Directory UMM :Data Elmu:jurnal:S:Small Ruminant Research:Vol35.Issue3.Jun2000:
Small Ruminant Research 35 (2000) 89±96
Review
A review of carcass conformation in sheep:
assessment, genetic control and development
S.J. Nsosoa,b,*, M.J. Youngb, P.R. Beatsonb
a
b
Botswana College of Agriculture, Private Bag 0027, Gaborone, Botswana
Animal and Veterinary Sciences Group, Lincoln University, Canterbury, New Zealand
Accepted 29 June 1999
Abstract
Stud breeders, farmers and meat traders have considered carcass conformation or shape in sheep an important trait. This
trait can be assessed on either carcasses or live animals for slaughter and breeding. Nevertheless, there is no single universally
accepted de®nition of the term carcass conformation across the sheep industry. The use of the word carcass conformation in
the sheep industry is further confused by the fact that different indices are used to describe a complex 3-dimensional shape,
which causes variation in the interpretation of results. This review of current knowledge on carcass conformation in sheep will
identify areas, which offer opportunities for research. Visual carcass conformation appears to be poorly related to meat yield
and is also probably predominantly under non-genetic control and as such has little commercial relevance. Visual carcass
conformation assessments appeal to farmers because they are cheap and easy to apply. In contrast, objective conformation and
muscularity (another measure of conformation) require measurements, which may be complicated, dif®cult or costly
depending on the system under consideration. However, precisely de®ned objective conformation and muscularity, which can
be standardised and automated are desirable in breeding and carcass classi®cation schemes. Though, muscularity is highly
heritable and is positively related to meat yield, information on objective conformation, muscularity and, their relationships to
meat yield and other production traits is not adequate. Furthermore, there is little information on whether objective
conformation is under genetic or non-genetic control. Provision of such information would lead to the design of ef®cient sheep
production systems. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Carcass conformation; Sheep and meat quality
1. Introduction
Visual carcass conformation or shape in sheep is
traditionally an important trait to stud sheep breeders
and meat traders (Meat and Livestock Commission,
1987). Historically, there has been confusion as to
*
Corresponding author. Tel.: 267-328831; fax: 267-328753.
E-mail address: [email protected] (S.J. Nsoso).
whether visual carcass conformation referred to the
proportional size of body parts, or the relationship of
the thickness of soft tissues to the skeletal size, or
both. Therefore, resulting in many different meanings
of this trait. Even today animal breeders, meat traders
and scientists usually have a personal impression of
visual carcass conformation, but rarely can they
clearly de®ne this to others (Butter®eld, 1988). This
lack of a common de®nition has led to dif®culties in
0921-4488/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 1 - 4 4 8 8 ( 9 9 ) 0 0 0 9 5 - 4
90
S.J. Nsoso et al. / Small Ruminant Research 35 (2000) 89±96
interpreting and drawing conclusions from the innumerable visual carcass conformation studies and publications available (Kempster et al., 1982). To have a
common de®nition some countries de®ne visual carcass conformation as ``the visual assessment of the
thickness of muscle and fat in relation to the size of the
skeleton'' (Butter®eld, 1988). Skeletal size in carcass
conformation is presumed to mean length or width or
other linear dimensions of the skeletal system. In
addition to lack of a common de®nition, the other
shortcoming of the use of the concept of visual carcass
conformation in assessment of both live animals and
carcasses is the lack of a precise description of complex 3-dimensional shape by a simple index. This can
result in variations of indices used in assessments
(Kempster et al., 1982) depending on such factors
as skill of assessor and part(s) of animal assessed. The
values of visually assessed carcass conformation in
sheep are considered as useful indicators of individual
animal carcass composition and various aspects of
measures of productivity (e.g. milk production, easy
of birth and easy movement). Visually assessed conformation as a useful indicator of carcass composition
has been the subject of many studies in the literature
whereas as a useful indicator of productivity it has
received little attention despite its paramount importance (Kempster et al., 1982) as means of selecting
breeding stock by stud sheep breeders. Therefore, the
aim is to review the current state of knowledge on
carcass conformation in sheep with the view of identifying areas, which offer opportunities for research.
