Carcass traits, cut yields, and compositional end points in high-lean-yielding
pork carcasses: Effects of 10th rib backfat and loin eye area1
T. D. Pringle2 and S. E. Williams
Animal and Dairy Science Department, The University of Georgia, Athens 30602-2771
ABSTRACT: Pork carcasses (n = 133) were used to
investigate the influence of carcass fatness and muscling on composition and yields of pork primal and subprimal cuts fabricated to varying levels of s.c. fat. Carcasses were selected from commercial packing plants
in the southeastern United States, using a 3 × 3 factorial
arrangement with three levels of 10th rib backfat depth
(< 2.03, 2.03 to 2.54, and > 2.54 cm) and three levels of
loin eye area (LEA; < 35.5, 35.5 to 41.9, and > 41.9 cm2).
Sides from the selected carcasses were shipped to the
University of Georgia for carcass data collection by
trained USDA-AMS and University of Georgia personnel and fabrication. Sides were fabricated to four lean
cuts (picnic shoulder, Boston butt, loin, and ham) and
the skinned belly. The four lean cuts were further fabricated into boneless cuts with s.c. fat trim levels of 0.64,
0.32, and 0 cm. The percentages of four lean cuts, boneless cuts (four lean cuts plus skinned, trimmed belly)
at 0.64, 0.32, and 0 cm s.c. fat, fat-free lean, and total
fat were calculated. Data were analyzed using a least
squares fixed effects model, with the main effects of
10th rib backfat and LEA and their interaction. Fatness
and muscling traits increased (P < 0.05) as 10th rib
backfat and LEA category increased, respectively. However, fat depth measures were not affected greatly by
LEA category, nor were muscling measures greatly affected by backfat category. The percentage yield of cuts
decreased (P < 0.05) as backfat category increased. Cut
yields from the picnic shoulder, Boston butt, and belly
were not affected (P > 0.05) by LEA category, whereas
the yield of boneless loin and ham increased (P < 0.05)
as LEA category increased. Compositionally, the percentage of four lean cuts, boneless cuts at varying trim
levels, and fat-free lean decreased incrementally (P <
0.05) as backfat depth increased, whereas parentage
total fat and USDA grade increased (P < 0.05) as backfat
depth increased. As LEA increased, percentage boneless cuts trimmed to 0.32 and 0 cm s.c. fat and fat-free
lean increased and total fat decreased; however, the
difference was only significant in the smallest LEA category. Collectively, these data show that decreased carcass fatness plays a greater role in increasing primal
and subprimal cut yields and carcass composition than
muscling even in lean, heavily muscled carcasses.
Key Words: Carcass Composition, Fat, Muscle, Pork
2001 American Society of Animal Science. All rights reserved.
Introduction
J. Anim. Sci. 2001. 79:115–121
stagnant market share, as consumers have been shown
to prefer meat products with minimal amounts of
trimmable fat (Savell et al., 1989). The pork industry,
however, has made great strides to reduce the fat content and improve the leanness of pork. One reason for
this improvement has been the pork industry’s ability
to effectively communicate enhanced value of leanness
down the marketing chain from consumers to producers. As technological and genetic tools to reduce fat in
pigs improve, and resulting lean meat yields increase,
it is important to understand the interrelationships between fat, muscling, and carcass value traits. This
allows continuous updating of carcass or value-based
pricing systems and ensures a consistent and uniform
message is being sent across the entire pork marketing
chain. Thus, this project was designed to determine
primal and subprimal cut yields and carcass compositional end points in pork carcasses varying in fatness
The Pork Chain Quality Audit indicated leanness
was one of the major packer/processor quality-related
problems in the industry (Cannon et al., 1996). At the
packer level, insufficient leanness accounted for over
75% of the total defect costs. The excess fat content of
retail pork products has been associated with pork’s
1
The authors would like to thank the Georgia Dept. of Agric.,
Animal Ind. Div. and the Agric. Marketing Serv. of the USDA for
financial support of this project. We also appreciate the assistance
of Ernie Morgan and Terry Harris in selecting carcasses and their
input into planning of this project.
2
Correspondence: 212 Animal Science Complex (phone: 706-5420997; fax: 706-542-0399; E-mail: [email protected]).
