The influence of the tasmanian Fine-Woolled Merino on carcass characteristics of lambs

Livestock Production Science, 4(1977) 191--202

191

© Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

THE INFLUENCE OF THE TASMANIAN FINE-WOOLLED MERINO ON CARCASS CHARACTERISTICS OF LAMBS

W.M. TEMPEST* and T.G. BOAZ

Department of Animal Physiology and Nutrition, The University, Leeds (Great Britain) (Received 13 August 1976)

ABSTRACT Tempest, W.M. and Boaz, T.G., 1977. The influence of the Tasmanian Fine-Woolled Merino on carcass characteristics of lambs. Livest. Prod. Sci., 4: 191--202. Growth and carcass characteristics have been studied in lambs bred so as to illustrate the influence of Fine-Woolled Merino ancestry in contributing from 0% to 100% of the genotype. Five groups of lambs were bred as follows: 0% Merino: Suffolk d × Scottish Halfbred 9 25% Merino: Suffolk d × (Merino d X Scottish Halfbred 9) 9 50% Merino: Merino d X Scottish Halfbred 9 75% Merino: Merino d X (Merino d × Scottish Halfbred 9 ) 9 100% Merino: Merino 6 X Merino 9 All the lambs were reared artificially on cold milk substitute after suckling their dams for one day only. They were weaned at six weeks of age and subsequently fattened on a barley plus fish meal concentrate diet to an empty body weight of approximately 35 kg, when they were slaughtered. Complete growth, slaughter and carcass records were taken. The main effects of increasing the proportion of Merino were to decrease the daily liveweight gain; to decrease the percentage of bone and increase the muscle:bone ratio in the trimmed carcass; in respect of carcass conformation to increase the percentage of thorax, rib, flank and foreloin, and decrease the percentage of upper leg and shoulder; to alter carcass shape, particularly leg shape by increasing its length and decreasing its thickness; and with regard to fat deposition, to increase the internal fat and decrease the external fat in the empty body. The growth, carcass composition and joint proportion differences can be related to the small mature size of the pure Merino, and thus its greater maturity at slaughter; shape and fat distribution differences typify the more primitive and less improved meat character of the Merino.

INTRODUCTION Tasmanian Fine-Woolled Merinos were imported into Britain from Australia in 1955. There has been a considerable amount of investigation of * Present address: Harper Adams Agricultural College, Newport, Shropshire (Great Britain)

192 the characteristics of their wool produced in the wetter British climate, from both the pure Merino and various crosses (Carter, 1967). Their fertility and prolificacy have been d o c u m e n t e d by Donald et al. (1968), and their breeding season b y Tempest and Boaz (1973). Their potential meat characteristics have been ignored, as their lamb carcasses are reputed to have few of the attributes usually associated with those of the British Down breeds. In Great Britain meat production is the essential role of sheep. If improvement o f wool is to be undertaken by the introduction of the Merino into the c o m m o n l y practised cross breeding programme, it is important to establish its effect on the meat characteristics of lambs so produced. One of the c o m m o n crossbred ewes which forms part of the British sheep stratification is the Scottish Halfbred (Border Leicester c~× Cheviot 9). This is usually mated with a Down ram (e.g. Suffolk) for meat lamb production on lowland farms. Alternatively, female lambs of this origin (Suffolk Halfbred) may be retained for breeding themselves and subsequently mated with a Down ram. The introduction of the Merino into such a programme, by mating with the Scottish Halfbred ewe, or in an earlier or later generation, although unquestionably improving wool quality, could have serious implications for growth efficiency and carcass quality of the lambs so bred. This paper reports the growth and carcass characteristics of lambs whose genotypes were derived 100%, 75%, 50%, 25% and 0% from a Tasmanian Fine-Woolled Merino flock kept at the Leeds University Field Station. All the lambs were removed from their dams when one day old and reared artificially. Thus, effects due to differences in milk yield of their dams were discounted. MATERIALS AND METHODS Details of the lambs are given in Table I. They were allowed to suckle their dams for 24 hours and were then removed and reared in a controlled environment house, with temperature maintained at 15°C, in groups of six. They were offered cold milk substitute ad libitum until 3 weeks old, followed b y an allowance of 0.57 litre per day from 3 to 6 weeks. They were weaned when 6 weeks old. Pelletted creep feed was also on offer, plus a TABLE I Details of lambs used in the investigation Breeding

