's OJ! lu»: weighl (adjllstcdJt

Suffolk males Suffolk females Charollais males Texel maleso (s.e.) C1 (s.e.) C1 (s.c.) a (s.e.)

MuscularityASL 10·648 (0·152)" 10·547 (0·136)' 10·772 (0·182)" 11·943 (0·195)"BSL 5·871 (0·130)"C 5·520 (0·116)" 5·613 (0·155)"" 6·205 (0·166)'ABSL 7·064 (0·116)" 6·822 (0·104)" 6-953 (0·139)·" 7·689 (0·149)'3MFL 3-994 (0·052)4 3-971 (0·046)· 3·771 (0·062)1' 4·161 (0·066)'TMSL 5·lO1 (0'050)" 4·945 (0·045)" 5·271 (0·060)' 5·981 (O·OMY

ShapeB:A 5·513 (0·092)" 5-253 (0·082)" 5·205 (0·111)1' 5·J67 (0·118)"

~.b.c Within rows, intercepts with different superscripts differ (P < 0·05).t Live weights were adjusted such that intercepts represent values at the mean weight for the 14 week age group within eachbreed-sex, which were 41·7, 36·7,38-1 and 30·0 kg for the Suffolk males, Suffolk females, Charollais and Texels. respectively.

Breed, muscularity and carcass traits in growing lambs 269

hble 3 COi:f)'icicIiIS ([ll};)}: 5 [~l{!llks/CIltJrollni, alid 7;'.1:els[or Iheregression 011 live weigh! and residual siandlll'd deoiat ionsIIlidcoefficiellis~ "'/1"/1 (C\lJ/ilrt'(/cho t tllc II111Swianfljillld B:!\ 1111'[/51/1'('50/11111117 I . J .

- Suff/Char Texels11 (s.e.) t [3 (s.c.) diH:j: Residual s.d.§ CV§

MlisclIl,lrity-t).(JlK (O·O()S)*"· ().(J01 (0·010) (]·70;\SIJ (]·064

0·002 (lHJ04) (J.(J4o«() .0(9)U. :f~* 0·58 0·094llSL/\1351- -0·005 (0 (]04) (J.(125 (OOOS)"" *~* 0·52 0·071JMFL (J·()(J7 (0·D02)··· {lOB «()·(J04)u* 0·24 0·056TMSL 0·003 (()O02) 0012 «()·om)'*" " 0·23 (]·040

Shape(J·O 11 ((]·003 ).*. (J.(l35 (O·(]06)u* ... (]·43 (]·077B: ;\

.1-'5lqwrscripts inti ica1(' .the significance of d i fferencesfr.olll zero.t Significance of the dllfererlCe.bctweeI~. the twu coefficients. " . ,~ pooled within breeds-sex est I!11a tes. CV calculated using the residual standard deviation,

t Significance of the difference between the tvv 0 allometriccoefficients.t Different from 1 (P < 0·05).

Table 4 Altomciric coeffieim/s (fll for Sl/f[olks/Clwrollais andTexcl« derived from tile doubtc logarithmic regressions of muscleJllickllesscs Oil tlltir associaltd skdcrallclIgths or muscle width

were small relative to the standard errors for linemeans W> 0·05). The effect of selection line wastherefore ignored in subsequent analyses,

The' coefficients for the regression on live weightrepresent the rate of development in musc.u~arity

between 14 and 26 weeks of age. These coefficients.pooled resid LlZlI standa I'd devia lions and coefficientsof variation (CV) (calculated using the residual s.d.).nrc shown for each of the muscularity and 13: Ameasures in 'fable 3. Increases in live weight were

associated with increases in the B : A measure and anumber of the muscularity measures. A significantnegative coefficient was estimated only for the ASLin the Suffolk's and Charollais (Suff /Char).Coefficients tended to be higher in the Texels,particularly for SSL and ABSL where the differencebetween the Texels and Suff/Char was mostpronounced (P < 0·001).

AllometryThe allometric coefficients reflect differences inrelative growth between muscle thickness and itsassociated skeletal dimension (Table 4). Musclethickness increased at a greater rate than itsassociated bone length (~ > 1·0), except for measuresof LTL thickness for the Suff/Char. Coefficients weregenerally higher for the Texels than for the Suff/Char. The differences were again most pronouncedfor measures based on the LTL (P < 0·01).

Relationship with composition and lean distributionIntercepts and coefficients for the regression of eachcomposition and lean distribution variable onadjusted live weight are shown in Appendix 1.Results for Jean distribution are only shown for thefour joints where the additional regression on one ormore of the muscularity measures was significant.Comparison between breed-sexes of how thesevariables change with live weight is not the focus ofthis study and therefore will not be considered in anydetail.

Partial coefficients for the regression of compositionand Jean distribution on each of the muscularity andB : A measures, when fitted individually with Jiveweight are shown in Table 5 and 6.

.....difft

Surf/Char TexelsX y !1 (s.e.) fj (s.e.)