Received March 14, 2000.
Accepted August 18, 2000.
115
116
Pringle and Williams
and muscling, emphasizing carcasses with high lean
yields.
Materials and Methods
Carcass Selection. One hundred thirty-three pork carcasses were selected from four packers: Gwaltney of
Smithfield, Smithfield, VA; ConAgra, Louisville, KY;
Bryan Foods, West Point, MS; and Lowell Packing, Fitzgerald, GA. Pork carcasses were selected within 24 h
postmortem based on 10th rib backfat depth and loin
eye area (LEA) by University of Georgia and USDAAMS market news personnel. Carcasses were selected
in three 10th rib backfat depth categories (< 2.03, 2.03
to 2.54, and > 2.54 cm), and within each fat category
carcasses were selected in three LEA categories (< 35.5,
35.5 to 41.9, and > 41.9 cm2). Carcass sex and weight
were allowed to randomly vary in the selected carcass
population and no genetic information was collected on
the selected carcasses. For selection, backfat depth and
LEA were measured using an optical grading probe
in plants with a Fat-O-Meter system (SFK Limited,
Hvidovre, Denmark) or ultrasound (Aloka 500-V, Corometrics Medical Systems, Wallingford, CT) in plants
without an optical grading probe system. These selection criteria resulted in a leaner population of carcasses
(56% USDA #1; 20% USDA #2; 11% USDA #3; and
13% USDA #4) than the national USDA grade consist
specified in Berg et al. (1999). Immediately after selection, carcasses were tagged for identification and USDA
muscle score and ham muscle score was evaluated using
a 3-point muscle score system (1 = thin, 2 = average, 3
= thick; USDA, 1985) recorded to the nearest tenth
degree by market news personnel. Within 48 h postmortem, the right side of each carcass was shipped via
refrigerated transport (2 to 4°C) to the University of
Georgia meat plant in Athens, GA.
Carcass Data Collection. Upon arrival at the University of Georgia, first rib, last rib, last lumbar vertebra,
and belly pocket (measured at a point in the center of
the flank, rectus abdominis) fat depth, and belly thickness and carcass length were measured. Thirty minutes
before fabrication, each side was ribbed between the
10th and 11th ribs and backfat depth (measured 3/4
the length of the longissimus muscle from the chine
bone) was measured and the longissimus muscle area
was traced. Loin eye area and loin eye depth (thickness
of the longissimus muscle measured through the center
of the muscle) were determined from the tracings using
a Sigma Scan digitizing tablet (Jandel Scientific, Corte
Madre, CA).
Carcass Fabrication. After carcass measurements
were recorded, each side was fabricated into bone-in
and boneless primals and subprimals, according to the
procedures outlined for fresh pork by the National Association of Meat Purveyors (NAMP, 1997). Briefly, the
diaphragm, membrane wing of the diaphragm, kidney,
and the tail (between the first and second coccygeal
vertebrae) were removed and weighed. Adjusted side
weight was recorded and the front and hind foot were
removed at the upper hock joint, whereas the jowl was
removed from a point measured 2.54 cm from the posterior edge of the ear dip. The jowl was skinned and the
fore and hind foot, the skinless jowl, and the jowl skin
were weighed. Each side was then fabricated into the
four lean cuts (401 fresh ham, 405 picnic shoulder, 406
Boston butt, and 410 loin), 408 belly, and 416 spareribs
using the procedures described by NAMP (1997). The
shoulder was separated from the loin and belly by a
straight cut between the second and third ribs. The
Boston butt and picnic shoulder were separated by a
cut approximately 2.54 cm ventral to the ventral edge
of the scapula. The loin and belly were separated from
the ham by a straight cut between the second and third
sacral vertebrae approximately perpendicular to the
shank bones. The loin and belly were separated by a
cut beginning immediately ventral to the scapula on
the anterior end and continuing to the ventral edge of
the psoas major muscle on the posterior end, following the natural curvature of the chine bone.
Each primal, fat trim, bone, and skin were weighed.
