The indicated yield of closely trimmed (1/2 inch of fat or less), boneless retail cuts expected to be derived from the major wholesale cuts (round, sirloin, short loin, rib, and square-cut chuck) of a carcass is indicated by the USDA Yield Grade. Yield grades are the most convenient and practical indicators of carcass composition that are utilized in the beef industry today. The beef yield-grading equation utilizes four measurable traits of each individual carcass. These include the amount of external fat (subcutaneous); the amount of kidney, pelvic, and heart fat (perinephric); the area of the ribeye (longissimus dorsi); and the hot weight of the carcass. The measured values of each of the four traits are placed into the yield-grading equation and result in values ranging from 1.0 to 5.9. Generally, the calculated value is considered solely by its whole-number value. For example, if the computation results in a designation of 3.9, the final yield grade is 3; it is not rounded to 4. The USDA Yield Grade equation is as follows:
= 2.50 + (2.50 x adjusted fat thickness in inches) + (0.20 x percent kidney, pelvic, and heart fat) + (0.0038 x hot carcass weight in pounds) — (0.32 x ribeye area in square inches) (1)
The amount of external fat is measured by the thickness of the fat over the ribeye muscle, measured perpendicular to the outside surface at a point three fourths of the length of the ribeye from its chine bone end. This measurement may be adjusted, as necessary, to reflect unusual amounts of fat on other parts of the carcass. The amount of kidney, pelvic, and heart fat is a subjective measurement considered in the equation. It includes the kidney knob, lumbar, and pelvic fat in the loin and round region, and heart fat in the chuck and brisket area. The area of the ribeye muscle is measured where this muscle is exposed by ribbing the carcass between the 12th and 13th ribs. The actual hot carcass weight (or chilled carcass weight x 102%) is utilized in Eq. 1.
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