% Merino

Suffolk Suffolk Merino Merino Merino

0 25 50 75 100

d × S c o t t i s h Halfbred 9 d X (Merino d × S c o t t i s h Halfbred 9)9 d X S c o t t i s h Halfbred 9 d × (Merino c~ × S c o t t i s h Halfbred 9)9 d × Merino 9

Number of lambs

Year

12

1969

12

1972

12

1969

12 12

1970 1970

193

small a m o u n t of hay. The lambs were subsequently fattened in an openfronted barn on a diet of 92% barley, 6% fish meal, 2% vitamin/mineral mixture (calculated analysis: 15% crude protein/dry matter; 13.0 megajoules metabolisable energy/kg dry matter) fed ad libitum. Lambs were slaughtered, to yield an 18-kg carcass, at the University Meat Animal Studies Centre. Dressing followed the normal British commercial procedure, and the components were weighed on removal from the lamb. Linear measurements were taken on the cold carcass, which was then trimmed of kidney, perirenal fat, diaphragm and tail to give a standard trimmed carcass. This was split along the vertebral column and the left side retained for dissection. The side was first jointed on an anatomical basis after Williams (1968), and each joint dissected into its c o m p o n e n t tissues. Joints were kept frozen whilst awaiting dissection. After dissection, a composite muscle sample was chemically analysed. The techniques have been described in full by Tempest (1975). The data were analysed by regression of the recorded parameters (y) on the percentage Merino contribution to the genotype (x). RESULTS

Growth performance The growth performance of the lambs is shown in Table II. Although the liveweights of the lambs were recorded pre-slaughter, the more accurate e m p t y b o d y weight (EBW) (liveweight minus weight of ingesta) was preferred as a basis of comparison between groups. It was planned to kill all lambs when they could be expected to have approximately the same EBW, b u t this was n o t achieved with the 25% Merino group, which were kept to a heavier weight as a result of slaughtering requirements outside the authors' control. Daily liveweight gain was significantly lower (P<0.001), and age at slaughter significantly greater (P < 0.001), as the proportion of Merino in the genotype increased from 0% to 100%. Trimmed carcass composition The composition of the trimmed carcass is shown in Fig. 1. The only tissue which showed a significant change (P<0.001) as the proportion of Merino in the genotype changed was bone, which decreased as a proportion of the trimmed carcass as the proportion of Merino increased. This meant that the muscle: bone ratio significantly increased (P<0.05), from 4.34 to 5.02, as the proportion of Merino increased from 0% to 100%. The proportion of muscle in the trimmed carcass decreased, and that of fat increased, with increasing Merino contribution, b u t these effects were n o t significant due to the large within-genotype variation.

142 271

56.7

52.7 122 311

3.9 37.1 21.0

25

3.7 34.8 18.3

0

% Merino

160 240

52.7

5.2 34.6 18.2

50

175 203

52.6

3.8 34.4 18.0

75

58 30

179 262 409 654

Tibialen~hT I.~glengthF Leg c ~ c u m f e r e n c e Buttock circum~rence

Eye muscle w i d t h A Eye muscle d e p t h B

615 224 262 259 224

Carcass l e n g t h depth Width-- Buttocks Ribs Shoulders

0

25

59 32

183 248 396 668

594 238 258 260 229

% Merino

55 28

189 282 398 630

600 248 239 245 194

50

56 32

191 258 388 623

580 228 236 255 209

75

Carcass, leg a n d eye muscle s h a p e (linear m e a s u r e m e n t s in m m )

T A B L E III

Birth w e i g h t (kg) E m p t y b o d y w e i g h t (kg) Carcass w e i g h t (kg) Carcass weight Empty body weight(%) Age (days) Daily liveweight gain (g)