SL A 0·635 (0·087)t 1·050 (0·]17)5L I) 0·947 (0·134) 1·773 (0·182)tSL AB_lh 0·79] (O·WOlt 1-411 (0·135)tFL 3M- Ih ]·]63 (O·09S) 1·205 (O·1l5)tSL TM- th 1·034 (0·058) 1·]57 (0·079)tA B ]·059 (0·10 1) ]·525 (0·]]7H

l~('~ rcSS ion Oil live lOt' ig111Intercepts [or the regression of the muscularitymeasures on adjusted live weight [or each breed-sexarc shown in Table 2. The intercept for each of themuscularity measures was higher for the Texel than(or anv of the other breed-sexes suggesting thatgrci1te,: development in muscu!a!'ity had occurred inthis breed bv 14 weeks of age. Differences at this agebetween the Suffolk and Charollais lambs were lesspronounced.

tv c:JT

able

5P

artia

lco

effic

ie/ll

s(s

.e.)

/01

'L

TL

nius

cnla

ritv

lIIea

sure

s,de

rive

dfr

omth

elI

Iulti

ple

regr

essi

o/l

ofea

chco

mpo

siti

onor

lean

dist

ribu

tion

vari

able

011

lim

'wei

ght

and

ihc

1111

15w

!aril

ym

easu

refo

rSu

jfolk

slC

haro

llais

and

Tcx

cls

ASL

13SL

AB

SL

Su

ff/C

har

tT

exel

sdi

ff:j:

Su

ff/C

har

Tex

els

clif

fS

uff

/Ch

arT

exel

sd

iff

Co

mp

osi

tio

nL

ean

(g/k

g)

21·6

20(3

·627

)....

*19

·169

(5·2

36)·

···*

17·1

53(4

·877

)"**

10·9

58(6

'258

)26

·059

(5·1

60)*

**17

·802

(6·6

59) .

...Fa

t(g

/kg

)-2

6·34

9(4

·367

)**"

-11·

793

(6·3

03)

-17

94

5(5

·836

)....

-4·7

15(7

-494

)-2

9·55

7(6

·221

)"*"

-9·3

63(8

·034

)"

L:B

0·04

1(0

·043

)0·

252

(0'0

63)"

""**

0·09

9(0

·054

)0·

202

(0·0

69)"

*0·

098

(0·0

59)

0·27

9(0

·076

)"""

Lea

nd

istr

ibu

tio

nLe

g(g

/kg

)-0

·745

(1.4

31)

0·14

6(2

·065

)0·

515

(1·7

45)

2·27

1(2

·243

)-0

·053

(1·9

46)

1·81

5(2

·S14

)Lo

in(g

/kg

)0·

335

(0·9

85)

2·53

4(1

-422

)0·

949

(1·2

15)

0·75

6(1

·554

)0·

954

(1·3

49)

1·85

6(1

·734

)B

est

end

(g/k

g)

1·77

3(0

·439

)"""

3·25

1(0

·633

)....

*1·

832

(0·5

56)*

*"3·

092

(0·7

11y"

··2-

426

(0·5

98)*

**3·

928

(0-7

68)*

**S

ho

uld

er(g

/kg

)-0

·420

(1'1

20)

-4-7

60(1

·617

)**

"-0

·851

(1·3

73)

-4·8

92(1

·765

)*"

-0·8

82(1

·520

)-6

·061

(1·9

62)*

"*

'­ o ::;, rc !!'

tS

up

ersc

rip

tsin

dic

ate

the

sig

nif

ican

ceof

dif

fere

nce

sfr

om

zero

.*S

ign

ific

ance

ofth

ed

iffe

ren

ceb

etw

een

the

two

coef

fici

ents

.

r:­ rc ~ !!'

Tab

le6

Par

tial

co<

1ftc

icnt

s(s

.c.)

jor

rhe

3MF

L,

TM

SLan

dB

:A

lIIe

f/S

Ure

s,de

rive

d/ro

mrh

e111

1111i

ple

regr

essi

onof

each

coni

posi

rion

orle

aII

disl

ribu

!ion

nari

ablc

onIit

iew

eigh

Iand

the

mus

cula

rily

orB

:Am

easu

rejo

rSu

ffolk

slC

lzl1

rol/a

isan

dTe

xcls

Su

ff/C

har

t

54·2

74(1

3-18

1)'"

-39·

814

(16-

204)

'0·

637

(0·l

l3}.

....

3-00

3(1

3-46

6)11

·703

(16·

553)

1·12

6(0

·115

)·.....

~ = ::;, qo ~ ......

:lJ ::;, 0..

~ ~ "'I

;t:" :::: ."

dif

f

B:A

Tex

els

-3·7

71(1

1·04

1)8-

392

(12·

890)

0·10

4(0

-120

)

4·69

1(3

·7U

)-1

·82

9(2

·600

)2·

591

(1·2

85)*

-4·5

91(2

-997

)

Su

ff/C

har

-2·7

66(6

·552

)7·

684

(7·6

50)

0·09

1(0

-071

)

2·17

6(2

·204

)1·

187

(1·5

43)

0-56

1(0

·762

)-0

·938

(1·7

79)

***"..d

iff

Tex

els

31·7

19(1

2·22

8)*

5·48

0(1

5-36

0)]·

015

(0'1

20}*

""

3-47

3(4

·799

)2·

990

(3·3

36)

2·86

6(1

·650

)-1

3·38

6(3

'683

)***

TM

SL

Su

ff/C

har

-1·2

88

(5·3

00)

0·45

7(3

·683

)2·

30}

(1'8

21)

