Beef Grading and EvaluationBeef 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

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.)

USDA Yield Grades

Photos courtesy of

the American Meat Science Association

Average Ribeye/Hot Carcass Weight

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 chine-bone 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

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

Starting Weight 885EndingWeight 1175Carcass Weight 715USDA Grade C-Backfat (in.) 0.40KPH (%) 2.5Ribeye (in.) 11.5Yield Grade 3.04

Example #1 Example #1

Starting Weight 850End Weight 1105Carcass Weight 655USDA Grade CBackfat (in.) 0.20KPH (%) 2.0Ribeye (in.) 11.9Yield Grade 2.83

Example #2 Example #2

Starting Weight 928Ending Weight 1238Carcass Weight 763USDA Grade SBackfat (in.) 0.20KPH (%) 2.0Ribeye (in.) 12.6Yield Grade 3.02

Example #3Example #3

Starting Weight 880Ending Weight 1249Carcass Weight 827USDA Grade S+Backfat (in.) 0.35KPH (%) 2.5Ribeye (in.) 15.9Yield Grade 1.93

Example #4 Example #4

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# BF HCW KPH REA• 1 .54 773 2.5% 14.1• 2 .33 865 1.5% 9.8• 3 .44 668 3.5% 10.7• 4 .5 885 2% 18.5• 5 .6 995 4% 15.3• 6 .8 700 4% 9.5

Answers

1. 2.45

2. 3.78

3. 3.4

4. 1.6

5. 3.7

6. 4.92

Carcass Grid

Carcass Grid

Questions?Photo courtesy of the American Meat

Science Association