2. Assessment of visual carcass conformation in
live sheep
Butter®eld (1988) arbitrarily divided visual carcass
conformation of live animals into that for breeding
stock and that for slaughter animals. This arbitrary
division was prompted by the differences in de®nitions that the people involved in meat production
attach to these subdivisions of animal production.
The author then pointed out that visual carcass conformation and that of the live animal are related, yet it
is usual for a breeder to talk about an entirely different
concept from that of the butcher using the word visual
conformation. The author then de®ned visual carcass
conformation of the live animal in breeding stock as
``the manner in which the total animal conforms to the
preconceived ideal animal by the beholder. Beauty in
the eye of the beholder concept''. In contrast the visual
carcass conformation of the live animal in slaughter
stock, is de®ned as ``thickness of muscle and fat in
relation to skeletal size''. In conclusion, there is a
feasibility of using a common de®nition for both or
choice of a de®nition for the carcass to be a component
of the live animal's visual conformation.
2.1. Assessment of visual carcass conformation in
carcasses of sheep
After examining the literature on visually assessed
carcass conformation as an indicator of carcass composition in sheep, Kempster et al. (1982) suggested
that studies on this value of conformation should be
aimed at addressing the question: ``What additional
information is provided about carcass composition by
an assessment of visual conformation among carcasses of the same weight and fatness?'' Assessment
of visual conformation at equal fatness is the most
appropriate because animals are of the same maturity
(Taylor, 1985, 1987) hence they are at the same stage
of growth and development (Kempster et al., 1987).
Few workers have examined their data in this way. The
few studies that have assessed visual carcass conformation of crossbred progeny in between sire-breed
comparison studies at equal fatness and at the same
weight in some instances. The ®ndings were the same.
There was relatively little difference between sirebreed means for visually assessed conformation, all
means were approximately within two points on a 15point scale (Fig. 1). Furthermore, there was very little
relationship between sire-breed means for visually
assessed carcass conformation and lean proportion
in carcass (Fig. 1) or proportion of lean in the higher
than lower priced cuts both within and between breeds
(Kempster et al., 1981, 1987). The prediction was
sensitive to the way fatness was controlled. Poor
control of fatness led to visual conformation identifying fatter rather than leaner carcasses. This is an
undesirable outcome but inevitable in commercial
classi®cation, when visually assessed conformation
scores are used to further classify carcasses in one
of the limited number of fat classes (Kempster et al.,
1981). However, Kempster et al. (1981) and Purchas
and Wilkin (1995) found that visually assessed con-
91
S.J. Nsoso et al. / Small Ruminant Research 35 (2000) 89±96
Fig. 1. Sire breed means for carcass lean proportion against
conformation score assessed at equal fatness. Sire breeds are
identified as follows: Border Leicester BL; Dorset Down DD;
Hampshire Down HD; Ile de France IF; North Country
Cheviot NCC; Oxford Down OD; Southdown SD; Suffolk SF; Texel TX; Wensleydale W; early flocks 1; late
flocks 2; results are averaged over the three dam breeds (adapted
from Kempster et al., 1987).
formation has merit for the prediction of lean to bone
ratio and M. longissimus depth.
The above ®ndings in general agree with those from
other sheep studies examining the value of carcass
conformation as an indicator of carcass composition
within breed, but without adjustment to equal fatness.
Findings from these studies have varied, but on balance have indicated that carcass conformation is
positively related to meat yield but the degree of
correlation is very low, so that predictions are subject
to considerable error (Kempster et al., 1982). A number of scientists consider carcass conformation as a
trait of less signi®cance. In contrast meat traders, tend
to agree that carcass conformation is an indicator of
retail yield and value (Kempster et al., 1987). Visual
conformation is included in the carcass classi®cation
scheme of sheep in the UK, not so much for its
relationship with the saleable meat yield but for its
visual appeal to buyers in local and export markets (A.
Cuthbertson, personal communication). To have consistency of carcass classi®cation and grading for visual
conformation, photographic scales are used (Kempster
et al., 1982). Animals of good conformation are
alleged to have carcasses with more lean meat, a
higher proportion of joints and lean meat in the
expensive cuts (loin/leg) than animals of poor conformation. These relationships are said to exist not
only within sheep breeds, but also in other species
(Meat and Livestock Commission, 1987).
