Relationship between sire tenderness EPD and progeny carcass performance
J. Bolsen, J. Minick Bormann, D. W. Moser, T. T. Marston
ABSTRACT: The objectives of this study were to determine how well a bull’s WarnerBratzler shear force (WBSF) Expected Progeny Difference (EPD) actually predicted his
progeny’s carcass performance, and to evaluate the effect of selection for WBSF EPD on
other carcass measurements. In 2002, eight Hereford bulls with divergent WBSF EPD
were mated randomly to crossbred cows. These EPD were developed from the NCBA
Carcass Merit Project, and the accuracies ranged from 0.20 to 0.43. Steers, bulls, and
cull heifers that were weaned in two groups were fed out and harvested with complete
carcass data collected. Measurements collected on all cattle (n = 98) included dressing
percent (DP), hot carcass weight (HCW), ribeye area (REA), 12-13th rib fat thickness
(FT), marbling score (MS), kidney pelvic heart fat (KPH), and yield grade (YG). A subset of cattle (n = 39) were evaluated for tenderness and sensory traits, including WarnerBratzler shear force (WBSF), myofibril tenderness (MT), overall tenderness (OT), color
(CO), purge loss (PL), juiciness (JU), flavor (FL), and average pH (PH). Data were
analyzed using the GLM procedure of SAS. The model for all carcass and sensory traits
included fixed effects of weaning group, sex, harvest group, and sire EPD level. Sire
WBSF EPD level did not have an effect (P > 0.05) on WBSF, MT, OT, CO, PL, JU, FL,
or PH. Low accuracies on the sire EPD and small progeny numbers probably contributed
to the lack of difference in tenderness between EPD levels. The regression of actual sire
WBSF EPD on progeny WBSF was 0.33 ± 0.44. In the larger data set, DP, HCW, REA,
FT, MS, KPH, and YG were unaffected (P > 0.05) by sire WBSF EPD level. These
results from a larger sample of progeny indicate that selection on tenderness EPD should
not affect other carcass traits.
Introduction
In today's consumer demand driven market economy, livestock producers have to
increase the quality of product they are producing. One quality that producers are trying
to capitalize on is producing a tender cut of meat, without sacrificing various other traits.
In order to do so there has been a push by producers to develop carcass EPD calculations.
The purpose of this study was to determine the correlation between a bull’s WarnerBratzler shear force (WBSF) EPD and his progeny’s actual Warner-Bratzler shear force
tenderness. It also looked at how a bull’s WBSF EPD may have affected the progeny’s
other carcass data and performance.
Materials and Methods
Bulls were selected with divergent WBSF EPD. Based upon their WBSF EPD,
the sires were categorized as either tender or tough (Table 1). The sires were mated
randomly to commercial Angus-based cows at the KSU Cow-calf unit.
Offspring were reared in two locations on native range pastures. Calves were
then categorized into two weaning types; early weaned and normal weaned. Upon
weaning, some bulls were castrated, and some were left intact. Calves were fed out at
two locations, and harvested in seven groups. Complete carcass data, including hot
carcass weight (HCW), dressing percent (DP), marbling score (MS), ribeye area (REA),
kidney-pelvic-heart fat (KPH), yield grade (YG), and 12-13th rib back fat (BF) was
collected on 104 head (20 bulls, 54 steers, and 30 heifers). A subset of 40 cattle (20
steers and 20 bulls) were evaluated for WBSF, purge loss, average pH, color, and taste
panel traits of myofibril tenderness, juiciness, flavor. For simplicity, these datasets will
be referred to as carcass dataset and quality dataset.
Warner-Bratzler shear forces were measured according to Lawrence et al. (2004).
Sensory panel analysis included color (visual and L*), myofibril tenderness, juiciness,
flavor, and average pH. Color was examined visually, by a panel of trained color judges.
Steaks were scored on a scale of one to eight (1 = bleached red, 2 = Very light cherry red,
3 = moderately light red, 4 = bright cherry red, 5 = slight dark red, 6 = moderately dark, 7
= dark red, 8 = very dark red) (Lawrence et al., 2004). The instrumental measurement for
L* scores lightness verses darkness, where lower number are darker. An eight point scale
was used to evaluate myofibril tenderness, and overall tenderness (1 = extremely tough, 2
= very tough, 3 = moderately tough, 4 = slightly tough, 5 = slightly tender, 6 =
moderately tender, 7 = very tender, 8 = extremely tender); juiciness (1 = extremely dry, 2
= very dry, 3 = moderately dry, 4 = slightly dry, 5 = slightly juicy, 6 = moderately juicy,
7 = very juicy, 8 = extremely juicy); and flavor (1 = extremely bland, 2 = very bland, 3 =
moderately bland, 4 = slightly bland, 5 = slightly intense, 6 = moderately intense, 7 =
very intense, 8 = extremely intense). Steaks were weighed before packaging and after a
14-day aging period. Purge loss was the percentage weight lost by the steaks over that
period.
Both data sets were analyzed by the GLM procedure of SAS (SAS, 2000). Fixed
effects included weaning category, harvest group (which included feeding location), sex,
and sire type (tender or tough). Harvest age was included as a covariate. WBSF was also
analyzed by a second model, where individual sire was used as a fixed effect instead of
sire type. This model was also used to perform a linear regression of progeny WBSF on
sire WBSF EPD.