The 401 fresh ham was then fabricated into a 402 fresh
ham, skinned, and trimmed to 1.27 cm s.c. fat. The
402 ham and skin were weighed and the 402 ham was
fabricated into the boneless inside ham (semimembranosus, gracillis, and adductor), outside ham (semitendinosus and biceps femoris), knuckle (vastus intermedius, vastus lateralis, tensor fasciae, and vastus medialis), light butt (gluteus medius), heel, and inner shank
muscles. The skin, fat trim, and bone were weighed. The
ham muscle groups were weighed individually (1.27 cm
s.c. fat) and progressively trimmed to 0.64, 0.32, and 0
cm s.c. fat trim, weighing the muscle groups and fat
trim between each step.
The 405 picnic shoulder was fabricated into a 405A
picnic shoulder, boneless, and a 405B picnic shoulder
cushion (triceps brachii), boneless. Picnic shoulder subprimals, bone, lean trim, and corresponding skin were
weighed. The picnic shoulder subprimals were further
trimmed of s.c. fat to 0.64, 0.32, and 0 cm, weighing
the subprimal and fat trim between each step.
The 406 Boston butt was fabricated into a 406A Boston butt, boneless and weighed along with the bone.
The 406A Boston butt was further fabricated into the
407 Boston butt, cellar, and lean trim, recording
weights for each. The 407 Boston butt was trimmed of
s.c. fat to 0.64, 0.32, and 0 cm, weighing the 407 Boston
butt and fat trim between each step.
The 410 loin was fabricated into a 411 loin, bladeless,
and weights were recorded for the 411 loin, blade bone,
and lean and fat trimmings. The 411 loin was fabricated
into a 412D loin, 11 rib center cut, chine bone off; blade
end; and sirloin end and each subprimal was weighed.
The psoas major muscle was removed from the 412D
and the sirloin end, trimmed to 0 cm fat, and weighed.
The 412D loin, blade end, and sirloin end were deboned
to form a 412E center cut loin, boneless, a boneless
blade, and a boneless sirloin, respectively. The 412E
Fat and muscling effects on pork composition
center cut loin, boneless blade, boneless sirloin, bone,
and lean trim were weighed. The 412E center cut loin,
boneless blade, and boneless sirloin were further
trimmed of s.c. fat to 0.64, 0.32, and 0 cm and the
trimmed subprimals and fat trim were weighed between each step.
The 408 belly was skinned to form a 409 belly and
the 409 belly and skin were weighed.
Chemical Analyses. After fabrication, the defatted
muscles and all lean trimmings from each side were
combined, hand-mixed and coarsely (1.27-cm plate)
ground (Hobart 4046, Troy, OH), and a 1-kg sample
was removed for proximate analysis. The sample was
vacuum-packaged, frozen at −20°C and stored frozen at
−20°C for subsequent fat and moisture determination.
Prior to fat and moisture analysis (less than 3 mo frozen
storage), the samples were thawed at 2°C for 18 h and
homogenized (Robot Coupe, model 27/01713,
Ridgeland, KS). Following homogenization, lean tissue
samples were weighed (≈1.0 g), in duplicate, and dried
at 90°C for 48 h to determine moisture content (AOAC,
1990). Lipid content was determined on duplicate subsamples of homogenized lean tissue samples using the
chloroform-methanol procedure outlined by Folch et al.
(1957). In brief, samples (≈2.5 g) were homogenized in
15 mL of methanol:chloroform (2:1) solution and allowed to stand for 1 h. Five milliliters each of chloroform
and 1 M KCl were added to the mixture and vortexed.
Samples were stored in an ice bath for 10 min and
centrifuged for 10 min at 20 × g. The aqueous phase
was aspirated and the organic phase was transferred
to preweighed, dried aluminum pans. The samples were
evaporated overnight to dryness, in a hood, and weighed
to determine lipid content.
Cut Yields and Compositional End Points. Primal and
boneless subprimal cut yields are expressed as a percentage of adjusted side weight. The picnic shoulder
and Boston butt cut weights used were those recorded
during fabrication. For the boneless loin, weights for the
psoas major muscle and 412E center cut loin, boneless
blade, and boneless sirloin at 0.64, 0.32, or 0 cm s.c.
fat trim, respectively, were summed. Weight for the
boneless ham at 0.64, 0.32, or 0 cm s.c. fat trim was
the summation of the weights for the inside ham, outside ham, knuckle, light butt, heel, and shank muscle
groups at the respective level of s.c. fat trim. Compositional end points were calculated as described in Table 1.