Growth performance of lambs

T A B L E II

52 29

199 272 371 609

571 238 230 214 179

100

= = = =

= = = = =

y = y =

y y y y

y y y y y

y =

y = y =

y =

49.2 191 184

y = y = y =

y =

4.2 35.8 17.6

100 +

bx

+

0.192x 0.120x 0.336x 0.540x

0.408x 0.072x 0.456x 0.380x 0.440x

bx

59.0 - 0 . 0 6 0 x 30.6 - 0 . 0 0 8 x

178.6 + 258.4 + 409.2663.8 -

612.4 231.6 + 267.8265.6229.0-

a

123.80 - 0 . 6 8 4 0 x 306.20 - 1 . 2 8 8 0 x

55.00 - 0 . 0 4 4 4 x

3.98 + 0 . 0 0 3 6 x 35.48 - 0 . 0 0 2 8 x 19.50- 0.0176x

a

-+0,0200 -+0.0257

-+0.0185 ±0.1779 50.0699 50.1560

-+0.0869 50.1315 ±0.1633 -+0.1739 50.1665

SE o f b

±0.0230 50.0808

50.0291

±0.0087 ±0.0163 ±0.0170

SE o f b

* NS

NS

NS

NS

Sig.

NS

NS NS NS

Sig.

195

oO

Muscle

NS

Fat

NS

Bone

**~

50

40

30

20

4

1O

M:B

0

25

50 % Merino

75

ratio

100

in G e n o t y p e

Fig.1. The relationship b e t w e e n percentage tissue c o m p o s i t i o n o f the trimmed carcass of lambs ( y ) and the percentage Merino in their g e n o t y p e (x). 0 = Mean value, ] = -+ 1 S.D. Regression equations: Muscle : y = 54.45 - 0.0314x

SE o f b = -+0.0242

Fat : y = 25.16 + 0.0480x Bone : y = 12.76 - 0.0213x M:B ratio: y = 4.28 + 0.0060x

SE of b = -+0.0253 SE of b = -+0.0017 SE of b = -+0.0018

Join t proportions C o m p o s i t i o n o f the carcass does n o t necessarily r e p r e s e n t q u a l i t y in t e r m s o f b u t c h e r p r e f e r e n c e , and p r o p o r t i o n a l d e v e l o p m e n t b y w e i g h t o f t h e d i f f e r e n t a n a t o m i c a l c o m p o n e n t s is a m o r e effective guide (Fig.2). O f t h e c o m p o n e n t s r e c o r d e d , t h e r e were significant increases in the prop o r t i o n s o f the t h o r a x ( P < 0 . 0 1 ) ( m a i n l y as a result o f t h e significant increase in p r o p o r t i o n o f the rib cage - - P < 0 . 0 5 ) , f l a n k ( P < 0 . 0 1 ) a n d f o r e l o i n ( P < 0 . 0 5 ) , and significant decreases in the p r o p o r t i o n s o f s h o u l d e r ( P < 0 . 0 5 ) , and u p p e r leg ( P < 0 . 0 0 1 ) , as t h e p r o p o r t i o n o f Merino in t h e g e n o t y p e increased.

Carcass, leg and eye-muscle shape Shape o f t h e carcass and o f its a n a t o m i c a l c o m p o n e n t s , p a r t i c u l a r l y joints and muscles, is o f m a j o r c o n s u m e r significance, b u t linear m e a s u r e m e n t s are involved and these are less a c c u r a t e and s u b j e c t t o greater o p e r a t o r v a r i a t i o n F r o m the results (Table III), it is e v i d e n t t h a t increasing the p r o p o r t i o n o f Merino in the g e n o t y p e was associated with a r e d u c t i o n in carcass length

196

25

Rib

Cage

*

20

Thorax

**

Neck

NS

J

j

15

10

0

o

m

O

~

Rrpa~NS Shoulder

*

Shin •

U

•

NS •

30

c~ o

Upper

Leg

**~

25

20 Ver~.

CoZ.

