Beef Quality Corner -- The Need for More Muscle

Livestock Update, November 2000

Bill R. McKinnon, Extension Animal Scientist, Marketing, Virginia Tech

The national fed beef quality audits conducted during 1991 and 1995 both pointed to the need to reduce the variability in ribeye size in beef carcasses. Both ribeyes that are too small and too large create inefficiency for the industry. Ribeyes with small cross sections (less than 11 sq. in.) are reflective of a relatively light degree of muscling within the carcass and create packaging and portion size control problems. Ribeyes that are too large (above 16 sq. in.) present packaging challenges and must be cut too thinly in many controlled portion size situations. Typically ribeyes that are too large are most frequently the result of excessively heavy carcasses.

The most recent carcass data generated from the Virginia Retained Ownership Program provides some insight into the relative muscling of Virginia cattle. Data from 191 cattle processed indicated that 42 carcasses or 22% had ribeyes under 11 square inches; while only 3 or 1.5% of the cattle produced ribeyes over 16 square inches.

The cross section of the ribeye muscle is exposed when the beef carcass is separated between the 12th and 13th rib for both quality and yield grading. Measurement of the ribeye muscle provides an indication of the relative muscularity of the whole carcass. Ribeye size is an important factor in the USDA Yield Grade equation that indicates relative red meat yield of the carcass.

Certainly, ribeye size is related to carcass weight with the ribeye size generally increasing as carcass weights get heavier. Ribeye size and carcass weight are tied together in the yield grade equation. For varying carcass weights, there are minimum ribeye area thresholds that are required to prevent an adverse adjustment in yield grade. Ribeye areas below the target level cause the numeric yield grade to increase; while, larger ribeyes tend to lower the yield grade. Remember the lower the numeric yield grade, the higher the cutability of the carcass. The table below presents the required ribeye area for various carcass weights to cause no adjustment in yield grade for muscling.

Required Ribeye Area sq. in.	Hot Carcass Weight lbs.
11.0	600
11.3	625
11.6	650
11.9	675
12.2	700
12.5	725
12.8	750
13.1	775
13.4	800
13.7	825
14.0	850
14.3	875
14.6	900

Again, when examining the most recent Va. ROP data, 67% of the cattle failed to have large enough ribeye area to prevent an adverse adjustment in yield grade.

The information suggests that producers interested in owning feeder cattle longer or marketing in a fashion that rewards relative muscling or yield grade may need to focus attention at increasing ribeye area. Simply evaluating breeding cattle from the rear view, concentrating on the thickness of the quarter does not get the job done. This type of evaluation may be useful when marketing offspring through a graded feeder cattle sales program. Serious improvement at the carcass level can be best done by focusing on bulls with positive and high accuracy EPD's for ribeye area or % retail cuts. A bull's own ultrasound measurement for ribeye size can be helpful, but it is only one measurement and will ultimately be less useful than EPD's generated from carcass data or ultrasound scanning from a number of offspring.

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