A Comparison of Eight Sire Breeds for Lamb Production: 2. Lamb Carcass Composition

A Comparison of Eight Sire Breeds for Lamb Production: 2. Lamb Carcass CompositionAuthor(s): G. J. More O'Ferrall and V. M. TimonSource: Irish Journal of Agricultural Research, Vol. 16, No. 3 (Dec., 1977), pp. 277-284Published by: TEAGASC-Agriculture and Food Development AuthorityStable URL: http://www.jstor.org/stable/25555878 .

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Ir. J. agric. Res. 16: 277-284, 1977

A COMPARISON OF EIGHT SIRE BREEDS FOR LAMB PRODUCTION

2. Lamb carcass composition

G. J. More O'Ferrall

An Foras TaUntais, Dunsinea, Castleknock, Co. Dublin

V. M. Timon

An Foras Taluntais, Beklare, Tuam, Co. Galway

ABSTRACT

Records of 2038 progeny collected over 6 years were used to compare eight different sire breeds of

sheep for carcass composition. Lambs were slaughtered at 36 and 45 kg liveweight. Suffolk (828

progeny), Texel (469) and Hampshire (347) were the breeds most widely represented. Carcass com

position was estimated by using the best neck joint (7-12th rib) as a predictor of carcass lean, fat

and bone. Differences between sire breeds in the percentage distribution of the carcass were not of major

importance. The most significant breed differences were in the composition of the carcass (per

centage lean, fat and bone). Texel-sired progeny had 3.5 % more lean and 4% less fat than average,

and 4% more lean and 4.7% less fat than Suffolks, the principal fat iamb sire breed used in Ireland.

Texels also had the largest eye-muscle area and best lean-to-bone ratio. Dorset Horn progeny ranked

second to the Texel in percentage lean and fat while the Dorset Down had the highest percentage fat

and lowest percentage lean and bone. These results indicate the great potential of the Texel breed as a lean meat' sire for mid-season

or heavy lamb carcass production for manufacturing where carcass composition is of major im

portance.

INTRODUCTION

There have been very few direct comparisons of sheep breeds for carcass quality and

composition, although much work has been devoted to obtaining efficient and ac

curate methods of carcass assessment by indirect means. This work has been reviewed

by Bowman (1) and Bradford (2);

Til



278 IRISH JOURNAL OF AGRICULTURAL RESEARCH, VOL. 16, NO. 3, 1977

This paper reports on a comparison of eight sire breeds for carcass composition based on the best neck sample joint (7th-12th rib). This joint was found by Timon

and Bichard (3) and subsequently confirmed by Kempster et al (4) to be a good

predictor of carcass lean, bone and fat. The phenotypic relationships between growth

rate, carcass measurements and carcass composition are also included in this paper.

MATERIALS AND METHODS

The data used in this study, already described (5), comprised 2038 lamb carcasses with

varying numbers representing each sire breed. At weaning, lambs were assigned at

random to two groups for slaughter at 36 or 45 kg liveweight. Following slaughter, carcasses were held overnight in the factory chill (2? to 3?C). They were then measured and jointed into three cuts: a) hind?comprising the leg and loin; b) best neck

comprising the 6th to 13th rib plus the breast or 'flap'; c) fore?comprising the

shoulder, middle neck and scrag and all parts forward of 6th rib. These three cuts were weighed and expressed as a percentage ofthe total carcass weight. The best neck was wrapped in polythene, taken back to the laboratory and stored in a chill at 2?C until dissection. Prior to dissection the joint was trimmed to a 6 rib cut (7th-12th rib

inclusive), with the 6th and 13th ribs along with the breast or flap being removed. The trimmed joint was dissected into bone and 'meat' (lean plus fat). The bones

were cleaned of meat, and expressed as a percentage ofthe total trimmed joint. The 'meat' was then minced twice prior to being chemically analysed to obtain the per centage lean and fat in the sample. This was taken to be an unbiased estimate of the carcass percentage lean and fat; Timon and Bichard (3) obtained correlations between the composition of this sample joint and the whole carcass of 0.94, 0.92 and 0.75 for

percentage muscle, percentage fat and percentage bone respectively. The area of the

longissimus dorsi ofthe 12th rib was traced from both sides ofthe carcass, measured by a planimeter and averaged to give the eye-muscle area (EMA) for each lamb.

The data were analysed by the method of least squares (6). Constants were fitted for year, breed of dam (BOD), age of dam (AOD), sex, type of birth/rearing (single, twin, other; B/REAR), breed of sire (BOS), slaughter weight group (SLWG), and for the interaction between breed of sire X slaughter group (BOS x SLWG).