NS

w

15

10

v

Flank

**

Loin

NS

c

o

5

o

o •

Foreloin

Lower

-v

*

Leg'NS

0 i

0

g

25

50 % Merino

75

1GO

in G e n o t y p e

Fig.2. The relationship between percentage joint proportions of the trimmed carcass of lambs (y) and the percentage Merino in their genotype (x). (A) Forequarter joints, (B) hindquarter joints. Regression equations: Rib-cage : y = 19.45 + 0.0128x S E Of b = + 0 . 0 0 3 4 Thorax : y = 14.23 + 0.0176x SE of b = -+0.0023 Neck : y = 10.47 + 0.0022x SE of b = -+0.0015 Breast : y = 10.49 - 0.0005x SE of b = +0.0005 Shoulder : y = 9.99 - 0.0047x SE of b = -+0.0012 Shin : y = 2.89 + 0.0013x SE of b = -+0.0007 Upper leg : y = 26.80 - 0.0229x SE of b = -+0.0019 Vertebral column : y = 18.37 + 0.0000x SE of b = -+0.0027 Flank .~ y = 8 . 9 4 + 0 . 0 0 8 6 x SE of b = +0.0018 Loin : y = 8.260.0053x SE of b = -+0.0023 Foreloin : y = 4.37 + 0.0037x SE of b = -+0.0010 Lower leg : y = 3.56 + 0.0007x SE of b = -+0.0010

197

(P<0.01) and width at the buttocks (P<0.01) and shoulders (P<0.05), and an increase in tibia length (P<0.001). Perhaps of greater importance to the consumer, leg and buttocks circumference decreased (P<0.01 and P<0.05 respectively) and also eye-muscle size decreased significantly (P<0.05). A diagrammatic representation (reconstructed from linear measurements) of the two extremes in carcass shape is shown in Fig. 3.

Key t o carcass m e a s u r e m e n t s T F P L K WB WR WS DB

= l e n g t h o f tibia = l e n g t h o f leg = l e n g t h o f pelvis = i n t e r n a l l e n g t h o f carcass = e x t e r n a l length o f carcass = width of buttock = w i d t h o f ribs = width of shoulder = d e p t h o f b u t t o c k (derived f r o m c i r c u m f e r e n c e and w i d t h ) ETH = external depth of thorax

L

( F o r precise d e f i n i t i o n s see T e m p e s t , 1975).

WS

V O ~ Merino

i 0 0 ~ Merino

Dorsal Aspect

O~ Merino

i009~ Merino

Lateral A s p e c t

Fig. 3. D i a g r a m m a t i c r e p r e s e n t a t i o n o f t h e e x t r e m e s in carcass s h a p e (carcass weights o f 0% M e r i n o l a m b s = 18.3 kg, 100% M e r i n o -- 17.6 kg, see Table II).

198

Depot fat distribution Fat distribution followed a well defined order according to genetic constitution (Fig. 4). Increasing the proportion of Merino in the genotype significantly increased (P<:0.001) internal fat deposition (omental, mesenteric and perirenal), whereas sub-cutaneous and intermuscular fat significantly decreased (/'<0.05). Intramuscular fat could not be physically isolated, but 5O

40

30

.

•

-

-

.

.

Subcutaneous

*

a._._..___ o o

Intermuscular

20

Omental

+ Mesenteric

~

m lO

*~

_-----------b Perirenal

+~

o-..---------Intramuscular

~

o

0

50

25 % Merino

75

100

in G e n o t y p e

Fig.4. T h e r e l a t i o n s h i p b e t w e e n d e p o t d i s t r i b u t i o n o f f a t in t h e e m p t y b o d y o f l a m b s ( y ) a n d t h e p e r c e n t a g e M e r i n o in t h e i r g e n o t y p e (x). ( I n t r a m u s c u l a r f a t is as a p e r c e n t a g e o f t h e m u s c l e tissue. ) Regression equations: S E o f b = +-0.0285 Subcutaneous : y = 45.44- 0.0868x S E o f b = -+0.0213 Intermuscular : y = 32.36- 0.0712x S E o f b = -+0.0085 Omental and mesenteric : y = 15.18 + 0.0850x SE o f b = -+0.0056 Perirenal : y = 7.01 + 0 . 0 7 3 3 x SE o f b = -+0.0026 Intramuscular " y = 3.90 + 0.0160x

TABLE IV Aspects of b o d y maturity % Merino 25

50

75

89.5

80.0

69.0

59.5

50.0

38.9

46.4

50.1

57.8

71.6

0 Estimated mature b o d y w e i g h t "- MW (kg) Stage o f maturity at slaughter (% EBW/MW) Rate o f gain o f mature weight (% M W G / w e e k )

2.43

2.37

2.43

2.39

100

2.47

y=

a

+

bx

0.3980x

SEofb

Sig.