2.2. Relationship between carcass conformation and
classification
In the UK meat market, lambs with good visual
conformation are valued more highly and receive
better prices than those with average or poor conformation. A typical price difference between successive
visually assessed conformation classes on a 5-class
scale would be about 3 p/kg (Meat and Livestock
Commission, 1987). These premiums are signi®cant,
however, there is little evidence that carcasses of good
conformation yield higher returns to the retailer than
those of poor conformation. Indeed, at any given level
of fatness, there is a tendency for carcasses of good
visual conformation to have lower yield of saleable
meat than those with poor visual conformation (Table
1). It can be concluded that, although the UK retailers
Table 1
The relationship between saleable meat yield and carcass classificationa
Conformation
Saleable meat yield in different fat classes (%)
1 (very lean)
2
3L
3H
4
E (best)
91.0
90.7
89.5
88.8
87.6
U
R (intermediate)
O
92.4
91.1
90.1
89.1
87.5
P (worst)
92.5
a
5 (very fat)
84.7
Saleable meat yield is expressed as a percentage of carcass weight. Statistical significance between classes are not reported in the original
document. Results adapted from Meat and Livestock Commission (1987).
92
S.J. Nsoso et al. / Small Ruminant Research 35 (2000) 89±96
do not get higher returns in terms of meat yield, they
get higher return through the premiums for good than
for poor carcass conformation. Based on these premiums charged by meat traders, which indicate what
consumers are willing to pay, it seems shape per se is
important rather than as an indicator of the content of
saleable meat in carcass. If this is the case, under what
conditions or circumstances is shape per se commercially valuable? Meat and Livestock Commission
(1987) reported a trial comparing two carcass cutting
techniques, i.e. steaking and conventional for carcasses of the same weight and fat class but differing
in visually assessed carcass conformation. The steaking method clearly demonstrated the superiority of
good conformation carcasses in terms of higher saleable meat yield than poor carcass conformation. The
difference in total saleable meat (steaks, breast, scrag,
®llet, lean, trim and mince) was 3% higher in good
than poor conformation carcasses. The differences
were evident in different parts of the carcass. The
good conformation carcasses had signi®cantly higher
yield in leg (6% in weight of steaks and 5% in area of
steaks) and loin (13% in weight of steaks and 17% in
area of steaks) than carcasses of poor conformation.
However, the conventional method only demonstrated
a 3% signi®cant advantage of good conformation
carcasses in weight of leg compared to poor carcasses
(Table 2). These differences mean better ®nancial
returns from carcasses of good than those of poor
visual conformation (Meat and Livestock Commission, 1987). To demonstrate the higher meat yield of
good than poor visual conformation carcasses, new
cutting techniques like steaking may be desirable.
Table 2
Comparison of yield of poor (class O) and good (class U)
conformation carcasses from conventional cutting and steaking
methodsa
2.3. Assessment of objective conformation in sheep
carcasses
Total weight of saleable meat by
steaking method (Including lean
trim, fillet, breast, scrag) (kg)
Poor
Good
32
25
599
32
28b
568
2.05
0.54
0.80
7.44
2.11b
0.55
0.83
7.45
5.2
5.4
Total weight of steaks (kg)
Average area (cm2)
0.40
61.4
0.44b
66.4b
Leg
Number of steaks
Total weight of steaks (kg)
Average area (cm2)
9.4
0.98
63.7
9.8
1.04b
66.8
Number of steaks
Total weight of steaks (kg)
Average area (cm2)
8.1
0.71
54.1
7.8
0.80c
63.1c
Shoulder
Number of steaks
Total weight of steaks (kg)
Average area (cm2)
2.5
0.35
84.9
2.4
0.33
81.3
All steaks
Number of steaks
Total weight of steaks (kg)
Average area (cm2)
25.1
2.43
63.6
25.4
2.60b
68.0
5.14
5.30b
Number of carcasses
Eye muscle depth (mm)
Carcass length (mm)
Conventional cuttingc
Weight of leg (kg)
Weight of chump (kg)
Weight of loin (kg)
Total weight of saleable meat
(includes mince, stew, kidney) (kg)
Steaking methodc
Topside
Number of steaks
Loin
a
Since the meat trading and farming sectors attach a
lot of importance to carcass conformation, when
results from visually assessed conformation studies
indicate that it is poorly related to meat yield, a few
studies have been undertaken to evaluate the relationship between objectively assessed conformation and
meat yield (Spurlock et al., 1966; Cunningham et al.,
1967; Kempster et al., 1982; Hopkins et al., 1997;
Abdullah et al., 1998; Tatum et al., 1998). Like
subjective conformation, objective conformation is
an attempt to describe a complex 3-dimensional shape
Carcasses compared at standard carcass weight of 16.8 kg,
and fat class 3L. Results adapted from Meat and Livestock
Commission, 1987.