Statistical Analysis. Carcass measures, cut yields,
and compositional end points were analyzed using a
least squares fixed effects model that included backfat
and LEA categories as main effects, as well as their
interaction (SAS Inst., Inc., Cary, NC). There were no
significant interactions between backfat and LEA in the
analysis. Least squares means were generated using
LSMEANS, and when the F-statistic for a main effect
was P < 0.05 the LSMEANS for that effect were separated using the PDIFF procedure of SAS.
117
Results and Discussion
Carcass Measures. Fat categories in this study were
selected to allow for a direct comparison of very lean
and lean pork carcasses within the USDA #1 grade with
pork carcasses in the other USDA grade categories.
Thus, these data should not be misconstrued as representative of the averages for the current U.S. pork carcass population. As expected, first rib, last rib, last lumbar vertebra, and 10th rib backfat depth increased (P
< 0.05) on carcasses as 10th rib backfat thickness category increased (Table 2). Side weight was greater (P <
0.05) in the fattest backfat category than in either of the
leaner categories; however, belly thickness and belly
pocket fat thickness were only different (P < 0.05) between carcasses in the leanest category (< 2.03 cm) and
the two fatter categories, and carcasses in the 2.03 to
2.54 and > 2.54 cm groups were similar (P > 0.05).
Neither carcass length, loin eye area, nor loin eye depth
was affected (P > 0.05) by backfat category; however,
carcasses in the leanest category had higher (P < 0.05)
carcass and ham muscle scores than carcasses in the
two fatter groups. These data agree with Neely et al.
(1979), who reported that carcass length and LEA were
similar in carcasses from lean and fat genetic lines;
however, they also reported that carcass weight was
not affected by genetic line.
Side weight and carcass length increased incrementally (P < 0.05) as LEA category increased (Table 3),
and carcasses in the largest LEA category (> 41.9 cm2)
had significantly greater depths of last rib backfat than
carcasses in the smallest LEA group. However, other
fat measures did not support this finding. As anticipated from the design of this study, LEA and loin eye
depth increased incrementally (P < 0.05) as LEA category increased, whereas USDA carcass and ham muscle
scores were significantly greater in the two largest LEA
groups than in the smallest LEA group.
Primal and Subprimal Cut Yields. Carcass yields of
bone-in picnic shoulder, Boston butt, and ham primal
cuts decreased incrementally (P < 0.05) as backfat category increased (Table 4), but only the fattest carcasses
generated reduced yields for bone-in loin compared to
the other backfat subclasses. In contrast, the yield of
trimmed belly increased as backfat category increased.
As the primal cuts were deboned and trimmed to 0.64,
0.32, and 0 cm s.c. fat, the differences in cut yields
across backfat categories were maintained. Martin et
al. (1981) reported similar decreases in yields of picnic
shoulder, Boston butt, ham, and loin and increased
yields of belly as carcass fatness increased, whereas
other studies have reported decreased carcass lean
yield as carcass fatness increased (Cross et al., 1975;
Orcutt et al., 1990; Berg et al., 1999). However, most
of the carcasses represented in those studies were substantially fatter, on average, than those in the current study.
Unlike the findings for backfat categories, LEA category did not affect (P > 0.05) the percentage yield of
118
Pringle and Williams
Table 1. Description of compositional end points
End point
Description
Four lean cuts, %
Boneless cuts with 0.64 cm fat trim, %b
Boneless cuts with 0.32 cm fat trim, %b
Boneless cuts with 0 cm fat trim, %b
Fat free lean, %
Total fat, %
Lean meat ratio
USDA grade
Muscle:bone
=
=
=
=
=
=
=
=
=
(bone-in four lean cuts weight with 1.27 cm s.c. fat/ASWa) × 100%
(boneless subprimals weight with 0.64 cm s.c. fat/ASW) × 100%
(boneless subprimals weight with 0.32 cm s.c. fat/ASW) × 100%
(boneless subprimals weight with 0 cm s.c. fat/ASW) × 100%
(fat free lean weight/ASW) × 100%
(trimmed and chemical fat weight/ASW) × 100 %
58.85 − (0.61 × 10th rib backfat, mm) + (0.12 × loin muscle depth, mm)
(4 × last rib fat depth, inches) − (1 × USDA muscle score)
(fat free lean weight/bone weight)
a
ASW = adjusted side weight, weight of the side following removal of the diaphragm, membrane wing of the diaphragm, kidney, and tail
(separated between the first and second coccygeal vertebrae).
