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While other traits are analyzed using an animal model, the carcass evaluation uses a sire/maternal
grandsire multiple-trait mixed model to determine sire Expected Progeny Differences (EPDs)
for carcass weight, USDA marbling score, 12th-rib fat thickness and ribeye area. Interim pedigree
estimated EPDs for carcass traits receive an ACC of .05.
The carcass data are phenotypically described in Table 1
with average adjusted measurements. Carcasses were adjusted to 480 days of age-at-slaughter.
The scoring system for marbling and its relationship to the USDA Quality Grading System is defined
in
Table 2. For a carcass to meet Certified Angus Beef (CAB) standards, it
must have a Modest ( average Choice) or higher marbling degree, be of "A" maturity
(the most youthful classification for beef), 10 to 16 square inch ribeye, less than one inch fat thickness,
less than 1,000 pound hot carcass weight and have a fine to medium marbling texture. For more details,
go to www.cabpartners.com.
Table 1. Phenotypic averages of steer and heifer carcasses
and ultrasound measures in the Angus database.
| |
360 < Age < 480 |
481 < Age < 660 |
| Heifers: |
Avg | SD1 |
Avg | SD |
| Average age-at-slaughter, days |
437 | 29 | 535 | 42 |
| Adj.2 carcass weight, lb. |
679 | 82 | 670 | 92 |
| Adj. fat thickness, in. |
.57 | .18 | .52 | .18 |
| Adj. ribeye area, sq. in. |
11.91 | 1.34 | 11.85 | 1.47 |
| Adj. marbling score |
6.30 | 1.41 | 5.88 | 1.30 |
| No. of heifers |
| 3,227 | | 3,137 |
Steers(carcass): |
| Average age-at-slaughter, days |
437 | 25 | 524 | 42 |
| Adj. carcass weight, lb. |
778 | 79 | 748 | 92 |
| Adj. fat thickness, in. |
.56 | .17 | .53 | .18 |
| Adj. ribeye area, sq. in. |
12.46 | 1.29 | 12.40 | 1.37 |
| Adj. marbling score |
6.04 | 1.02 | 5.61 | 1.17 |
| No. of steers |
| 55,874 | | 18,838 |
Steers (ultrasound): |
320 < Age < 480 |
| Average age-at-scanning, days |
412 | 34 | |
| Equivalent carcass weight, lb. |
706 | 104 |
|
| Adj. fat thickness, in. |
.36 | .12 | |
| Adj. ribeye area, sq. in. |
11.75 | 1.70 | |
| Equivalent marbling score |
5.33 | .66 | |
| No. of ultrasound steers |
| 6,623 |
1SD = standard deviation. |
| 2Carcasses were adjusted to 480 days of age at slaughter. |
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Table 2. USDA quality grading system and marbling score.
Quality
Grade |
Amount of
Marbling |
Numerical
Score |
| Prime + |
Abundant |
10.0 - 10.9 |
| Prime |
Moderately abundant |
9.0 - 9.9 |
| Prime - |
Slightly abundant |
8.0 - 8.9 |
| Choice + |
Moderate |
7.0 - 7.9 |
| Choice |
Modest |
6.0 - 6.9 |
| Choice - |
Small |
5.0 - 5.9 |
| Select |
Slight |
4.0 - 4.9 |
| Standard |
Traces |
3.0 - 3.9 |
| Standard |
Practically devoid |
2.0 - 2.9 |
| Utility |
Devoid |
1.0 - 1.9 |
|
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