b
A statistically significant difference (P < 0.05).
c
Saleable meat from steaking method is without bone but is
bone-in from conventional method.
with a simple index. However, unlike visual conformation it is based on precisely de®ned and standardised measurements (De Boer et al., 1974), which
leads to easier comparison and interpretation of results
from experiments and other sources. Research on
S.J. Nsoso et al. / Small Ruminant Research 35 (2000) 89±96
objective conformation has characterised conformation in terms of the ratio of carcass weight with length
(Kempster et al., 1982; Hopkins et al., 1997; Abdullah
et al., 1998; Tatum et al., 1998). Generally, the results
have indicated that this is less well related to meat
yield than visual conformation scores. However, in
carcass assessment objective measurements are easier
to standardise and are more easily adapted to automatic recording than visual conformation scores,
hence there has been a persistent interest in their
research and use (Kempster et al., 1982; Harrington
and Kempster, 1989; Kirton, 1989; Abdullah et al.,
1993; Kirton et al., 1993). Attempts should be made to
extend the research to other objective conformation
assessments in different parts of the body, which
directly measure actual tissue contents.
2.4. Genetic control and development of
conformation
There is not much information available on genetic
control of either subjectively or objectively assessed
conformation in live animals. The studies of Lopezde-Torre et al. (1991) and Conington et al. (1998)
reported low heritability (
Review
A review of carcass conformation in sheep:
assessment, genetic control and development
S.J. Nsosoa,b,*, M.J. Youngb, P.R. Beatsonb
a
b
Botswana College of Agriculture, Private Bag 0027, Gaborone, Botswana
Animal and Veterinary Sciences Group, Lincoln University, Canterbury, New Zealand
Accepted 29 June 1999
Abstract
Stud breeders, farmers and meat traders have considered carcass conformation or shape in sheep an important trait. This
trait can be assessed on either carcasses or live animals for slaughter and breeding. Nevertheless, there is no single universally
accepted de®nition of the term carcass conformation across the sheep industry. The use of the word carcass conformation in
the sheep industry is further confused by the fact that different indices are used to describe a complex 3-dimensional shape,
which causes variation in the interpretation of results. This review of current knowledge on carcass conformation in sheep will
identify areas, which offer opportunities for research. Visual carcass conformation appears to be poorly related to meat yield
and is also probably predominantly under non-genetic control and as such has little commercial relevance. Visual carcass
conformation assessments appeal to farmers because they are cheap and easy to apply. In contrast, objective conformation and
muscularity (another measure of conformation) require measurements, which may be complicated, dif®cult or costly
depending on the system under consideration. However, precisely de®ned objective conformation and muscularity, which can
be standardised and automated are desirable in breeding and carcass classi®cation schemes. Though, muscularity is highly
heritable and is positively related to meat yield, information on objective conformation, muscularity and, their relationships to
meat yield and other production traits is not adequate. Furthermore, there is little information on whether objective
conformation is under genetic or non-genetic control. Provision of such information would lead to the design of ef®cient sheep
production systems. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Carcass conformation; Sheep and meat quality
1. Introduction
Visual carcass conformation or shape in sheep is
traditionally an important trait to stud sheep breeders
and meat traders (Meat and Livestock Commission,
1987). Historically, there has been confusion as to
*
Corresponding author. Tel.: 267-328831; fax: 267-328753.