b
The belly and jowl cuts were the only boneless subprimals included not trimmed to the stated fat trim level.
Table 2. Least squares means for carcass measures across
10th rib backfat depth categories
10th rib backfat depth, cm
Dependent variable
n
Adjusted side weight, kg
First rib fat depth, cm
Last rib fat depth, cm
Last lumbar vertebrae fat depth, cm
Tenth rib backfat depth, cm
Belly thickness, cm
Belly pocket fat depth, cm
Carcass length, cm
Loin eye area, cm2
Loin eye depth, mm
Carcass muscle scorea
Ham muscle scorea
<2.03
SEM
2.03–
2.54
SEM
>2.54
SEM
60
37.1b
3.45b
1.83b
1.37b
1.48b
1.96b
2.49b
81.4
39.4
52.7
267b
273b
—
0.53
0.10
0.08
0.05
0.05
0.08
0.10
0.38
0.45
0.64
2.6
2.8
31
38.5b
3.96c
2.47c
1.93c
2.31c
2.51c
3.02c
80.8
38.7
52.1
255c
261c
—
0.85
0.15
0.12
0.10
0.08
0.13
0.15
0.61
0.72
1.03
4.1
4.5
42
43.8c
4.73d
3.52d
2.74d
3.31d
2.77c
2.90c
82.1
38.6
53.2
254c
261c
—
0.62
0.10
0.09
0.08
0.06
0.08
0.10
0.43
0.53
0.75
3.0
3.2
100 = thin; 200 = average; 300 = thick.
Means in the same row with different superscripts differ (P < 0.05).
a
b,c,d
Table 3. Least squares means for carcass measures across loin eye area categories
Loin eye area, cm2
Dependent variable
n
Adjusted side weight, kg
First rib fat depth, cm
Last rib fat depth, cm
Last lumbar vertebra fat depth, cm
Tenth rib fat depth, cm
Belly thickness, cm
Belly pocket fat depth, cm
Carcass length, cm
Loin eye area, cm2
Loin eye depth, mm
Carcass muscle scorea
Ham muscle scorea
< 35.5
SEM
35.5–
41.9
SEM
> 41.9
SEM
33
35.5b
4.22
2.42b
1.96
2.41
2.31
2.64
79.6b
31.3b
44.2b
249b
254b
—
0.83
0.13
0.12
0.10
0.07
0.10
0.15
0.58
0.70
1.00
4.0
4.3
52
40.1c
3.84
2.59bc
2.06
2.35
2.44
2.90
81.7c
38.6c
52.6c
262c
270c
—
0.58
0.10
0.08
0.08
0.05
0.08
0.10
0.41
0.49
0.70
2.8
3.0
48
43.9d
4.09
2.82c
2.03
2.34
2.49
2.87
83.0d
46.8d
61.2d
264c
271c
—
0.62
0.10
0.09
0.08
0.06
0.08
0.10
0.43
0.53
0.75
3.0
3.2
100 = thin; 200 = average; 300 = thick.
Means in the same row with different superscripts differ (P < 0.05).
