The students are back in Knoxville for another semester here at the University of Tennessee. With the beginning of the semester, professors have a syllabus that will help students achieve their desired grade for the semester, which we hope is an A. Not only are our students trying to make the grade, but we also try to make our cattle achieve the best yield and quality grade possible. However, what do each of these grades mean? What are they predicting?
After a 24-48 hour period in the cooler after harvest, cattle will go through the grade chain to be evaluated by USDA graders and camera grading systems. The USDA Agricultural Marketing Service is responsible for training and monitoring graders. To prepare for grading, carcasses are cut between the 12th and the 13th rib or “ribbed” to reveal the ribeye about 15-20 minutes before they make it to the grading station. This allows the muscle of the ribeye to oxygenate and help the carcass put it’s best foot forward to maximize marbling scores and improve grades.
There are two major grades evaluated in beef carcasses: yield and quality grades. Yield grades are not used as marketing at the retail level but are important for sorting carcasses into groups based on expected red meat yields or cutability at the processing plant. To determine yield grade, four major factors are used: external fat thickness, ribeye area, hot carcass weight, and the percent of kidney, pelvic, and heart fat. These measurements are placed into an equation to estimate yield grade. Yield grades range from 1 to 5, where 1 is a heavy muscled, trim carcass, and 5 is a light muscled, extremely fat carcass.
However, the yield grade equation has not changed since the 1960s and does not necessarily reflect today’s cattle, as they are larger framed and heavier muscled with heavier finishing weights, compared to cattle when the equations were developed, which were smaller, lighter muscled, and fatter. Because of the changed cattle style and heavier final finished weights, many cattle finish outside of the traditional 1-5 yield grade range and are rounded into one of the five grades. There is a concerted effort to overhaul the grading system to modernize the program to match the cattle of today.
Contrastingly, quality grade segregates carcasses based on expected eating experience. Quality grades are evaluated on two major factors: marbling score and animal maturity. Marbling scores are assigned based off the amount of marbling in the ribeye. Marbling is the intramuscular flecks of fat that appear in the Longissimus dorsi muscle, or the ribeye muscle. It is strongly related with better eating experiences, as more marbling is correlated with more tender and juicy steaks.
However, another major component of quality grade is physiological maturity. As animals age, they form stronger crosslinks of collagen, a connective tissue that has a negative impact on tenderness. Because of this, quality grades are split into two major groups: young cattle (less than 42 months of age; A and B maturity) and older cattle (over 42 months of age; C, D, and E maturity). Young cattle, such as fed steers and heifers, are eligible for the most common quality grades: Prime, Choice, Select, and Standard. Older cattle, such as cull cows and bulls, are only eligible for Commercial, Cutter, Canner, and Utility. Maturity is typically evaluated using thoracic vertebrae ossification and using lean color in the ribeye, however, some plants also use dentition. Dentition maturity is estimated by the number of pairs of permanent incisors and the wear on those incisors are present on the bottom jaw of cattle. However, these are physiological markers of maturity that may not directly coincide with chronological age of those cattle, as ossification may occur early or permanent incisors may erupt early as well. It is important to note that age is only being estimated and due to physiological limitations, is nearly impossible to be exactly on the nose when it comes to animal age.
The USDA grading systems for beef were developed to help standardize and create uniform grades for livestock and meat. Grading standards for dressed beef were first established in 1916. These standards were updated continuously through 1924, when the United States Agricultural Products Inspection and Grading Act was authorized to provide funds for the federal grading of livestock and meat. By 1917, grades were also developed for hogs and sheep. The official US Standards and Classes and Grades of Slaughter Cattle came to fruition in 1928. Originally, grading was under the Bureau of Agricultural Economics, but it has been controlled by the Agricultural Marketing Service since 1939. There have been many changes since the original quality grades, including name changes throughout the 1940s and 1950s, as well as and the introduction of the Select grade in 1996, the last major change to quality grades. The introduction of a cutability-based grading system (yield grades) that were adopted in 1965 to help sort carcasses based on expected yields.
The combination of yield and quality grades have helped to add value, sort large groups of cattle, and help educate consumers on what kind of product they are getting. If cattle are making the grade, they will have a high percentage of red meat yield with a great eating experience for consumers.