-6·0

96(4

·065

)

86·1

20(1

3-50

0)**

*-8

2·06

2(1

6·95

5}**

··0·

632

(0·1

32)*

**

dif

f:j:

Tex

els

8·10

0(4

·715

)6-

036

(3·2

75)

4-49

0(1

'66

2)"

-13

-94

J(3

'61

7)'

"

3M

FL

(4·6

15)*

*(3

·206

)«(1

·627

)(3

'54

0)"

"

Co

mp

osi

tio

nL

ean

(g/k

g)

Fat

(g/k

g)

L:B

Lea

nd

istr

ibu

tio

nLe

g(g

/kg

)13

-386

Loi

n(g

/kg

)9·

534

Bes

ten

d(g

/kg

)0·

565

Sh

ou

lder

(g/k

g)

-12·

9<)8

tS

up

ersc

rip

tsin

dic

ate

the

sign

ific

<ln

ceof

dif

fere

nce

sfr

om

zero

.:j:

Sig

nif

ican

ceo

fth

ed

iffe

ren

ceb

etw

een

the

two

coef

fici

ents

.

Breed, muscularity and carcass traits in growing lambs271

Table 7 J<I'S;r1,I~{lJ corrcla! ions (/i-olll reg rcssions em livewcig!ll) between tlteIlIliscullirily and B : A mCflSIlreS for 5ujfolks/Clmro/lais (pooled(',-;1;111111('5) IIl1d Icxcls

0) Suffolks/Charollais;\SL I3SL ABSL 3MFLIndices TMSL B;A

Muscularit YA5LiJ'L13SL 0,56

AI3SL 0,84 0-93

Hind leg 3MFL 0,14t 0-19'1' 0·20tWholesidc TMSL ()-53 0-52 0·59 0-38t

Shape: IJ'L 13: A -{),15 ()-74 0-43 0-11 0·19

(b) 'Ii'Xl!!S;\SL BSL ABSLIndices 31\1FL TMSL B:A

MuscularityUL ASL

I3SL 0-71AI3SL 0-89 0-96

Hind leg 3MFL 0·52'1' 0-56t 0-60tWhole side TMSL 0-56 0-61 0-64 0·74t

Shape: IJ'L B;A 0·]6 0·8] 0·60 0-38 (JAD

In (a) correlations less than 0,18 do not differ from zero (P > a,OS}.In (b) correlations less than 0·27 do not differ from zero (P > 0-05),i- Correlations are significantly different between the two groups (P < O-OS).

All five of the muscularity measures were positivelyassociated with increased lean content andnegatively associated with carcass fat content in theSuff/Char. The positive association with leannesswas also present for most of the muscularitymeasures in Texels. Muscularity was not associatedwith fatness in the Texels (P> 0-05). lncreases in eachmuscularity measure were associated with increasesin the carcass lean to bone ratio ill Texels. However,this was only so for 3MFL and TMSL in the Suff/Char. The regression on 13 : A was not significant forany of the composition measures.

'111e relationship between the muscularity measuresand proportion of lean in the high priced joints (legand loin) was weak. A significant relationship wasonly present with 3MFL in the Suff /Char. where anincrease in 3MFL was associated with a higherproportion of total lean in both joints. Differences inmuscularitv however, were associated with theproportion' of lean found in the best end andshoulder joints. Higher LTL muscularity wasassociated with an increase in the proportion of leanfound in the best end joint in each breed, as was ahigher value for 3MFL in the Texels. Increases in eachmuscularity measure was also associated with areduction in the proportion of total lean in theshoulder for Texels, but this association was only

important for 3MFL in the Suff/Char, Even wherethese associations were significant, the amount oftotal variation in lean proportion in any jointaccounted for by both the regression on live weightand the muscularity measure was low « 50u!.))_

Correlations between the muscularityand B : A measuresCorrelation between residuals (from the regression ofeach measure on live weight), for each muscularityand shape measure, estimated for the Texels, and thecommon coefficient calculated for the Suffolk andCharollais are shown in Table 7.

Correlations between the ASL and BSL were high(0·56 to 0·71). As expected correlations between boththese and ABSL were also high (>0'84). Allcorrelation estimates were higher in the Texels thanin the Suff/Char, with the differences often beingsignificant. This was the case for correlationsbetween hind leg muscularity and each of the LTLmuscularity measures where estimates for SuffiCharwere consistently low «0·21) whereas those forTexels were high (>0-52). The same was also true forestimates between hind leg muscularity and thewhole carcass measure (TMSL). With the exceptionof BSL and ABSL, correlations between the measuresof muscularity and the LTL shape werecomparatively low,

In contrast, Purchas ct at. (1991) and Abdullah e! al.(1998), reported higher muscularity at a fixed carcassweight. in Southdown lambs from lines selected forhigh uersus low weight-adjusted back fat depth forfive generations. This suggests a positive associationexists between muscularity and fatness in theSouthdown breed, but neither study quantified thestrength of the relationship, which although positive,may be weak. Abdullah 1'1 al. (1998) stated that theirresults were in i1greement with those reported bySimm and Murphy (1996) where crossbred progenyof Suffolk rams selected for improved lean grO\'\'thhad lower conformation scores at the same carcassweight than those of unselected rams. However, it isimportant to note that the progeny of rams from theunselected line were fatter which, given the positivecorrelation between fatness and conformation,would contribute towards a higher conformationscore. 'The Suffolk lines used in the current study arethe same as for the rams used by Sirnrn and M urphy(1996). Results of our preliminary analyses refute theconclusions of Abdullah ct al. (1998). Whencompared at the same live weight, differencesbetween lines in each of the muscularity measureswere non-significant, but tended to be higher in the