RESULTS

Means

Table 1 shows the means, standard deviations and coefficients of variation of carcass traits, In common with other studies of carcass composition, by far the greatest



MORE O'FERRALL AND TIMON: LAMB PRODUCTION, 2 279

TABLE 1: The mean (X), standard deviation (sd) and coefficient of variation (cv) of lamb carcass traits

Trait x sd cv(%)

% hind 47.28 1.84 3.9 % best neck 15.74 1.33 84

%fore 36.82 1.93 5.2 Hind wt/leg length 0.70 0.08 11.9

%lean 56.70 4.98 8.8

%fat 26.03 5.48 21.1

%bone 16.92 2.05 12.1 Lean-to-bone ratio 3.41 0.42 12.5

Eye-muscle area (cm^) 11.45 1.63 14.3

TABLE 2: Level of significance of the mean squares and residual mean square for lamb carcass traits from analysis of variance

Source of % % % HINDW/ % % % Lean variation df hind best fore LEGL fat lean bone to- EM A

neck bone

Breed of dam 10 ** *** ** * *** ** *** *** ns

ggj? I **# ##* #*# ** #** *** *** **# JSJJJ

Birth/rearing type 2 ns ns ns ** ns ** ns ns **

Age of dam 5 ns ns ns ns * ns *** ns ns

Years 5 *** *** *** *** *** *** ns *** ***

Slaughter wt 1 ns *** ns *** *** *** *** *** ***

Breed of sire 7 ns *** *** *** #** *** *** *** ***

Breed of sire X

slaughter wt 7 * ns * ** ns ns ns ns *

Residual mean

square 1999 3.4 1.8 3,7 0.007 30 25 4,2. 0.18 2.6

variation was in percentage fat; the percentage bone and lean-to-bone ratio were

intermediate, while the percentage lean was the least variable of the three tissue

components.

Table 2 shows the significance levels and residual mean squares from the analysis

of variance of the traits. Breed of dam and sex had a significant effect on all traits

except EM A, while the difference between years was also significant for all traits

except percentage bone. Type of birth/rearing and age of dam had lesser effects on

all traits.

Although the intention was to have a difference of 9 kg liveweight (36 vs 45 kg)

between the two slaughter groups the difference in fact was only 5.5 kg liveweight or

2.5 kg carcass weight (15.7 vs 18.2 kg). The lighter slaughter group had a significantly

higher percentage lean (57.3 vs 55.4 %), lower percentage fat (24.9 vs 28.3 %) and lower

percentage bone (16.1 vs 17.3 %). In the distribution of the carcass the only significant

(p<0.05) difference was the higher percentage best neck in the heavier slaughter '

group.; .




Breed of sire There were highly significant differences between breed of sire for all traits except

percentage hind. The least squares constants for the different sire breeds for percentage distribution of the carcass are shown in Table 3 and for percentage carcass com

position in Table 4. These are shown graphically in Figs 1 and 2 where the breed

constants are expressed as standard deviation units above or below the overall mean.

Although represented by fewer progeny, Dorset-sired lambs were above average for

the proportion ofthe carcass in the hind and best neck; this would indicate that both

Dorset breeds should yield a greater proportion of high-priced cuts. Texel lambs, on

the other hand, had a higher percentage fore, and below average percentage hind and

best neck. Dorset Down lambs had the best conformation and 'blockier' carcasses

as indicated by the HINDW/LEGL ratio.

Some ofthe major differences between the sire breeds were in carcass composition.

Perhaps the most significant was that the Texel lambs had very much higher than

TABLE 3: Number of progeny per sire breed and least squares constants for percentage distribution of carcass __^^

No. of % % % Hindwt/ progeny hind best neck fore leg length

Overall mean (u) 2038 47.3 16.0 36.6 0.704 Suffolk 828 0.00ab 0.11bc 0.16b 0.019b

Texel 469 -0.12b -0.586 0.46a -0.016c Dorset Horn 42 0.64 a

0.10bcd 0.06ab -~0,008bc

Hampshire 347 -0.25b 0.34b -0.27b 0.017b Oxford Down 119 0.00ab 0.29de 0.19ab ~0,022c

Lincoln 68 -0.30b -0.36d6 0.60a -0.079d lie de France 71 -0.20b -0.22ode 0.35ab 0.010b

Dorset Down 94 0,26ab 0.90a -L24c 0.080*

ab ed ^Constants with the same superscripts are not significantly different from one another (p > 0.05)

TABLE 4: Least squares constants for percentage carcass composition, lean-to-bone ratio and eye-muscle area (EM A)

% % % Lean-to lean fat bone bone EMA (cm2)

Overall mean (u) 56.35 26.61 16.72 3.42 11.38 Suffolk ?0.50bc 0.78b ~~0.04ab -0.03bcd -0.13bc

Texel 3.57a -3.94c 0.27a 0.16a 0.63a DorsetHorn 1.06b -0.82b -0.08ab 0.08abcd 0.21abc Hampshire -0.63bc 1.01b -0.29bc 0.02bc -~0.17bc Oxford Down ? 0.28bc ?-0.02b 0.40a -0.10de -0.31cd

Lincoln ~0.23bc -0.38b 0.79a -0.20* -0.70d lie de France . ? 1.29bc 0.15b 0.53a ? 0.08bcde ?0.08bcd

PorsetDown _l,70c 3.21a -1.56d 0.16a 0.55a

abed econstants with the same superscripts are not significantly different from one another (p > 0.05)




HIND% i.00m?