E-mail address: [email protected] (S.J. Nsoso).
whether visual carcass conformation referred to the
proportional size of body parts, or the relationship of
the thickness of soft tissues to the skeletal size, or
both. Therefore, resulting in many different meanings
of this trait. Even today animal breeders, meat traders
and scientists usually have a personal impression of
visual carcass conformation, but rarely can they
clearly de®ne this to others (Butter®eld, 1988). This
lack of a common de®nition has led to dif®culties in
0921-4488/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 1 - 4 4 8 8 ( 9 9 ) 0 0 0 9 5 - 4
90
S.J. Nsoso et al. / Small Ruminant Research 35 (2000) 89±96
interpreting and drawing conclusions from the innumerable visual carcass conformation studies and publications available (Kempster et al., 1982). To have a
common de®nition some countries de®ne visual carcass conformation as ``the visual assessment of the
thickness of muscle and fat in relation to the size of the
skeleton'' (Butter®eld, 1988). Skeletal size in carcass
conformation is presumed to mean length or width or
other linear dimensions of the skeletal system. In
addition to lack of a common de®nition, the other
shortcoming of the use of the concept of visual carcass
conformation in assessment of both live animals and
carcasses is the lack of a precise description of complex 3-dimensional shape by a simple index. This can
result in variations of indices used in assessments
(Kempster et al., 1982) depending on such factors
as skill of assessor and part(s) of animal assessed. The
values of visually assessed carcass conformation in
sheep are considered as useful indicators of individual
animal carcass composition and various aspects of
measures of productivity (e.g. milk production, easy
of birth and easy movement). Visually assessed conformation as a useful indicator of carcass composition
has been the subject of many studies in the literature
whereas as a useful indicator of productivity it has
received little attention despite its paramount importance (Kempster et al., 1982) as means of selecting
breeding stock by stud sheep breeders. Therefore, the
aim is to review the current state of knowledge on
carcass conformation in sheep with the view of identifying areas, which offer opportunities for research.
2. Assessment of visual carcass conformation in
live sheep
Butter®eld (1988) arbitrarily divided visual carcass
conformation of live animals into that for breeding
stock and that for slaughter animals. This arbitrary
division was prompted by the differences in de®nitions that the people involved in meat production
attach to these subdivisions of animal production.
The author then pointed out that visual carcass conformation and that of the live animal are related, yet it
is usual for a breeder to talk about an entirely different
concept from that of the butcher using the word visual
conformation. The author then de®ned visual carcass
conformation of the live animal in breeding stock as
``the manner in which the total animal conforms to the
preconceived ideal animal by the beholder. Beauty in
the eye of the beholder concept''. In contrast the visual
carcass conformation of the live animal in slaughter
stock, is de®ned as ``thickness of muscle and fat in
relation to skeletal size''. In conclusion, there is a
feasibility of using a common de®nition for both or
choice of a de®nition for the carcass to be a component
of the live animal's visual conformation.
2.1. Assessment of visual carcass conformation in
carcasses of sheep
After examining the literature on visually assessed
carcass conformation as an indicator of carcass composition in sheep, Kempster et al. (1982) suggested
that studies on this value of conformation should be
aimed at addressing the question: ``What additional
information is provided about carcass composition by
an assessment of visual conformation among carcasses of the same weight and fatness?'' Assessment
of visual conformation at equal fatness is the most
appropriate because animals are of the same maturity
(Taylor, 1985, 1987) hence they are at the same stage
of growth and development (Kempster et al., 1987).
Few workers have examined their data in this way. The
few studies that have assessed visual carcass conformation of crossbred progeny in between sire-breed
comparison studies at equal fatness and at the same
weight in some instances. The ®ndings were the same.
