When the meat grader stamps a side of beef with a U.S. Department of Agriculture (USDA) quality grade, he is estimating its palatability. That stamp of approval on a Choice or Prime carcass predicts quality so that consumers have the confidence to pay more. Producers who sell in a value-based system also earn more. But how do the graders decide which stamp to use? What separates a Choice carcass from a Select?

The USDA began developing grades for beef carcasses in 1916. Designed to offer uniformity when reporting livestock markets, the grades were put to the test when used for ordering meat during World War I.
“After the war, quality grades were incorporated into hotel, restaurant, dining car service and hospital buying, similar to the way retailers use grades to order meat today,” explained John Unruh, Kansas State University meat scientist.  
While there have been adjustments throughout the years, Colorado State University meat scientist Daryl Tatum said the fundamentals of the system remain.
The primary quality grade factor for young cattle is marbling, or the intramuscular fat within the ribeye. Graders evaluate this after the carcass has been cut between the 12th and 13th ribs, or “ribbed.” The amount of marbling in the ribeye is described by specific marbling scores, from “Abundant” for high Prime to “Slight” for the Select grade, and lower scores for even lower grades.
See figure 1 for six ribeyes that exemplify three USDA quality grades. Moderate, Modest and Small correlate with the three levels of Choice beef; Slight marbling is Select grade; Abundant (not shown), Moderately Abundant and Slightly Abundant marbling are initial indicators of Prime grade beef.
These scores correspond to initial quality grades, but other characteristics come into play. Desirable ribeyes exhibit an adequate amount of finely dispersed marbling within firm, fine-textured, bright, cherry-red colored lean, Unruh said. As an animal matures, these muscle characteristics transform.

Cattle develop at different rates. Maturity refers to the physiological development of an animal rather than the chronological age.
“Maturity is really a composite evaluation of a couple of things,” Tatum said. “One has to do with the skeletal characteristics and the other relates to the color and texture of the lean.”
As cattle mature, their cartilage gradually turns to bone, he explained. This process, called ossification, helps graders determine a bone maturity grade. Maturity grades range from A to E as more ossification along the backbone becomes evident. Graders also look at the shape and color of the rib bones when determining bone maturity grade.
This classification is then adjusted based on the color and texture of the lean.
“As animals mature, the color of their muscle changes from a bright pink to a dark purplish-red color,” Tatum said. “The texture of the lean on the cut surface of the ribeye also gets coarser.”  
When combining skeletal and lean maturity, the overall maturity classification won’t vary more than one grade from the bone maturity score.
Final Quality Grade
The final quality grade is determined by the graders’ quick calculations of where maturity and marbling scores meet. Carcasses of greater maturity aren’t eligible for the most desirable quality grades, regardless of the amount of marbling. However, Tatum said most of the cattle finished in the United States fall into the “A” maturity range. That’s why degree of marbling tends to be the determining factor.
Chelsea Good is a Certified Angus Beef industry information specialist.


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