1 Dbestneck% 41

I3fORE% I m / f ^HINDW/LEGL I

0-4- %

i ":

1 I I fli fl ! I

i 4v. 'i I ihM j II I U| I

-j I I -0-6-* W |

^-09o g Suf. Texel Dor.Horn Hamp. Ox.Own. Lincoln He de Fr. Dor. Dwn.

Fig. I: Sire breeds expressed as standard deviations above or below the mean

average percentage lean, bigger eye-muscle areas and a very low percentage fat in the

carcass compared to any of the other breeds. The Dorset Horn ranked second but still had 2.5% less lean and over 3% more fat than the Texels. The Suffolk- and

Hampshire-sired lambs had similar carcass composition; both were below average in

percentage lean and considerably above the mean in percentage fat. The Dorset

Down gave the fattest carcasses and also were considerably below average for per

centage lean and bone. Their progeny had a good lean-to-bone ratio and large eye

muscle area but this may have been due to some extent to their heavier carcass weight at slaughter. The interactions between BOS x SLWG were mostly non-significant or only slightly so in percentage hind, percentage fore and EM A.

Phenotypic correlations

Table 5 shows the phenotypic correlations between some growth traits* carcass

measurements and carcass composition. Although many of the correlations were

significant, none of those between growth traits or carcass measurements and carcass

composition were very high, confirming the lack of usefulness of such measures in

predicting carcass composition (3, 7).



to M & i?i ? o c > o > O 2 c c > r ia w td > o O

TABLE 5: Phenotypic correlations between various growth traits, carcass measurements and composition

% Lean

ADG ADG CWT/HINDW/ CAN % best % % % % to

WWT BW BF CWA CARL LEGL CARL LEGL WT hind neck fore fat lean bone bone EMA

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

1. Birth wt .40 .19 .26 .33 .13 .05 .06 0.3 .32 -.05 -0.5 .12 -.11 .04 .17 -.13 .09 2. Weaning wt .96 .71 .71 .12 -.11 .27 .27 .43 -06 .03 .08 -.05 .00 .11 -.12 .24

3. ADG birth-weaning .70 .69 .09 -.13 .28 .28 .38 -.05 .04 .05 -.02 -.01 .07 -.09 .23

4. ADG birth-slaughter .95 .03 -.24 .24 .28 .37 -.05 .04 .04 -.02 -.03 .09 -.12 .18

5. Carcass wt for age .07 -.23 .42 .41 .39 -.08 .02 .05 .06 -.06 -.02 -.05 .24 6. Carcass length .43 .16 .15 .40 .00 -.03 .08 -.03 .02 .06 -.04 .13

7. Leglength -.16 -.50 .21 -.05 ?.05 .17 ?.20 .12 ,21 -.10 -.06 8. Carcass wt/length .84 ,23 ?.08 ?.08 .18 -.18 .05 .28 ?.23 .18

9. Hingwt/leg length .14 .28 .21 -.30 .41 -.23 -.47 .28 .30

10. Carcass bone wt ?.08 .18 ?.08 ?.18 .05 .28 ?.23 .18

11. % hind .06 -.31 .08 -.03 -.09 .08 -.01

12. %bestneck -.41 .26 -.14 .26 .18 .08

13. %iom -.24 .11 .26 -.16 .00 14. %fat -.79 -.58 ,03 -.11

15. %Ieaa .24 ,29 .15

16. %bone .75 -.10 17. Lean-to-bone :19 18. Eye muscle area ?

df =1999 Values above 0.06 are significant at the 5% level and those above 0.08 are significant at the 1% level




j Blean %

?'6] I Dfat% r,

H BONE % 0-4- _ H LEAN TO BONE I

8 0-21 '

111 I n r. < I a I ll - n >! I iw n ll i i i I 11 jl I | |p, I; 1 J ;j i ?"Ti '

F ri"iTr tfp sP in

"-6.2-J I I U ill I ! !

* II

"H" -1 1 ' 8

'

-06-J ! gi Suf J Texel Dor. Horn Hamp. Ox. Own. Lincoln lledeFr. Don Own.