Only one previous study has investigated therelationships between muscularity and composition.Waldron et al. (19Y2) estimated phenotypic andgenetic correlations between four musculi1ritvmeasures, based on the weight or dimensions of tIleLTL and carcass length, and ICZl!l and fat weight andlean to bone ratio in the carcass of Romnev crosslambs. Phenotypic correlations with lean weight andlean to bone ratio were positive for each meas u1'(.'.

Phenotypic correlations with fatness were small vetpositive with three of the measures «0·30), l;utnegative with the fourth measure that incorporatedthe width of the LTL. The fact that \.valdmn c! [II.(1992) used tissue weights and fitted age as acovariate in their model docs not ('111m-\' goodcomparisons to be made with the results of thisstudy. Nevertheless, Waldron 1'1 01.'s results arc ingeneral accordance with those presented here.

l~clafjolls/lilJSwitll COIII!losiliol/

Although dimensionless, the muscularirv n'('i1SLlI\'S

were not completely independent of live wei('ht"cross breeds-sexes. S(? too coml?osition chtlngedO'lsanimals grew. Once adjustments tor llw effects of liveweight were made, higher muscularirv wasassociated with ,)11 increased carcass lean content anddecreased f"t content in the Suff/Char. The same wastrue of lean content in the Tcxcls yet not for fi1tncss.

Jones, Lewis, Young, Wolf and Warkup

and other breeds 111 terms of their developll1entduring growth.

The greater and more uniform development ofmuscularity with growth in Texels coincided withlighter live weights at all ages compared with theCharollais and Suffolks. Direct comparisons ofweights at an age should be made cautiously sincethe lambs were obtained from different sources.Nevertheless, it is worth noting that Suffolk andCharollais males were on average proportionately0·39 and 0·27 heavier respectively than Texel males at14 weeks and this increased to 0-49 for the Suffolks inthe 26 week age group. Slower rates of growth forTexels, particularly in relation to Suffolk lambs, havealso been reported in numerous other studies forpurebred and crossbred lambs (Wolf et al., 1980;McEwan et at., 1988; Leymaster and Jenkins, 1993).Clearly, much still remains unknown about theunderlying biological differences between the Texel

Numerous studies have shown that Texels differfrom other breeds in terms of composition, beingleaner and with a higher lean to bone ratio whencompared at either a fixed weight or fatness (VVolf ct171., 1980; Cameron and Drury, 1985; Kempster el al.,1987; Ellis ct 171., 1997). Although thought to be moremuscular, few studies have compared muscularity inTexels with that in other breeds. Hollowav ct nl.(1994) and Hopkins 1'1 ot. (1997) considered ameasure in the hind leg and found that the crossbredprogeny of Texel rams at a fixed carcass weight weremore muscular than those sired by rams from fourother breeds. However, neither study included lambssired by Suffolk or Charollais rams, which along withthe Texel, are the most important terminal sire breedsin the UK (Maniatis and Pollett. 1998).

Differences between the Texcls and both Suffolk andCharollais lambs in the developments of muscularitywith gro\,vth were clearly observed. Despite beinglighter, Texel lambs had higher values for.cach of.~hcmuscularity measures at 14 weeks 01 age. 1hesubsequent rate of development also tend~d to t?Chigher for each measure, particularly tor '? Lmuscularitv. In addition to these results, partialcorrelations between the different measures in thesubsequent analysis were also consistently higher forthe Texels, implying that they differed in the waymuscularity developed throughout the carcass,tending to be more uniform than in the other breeds.

DiscussionRegressioll 011 live weight and a/lewelryThe results presented here avreed with those ofAbdullah et al. (1998) for SouthdO\-\'n in that for ei1.chbreed-sex, hind leg muscularity incre~scd \.vlthgrowth. However. muscularity in other reglOns 01 thecarcass did not develop in the same V.lay across allbreeds and sexes.

272

Breed, muscularity and carcass traits in growing Iambs 273

selection line, Since purebred lambs were used in this~ltrrcnt study, ilny line diff?rences arc expected to be1110rL' pronounced than lor the crossbret~ lambsconsidered by Simrn and Murphy (l996~. Differencesin conformiltion score should not therefore, be usedas an indicillion of differences. in muscularity,CSpCCiillly where CilrCDSSeS vdry in fatness.

1~l'il1liOlr5IJi}Js{oil!} !COII dislrilmlioll

Rclatinnships between muscularity and leandistribution tended to be weak, The proportion oflean found in the higher priced joints was onlyZlssociated, albeit positively, with increases in thehind leg measure in the Suff/Char. Any correlatedchanges in joint proportions as a consequence ofdifferences in muscularity Me therefore likely to be ofnegligible commercial i~llportance. Simi~ar

conclusions were drawn In previOUS studiesinvesligating the effect of conformation on thedistribution of lean in the carcass (jackson andMansour, 1974; Kempster ct al., 1(81). The results ofthis study show that even when measures arc usedwhich are specifically related to the shape ofindividual joints and arc largely independent offiltness, there remains little scope for affecting thedistribution of lean in the lamb carcass throughchanges in shape.

