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partially separated into a hindquarter and forequarter by cutting it with a saw and knife insofar as practicable, as follows: A saw cut perpendicular to both the long axis and split surface of the vertebral column is made across the 12th thoracic vertebra at a point which leaves not more than one-half of this vertebra on the hindquarters. The knife cut across the ribeye muscle starts-or minates opposite the above-described saw cut. From that point it extends across the ribeye muscle perpendicular to the outside skin surface of the carcass at an angle toward the hindquarter which is slightly greater (more nearly horizontal) than the angle made by the 13th rib with the vertebral column of the hindquarter posterior to that point. As a result of this cut, the outer end of the cut surface of the ribeye muscle is closer to the 12th rib than is the end next to the chine bone. Beyond the ribeye, the knife cut shall continue between the 12th and 13th ribs to a point which will adequately expose the distribution of fat and lean in this area. The knife cut may be made prior to or following the saw cut but must be smooth and even, such as would result from a single stroke of a very sharp knife.

(f) Other methods of ribbing may prevent an accurate evaluation of the grade determining characteristics. Therefore, carcasses ribbed by other methods will be eligible for grading only if an accurate grade determination can be made by the official grader under the standards.

(g) Beveling of the fat over the ribeye, application of pressure, or any other influences which alter the characteristics of the ribeye or the thickness of fat over the ribeye may prevent an accurate grade determination. Therefore, carcasses subjected to such influences may not be eligible for a grade determination. Also, carcasses with more than minor amounts of lean removed from the major sections of the round, loin, rib, or chuck will not be eligible for a grade determination.

(h) When both sides of a carcass have been ribbed prior to presentation for grading and the characteristics of the two ribeyes (area, marbling, color, texture, and firmness) would justify different quality and/or yield grades, the final grade of the carcass shall reflect the "highest" of each of these grades as determined from either side.

(i) The quality grade and yield grade descriptions are defined primarily in

terms of beef carcasses. However, they also apply to the grading of hindquarters, forequarters, and certain individual primal cuts-loins, short loins, and ribs. A portion of these or other primal cuts as well as plates, flanks, shanks, and briskets likewise can be graded if attached by their natural attachments to a rib, loin, or short loin. Since bull carcasses are eligible for yield grade only, they may be graded only as carcasses, sides, or hindquarters. This is because yield grades for forequarters and forequarter cuts and for trimmed hindquarters and trimmed hindquarter cuts include consideration of standard percentages of kidney, pelvic, and heart fat based on the quality grade. Other special major cuts or carcasses ribbed other than between the 12th and 13th ribs may be approved for grading by the Agricultural Marketing Service provided such deviations are necessary to meet either the demand of export trade or changing trade practices. In such cases, grading shall be based on the requirements specified in these standards and shall be consistent with the normal development of grade characteristics in various parts of a carcass of the quality level involved.

(j) Carcasses qualifying for any particular grade may vary with respect to their relative development of the various grade factors. There will be carcasses which qualify for a particular grade, some of whose characteristics may be more nearly typical of another grade. For example, in comparison with the descriptions of maturity contained in the standards, a particular carcass might have a greater relative degree of ossification of the cartilages on the ends of its lumbar vertebrae than its other evidences of maturity. In such instances, the maturity of the carcass is not determined solely by the ossification of the lumbar vertebrae but neither is this ignored. All of the maturity-indicating factors are considered. In making any composite evaluation of two or more factors, it must be remembered that they seldom are developed to the same degree. Because it is impractical to describe the nearly limitless number of recognizable combinations of characteristics, the standards for each quality grade and yield grade describe only beef which has a relatively similar degree of development of the various factors affecting its quality and yield. Also, the quality grade and yield grade standards each describe beef which is representative of the lower

limits of each quality grade and yield grade.