There was relatively little difference between sirebreed means for visually assessed conformation, all
means were approximately within two points on a 15point scale (Fig. 1). Furthermore, there was very little
relationship between sire-breed means for visually
assessed carcass conformation and lean proportion
in carcass (Fig. 1) or proportion of lean in the higher
than lower priced cuts both within and between breeds
(Kempster et al., 1981, 1987). The prediction was
sensitive to the way fatness was controlled. Poor
control of fatness led to visual conformation identifying fatter rather than leaner carcasses. This is an
undesirable outcome but inevitable in commercial
classi®cation, when visually assessed conformation
scores are used to further classify carcasses in one
of the limited number of fat classes (Kempster et al.,
1981). However, Kempster et al. (1981) and Purchas
and Wilkin (1995) found that visually assessed con-
91
S.J. Nsoso et al. / Small Ruminant Research 35 (2000) 89±96
Fig. 1. Sire breed means for carcass lean proportion against
conformation score assessed at equal fatness. Sire breeds are
identified as follows: Border Leicester BL; Dorset Down DD;
Hampshire Down HD; Ile de France IF; North Country
Cheviot NCC; Oxford Down OD; Southdown SD; Suffolk SF; Texel TX; Wensleydale W; early flocks 1; late
flocks 2; results are averaged over the three dam breeds (adapted
from Kempster et al., 1987).
formation has merit for the prediction of lean to bone
ratio and M. longissimus depth.
The above ®ndings in general agree with those from
other sheep studies examining the value of carcass
conformation as an indicator of carcass composition
within breed, but without adjustment to equal fatness.
Findings from these studies have varied, but on balance have indicated that carcass conformation is
positively related to meat yield but the degree of
correlation is very low, so that predictions are subject
to considerable error (Kempster et al., 1982). A number of scientists consider carcass conformation as a
trait of less signi®cance. In contrast meat traders, tend
to agree that carcass conformation is an indicator of
retail yield and value (Kempster et al., 1987). Visual
conformation is included in the carcass classi®cation
scheme of sheep in the UK, not so much for its
relationship with the saleable meat yield but for its
visual appeal to buyers in local and export markets (A.
Cuthbertson, personal communication). To have consistency of carcass classi®cation and grading for visual
conformation, photographic scales are used (Kempster
et al., 1982). Animals of good conformation are
alleged to have carcasses with more lean meat, a
higher proportion of joints and lean meat in the
expensive cuts (loin/leg) than animals of poor conformation. These relationships are said to exist not
only within sheep breeds, but also in other species
(Meat and Livestock Commission, 1987).
2.2. Relationship between carcass conformation and
classification
In the UK meat market, lambs with good visual
conformation are valued more highly and receive
better prices than those with average or poor conformation. A typical price difference between successive
visually assessed conformation classes on a 5-class
scale would be about 3 p/kg (Meat and Livestock
Commission, 1987). These premiums are signi®cant,
however, there is little evidence that carcasses of good
conformation yield higher returns to the retailer than
those of poor conformation. Indeed, at any given level
of fatness, there is a tendency for carcasses of good
visual conformation to have lower yield of saleable
meat than those with poor visual conformation (Table
1). It can be concluded that, although the UK retailers
Table 1
The relationship between saleable meat yield and carcass classificationa
Conformation
Saleable meat yield in different fat classes (%)
1 (very lean)
2
3L
3H
4
E (best)
91.0
90.7
89.5
88.8
87.6
U
R (intermediate)
O
92.4
91.1
90.1
89.1
87.5
P (worst)
92.5
a
5 (very fat)
84.7
Saleable meat yield is expressed as a percentage of carcass weight. Statistical significance between classes are not reported in the original
document. Results adapted from Meat and Livestock Commission (1987).
92
S.J. Nsoso et al. / Small Ruminant Research 35 (2000) 89±96
do not get higher returns in terms of meat yield, they
get higher return through the premiums for good than
for poor carcass conformation. Based on these premiums charged by meat traders, which indicate what
consumers are willing to pay, it seems shape per se is
important rather than as an indicator of the content of
saleable meat in carcass. If this is the case, under what
conditions or circumstances is shape per se commercially valuable? Meat and Livestock Commission
(1987) reported a trial comparing two carcass cutting
techniques, i.e. steaking and conventional for carcasses of the same weight and fat class but differing
in visually assessed carcass conformation. The steaking method clearly demonstrated the superiority of
good conformation carcasses in terms of higher saleable meat yield than poor carcass conformation. The
difference in total saleable meat (steaks, breast, scrag,
®llet, lean, trim and mince) was 3% higher in good
than poor conformation carcasses. The differences
were evident in different parts of the carcass. The
good conformation carcasses had signi®cantly higher
yield in leg (6% in weight of steaks and 5% in area of
steaks) and loin (13% in weight of steaks and 17% in
area of steaks) than carcasses of poor conformation.