Correlation» Ih'tWt'CII II/t' 11Il1~clIl{/rily and B : A measuresA large number of measures would be required if therelationships between muscularity in all regions ofthe carcass were to be investigated comprehensively.From a commercial viewpoint increased muscularityis likely most important in the high priced joints. Ittherefore follows that measures based in the loin andleg {such as the LTL and 3MFL measures used here),should form the main focus of investigations intopotential measures of carcass muscularity. Therelationship with these measures can also be used asa good basis to evaluate the usefulness of moregenerJI whole carcass measures (TM5L), or measureswhich can be obtained relatively simply on the cutcarcass (B : A).

Correlation estimates between the three LTLmuscularity measures were high suggesting that theLTL muscularity may be adequately described usingany of the measures. Estimates between. thesemeasures and muscularity in the hind limb alsotended to be high in the Tcxels (>0·51), but were lowin the Suff/Char «0·21). This implies thatmuscularity in one region may not always be a goodindicator of the degree of muscularity in the other,across breeds. Equally, correlations between TMSLand measures in the loin and leg were high in theTexels, but less with hind leg muscularity in theSurf/Char. Whereas carcass muscularity may be

ll,de~u~te!t descri~ed using a single measure such as1 MSL III Icxyls, this seems less appropriate for lambsfrom the 5utfolk and Charollais breeds. Two or moreseparate meas~lres mllY be required if characterizingthe muscularity of each region is consideredsufficiently important.

With the exception of BSL and ABSL, correlationsbetween B: A and other musculanrv measurestended to be low and hence the 13: A measure isunlikely to be useful as a general measure ofmuscularity through the carcass. This may in partreflect J greater effect of measurement errors giventhat both dimensions in the measure are small andare token on soft tissues. Nevertheless, the B: Ameasure may hove some value as an indicator of BSLwhere a measure of side length is not available.

Live weights for animals in the present study, withthe exception of anima Is in the lower age group,were similar to the range over which pedigreeanimals are evaluated as part of selectionprogrammes in the UK. The results of the studyindicate that improved muscularity is not associatedwith detrimental effects in composition or leandistribu tion a t the phenotypic level, onceadjustments for differences in live weight are made.This suggests that muscularity could be incorporatedinto selection programmes, which include reducingfatness among the objectives, without unduereductions in selection responses. However, to beincorporated effectively methods of assessing themuscularity of the live animal may be required. Atpresent, such methods are not available and furtherresearch would be needed for these to be developed.

Selection for improved muscularity per se is relevantonly if improvement in the shape and thickness ofmuscle in cuts has commercial value. As mentionedby Hopkins (1996), unless consumer purchasingdecisions are significantly affected by the surfacearea of muscle and shape of cuts, then thedevelopment of methods for assessing muscularitywould not be useful. At present a consumerpreference for cuts from more muscular joints isassumed rather than known. This still requiresconfirmation through market research.

Conciusions

This study has clearly shown that muscularity can beassessed objectively in the carcass in a vvay that islargely independent of fatness. Followingadjustments for live weight, increases in muscularityare associated with increases in L: B ratio, carcasslean content, and in the Suffolk and Charollaisbreeds, with decreases in fat content. Additionally,

274 Jones, Lewis, Young, Wolf and Warkup

increased muscularity is not deleterious to theproportion of lean in the high value joints.

The challenge now is to determine genetic andphenotypic parameters among muscularity measuresand other carcass traits and to assess the feasibility ofincorporating such mcasu rcmcn Is into selectionprogrammes. The latter is likely to depend on thescope for developing useful measures of muscularityon the live animal. Still, selection for increasedmuscularity is useful only if it increases economicreturns to one or more sectors of the sheep industry.Therefore, there exists a need to accurately determinethe value of muscularity per 51? to the consumer,processor and to the lamb producer.

AcknowledgementsThe financial support of the Meat and LivestockCommission (MLC), Department for Environment, Foodand Rural Affairs (DEFRA) and the Scottish ExecutiveEnvironment and Rural Affairs Department (SEERAD) forthis research is gratefully acknowledged. This work is partof Huw Jones' CASE studentship. which is jointly fundedby the Biotechnology and Hio!ogical Sciences ResearchCouncil (HBSRC) and the MLC We are grilteflll to SACcolleagues Jack FitzSimons, Jim Fraser, Joanne Donbavandand Mark Rarnsev, and Dewi Jones from the Institute ofRural Studies, Abervstwvth (IRS). VVe also thank DaveAllcroft (Biomathematics zinc! Statistics Scotland), 1.1n \Vlliteand Professor W. C. Hill (University of Edinburgh) for theiranalytical advice, SAC receives financial support fromSEERAD.

ReferencesAbdullah, A. Y., Purchas, R. W. and Davies, A. S. 1998.Patterns of change with growth for rnuscularitv and othercomposition characteristics of Southdown rams'selected forhigh and low backfat depth. New Zenlmu! [ourna! of/vgricnttura! Research 41: 367-376. .

