United States

Department of

Agriculture

Agricultural 

Marketing

Service

Livestock

and Seed

Division

United States Standards

for Grades of

Lamb, Yearling Mutton, and

Mutton Carcasses

Effective date July 6, 1992
1

United States Standards for Grades of Lamb, Yearling Mutton,

 and Mutton Carcasses

The following is a reprint of the Official United States Standards for the Grades of Lamb,

Yearling Mutton, and Mutton Carcasses promulgated by the Secretary of Agriculture under the

Agricultural Marketing Act of 1946 (60 Stat. 1087; 7 U.S.C. 1621-1627) as amended and related

authority in the annual appropriation acts for the Department of Agriculture. The standards are

reprinted with amendments effective July 6, 1992.

Development of the Standards

The official standards for grades of lamb and mutton carcasses were initially promulgated and

made effective on February 16, 1931. The standards were amended in October 1940

(Amendment No. 1 to S.R.A. 123) so as to change the grade designations Medium and common

to Commercial and Utility, respectively. In April 1951, the official standards were again amended

(Amendment No. 2 to S.R.A. 123). By this amendment, Prime and Choice grades were combined

and designated as Prime. The Good grade was renamed Choice, which also became the highest

grade for carcasses of mutton older than yearlings. The top two-thirds of the Commercial grade

was combined with the top two-third of the Utility grade and designated as Utility, thereby

eliminating the Commercial grade name. The lower one-third of the Utility grade was combined

with the Cull grade and designated as Cull. This amendment also provided for reflecting the

minimum requirements for each grade, specified the grade requirements for varying degrees of

maturity, and clarified the method for differentiating between lamb, yearling mutton, and mutton

carcasses.

In February 1957, the standards for grades of lamb carcasses were amended (Amendment 3 to

S.R.A. 123) by reducing the quality requirement for Prime and Choice grade carcasses from more

mature lambs, but corresponding reductions in the quality requirements for these grades were not

made for carcasses from very young lambs. The quality requirements for the Good grade were

increased slightly, particularly for carcasses from young lambs. Quality requirements for the

Prime, Choice, and Good grades of yearling mutton and for the Choice and Good grades of

mutton were also modified to coordinate them with the changes made in the standards for lamb

carcasses. This amendment also made provision for all lamb, yearling mutton, and mutton

carcasses with quality indications equivalent to the lower limit of the upper third of the Good

Grade to be graded Choice provided they had a development of conformation equivalent to the

midpoint of the Choice grade or better. Practically all references to quantity of external and

kidney and pelvic fats were also eliminated by this amendment, and other minor changes were

made in the phrasing of the standards to clarify them and to facilitate their interpretation. These

changes were recommended by an industry-wide committee appointed by the National Wool

Growers Association and reflected the results of meetings with various segments of the industry

at Salt Lake City, Ft. Worth, Denver, and Washington, D.C.
2

In March 1960, the standards for grades of lamb and mutton carcasses were amended

(Amendment 4 to S.R.A. 123) by reducing both the conformation and quality requirements for the

Prime and Choice grades. The conformation requirements for lambs in the Prime and Choice

grades were reduced about one-half grade. The quality requirements for very young lambs in

both grades were reduced in the Prime grade about a full grade and in the Choice grade about

two-thirds of a grade. In addition, a minimum degree of external fat covering was prescribed for

the Prime and Choice grades. The emphasis placed on internal factors considered in evaluating

quality was decreased by reducing the emphasis on feathering between the ribs, eliminating

consideration of overflow fat, and increasing the emphasis on firmness of fat and lean. These

changes were developed through meetings with various segments of the industry at Kansas City,

Omaha, and Washington, D.C., after some organizations requested that the grading of lamb and

mutton carcasses be suspended.

In March 1969, the standards were revised by adopting yield grade standards for optional use

with the quality grades. These yield grades standards were based on the results of studies

conducted by the Department, several land-grant universities, and the industry on lamb carcass

cutability. The information from these studies indicated that carcasses of the same weight and

grade differed widely in their yields of trimmed retails cuts and value. These studies also

disclosed that differences in cutability resulted primarily from differences in external and internal

fatness of the carcasses. At the annual meeting of the American Society of Animal Science in

1967 ( J. Anim. Sci. 26:896), the specific research on which the yield grades were based was

reported by D.D. Johnston. Based on that research, and at the request of the National Wool

Growers Association, the Department proposed the yield grade standards on August 16, 1968,

and they became effective on March 1, 1969. Changes also were made in the “Application of

Standards” section as need to implement the yield grades and to clarify some other points. No

changes were made in the quality grade standards. 