Fig. 2: Sire breeds expressed as standard deviations above or below the mean

DISCUSSION

The results of this study agree with the findings of other workers, reviewed by Brad ford (2), who observed that the degree of fatness causes the greatest variation in carcass composition. The degree of fatness or finish is influenced largely by the weight of the animal at slaughter in relation to its potential mature weight. For instance, for a 2.5-kg difference in carcass weight there was a 3.3 % difference in fatness but only 2% difference in lean. Similar differences in percentage fat have been reported for

different weight classes of lamb by Lambuth <?? al (8) and by Vesely and Peters (7). The

latter workers also reported significant differences between breeds for percentage fat

and percentage muscle in different weight carcasses. The lack of interaction between

breed of sire and slaughter weight for composition is largely to be expected. The

interaction in carcass distribution is mainly due to the fact that the Dorset Down and

He de France lambs in the 45-kg slaughter group had a lower percentage hind and

a higher percentage fore than those killed at the lighter slaughter weight; the reverse

was the case for the other breeds.

From the standpoint of the consumer^ optimum carcass composition must imply an acceptable amount of fat and a high muscle-to-bone ratio, and this is determined




largely by the slaughter weight ofthe animal. Bradford (2) has suggested that slaugh

tering crossbred lambs at 60 to 66 % of the mean adult weight of the parental breeds

should be a good guide to their desired slaughter weight. However, he points out that

there is considerable both within- and between-breed differences in the proportion of fat, the distribution of fat and the size and shape of muscles in a carcass. The

between-breed differences were certainly borne out in this comparison where the

Texel-sired lambs at the same bodyweight contained over 3 % more lean and had 4% less fat than the Suffolk, which is the principal fat lamb sire in Great Britain and Ireland. However, until the producer is given a reasonable premium for the production

of lean carcasses there is unlikely to be any great change in the use of sire breeds. Should a requirement develop for larger lamb carcasses (over 25 kg) for manufac

turing purposes then it would appear that the somewhat slower growing but much leaner Texel breed would be very suitable for this purpose.

Kernpster et al (4) have outlined the areas of animal production where carcass

evaluation is necessary and this is particularly desirable in large-scale breeding schemes. In such schemes it is desirable that indirect means of predicting carcass

composition be obtained to minimise the cost. However, the precision achieved to date with prediction measurements has largely proved unacceptable (8, 9, 10) and it would

appear that the more costly sample joint dissection is still necessary to obtain an accurate assessment of rams within a particular breed on the basis of a sib or progeny test.

ACKNOWLEDGMENTS

The authors wish to thank Messrs C. O'Haire, T. Gonoud, J. Cronin, G. Seale and A. Mahon for skilled assistance in managing the flock and in carcass dissection for various periods over the 7 years.

REFERENCES

1. Bowman, J. C. Meat from sheep. Anim. Breed. Abstr. 34: 293, 1966. 2. Bradford, G. E. Breeding plans for improvement of meat production and carcass merit in the

meat breeds of sheep. Proc. 1st Wld Congr. Genet. Appl. Anim. Prod., Madrid, 1: 725, 1974. 3. Timon, V. M. and Bichard, M. Quantitative estimates of lamb carcass composition 1. Sample

joints. Anim, Prod. 7: 173, 1965. 4. Kempster, A, J., Avis, P. R. D., Cuthbertson, A. and Harrington, G. Prediction of the lean

content of lamb carcasses of different breed types. X agric. Sci., Camb. 86: 23, 1976. 5. More O'Ferrall, G. J. and Timon, V. M. Comparison of eight sire breeds for lamb production.

1. Lamb growth and carcass measurements. Ir. J. agric. Res. 16: 267, 1977. 6. Harvey, W. R. Least squares analysis of data with unequal subclass numbers. A.R.S. 20-8,

U.S.D.A. 1960. 7. Vesely, J. A. and Peters, H. F. Muscle, bone and fat and their interrelationships in five breeds

of lambs. Can. X Anim. Sci. 52: 629, 1972. 8. Lambuth, T. R., Kemp, J. D. and Glimp, H. A. Effect of rate of gain and slaughter weight on

lamb carcass composition. /. Anim. Sci. 30: 27, 1970. 9. Latham, S. D., Moody, W. G, and Kemp, J. D. Techniques for estimating lamb carcass com

position. J. Anim. Sci. 25: 492, 1966. 10. Spurlock, G. M,, Bradford, G. E. and Wheat, J. D. Live animal and carcass measures for the

prediction of carcass traits in lamb. /. Anim: Sci. 25: 454, 1966.

Received February' 8,1977



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A Comparison of Eight Sire Breeds for Lamb Production: 2. Lamb Carcass Composition