Abdullah, A. Y./ Purchas, R. W., Davies, A. S. and Kirton,A. H. 1993. Relationships between objective and subjectivemeasurements of carcass muscularitv Proceedings of the NewZealand Sonely of /vniuut! Product ion 53: 397-402.

Boer, H. de, Dumont, B. L., Pomeroy, R. W. and Weniger,j. H. 1974. Manual on EAAP reference methods for theassessment of carcass characteristics in cattle. LiveslockProduction Science 1: 151-164.

Cameron, N. D. and ~rury, D. J. 1985. Comparison ofterminal sire breeds tor growth and carcass traits ll1

crossbred lambs. Anima! Production 40: 315-322.

C:uthbertson, A" Harrington, G. and Smith, R. J. 1972.Tissue separation - to assess bed and lamb variation.Proceedings of the British Society of Anima! Produclion (newsmcs), vol. L pp. 113-122. .

Ellis, M., ~ebster, G. M" Merrell, B. G. and Brown, L1997. The influence of terminal sire breed on carcassco~position and eating quality of crossbred lambs. AnimalSCIence 64: 77-86.

Genstat. 1994. Gcnslal53. Clarendon Press, Oxford.

Harrington, G. and Kempster, A. J. 1':>89. Improvin> 1

Ci'll'Ca,s,'s composition 10 n,wet modern consut1wr del' g <lImb) . .' . .. . '_ .lant . In

1\f'IIiOdilL!WII, S/(}'I't~l. :liId nul n! 1011 III shcl'fI (cd. 0Dyrmundsson and S. l'horgcirsson). pp. 79-00. . R.

Holloway, 1.J./ Purchas, R. W., Power, M. T. and Tho .N A '1 (\0 ,I \.. .: , • I IllSon

. , n-t.1 comparison nl l. lt' C,lrC<lSS ~llld meal Cjll I' '/\\\" 1 'SI'-,,,,·),, an -j Tex '1- -I' ". I' bs I) . a Ity of,s, Lt ss .uu to' C t. oss 1.1m am s. ro(l'ci!IIlR' .r fNet» Zealand Socii'ly o( /vnima! Production 54: 2D0-213.' s (1 I Ii'

Hopkins, D. L. 19%. The relationship bl>lIveen mus·"ll-.'I l . I ',' .~. I .Il1ly

muse c: )DlW ratio ,Uk, Clll, dlmt1nSI(ln,s" in mal« '11'" t" I". . ... . . '. (. r- III enll1 e

lamb c;nCaSSL'S and the measurement til IHltscularit\, .,'. 1 ' AI" _., lISlIlgImage ana )'SIS. ! cot SClI'IICC 44: 307-317. -

H?ykins, D: L, Fog.ll'~Y~ N. M. and Menzies, D. J. 1997Differences III COI1lIX)SlllOn muscularirv muscle to b .. , . . , ' . ' . ~ tonerauo and cut dimensions between SIX lamb l'enotyne' A1'SCIl'II(C 45: 439-450. ' , [c,. 1,1!

HOI?kins, D. L., I'i rlnl, ,K. L., Roberts, A. H. K. and Bealli~,

A. S.. 1903 ..Changes 111 I'll depths and muscle dimensions ingrowlt1g lambs as measured bv real-time 1l111'~Sl" j< " _. • • ". lUllt.Aust mlinu [ourna! t!t E.\")Il'I"III/I'i1lal AgnclIlJlln' 33: 707-712.

Huxley, ]. S. 1':>32. Prohlcm« or rclntiuc Srowl!I. MethuenLondon. '

jackson, T. H. al~d Mansour, Y. A. 1974. Differencesbetween groups 01 lamb carcasses clH)sen for good andpoor conformation. AI/11Im! Product10/1 19: 93-105.

jones, H, E., Simm, G., Dingwall, W. S. and Lewis, R. M.1999. Genetic relationships bel ween visual and objectivemeasures of carcass composition in crossbred lambs. A/lin IScience 69: 553-561. fa

Ke!l1pster, A. J./ Croston, D., Guy/ D. R. and Jones, D. W.1987. GI:O\-vlh and carcass characteristics of crossbred lambsby ten sire breeds, compared at the same estimated carcasb . L,,5:>su cutaneous L1t proportion. A/lima! Proauction 44: 83-98.

K.empst~r, A. J., Croston, D. and Jones, D. W. 1981. Value01 cOnl(:rnl.1ti~)n as an indicator of sheep CZircasscomposition Within and between breeds, Anima! ProduClioll33: 39-49.

Kirton, A. H., Woods, E.G. and Dunganzich, D. M. 1983.Comparison of well and poorly muscled lamb carcasses asselectc(~ by _ experiel~ced 111('(11 ind ustry personnel.Proceedings (if the Ncio Zealand Sociely of Aninmi Produclioll43: 111-113.

Lewis, R. M., SiJ~lm, G., Dingwall, W. S. and Murphy, S. V1996. Selection lor lean growth in terminal sire sheep to

produce leaner crossbred progeny. Animal Science 63:133-142.

~eymaster, K. A. and Je~kins, T G. 1993. Comparison ofTexel-sired and Suffolk-sired crossbred lambs for survival,growth and compositional traits. [ournal of Animal Science71: 859-869.