-*0.0060

***

y =

89,50-

y =

37,60 + 0.3072x

-*0.0400

**

y ffi

2,40 + 0 . 0 0 0 4 x

±0.0004

NS

199

chemical analysis of the muscle for fat showed intramuscular fat significantly increased (P<0.01) with increasing percentage of Merino. DISCUSSION AND CONCLUSIONS

It is significant that the carcasses of pure Merino lambs were reasonably acceptable in terms of carcass composition and joint proportions by weight, but that carcass and joint shape left much to be desired. These lambs received a much higher plane of nutrition in early life than that normally available to those reared in a typical range environment. Pure Merino lambs, contemporaries of those in this experiment, had a growth rate of only 115 g per day (184 g in this experiment) when reared by the ewe to weaning at 96 days. It suggests that much of the criticism of the growth of the pure Merino might be overcome were attention given more to ewe milk yield potential in selection programmes, although Langlands (1972) considers this to be of secondary significance. He concluded that Merino lambs grew slowly because of their lower voluntary food intake. However, certain genetic characters are not overcome by nutrition, as shown by the progressive improvement in some carcass criteria as the Merino influence was reduced. Two basic characters seem to be mainly involved: mature body size itself (Seebeck, 1966) and the rate of attainment of mature body size (McClelland et al., 1973) (provided there are no extremes in the pattern of growth). Table IV shows the differences in the mature bodyweight (MW) of the five genotypes examined, and it is evident that the respective lambs were slaughtered at a progressively greater stage of maturity (% EBW/MW) as the proportion of Merino in the genotype increased. As for rate of attainment of mature body weight (measured as the percentage of mature weight gained per week), there were no differences between the genotypes (Table IV), despite wide differences in daily liveweight gain (Table II). Most of the differences in carcass characteristics to which attention has been drawn can be explained by stage of maturity at slaughter. The carcasses from Iambs which were more mature at slaughter would be expected to contain a greater proportion of those tissues and body parts which are recognised to be late maturing, and a lower proportion of the recognised early maturing tissues/body parts; and vice versa for the carcasses of lambs which were less mature at slaughter (Hammond, 1932). Thus the carcasses of 100% Merino, which were more mature at slaughter, had a lower proportion of bone (early maturing tissue), a higher proportion of fat (late maturing tissue), and a higher muscle:bone ratio (late maturing) than those of 0% Merino. They also had a higher proportion of thorax, primarily due to higher proportion of rib-cage, with higher proportions of flank and foreloin, and lower proportions of leg and shoulder joints. These data agree with the general concept derived from growth coefficients (e.g. Butterfield and Berg, 1966; Elsley et al., 1964) that the thorax and ab-