a
b,c,d
119
Fat and muscling effects on pork composition
Table 4. Least squares means for the yield of primal and boneless subprimal cuts,
trimmed to varying levels of subcutaneous fat and expressed as a percentage
of adjusted side weight, across 10th rib backfat depth categories
10th rib backfat depth, cm
2.03–
2.54
Primal and subprimal cutsa
< 2.03
n
60
Bone-in PS with 1.27 cm s.c. fat
Boneless PS with 0.64 cm s.c. fat
Boneless PS with 0.32 cm s.c. fat
Boneless PS with 0 cm s.c. fat
13.33d
10.66d
10.43d
10.13d
0.17
0.14
0.14
0.13
12.72e
10.03e
9.82e
9.41e
0.27
0.22
0.22
0.21
11.42f
8.94f
8.78f
8.38f
0.20
0.16
0.16
0.15
Bone-in BB with 0.64 cm s.c. fat
Boneless BB with 0.64 cm s.c. fat
Boneless BB with 0.32 cm s.c. fat
Boneless BB with 0 cm s.c. fat
9.52d
7.50d
7.23d
6.85d
0.11
0.09
0.09
0.08
8.87e
7.05e
6.78e
6.38e
0.17
0.15
0.15
0.13
8.26f
6.56f
6.30f
5.94f
0.12
0.11
0.11
0.09
11.67d
SEM
—
31
SEM
—
> 2.54
42
SEM
—
0.21
12.37d
0.33
13.21e
0.24
Bone-in, full loin with 0.64 cm s.c. fat
Boneless loin with 0.64 cm s.c. fatb
Boneless loin with 0.32 cm s.c. fat
Boneless loin with 0 cm s.c. fat
d
23.14
17.58d
16.47d
14.86d
0.21
0.17
0.16
0.15
d
22.54
17.21d
15.72e
14.12e
0.34
0.28
0.25
0.24
e
21.44
16.28e
14.90f
13.55f
0.24
0.20
0.18
0.17
Bone-in, ham with 1.27 cm s.c. fat
Boneless ham with 0.64 cm s.c. fatc
Boneless ham with 0.32 cm s.c. fat
Boneless ham with 0 cm s.c. fat
26.07d
20.28d
19.53d
18.44d
0.16
0.17
0.17
0.16
24.50e
18.17e
17.27e
16.11e
0.26
0.27
0.28
0.26
23.46f
16.76f
15.90f
14.83f
0.19
0.20
0.20
0.19
Skinless belly
PS = picnic shoulder; BB = Boston butt.
Boneless loin at varying s.c. fat depths was calculated by summing the weights of the center cut loin,
blade end, and sirloin end at varying fat depths and the short tender and butt tender, expressed as a
percentage of side weight.
c
Boneless ham at varying s.c. fat depths was calculated by summing the weights for the inside, outside,
knuckle, light butt, and shank, expressed as a percentage of side weight.
d,e,f
Means in the same row with different superscripts differ (P < 0.05).
a
b
bone-in primal cuts (Table 5). However, fabrication of
the loin and ham to boneless cuts with varying levels
of s.c. fat resulted in significant differences in yields
across LEA groups. For boneless cut yields with varying
trim levels from the ham, the lightest-muscled group
had lower yields (P < 0.05) than the two heavier-muscled groups (Table 5). However, for boneless loin
trimmed to 0.64 cm s.c. fat, the yield was greater (P <
0.05) in the largest LEA category than in the two
smaller LEA categories. Further trimming to 0.32 or 0
cm s.c. fat resulted in differences (P < 0.05) across all
LEA categories for boneless loin yields. These data imply that increased muscling, as evidenced by differences
in LEA, had a greater effect on boneless subprimal cut
yields from the loin and ham than cut yields from the
picnic shoulder and Boston butt, particularly when the
loin and ham primals had less than 0.64 cm fat trim.
Compositional End Points. Table 6 contains the means
of compositional traits by backfat groups. As backfat
category increased, percentages of four lean cuts, boneless cuts (at all trim levels), fat-free lean, and the lean
meat ratio all decreased, each backfat class being different (P < 0.05) from the others. Conversely, percentage
total fat and USDA grade increased incrementally (P
< 0.05) as backfat class increased. Furthermore, carcass
bone and skin percentages decreased as fat category
increased. The decrease in bone and skin percentages
is a result of the inverse relationship between fat and
these two tissues. Fat is a late-maturing tissue and
grows at a proportionally faster rate than the earlymaturing skin and bone tissues, resulting in a dilution
effect for them relative to adjusted side weight (Berg
and Butterfield, 1976). The only end point not affected
(P > 0.05) by backfat category was the muscle:bone
ratio, substantiating the findings for LEA and loin eye
depth (Table 2). It is also noteworthy that although the
majority (> 80%) of the pork carcasses in the two leanest
backfat classes would be classified as USDA #1, there
was more than a 5% difference in percentage fat-free
lean and total fat and more than a 3% difference in all
other measured compositional end points between the
< 2.03- and the 2.03- to 2.54-cm categories.