McEwan, J. c, Hanrahan, J. P. and Fitzs irnons, J. M. 1988.Growth, and carcass traits of pure bred Texel and Suffolksheep. Proceedings of thr NtH' Zealand Socicri, of AnimalProduction 48: 41-48. . .

Mani~lis, N. and Po IIott, G. E. 1998. The dynamics of~enetlC resources at national level - the British sheepindustry as a case study. Proceedings of lite sixth worldcongress on genctics applied 10 lioestock production, AI'midllli',vol. 27, pp. 219·222.

v:;<

'"!~ ~ 0.

. :3 c <n

f'l C .--

t.l ::. q t.l = 0.. f'l

t.l >-( n t.l <J'

l[J

')

-,

:J~

..>

1")

..:0.

.tJ

".

"~c --.

l~[ll

t.ll

lt~8~

~;~!'J

::-8

,......

...,

.""'

\-::

:'"-

-==

'::t

~~?=~5.3~

;:"3

':""-

Ul

-J-.-e

:lr

lC

Lr:

.~

~-c

';J~~

<;.

=:~.:

:;"g)

Ii,W

...:::.

r:'

c_

__,

.G

'Cu

::'-~-.v

;':~

;::"

7\f

;:--:;

j.:...

.:s

r;u

....::-.~

~0.

..W

nI"

"'5.

rJz,

2'-

II.Cr--,~

;:::'.

..J_

2.~

",i~

~'!!"

~'-,

~::.

:~

U:;

:j>

~~c

P;:;::-'l

r:-.J

~r!,

::J

~_

.~:

::-

C~

~r;.

=':

:J-+

:.<:

v.(J

)%

;0

-...

...-J

,1:

:~.

~'"'

:.J'

,r:-

::r;;C

Jr.=-~

N'f

.V

.•

:;i

::,;

::l

\0"'.

_c

__V

::::::

.0

-U

1:;

=..5

T...J

,.S

--<>

*'"Q

.::.

..(':

•-'...

0"

-+:.

;=;n.

..-.

.s,(

').

'r,¥

,-,'-C

',

__c..

.0-

.._

U":

.

:;.

..c()

~:::

rvc:-

:J~S

J1:=:;:::?~~

.....,......

::i~=..

r:,-o

:;j

I}

lo:.

(";;

'...o

J",

f;::::;-

:t:

'(j'"

,...

';:'

t/',

:oJ

0>

_.:::

~;J

~';E~

';'

s-~

~=:

:<a-

-o~.

G:c

-J

-;:,

:::::

yU

;.g:

.:;;~

;-::::

-....

-C

t..:

:Jo

-l::

::In

......,

-,

._

r-

;s::3

>-

...:.;

-,.

"..

..

:::::1

_-J

~~

;:j

OJ ::l

00

0..

~0

.;>-

_.

~:::;

::rtF

: ::t:Jo

P.:l

rr.

...

~~

r: v:-n

:;"

tv<

.n0

-·

c'=

tv~

~~?

~r;;CJ

:;'~

3.5

h~

v....

-...:J

r;-e

rf:-:E

;F--

~:8

5":::::

~~~

.-,;,.

r;~

2-.0

3~

-'

... ::::;

:-.0

..-~

Vl;

;'-.,

c,r-.

,.."J

\,[;

,

_0

-,

_::

J'

,\'

,~.~

'"':;

';f,

::I

~~r;.

N~

••1'

:..-

;.~

--.

Di:

!:2

CJl

(':.

nt~;~

(;i\

-'(

'""'

w(7

,-­

.:o

J-.

~'.J"<

"<~

_.

r;;

~r)

0..;;

~.:5

l·i.~f

t'~f

VJ:;

~J.?

'l;0-

::C

)~

-.""'0

_'i:,..~.

;.:.~

g'~

~~

~-

..''..

'"~

r::"'=

ia.

..s:-

o..

~;:::D..'

v.....

~.~'f;

_0

2,::

i"c

::;;

C~

~::r

.;~,...,

<-.

0,

_-J.

Ioo'!,

r,:...

..""

0C

)\SA

~=:

:=­

~-

c~

';::Co

"<:;-.

<~.

7-~~

~J~

3'[j.

Z§.

=..:::-

.::;

;,3:<

:s.,~3-~

~ir

:

~'8'

~-v

n.!

'Cur

:Co

l

!':l~;::;?"

hJ3

~..

'f;:

.t/'

.~

Wr-

~;:.

I

~~8::l

.~

_a.

Jo:;:

.....J

:~

~'~

.:n

g::

:-'0

..'"

c'...en

:J:z.

~

8c

CJ

~2.

.2~

::::;

0

~~.~

~J~

~.P

~.

§,~

..,

~.-

?'

-..u("''J~

;j2

,25

••r:

;:::

.t"

;>

~2:

c'.

.enV

1,2

;,...

,I

-.J

-.!

..J

V*'"

:oJ

•

~::;-:2">

,-;;;

.~

~

;;:-

....,I

:J

,~'

5~

......

0..

.-

r.r.

:::;

0;.

;::~

•~,

rt:

:oJ

("'"~

~::J

C...

O-g:~

~:--<

CJ_.

.V

i:J

f-..J

:1

-;0

tJ1

':;'

0--o

x:

G(t

,

r.r.;::

On

o.J

­__

::;n

~...

.J.

:J

~~

~

r:;

8:E

:;(=

;s.

=.~

.:­~

"J.

t:e

c ~::t:

'-!.:.

o..;

?,::

~•

-,~~

~...

,J...

....,

r::'-',

::So

..crS

~.

_."\OD..-~

Sf!:

:rv.

g-~

::.0

-.J

n;1

_..

....

..•

-J~.

:.t:

.-,

:':j

~.

::r'

::;j

:J'::o

J~

~::;

:::~~=.c..

a..::

-..'""

-;1

(J)

(j')~

:::,

."t:.>

~:;'

~("

)~

;:~

:::;~

:.t.l

v:.:s

ti:--

2"E

:::

0-9

,"s

~'-

r3­

c~

:5..0

..'

"'"'0,

VI

~--.l

V~.~w

~~!

-.

"""i

.-.

""'t

-::.

__

(j)-

~cJ;;;'

CJ

~v

VJ

r;:-CJ

0.,.

r"J

.....

::J-.

0..

:::;

",<

0

~R'

6:E,

~7

;J~:;'

::'-r

W~

r3:;~tr.~

,..:;=

x·0.

.

Z::

;-'N