However, the conventional method only demonstrated
a 3% signi®cant advantage of good conformation
carcasses in weight of leg compared to poor carcasses
(Table 2). These differences mean better ®nancial
returns from carcasses of good than those of poor
visual conformation (Meat and Livestock Commission, 1987). To demonstrate the higher meat yield of
good than poor visual conformation carcasses, new
cutting techniques like steaking may be desirable.
Table 2
Comparison of yield of poor (class O) and good (class U)
conformation carcasses from conventional cutting and steaking
methodsa
2.3. Assessment of objective conformation in sheep
carcasses
Total weight of saleable meat by
steaking method (Including lean
trim, fillet, breast, scrag) (kg)
Poor
Good
32
25
599
32
28b
568
2.05
0.54
0.80
7.44
2.11b
0.55
0.83
7.45
5.2
5.4
Total weight of steaks (kg)
Average area (cm2)
0.40
61.4
0.44b
66.4b
Leg
Number of steaks
Total weight of steaks (kg)
Average area (cm2)
9.4
0.98
63.7
9.8
1.04b
66.8
Number of steaks
Total weight of steaks (kg)
Average area (cm2)
8.1
0.71
54.1
7.8
0.80c
63.1c
Shoulder
Number of steaks
Total weight of steaks (kg)
Average area (cm2)
2.5
0.35
84.9
2.4
0.33
81.3
All steaks
Number of steaks
Total weight of steaks (kg)
Average area (cm2)
25.1
2.43
63.6
25.4
2.60b
68.0
5.14
5.30b
Number of carcasses
Eye muscle depth (mm)
Carcass length (mm)
Conventional cuttingc
Weight of leg (kg)
Weight of chump (kg)
Weight of loin (kg)
Total weight of saleable meat
(includes mince, stew, kidney) (kg)
Steaking methodc
Topside
Number of steaks
Loin
a
Since the meat trading and farming sectors attach a
lot of importance to carcass conformation, when
results from visually assessed conformation studies
indicate that it is poorly related to meat yield, a few
studies have been undertaken to evaluate the relationship between objectively assessed conformation and
meat yield (Spurlock et al., 1966; Cunningham et al.,
1967; Kempster et al., 1982; Hopkins et al., 1997;
Abdullah et al., 1998; Tatum et al., 1998). Like
subjective conformation, objective conformation is
an attempt to describe a complex 3-dimensional shape
Carcasses compared at standard carcass weight of 16.8 kg,
and fat class 3L. Results adapted from Meat and Livestock
Commission, 1987.
b
A statistically significant difference (P < 0.05).
c
Saleable meat from steaking method is without bone but is
bone-in from conventional method.
with a simple index. However, unlike visual conformation it is based on precisely de®ned and standardised measurements (De Boer et al., 1974), which
leads to easier comparison and interpretation of results
from experiments and other sources. Research on
S.J. Nsoso et al. / Small Ruminant Research 35 (2000) 89±96
objective conformation has characterised conformation in terms of the ratio of carcass weight with length
(Kempster et al., 1982; Hopkins et al., 1997; Abdullah
et al., 1998; Tatum et al., 1998). Generally, the results
have indicated that this is less well related to meat
yield than visual conformation scores. However, in
carcass assessment objective measurements are easier
to standardise and are more easily adapted to automatic recording than visual conformation scores,
hence there has been a persistent interest in their
research and use (Kempster et al., 1982; Harrington
and Kempster, 1989; Kirton, 1989; Abdullah et al.,
1993; Kirton et al., 1993). Attempts should be made to
extend the research to other objective conformation
assessments in different parts of the body, which
directly measure actual tissue contents.
2.4. Genetic control and development of
conformation
There is not much information available on genetic
control of either subjectively or objectively assessed
conformation in live animals. The studies of Lopezde-Torre et al. (1991) and Conington et al. (1998)
reported low heritability (