200 d o m i n a l areas are late m a t u r i n g , a n d t h a t t h e l i m b s are o f i n t e r m e d i a t e m a t u rity. H a m m o n d {1960) h a d also i n d i c a t e d t h a t " t h e d e p t h o f rib m a y go so far as t o increase t h e p r o p o r t i o n o f this p a r t " , in e x t r e m e l y m a t u r e animals. T h e 100% M e r i n o carcasses also h a d a h i g h e r p r o p o r t i o n o f f a t in t h e muscle, w h i c h H a m m o n d ( 1 9 6 0 ) a n d R e e d a n d H o u s t o n ( 1 9 6 9 ) h a v e i n d i c a t e d is a sign o f g r e a t e r m a t u r i t y . T h e r e was h o w e v e r an i m p o r t a n t carcass c h a r a c t e r i s t i c w h i c h c o u l d n o t be e x p l a i n e d b y stage o f m a t u r i t y at slaughter. T h e late d e v e l o p i n g e x t e r n a l f a t s w e r e a l o w e r p r o p o r t i o n o f t h e t o t a l f a t o f the m o r e m a t u r e 1 0 0 % Merino, a n d t h e e a r l y d e v e l o p i n g i n t e r n a l fats w e r e in f a c t a higher p r o p o r t i o n o f t h e t o t a l f a t o f t h e m o r e m a t u r e 100% M e r i n o carcass. T h e t o t a l w e i g h t o f f a t in the e m p t y b o d y w a s n o t i n f l u e n c e d significantly b y t h e g e n o t y p e o f t h e l a m b s a n d was e q u a l t o 6 . 3 0 kg + 0 . 0 1 7 4 x ( w h e r e x = the p e r c e n t a g e Merino in t h e g e n o t y p e , a n d SE o f b = + 0 . 0 0 9 1 ) . This p a t t e r n o f f a t d e p o s i t i o n r e s e m b l e s closely t h e wild or m o r e p r i m i t i v e b r e e d s such as t h e S o a y ( D o n a l d e t al., 1 9 7 0 ) a n d o t h e r breeds, such as t h e Finnish L a n d race (McClelland a n d Russel, 1 9 7 2 ) , w h i c h are u n i m p r o v e d f o r m e a t characteristics. ACKNOWLEDGEMENTS T h e a u t h o r s are g r a t e f u l t o t h e A g r i c u l t u r a l R e s e a r c h Council f o r t h e p r o v i s i o n o f t h e M e r i n o s h e e p a n d f o r financial assistance; t o Mr. R. J o n e s f o r d a y - t o - d a y c o n d u c t o f t h e e x p e r i m e n t ; a n d t o Mr. F. Cass f o r care o f t h e sheep. REFERENCES Butterfield, R.M. and Berg, R.T., 1966. A classification of bovine muscles based on their relative growth patterns. Res. Vet. Sci., 7: 326--332. Carter, H.B., 1967. The Merino Sheep in Great Britain (II). Text. Inst. Ind., 5: 97--99. Donald, H.P., Read, J.L. and Russell, W.S., 1968. A comparative trial of crossbred ewes by Finnish Landrace and other sires. Anita. Prod., 10: 413--421. Donald, H.P., Read, J.L. and Russell, W.S., 1970. Influence of litter size and breed of sire on carcass weight and quality of lambs. Anim. Prod., 12: 281--290. Elsley, F.W.H., McDonald, I. and Fowler, V.R., 1964. The effect of plane of nutrition on the carcass of pigs and lambs when variations in fat content are excluded. Anim. Prod., 6: 141--154. Hammond, J., 1932. Growth and Development of Mutton Quality in Sheep. Oliver and Boyd, Edinburgh and London, 597 pp. Hammond, J., 1960. Farm Animals, their Growth, Breeding and Inheritance. 3rd Edn., Edward Arnold, London, 322 pp. Langlands, J.P., 1972. Growth and herbage consumption of grazing Merino and Border Leicester lambs reared by their mothers or fostered by ewes of the other breed. Anim. Prod., 14: 317--322. McClelland, T.H. and Russel, A.J.F., 1972. The distribution of body fat in Scottish Blackface and Finnish Landrace lambs. Anim. Prod., 15: 301--306. McClelland, T.H., Russel, A.J.F. and Jackson, T.H., 1973. Lamb growth, efficiency of food utilisation and body fat at four stages of maturity in four breeds of different mature body weight. Proc. Br. Soc. Anin~ Prod., 2 : 8 3 (Abstr.).