Results and Discussion
Means, standards deviations, minimums, and maximums for carcass traits and
quality traits are shown in Tables 2 and 3. In the carcass dataset, significant fixed effects
(P < 0.05) were: weaning category for DP, HCW, BF, KPH, and YG; sex for DP, HCW,
REA, and YG; and kill group for DP, HCW, REA, and KPH (Table 4). As expected,
bulls had the highest DP and HCW, the largest REA, and lowest YG. Heifers had the
lowest DP, lightest HCW, smallest REA, and highest YG. Steers were intermediate to
bulls and heifers for the carcass traits. Early weaned calves had higher DP and HCW
than conventionally weaned calves. In addition, they exhibited more overall fatness with
increased BF and KPH, and higher YG. The covariate of age at harvest was a significant
effect (P < 0.05) for YG only. Sire type (tough or tender) did not significantly affect (P >
0.05) any of the carcass traits. However, calves sired by tender EPD sires tended (P <
0.10) to have greater BF than calves sired by tough EPD sires.
In the quality dataset, sex was a significant effect (P < 0.05) for WBSF, color, L*,
myofibril tenderness, overall tenderness, and average pH (Table 5). In general, steaks
from steers were more tender, lighter colored, and had a lower average pH. The only
variable influenced (P < 0.05) by weaning category was color. Early weaned calves had
lighter colored steaks than conventionally weaned calves. Sire type was of no
significance (P > 0.05) for any trait except purge loss (P = 0.03). Steaks from calves
sired by tough sires lost more water than steaks from calves sired by tender sires.
Least squares means by sire for WBSF are shown in Table 6. Sire significantly
affected WBSF, however sires did not rank as expected from their EPD. The linear
regression of sire EPD on progeny WBSF was 0.33 ± 0.44 (P = 0.4620). This regression
would be expected to be 1 if the EPD is doing a good job of predicting progeny
performance. These results are probably due to the relatively low accuracies of the EPD
and the low numbers of progeny per sire evaluated. The re-ranking of sires explains why
there was no difference (P > 0.05) in WBSF between calves sired by tough bulls and
calves sired by tender bulls. On a larger number of progeny, sire type did not affect any
of the carcass traits. This would indicate that producers can select on WBSF EPD
without negatively impacting carcass characteristics.
Implications
In this study, there was no difference in WBSF between calves sired by tender
EPD bulls and tough EPD bulls. Low sire accuracy and low progeny number per sire
contributed to this result. Producers wishing to improve tenderness in their herds should
select sires with higher accuracies as they become available. These results show that
selection for WBSF EPD should not cause any unwanted changes in the other carcass
traits.
Literature Cited
Lawrence, T.E., M.E. Dikeman, M.C. Hunt, C.L. Kastner, and D.E. Johnson. 2004.
Effects of enhancing beef longissimus with phosphate plus salt, or calcium lactate
plus non-phosphate water binder plus rosemary extract. Meat Science. 67:129137.
SAS. 2000. SAS User’s Guide. Cary, NC: SAS Institute, Inc.
Table 1. WBSF EPD and accuracies of sires, and the number of progeny evaluated for
carcass traits and quality traits.
Sire
WBSF EPD (kg)
WBSF acc
Carcass n
Quality n
1
-0.48
0.37
19
3
2
-0.27
0.41
10
2
3
-0.26
0.43
7
7
4
-0.15
0.26
8
8
5
0.07
0.28
14
6
6
0.15
0.22
5
5
7
0.15
0.25
20
5
8
0.18
0.20
21
4
Table 2. Means, standards deviations, minimums, and maximums for carcass traits.
n
Mean
Std Dev
Minimum
Maximum
DP (%)
104
63.21
2.50
55.90
68.70
HCW (kg)
104
329
41
237
441
REA (cm2)
99
83.9
9.7
67.1
113.5
BF (cm)
91
1.17
0.41
0.41
2.54
KPH (%)
99
2.3
0.5
1.5
3.5
YG
89
2.93
0.63
1.34
4.41
MS
104
516
87
390
800
Table 3. Means, standards deviations, minimums, and maximums for quality traits.
n
Mean
Std. Dev.
Minimum
Maximum
Color
40
4.4
1.54
2.04
7.54
Purge loss (%)
40
0.0125
0.0168
0.0067
0.1124
L*
40
42.70
3.95
31.35
48.36
WBSF (kg)
40
5.05
1.38
2.74
9.51
Myofibril tenderness
39
5.47
0.93
3.58
7.50
Juiciness
39
5.71
0.45
4.67
6.50
Flavor
39
5.75
0.36
4.75
6.42
Overall tenderness
39
5.65
0.93
3.67
7.50
Average pH
39
5.78
0.31
5.44
6.66
Table 4. LS Means by sex and wean type for carcass traits.
Sex
Wean type
Bulls
Heifers
Steers
P
Early
Normal
P
65.47
63.17
64.21
0.0142
65.17
63.40
0.0002
HCW (kg)
362
290
354
0.0003
345
325
0.0116
REA (cm2)
92.4
77.1
87.1
0.0143
NS
NS
BF (cm)
NS
NS
NS
1.24
0.91
0.0059
KPH (%)
NS
NS
NS
2.45
2.18
0.0257
YG
2.38
3.32
2.94
3.12
2.64
0.0089
DP (%)
0.0079
Table 5. LS Means by sex for quality traits.
Bull
Steer
P
WBSF (kg)
5.64
4.45
0.0048
Color
5.47
3.28
0.0001
L*
41.28
44.12
0.0213
Myofibril tenderness
5.61
5.81
0.0414
Overall tenderness
5.31
6.07
0.0267
Average pH
5.93
5.70
0.0274
Table 6. Progeny WBSF LS means by sire.
Sire
n
Progeny WBSF LS mean (kg)
6
5
3.88a
8
4
4.34a
1
3
4.48a
4
8
4.60a
3
7
5.07ab
2
2
5.21abc
7
5
6.09bc
5
6
6.41bc
a
Means in the same column with a different superscript are different (P < 0.05)