~~~

3 r.J'-

A' ... ~ "" ~ Iv 00 I ::t. :: -:

: ::;.,

Iv *'" \f) ~ ~ s.r .., 10 a a-'-:;:: Iv o a ......,

~ .., t.l

Ap

pen

dix

1Il

ltcre

epts

«(X

)nnd

«Jf:f

fit:i£

'llis

([3J./

iJrm

el!h

rced

-sex

for

tlll

're

sres

sitm

o[ea

chco

mpo

sitio

nal

ldle

all

dist

rihu

tion

"ari

able

011

/iilt'

wt'i

ght(

adjl

l:,tc

d)t

.... V> =

Suf

folk

mal

esS

uffo

lkfe

mil

les

Ch

aro

llai

sm

ilk

sT

exel

mal

esS

uff

/Ch

arle

xe

Isa

(s.e

.)a

(s.e

.)a

(s.c

.)0:

(s.c

.)B

(s.l

'.)+

13(s

.c.)

dift

'§

Co

mp

osr

nit

ion

Lea

n(g

/kg

)58

8·34

0(6

·306

)"56

3·55

2(5

·637

)h61

O·3

G6

(7·5

62

)'68

1·12

1(8

,100

),1-2

·55

5(0

·20

4)*

"'*

-2·4

97

(0·4

35

)***

Fat

(g/k

g)

207·

467

(7·3

91).,

251·

272

(6·6

06)"

197·

013

(8·8

62)"

126·

677

(9·4

93)'"

3·97

0(0

·23

9)"

'**

4·17

6(0

-51

0)*

**L

:B2·

999

(0·0

69)"

3·26

2(0

·062

)h3·

368

(0·0

83)1

-3·

856

(0·0

88

)'0

01

1(l

1-00

2)**

*0·

022

(0·0

05

)***

Lea

nd

istr

ibu

tio

nL

eg(g

/kg

)29

3·76

4(2

·138

)-'

303·

376

(1·9

11)h

285·

338

(2·5

63)"

307·

010

(2·7

46)1

--0

·30

5(0

·06

9)*

**-1

·00

0(0

·14

7)*

****

:(.

Loi

n(g

/kg

)11

7·79

2(1

-489

)"11

6·22

5(1

·331

)"11

1·85

9(l

·78

6r'

101·

924

(1-9

13

)'0·

035

(0·0

48)

0-46

0(0

·10

3)*

"***

Jl.

Bes

ten

d(g

/kg

)60

·008

(0·7

44)"

59·3

46(0

·665

),'h

57·9

08(0

·893

)\'

51·7

36(0

-956

)<-0

·07

6(0

·02

4)*

*0·

149

(0·0

51

)*"

***

Sh

ou

lder

(g/k

g)

198·

659

(1·7

25)"

196·

587

(1-5

42)·1

210·

255

(2·0

69)b

208·

502

(2.2

16)h

-0·1

54

(0·0

56r'

*-0

·33

9(0

·11

9)*

*

r:r.; .... o ~_. ::l r:r:< t.l 3 cr [J)

.l.h

.ed

Wit

hin

row

s/in

terc

epts

wit

hd

iffe

ren

tsu

per

scri

pts

dif

fer

(I'<

0.(5

).t

Liv

ew

eig

hts

wen

'ad

just

edsu

chth

atin

terc

epts

rep

rese

nt

val

ues

atth

em

ean

wei

gh

tat

14w

eek

for

each

breed~sex,

wh

ich

wer

e4

1·7

,36

·7,3

8·1

and

30-0

kgfo

rth

eS

uffo

lkm

ales

,S

uffo

lkfe

mal

es!

Ch

aro

llai

sm

ales

and

Tex

elm

ales

resp

ecti

vely

.t

Su

per

scri

pts

ind

icat

eth

esi

gnif

ican

ceof

dif

kre

nce

sfr

omze

ro.

§S

igni

fica

nce

ofth

ed

iffe

n'n

cebetwe(~n

the

two

reg

ress

ion

coef

fici

ents

.N '-.

JU

1