201

Reed, R. and Houston, T.W., 1969. A possible new approach to the characterization of ageing tissue. Gerontologia, 15: 101--120. Scebeck, R.M., 1966. Composition of dressed carcasses of lambs. Proc. Aust. Soc. Anita. Prod., 6: 291--297. Tempest, W.M., 1975. The effect of artificial rearing on the growth, development and carcass characteristics of lambs. Ph.D. Thesis, University of Leeds, 404 pp. Tempest, W.M., and Boaz, T.G., 1973. The seasonality of reproductive performance of Merino sheep in Britain. Anita. Prod., 17: 33--41. Williams, D.R., 1968. A comparison between a method of jointing meat carcasses based upon their anatomical structure and a method based upon standardized butchering practice. I. Description of the jointing methods. J. Agric. Sci. Camb., 71 : 297--301. Rf~SUM~. Tempest, W.M. et Boaz, T.G., 1977. L'influence du M~rinos ~ lalne fine de la Tasmanie sur les traits caract~ristiques de carcasse d'agneaux. Livest. Prod. Sci., 4 : 1 9 1 - - 2 0 2 (en anglais). Sur des agneaux ~Jev~s pour ~tudier l'influence progressive de 0 ~ 100% du g~notype du caract~re Merinos ~ laine fine, les principales caract~ristiques de la croissance et des carcasses ont ~t~ ~tudi~e~ Cinq groupes d'agneaux ont ~t~ prepares: 0% Merino: Suffolk d × Scottish Halfbred e 25% Merino: Suffolk d × (Merino d X Scottish Halfbred 9) 9 50% Merino: Merino d X Scottish Halfbred 9 75% Merino: Merino d X (Merino d X Scottish Halfbred 9) 100% Merino: Merino d X Merino 9 Tous les agneaux furent ~lev~s artificiellement au lait froid de remplacement apr~s un jour seulement d'allaitement maternel, lls furent sevr~s ~ l'~ge de 6 semaines et ensuite engralss~s avec un r~gime concentr~ ~ base d'orge et de farine de poisson jusqu'au poids vif vide d'environ 35 kg. Les r~sultats de croissance d'abattage et de qualit~ des carcasses furent enregistr~s. Les principaux effets de la part croissante du caract~re Merinos furent: une diminution ou du gain m o y e n quotidien une r~duction de la proportion d'os et une amelioration du rapport muscle/os dans la c arcasse -- en ce qui concerne la " c o n f o r m a t i o n " une augmentation de la proportion de thorax, de cSte et une diminution de celle du gigot, de l'~paule et du rein une alteration de la forme des carcasses particuli~rement au niveau des gigots, par l'accroissement de sa longueur et diminution de l'~paisseur sur le plan de l'adiposit~ l'accroissement de la graisse interne et la diminution de celle de couverture. Les differences de croissance et de composition des carcasses peuvent ~tre reli~es ~ la petite taille adulte du Merinos pur. Les differences de conformation et de distribution de la graisse caract~risent les capacit~s plus primitives et moins am~lior~es du Merinos pour la production de la viande. -

-

-

-

-

-

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KURZFASSUNG Tempest, W.M. und Boaz, T.G., 1977. Der Einfluss des tasmanischen Feinwollmerino auf die SchlachtkSrpereigenschaften yon I.~mmern. Livest. Prod. Sci., 4 : 1 9 1 - - 2 0 2 (in Englisch ).

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Es wurden Wachstum und Schlachtk6rpereigenschaften bei I.~/mmern untersucht, wobei der Einfluss der Feinwollmerino-Abstammung illustriertwurde, der 0 % bis 1 0 0 % des Genotyps betrug. Fiinf Gruppen yon L ~ m m e r n wurden wie folgt erzeugt: 0 % Merino: Suffolk d × Scottish Halfbred 9 2 5 % Merino: Suffolk d X (Merino d X Scottish Halfbred 9) 9 5 0 % Merino: Merino d × Scottish Halfbred 9 7 5 % Merino: Merino d X (Merino d X Scottish Halfbred 9) 9 1 0 0 % Merino: Merino d × Merino 9 Nach einer eint~igigen S~ugeperiode wurden alle L~immer mit kaltem Milchaustauschfutter aufgezogen. Im Alter von sechs Wochen wurden sie abgesetzt und anschliessend mit einer aus Gerste und Fischmehl bestehenden Ration bis zu einem Schlachtgewicht yon ca. 35 kg gem~tet. Es erfolgte eine vollst~ndige Sammlung der Daten tiber Wachstum, Schlachtung und SchlachtkSrper. Mit steigendem Merino-Anteil zeigte sich folgendes Bild: -- geringere t~iglicheZ u n a h m e -- A b n a h m e des prozentualen Knochenanteils und Z u n a h m e des Muskelfleisch/ZnochenVerh~fltnisses im hergerichteten Schlachtk/Srper -- Erh6hung des Thorax- und Rippenanteils hinsichtlich der Ausbildung des Schlachtk~Srpers und prozentuale A b n a h m e von Keule, Lende und Bug -- Ver~inderung der F o r m des Schlachtk6rpers, insbesondere der Keulenform dutch gr6ssere L~nge und verringerte Breite hinsichtlich Verfettungsgrad Z u n a h m e der inneren Verfettung des Schlachtk6rpers sowie geringere Fettabdeckung. Die Unterschiede hinsichtlich Wachstum und Zusammensetzung des SchlachtkSrpers k6nnen dutch die geringe Gr6sse der ausgewachsenen, reinrassigen Merinos erkl~t werden. Die Unterschiede im Schlachtk~Srpertyp sowie in der Fettverteilung kennzeichnen die primitiveren und unzureichenden Eigenschaften der Fleischbildung des Merinoschafs. -

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