In agreement with findings for the yields of individual
bone-in primals (Table 5), percentage of four lean cuts
was not affected (P > 0.05) by LEA category (Table 7).
This suggests that muscling had little influence on
bone-in primal cut yields. It was interesting that USDA
grade, which predicts percentage of four lean cuts, increased significantly as LEA category increased. The
increase in USDA grade is related to differences in last
rib backfat depth across LEA group, noted earlier (Table 3); although these findings seem somewhat contradictory, the differences in USDA grade were minimal.
Yields in the smallest LEA group were lower (P < 0.05)
for the percentage boneless cuts with 0 cm s.c. fat and
percentage fat-free lean and higher (P < 0.05) for per-
120
Pringle and Williams
Table 5. Least squares means for the yield of primal and boneless subprimal cuts,
trimmed to varying levels of subcutaneous fat and expressed as a percentage of
adjusted side weight, across loin eye area categories
Loin eye area, cm2
35.5–
41.9
Primal and subprimal cutsa
> 35.5
n
33
Bone-in PS with 1.27 cm s.c. fat
Boneless PS with 0.64 cm s.c. fat
Boneless PS with 0.32 cm s.c. fat
Boneless PS with 0 cm s.c. fat
12.66
9.89
9.68
9.25
0.26
0.22
0.21
0.20
12.43
9.89
9.70
9.31
0.18
0.15
0.15
0.14
12.37
9.85
9.65
9.36
0.19
0.16
0.16
0.15
Bone-in BB with 0.64 cm s.c. fat
Boneless BB with 0.64 cm s.c. fat
Boneless BB with 0.32 cm s.c. fat
Boneless BB with 0 cm s.c. fat
8.88
7.04
6.73
6.31
0.16
0.15
0.14
0.12
8.77
6.94
6.69
6.33
0.11
0.10
0.10
0.09
9.00
7.12
6.88
6.53
0.12
0.11
0.11
0.09
Skinless belly
12.58
0.32
12.61
0.22
12.06
0.24
Bone-in, full loin with 0.64 cm s.c. fat
Boneless loin with 0.64 cm s.c. fatb
Boneless loin with 0.32 cm s.c. fat
Boneless loin with 0 cm s.c. fat
21.92
16.49d
15.11d
13.47d
0.33
0.27
0.25
0.23
22.35
16.99d
15.70e
14.20e
0.23
0.19
0.17
0.16
22.84
17.59e
16.29f
14.87f
0.24
0.20
0.18
0.17
Bone-in, ham with 1.27 cm s.c. fat
Boneless ham with 0.64 cm s.c. fatc
Boneless ham with 0.32 cm s.c. fat
Boneless ham with 0 cm s.c. fat
24.53
17.90d
17.02d
15.83d
0.25
0.26
0.27
0.25
24.83
18.68e
17.85e
16.72e
0.17
0.18
0.19
0.17
24.67
18.62e
17.82e
16.83e
0.19
0.20
0.20
0.19
SEM
—
52
SEM
—
> 41.9
48
SEM
—
PS = picnic shoulder; BB = Boston butt.
Boneless loin at varying s.c. fat depths was calculated by summing the weights of the center cut loin,
blade end, and sirloin end at varying fat depths and the short tender and butt tender, expressed as a
percentage of side weight.
c
Boneless ham at varying s.c. fat depths was calculated by summing the weights for the inside, outside,
knuckle, light butt, and shank, expressed as a percentage of side weight.
d,e,f
Means in the same row with different superscripts differ (P < 0.05).
a
b
centage of total fat and bone than the two larger LEA
categories. As expected, the lean meat ratio and muscle:bone ratio increased incrementally (P < 0.05) as LEA
category increased.