(k) For steer, heifer, and cow beef, quality of the lean is evaluated by considering its marbling and firmness as observed in a cut surface in relation to carcass evidences of maturity. The maturity of the carcass is determined by evaluating the size, shape, and ossification of the bones and cartilages-especially the split chine bones-and the color and texture of the lean flesh. In the split chine bones, ossification changes occur at an earlier stage of maturity in the posterior portion of the vertebral column (sacral vertebrae) and at progressively later stages of maturity in the lumbar and thoracic vertebrae. The ossification changes that occur in the cartilages on the ends of the split thoracic vertebrae are especially useful in evaluating maturity and these vertebrae are referred to frequently in the standards. Unless otherwise specified in the standards, whenever reference is made to the ossification of cartilages on the thoracic vertebrae, this shall be construed to refer to the cartilages attached to the thoracic vertebrae at the posterior end of the forequarter. The size and shape of the rib bones also are important considerations in evaluating differences in maturity. In the very youngest carcasses considered as "beef," the cartilages on the ends of the chine bones show no ossification, cartilage is evident on all of the vertebrae of the spinal column, and the sacral vertebrae show distinct separation. In addition, the split vertebrae usually are soft and porous and very red in color. In such carcasses, the rib bones have only a slight tendency toward flatness. In progressively more mature carcasses, ossification changes become evident first in the bones and cartilages of the sacral vertebrae, then in the lumbar vertebrae, and still later in the thoracic vertebrae. In beef which is very advanced in maturity, all the split vertebrae will be devoid of red color, very hard and flinty, and the cartilages on the ends of all the vertebrae will be entirely ossified. Likewise, with advancing maturity, the rib bones will become progressively wider and flatter until in very mature beef the ribs will be very wide and flat.

(1) In steer, heifer, and cow beef, the color and texture of the lean flesh also undergo progressive changes with advancing maturity. In the very youngest carcasses considered as "beef," the lean

flesh will be very fine in texture and light grayish red in color. In progressively more mature carcasses, the texture of the lean will become progressively coarser and the color of the lean will become progressively darker red. In very mature beef, the lean flesh will be very coarse in texture and very dark red in color. Since color of lean also is affected by variations in quality, references to color of lean in the standards for a given degree of maturity vary slightly with different levels of quality. In determining the maturity of a carcass in which the skeletal evidences of maturity are different from those indicated by the color and texture of the lean, slightly more emphasis is placed on the characteristics of the bones and cartilages than on the characteristics of the lean. In no case can the overall maturity of the carcass be considered more than one full maturity group different from that indicated by its bones and cartilages.

(m) The preceding two paragraphs also are applicable to the determination of quality in bullock beef except for carcasses having darker colors of lean than specified in the standards for the quality level for which they would otherwise qualify. In such carcasses, maturity will be evaluated on the basis of skeletal characteristics only, and the final grade will be determined in accordance with the procedures specified in the standards for grading "dark-cutting beef."

(n) In determining compliance with the maximum maturity limits for the Prime, Choice, Good, and Standard grades for steer, heifer, and cow carcasses, color and texture of the lean are considered only when the maturity-indicating factors other than color and texture of the lean indicate only a slightly more advanced degree of maturity than that specified as maximum for these grades, and provided further that the lean is considerably finer in texture and lighter in color than normal for the grade and maturity involved. The same principle, in reverse, is likewise applicable to determining compliance with the minimum maturity limits of the Commercial grade.

(0) These standards are applicable to the grading of beef throughout the full range of maturity within which cattle are marketed. However, in steer, heifer, and cow carcasses, the range of maturity permitted within each of the grades varies considerably. The Prime, Choice, Good, and Standard grades are restricted to

beef from young cattle; the Commercial grade is restricted to beef from cattle too mature for Prime, Choice, Good, and Standard, and the Utility, Cutter, and Canner grades may include beef from animals of all ages. By definition, bullock carcasses are restricted to those whose evidences of maturity do not exceed those specified for the juncture of the two youngest maturity groups referenced in the standards for steer, heifer, and cow carcasses. Except for the youngest maturity group, within any specified grade, the requirements for marbling increase progressively with evidences of advancing maturity. In the youngest maturity group, the marbling requirements do not increase progressively with evidences of advancing maturity. For each grade, the firmness requirements are different for each maturity group, but, within each maturity group, the firmness requirements do not increase progressively with evidences of advancing maturity. Also, regardless of the extent to which marbling may exceed the minimum of a

grade, a carcass must meet the minimum firmness requirements for its maturity to qualify for that grade. To facilitate the application of these principles, the standards recognize five different maturity groups and seven different degrees of marbling. The five maturity groups are identified in Figure 1 as A, B, C, D, and E in order of increasing maturity. The limits of these five maturity groups are specified in the grade descriptions for steer, heifer, and cow carcasses. The A maturity portion of the figure is the only portion applicable to bullock carcasses. The degrees of marbling referenced in the specifications, in order of descending quantity are: Slightly abundant, moderate, modest, small, slight, traces, and practically devoid. However, for carcass evaluation programs and other purposes, three higher degrees are recognized— moderately abundant, abundant, and very abundant. Illustrations of the lower limits of nine of these ten degrees of marbling are available from the Department of Agriculture.

