Carcass EPDs were calculated from an integrated analysis of the Beef Improvement Records carcass and ultrasound databases. The genetic evaluation produces a single set of EPDs for carcass weight, marbling score, ribeye area, and fat thickness on an age-constant basis. The units of measure for the EPDs are in carcass trait format. The carcass and ultrasound data contributing to the evaluation are described in Table 1 and Table 2 with average adjusted measurements.

Ultrasound images incorporated into the carcass EPDs were collected by field technicians certified by the Ultrasound Guidelines Council (UGC). The images were interpreted through one of the American Angus Association's authorized ultrasound processing labs by UGC-certified lab technicians.

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Table 1. Angus phenotypic averages of steer and heifer carcasses.

360 < Age < 480 481 < Age < 660 Heifers: Avg SD1 Avg SD Average age-at-harvest, days 437 29 535 43 Adj.2 carcass weight, lb. 680 82 671 92 Adj. fat thickness, in. .58 .18 .52 .18 Adj. ribeye area, sq. in. 11.91 1.35 11.86 1.48 Adj. marbling score 6.39 1.22 5.86 1.30 No. of heifers 3,205 3,082 Steers: Average age-at-harvest, days 437 25 524 41 Adj. carcass weight, lb. 778 79 748 92 Adj. fat thickness, in. .56 .17 .53 .18 Adj. ribeye area, sq. in. 12.47 1.29 12.40 1.37 Adj. marbling score 6.04 1.00 5.62 1.16 No. of steers 56,169 18,862 1SD = standard deviation. 2Carcasses were adjusted to 480 days of age at harvest.

Table 2: Yearling Angus live-animal and ultrasound measures

Bulls      Heifers      Steers      Trait Avg SD1 Avg SD1 Avg SD1 Age, days 370 26 390 30 411 35 Gain, lbs/day 2.93 .66 1.54 .50 2.79 .66 Adj. scan weight, lb. 1,114 133 868 110 1,079 158 Adj. %IMF, % 3.70 .95 4.57 1.18 4.73 1.26 Adj. ribeye area, sq. in. 12.37 1.70 9.71 1.59 11.84 1.78 Adj. 12-13th rib fat thickness, in. .28 .10 .27 .11 .36 .12 Adj. rump fat thickness, in. .31 .11 .31 .12 .38 .13 No. of animals 540,510     387,874     7,844      1SD = standard deviation.

As a review, the scoring system for marbling and its relationship to the USDA Quality Grading System is defined in Table 3. 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 3. 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