Although differences were noted in compositional end
points across both backfat and LEA categories, the differences were of greater magnitude across backfat cate-
gories. In general, the differences in end points across
all LEA groups (Table 7) were less than the differences
between adjacent backfat categories (Table 6) for the
same end points. This finding agrees with previous research on the influence of pork carcass fatness and
muscling on percentage carcass yields (Cross et al.,
1975; Orcutt et al., 1990; Berg et al., 1999); however,
Table 6. Least squares means for compositional end points across
10th rib backfat depth categories
10th rib backfat depth, cm
End pointsa
< 2.03
SEM
2.03–
2.54
SEM
> 2.54
SEM
n
Four lean cuts, %
Boneless cuts at 0.64 cm trim, %b
Boneless cuts at 0.32 cm trim, %b
Boneless cuts at 0 cm trim, %b
Fat free lean, %
Total fat, %
Bone, %
Skin, %
Lean meat ratio
USDA grade
Muscle:bone ratio
60
71.68c
69.04c
66.74c
63.37c
58.57c
18.13c
8.18c
4.07c
56.16c
0.80c
7.17
—
0.30
0.30
0.30
0.29
0.42
0.43
0.10
0.09
0.29
0.12
0.12
31
68.27d
66.53d
63.60d
60.03d
52.96d
25.71d
7.53d
3.87cd
51.00d
1.88d
7.10
—
0.48
0.51
0.51
0.48
0.71
0.72
0.16
0.15
0.47
0.20
0.20
42
64.27e
63.30e
60.67e
57.59e
49.88e
30.16e
6.86e
3.67d
45.07e
3.50e
7.50
—
0.35
0.36
0.36
0.35
0.51
0.53
0.12
0.10
0.34
0.14
0.14
a
For description of compositional end points see Table 1.
The belly and jowl cuts were the only boneless subprimals not trimmed to the stated fat trim level.
Means in the same row with different superscripts differ (P < 0.05).
b
c,d,e
121
Fat and muscling effects on pork composition
Table 7. Least squares means for compositional end points
across loin eye area categories
Loin eye area, cm2
End pointsa
< 35.5
SEM
35.5–
41.9
SEM
> 41.9
SEM
n
Four lean cuts, %
Boneless cuts at 0.64 cm trim, %b
Boneless cuts at 0.32 cm trim, %b
Boneless cuts at 0 cm trim, %b
Fat free lean, %
Total fat, %
Bone, %
Skin, %
Lean meat ratio
USDA grade
Muscle:bone ratio
33
67.62
65.69
62.86c
59.19c
51.98c
26.15c
7.87c
3.92
49.47c
1.81c
6.69c
—
0.46
0.50
0.50
0.47
0.69
0.71
0.16
0.14
0.45
0.19
0.19
52
68.05
66.50
63.94cd
60.63d
54.18d
24.35d
7.45d
3.74
50.85d
2.00cd
7.37d
—
0.32
0.34
0.33
0.32
0.47
0.49
0.11
0.10
0.32
0.13
0.13
48
68.55
66.68
64.21d
61.17d
55.26d
23.51d
7.25d
3.95
51.91e
2.36d
7.72e
—
0.35
0.35
0.35
0.33
0.49
0.49
0.12
0.10
0.34
0.14
0.13
a
For description of compositional end points see Table 1.
The belly and jowl cuts were the only boneless subprimals not trimmed to the stated fat trim level.
c,d,e
Means in the same row with different superscripts differ (P < 0.05).
b
Powell et al. (1983) and Orcutt et al. (1990) reported
that LEA had a greater influence than backfat on compositional end points defined on a weight basis. Although LEA did not have as great an impact on composition as backfat, it still had a significant influence on
most pork carcass compositional end points and thus
carcass value, suggesting that muscling should be accounted for as a value determinant in pork.
Implications
Results from this study showed that fatness and muscling can be selected for independently and that fatness
continues to be the most important determinant of cut
and carcass yields, even in very lean, heavily muscled
carcasses. However, muscling does contribute significantly to carcass value and may become a more important contributor to lean value differences in market
hogs as the swine industry continues to increase muscling and reduce fatness. It is also obvious from these
data that the current USDA slaughter hog system does
not adequately segregate carcasses based on compositional differences and needs revision in order for the
swine industry to enhance communication of value
throughout the marketing chain.
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