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Opinions and comments by: James I. Sprague, Livestock Nutritionist Headline in Feedstuffs Newspaper The heading CURRENT CARCASS MATURITY GRADE INACCURATE, CONFUSING, COSTLY, appeared in the October 15, 2001 issue of Feedstuffs Newspaper. It was the heading of the column "Bottom Line of Nutrition/Beef," by Kenny Eng. Research and possible solutions were outlined by him in that column. A system of ageing the animal by the appearance of teeth and teeth changes is being studied by the research community at West Texas A&M University at Canyon, Texas (Lawrence et. al J. Anim. Sci.79:1683). Complaints (and surprises) Over the years we have heard this comment, "The grader called my beautiful young animal a hard bone. That is impossible." We also have seen many pens of "agey" cattle make more choice carcasses than we expect. There is also a negative bias of the age determination of calf fed heifers. Dr. Eng explained that he experienced a personal example of the problem with calf fed Holstein steers that were discounted to standard grade because of the "hard bone" problem. It appears the system of deciding the age based on the bone needs improvement. The federal grading system for carcass age determination is not exempt from the need of improvement. And the grading service probably recognizes that the problem exists. Getting the Facts The first fact -- The system of looking at bones is not as accurate as we would like. Here is a quote from the research report of Ty Lawrence from West Texas A&M research paper: "These data show little evidence of agreement between age estimates derived from the USDA ossification-based maturity system and counting the number of permanent incisors present at slaughter." The second fact -- The data has been buried in the science literature until Kenny Eng had courage to bring the research to our attention. The third fact -- County fairs and livestock shows use dentition to classify cattle for entry to specific age classes. This system has appeared to work with few complaints. A system of dentition is still used by the major steer shows to prevent agey cattle from being entered. Some purebred shows also require proof of birth by registration records plus an evaluation of the maturity "mouthing" for teeth inspection. The fourth fact -- Dr. Eng's economic evaluation of this problem of beef grading deserves attention by the industry as we move to so called "value based marketing." For example, the Texas researchers point to the discrepancy of the maturity classification of heifers, young first calf cows, or spayed heifers that were raised together. Here is a quote from their research: "A major factor influencing skeletal maturity is estrogen content in the animal. In cattle this concept was illustrated by Field et. al (J. An. Sci. 1996), who reported that single-calf cows exhibited more advanced skeletal maturity than virgin heifers, which themselves exhibited more advanced skeletal development than spayed heifers, even though all were born within 45 days and raised together." The fifth fact -- A change at the packing house may be difficult. The heads are processed at a different part of the slaughtering area than the carcasses. Therefore, considerable time and effort would be needed to coordinate the aging of the animal by the inspection of the teeth and its subsequent use in determining the ultimate USDA grade of the animal. Do Maturity Grades Predict Tenderness and Palatability? The answer is, not always. There are many factors that affect tenderness and palatability other than maturity of the animal, including genetics, fat content (marbling for palatability), and aging of the carcass after slaughter. The West Texas A&M demonstrated "the carcass traits accounted for a relatively small proportion of the variation in tenderness of longissimus steaks, and dental classification was not related to tenderness" (J. An. Sci. p2092. 2001). Ouch, this is disappointing. They used 14 days of aging for their research. (Most carcasses are not aged that long.) They note that the results of their lack of correlation between the age of the animal and tenderness of the steaks is both contrary and supportive of former research. Maturity, Only One Factor of Grading Beef Carcasses The problem remains that the grade of animal does not always determine the eating quality of the steaks and roasts. But if age determination is going to be used for the USDA grade, and determining the economic value of carcasses, many of us would like the system to be as accurate as possible. One of the concluding implications of the West Texas A& M research is interesting: "Replacing the USDA ossification-based maturity classification system with one based on the number of permanent incisors present at slaughter would allow beef producers to determine the age of their cattle prior to slaughter and would aid USDA meat graders in grouping cattle into less-variable age categories." © Questions or comments regarding articles by Dr. Jim Sprague can be address to625 Grandview Ave., Newton, Kansas, 67114, or call him at (620) 283-8692.
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