Beef Grading and Evaluation
Photo courtesy of the American Meat
Science Association
Which one would you choose?
Think about the type of animal that might
produce the best carcass.
How about now??
Two Grading Systems
Quality Grade
- Age & marbling
Prime
Choice
Select
Standard
Yield Grade
- muscle & fat
YG1
YG2
YG3
YG4
YG5
Carcass Quality Grading
1
Assumes that firmness of lean is completely developed with the degree of marbling and that the carcass is not a “dark cutter.”
2
Maturity increases from the left to right (A through E).
3
The A maturity portion of the figure is the only portion applicable to bullock carcasses.
Photo courtesy of the American Meat
Science Association
Photos courtesy of
the American Meat
Science
Association
Marbling Deposition
Changes in rib fat depth and marbling score
relative to hot carcass weight at slaughter.
Bruns, Pritchard, Boggs,
JAS 2004. 82:1315-1322
USDA Yield Grades
The Yield Grades are based on the following mathematical (regression) equation:
Yield Grade = 2.50 + (2.50 x adjusted fat thickness, in.) + (0.20 x % kidney, pelvic, and heart fat) + (0.0038
x hot carcass weight, lb.) – (0.32 x area of ribeye, sq. in.)
Photos
courtesy of
the American
Meat Science
Association
Measuring Fat Thickness
External fat thickness is measured at the
12th/13th rib interface, perpendicular to the
outside surface of the carcass at a point ¾
of the length of the ribeye from its chinebone end.
Measuring Ribeye Area
A grid calibrated in 0.1 sq. in. units may
be used to measure the area of the ribeye
muscle at the 12th/13th rib interface
Average Ribeye/Hot Carcass Weight
Photos courtesy of the American
Meat Science Association
Photos courtesy of the
American Meat Science
Association
Photos courtesy of the
American Meat Science
Association
Photos courtesy of the
American Meat Science
Association
Example #1
Starting Weight
EndingWeight
Carcass Weight
USDA Grade
Backfat (in.)
KPH (%)
Ribeye (in.)
Yield Grade
885
1175
715
C0.40
2.5
11.5
3.04
Example #2
Starting Weight
End Weight
Carcass Weight
USDA Grade
Backfat (in.)
KPH (%)
Ribeye (in.)
Yield Grade
850
1105
655
C
0.20
2.0
11.9
2.83
Example #3
Starting Weight
Ending Weight
Carcass Weight
USDA Grade
Backfat (in.)
KPH (%)
Ribeye (in.)
Yield Grade
928
1238
763
S
0.20
2.0
12.6
3.02
Example #4
Starting Weight
Ending Weight
Carcass Weight
USDA Grade
Backfat (in.)
KPH (%)
Ribeye (in.)
Yield Grade
880
1249
827
S+
0.35
2.5
15.9
1.93
Activity
• Complete the yield grade
calculation activity.
Yield Grade Formula
• Yield Grade = 2.5
»
»
»
»
+ 2.5 X Adjusted Fat thickness ( BF)
+ .0038 X Hot Carcass Weight
+ .2 X Kidney Pelvic and Heart Fat % (KPH)
- .32 X Rib Eye Area (REA)
Calculate The Yield Grades
•
•
•
•
•
•
•
Steer#
1
2
3
4
5
6
BF
.54
.33
.44
.5
.6
.8
HCW
773
865
668
885
995
700
KPH
2.5%
1.5%
3.5%
2%
4%
4%
REA
14.1
9.8
10.7
18.5
15.3
9.5
Answers
1.
2.
3.
4.
5.
6.
2.45
3.78
3.4
1.6
3.7
4.92
Carcass Grid
Carcass Grid
Questions?
Photo courtesy of the American Meat
Science Association