RELATIONSHIP BETWEEN MARBLING, MATURITY, AND CARCASS QUALITY GRADE •

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Assumes that firmness of lean is comparably developed with the degree of marbling and that the carcass is not a "dark cutter."

**Maturity increases from left to right (A through E).

***The A maturity portion of the Figure is the only portion applicable to bullock carcasses.

Figure 1

(p) The relationship between marbling, maturity, and quality grade is shown in Figure 1. This figure assumes that the firmness of lean is comparably developed with the degree of marbling and that the carcass is not a "dark cutter." From this figure it can be seen, for instance, that the minimum marbling requirement for Choice varies from a minimum small amount for carcasses

throughout the youngest maturity group to a maximum small amount for carcasses having the maximum maturity permitted in Choice. Likewise, in the Commercial grade the minimum marbling requirement varies from a minimum small amount in beef with the minimum maturity permitted to a maximum moderate amount in beef from very mature animals. The marbling and other lean

flesh characteristics specified for the various grades are based on their appearance in the ribeye muscle of properly chilled carcasses that are ribbed between the 12th and 13th ribs. For carcass evaluation programs and other purposes, in the Prime and Commercial grades, each additional degree of marbling (up to three) greater than specified as minimum for each of these grades is equal to one-third of a grade of higher quality.

(q) References to color of lean in the standards for steer, heifer, and cow beef involve only colors associated with changes in maturity. They are not intended to apply to colors of lean associated with so-called “dark-cutting beef." Dark-cutting beef is believed to be the result of a reduced sugar content of the lean at the time of slaughter. As a result, this condition does not have the same significance in grading as do the darker shades of red associated with advancing maturity. The dark color of the lean associated with "dark-cutting beef" is present in varying degrees from that which is barely evident to so-called "black cutters" in which the lean is actually nearly black in color and usually has a "gummy" texture. Although there is little or no evidence which indicates that the "dark cutting" condition has any adverse effect on palatability, it is considered in grading because of its effect on acceptability and value. Depending on the degree to which this characteristic is developed, the final grade of carcasses which otherwise would qualify for the Prime, Choice, or Good grades may be reduced as much as one full grade. In beef otherwise eligible for the Standard or Commercial grade, the final grade may be reduced as much as onehalf of a grade. In the Utility, Cutter, and Canner grades, this condition is not considered.

(r) The yield grade of a beef carcass is determined by considering four characteristics: (1) The amount of external fat, (2) the amount of kidney, pelvic, and heart fat, (3) the area of the ribeye muscle, and (4) the carcass weight.

(s) The amount of external fat on a carcass is evaluated in terms of the thickness of this 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. In determining the amount of

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this adjustment, if any, particular attention is given to the amount of fat in such areas as the brisket, plate, flank, cod or udder, inside round, rump, and hips in relation to the actual thickness of fat over the ribeye. Thus, in a carcass which is fatter over other areas than is indicated by the fat measurement over the ribeye, the measurement is adjusted upward. Conversely, in a carcass which has less fat over the other areas than is indicated by the fat measurement over the ribeye, the measurement is adjusted downward. In many carcasses no such adjustment is necessary; however, an adjustment in the thickness of fat measurement of one-tenth or two-tenths of an inch is not uncommon. In some carcasses a greater adjustment may be necessary. As the amount of external fat increases, the percent of retail cuts decreaseseach one-tenth inch change in adjusted fat thickness over the ribeye changes the yield grade by 25 percent of a yield grade.