In October 1980, the standards and the related regulations for grades of lamb, yearling mutton,

and mutton carcasses were amended to provide generally for grading only in carcass form and

only in the establishment where the animal was slaughtered or initially chilled. This amendment

was adopted to reduce the variation in grading by limiting the conditions under which grading

could be accomplished.

In October 1982, the standards were revised to permit carcasses with only one break joint to

be classed as lamb if their other maturity characteristics were typical of lamb. In addition, the

quality grade standards were simplified by dropping feathering as a quality factor and basing the

grade on flank fat streakings in relation to maturity with a minimum firmness specified for each

grade. Other changes were: (1) standardization of the quality and conformation compensations,

(2) addition of muscling requirements to the conformation descriptions for each grade, and (3)

elimination of the Cull grade form lamb and yearling mutton carcasses. These changes resulted

form discussions with the National Wool Growers Association whose members felt that the

detrimental to their interests. Research conducted for the Department by Texas A&M University

in 1966 and 1967 supported their claim and indicated that the emphasis placed on the break joints

in classing should be reduced. If also showed that the quality grades could be simplified and at

the same time would be improved as predictors of palatability. These changes were officially

proposed on June 1, 1982 and became effective on October 17, 1982.
3

In July 1992, the standards were revised to “couple” the quality and yield grades (require that

carcasses be identified for both quality and yield when officially graded), and to require removal

of most of the kidney and pelvic fat prior to grading. In addition, leg conformation score was

eliminated as a yield grade factor, and the fat thickness range in each yield grade was shifted and

narrowed. These changes were initiated in response to request from producers--represented by

the American Sheep Industry (ASI) Association--to provide an improved communication tool to

efficiently reflect consumers’ preferences for lean meat products back to producers. Before the

changes were proposed several studies of possible revisions were jointly conducted by the

Department, ASI, several land-grant Universities, and several major lamb slaughterers. These

studies indicated that grade changes would encourage the production of leaner lambs, and that the

revised grades could be accurately applied. The changes were officially proposed on November

20, 1991, and were overwhelmingly supported by all industry segments except lamb feeders and

lamb slaughterers and processors. Those two segments of the industry were split on the changes. 

The revised standards became effective on July 6, 1992.

§54.121 Scope.

These standards for grades of lamb, yearling mutton, and mutton are written primarily in terms

of carcasses. However, they also are applicable to the grading of sides. To simplify the phrasing

of the standards, the words “carcass” and “carcasses” are used also to mean “side” or “sides.” 

 

§54.122 Differentiation between lamb, yearling mutton, and mutton carcasses.

(a) Ovine carcasses are classified as lamb, yearling mutton, or mutton depending upon their

evidences of maturity as indicated by the development of their muscular and skeletal systems. 

Typical lamb carcasses tend to have slightly wide and moderately flat rib bones and a light red

color and fine texture of lean. By contrast, typical yearling mutton carcasses have moderately

wide rib bones which tend to be flat and a slightly dark red color and slightly coarse texture of

lean. Typical mutton carcasses have wide, flat, rib bones and a dark red color and coarse texture

of lean. 

(b) In the dressing of ovine carcasses, both front cannon bones (trotters) normally are left

attached to the carcass although in some instances, one or both trotters may be removed. If

present, trotters will terminate in perfect break joints (all ridges forming the break joints are intact

and well defined), imperfect break joints, or spool joints. For determining the maturity of ovine

carcasses, an imperfect break joint is considered the same as a spool joint and it is assumed that

there was a spool joint on any missing trotter. These variations, as indicated by the following

guidelines, are important considerations in determining whether a carcass is classed as lamb,

yearling mutton, or mutton. 

(c) A carcass with perfect break joints on both trotters will be classed lamb or yearling mutton

based on its other evidences of maturity. 

(d) A carcass with spool joints on both trotters will be classed as yearling mutton or mutton

based on its other evidences of maturity. Mutton carcasses always have spool joints on both front

trotters. 
4

(e) A carcass which has a perfect break joint on one trotter and has either: (1) A spool joint on

the other trotter, or (2) has had the other trotter removed, will be classed as a lamb if its other

maturity characteristics are not more advanced than described in the grade specifications as

typical of the more mature lamb group. Otherwise, such carcasses will be classed as yearling

mutton. Maturity within the lamb class shall be based on the combination of lean and all skeletal

characteristics. 