(t) The amount of kidney, pelvic, and heart fat considered in determining the yield grade includes the kidney knob (kidney and surrounding fat), the lumbar and pelvic fat in the loin and round, and the heart fat in the chuck and brisket area which are removed in making closely trimmed retail cuts. The amount of these fats is evaluated subjectively and expressed as a percent of the carcass weight. As the amount of kidney, pelvic, and heart fat increases, the percent of retail cuts decreases-a change of 1 percent of the carcass weight in these fats changes the yield grade by 20 percent of a yield grade.

(u) The area of the ribeye is determined where this muscle is exposed by ribbing. This area usually is estimated subjectively; however, it may be measured. Area of ribeye measurements may be made by means of a grid calibrated in tenths of a square inch or by other devices designated by the Agricultural Marketing Service of the U.S. Department of Agriculture.1 An increase in the area of ribeye increases the percent of retail cuts-a change of 1 square inch in area of ribeye changes the yield grade by approximately 30 percent of a yield grade.

(v) Hot carcass weight (or chilled carcass weight x 102 percent) is used in determining the yield grade. As carcass

1 Information concerning such devices may be obtained from the Agricultural Marketing Service, Livestock Division.

weight increases, the percent of retail cuts decreases-a change of 100 pounds in hot carcass weight changes the yield grade by approximately 40 percent of a yield grade.

(w) The standards include a mathematical equation for determining yield grade. This grade is expressed as a whole number; any fractional part of a designation is always dropped. For example, if the computation results in a designation of 3.9, the final grade is 3-it is not rounded to 4.

(x) The yield grade standards for each of the first four yield grades list characteristics of two carcasses of two different weights together with descriptions of the usual fat deposition pattern on various areas of the carcass. These descriptions are not specific requirements-they are included only as illustrations of carcasses which are near the borderlines between groups. For example, the characteristics listed for Yield Grade 1 represent carcasses which are near the borderline of Yield Grades 1 and 2.

These descriptions facilitate the subjective determination of the yield grade without making detailed measurements and computations. The yield grade for most beef carcasses can be determined accurately on the basis of a visual appraisal.

[40 FR 11538, Mar. 12, 1975]

$ 53.103 Specifications for official United States standards for grades of carcass beef (yield).

(a) The yield grade of a beef carcass is determined on the basis of the following equation: Yield grade-2.50+ (2.50 x adjusted fat thickness, inches) + (0.20 x percent kidney, pelvic, and heart fat)+(0.0038 X hot carcass weight, pounds) -(0.32 x area ribeye, square inches).

(b) (1) The yield grade of a hindquarter, forequarter, or cut eligible for grading also is determined on the basis of the above equation in which the hot carcass weight is determined by multiplying the chilled weight of the cut by an appropriate factor as applicable to the cut and its style of preparation.

(2) The factors shown below shall be applicable to hindquarters and forequarters produced by ribbing as described herein, and to ribs, trimmed full loins, and trimmed short loins which are trimmed as described in Items 103, 172,

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(3) A slightly larger factor, appropriate to reflect the weight of the cut as a percent of hot carcass weight, shall be used for ribs, full loins, or short loins which are more closely trimmed than described in the referenced IMP Specifications. Similarly, a smaller factor shall be used for determining the yield grade of these cuts when trimmed less closely than specified or when they include portions or all of adjacent cuts.

(4) In addition, for forequarters and forequarter cuts and for trimmed hindquarters and trimmed hindquarter cuts, the following standard percentages of kidney, pelvic, and heart fat, as applicable to the quality grade of the quarter or cut, also shall be used in the equation: Kidney, pelvic,

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(5) For untrimmed hindquarters and for untrimmed hindquarter cuts, the quantity of kidney and pelvic fat is estimated as a percent of the hot side weight.

(c) The following descriptions provide a guide to the characteristics of carcasses in each yield grade to aid in determining yield grades subjectively.

(1) Yield Grade 1. (1) A carcass in yield grade 1 usually has only a thin layer of external fat over the ribs, loins, rumps, and clods and slight deposits of fat in the flanks and cod or udder. There is usually a very thin layer of fat over the outside of the rounds and over the tops of the shoulders and necks. Muscles are usually visible through the fat in many areas of the

carcass.

(ii) A 500-pound carcass of this yield grade which is near the borderline of yield grades 1 and 2 might have threetenths inch of fat over the ribeye, 11.5

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