(f) Except for the above referenced considerations given to break joints and spool joints, in

making other maturity evaluations more consideration is given to the characteristics of the flesh

than is given to the characteristics of the skeleton. 

 

§54.123 Application of standards. 

(a) Grade Factors. (1) The grade of an ovine carcass is based on separate evaluations of two

general considerations: Palatability-indicating characteristics of the lean and conformation, herein

referred to as “quality,” and the estimated percent of closely trimmed (0.10 inch fat or less),

semi-boneless and boneless, major retail cuts to be derived from the carcass, herein referred to as

“yield.” The term “quality” has traditionally been used to refer only to the palatability-indicating

characteristics of the lean without reference to conformation. Its use herein to include

consideration of conformation is not intended to imply that variations in conformation are either

directly or indirectly related to differences in palatability. When officially graded by a Federal

meat grader, the grade of an ovine carcass shall consist of a combination of both a quality grade

and a yield grade. The yield grade designation may be removed from officially graded ovine

carcasses, sides, quarters, wholesale cuts, or combinations of wholesale cuts on which the external

fat (natural or trimmed) does not exceed 0.25 inch in thickness at any point. The yield grade

designation may be removed from boneless subprimal cuts or retail cuts (bone-in or boneless)

without trimming of external fat. In instances where removal of the yield grade designation is

permitted, the USDA grade may consist of the quality grade designation only. 

(2) The grade standards are written so that the quality and yield grade standards are contained

in separate sections. The quality grade section is divided further into three separate sections

applicable to lamb, yearling mutton, and mutton carcasses. There are four quality grades within

each class -- Prime, Choice, Good, and Utility for lamb and yearling mutton, and Choice, Good,

Utility, and Cull for mutton. There are five yield grades applicable to all classes of ovine

carcasses, denoted by numbers 1 through 5, with Yield Grade 1 representing the highest degree of

cutability. 

(3) To be eligible for grading, ovine carcasses cannot have more than 1.0 percent of their

carcass weight in kidney and pelvic fat. If more than 1.0 percent of kidney and pelvic fat is

present in the carcass naturally, the excess fat must be removed prior to offering it for grading. 

The fat considered in making this determination includes the kidney knob (kidney and surrounding

fat) and the lumbar and pelvic fat in the loin and leg. The amount of these fats is evaluated

subjectively and expressed as a percent of the carcass weight. Trimming of external fat for the

purpose of altering the yield grade shall be considered a fraudulent or deceptive practice in

connection with the services requested for such carcasses. Carcasses that have had external fat or

lean removed for Federal meat inspection compliance may be graded only if the official grader
5

determines that an accurate grade determination can be made. Entire carcasses with more than

minor amounts of lean removed from the major wholesale cuts (leg, loin, rack, and shoulder) shall

not be eligible for a grade determination. However, the portions of such carcasses not affected by

lean removal shall be eligible for grading, provided an accurate grade determination can be made. 

(4) Carcasses qualifying for any particular grade may vary with respect to the relative

development of their individual grade factors, and there will be carcasses which qualify for a

particular grade in which the development of some of these individual grade factors will be more

typical of other grades. Because it is impractical to describe the nearly limitless number of such

recognizable combinations of characteristics, the standards for each quality and yield grade

describe only carcasses which have a relatively similar development of individual factors and

which are also representative of the lower limits of each grade. In the quality grade standards,

examples of the extent to which superiority in quality may compensate for deficiencies in

conformation, and vice versa, are indicated for each grade. In the Prime and Choice grades

certain minimum requirements for external fat covering also are indicated. 

(b) Quality grades. (1) The quality grade of an ovine carcass is based on separate evaluations

of two general considerations -- the quality, or the palatability-indicating characteristics of the

lean, and the conformation of the carcass. 

(2) Conformation is the manner of formation of the carcass with particular reference to the

relative development of the muscular and skeletal systems, although it also is influenced to some

extent by the quantity and distribution of external finish. However, external fat in excess of that

normally left on retail cuts is not considered in evaluating conformation. The conformation

descriptions included in each of the grade specifications refer to the thickness of muscling and to

an overall degree of thickness and fullness of the carcass. However, carcasses which meet the

requirements for thickness of muscling specified for a grade will be considered to have

conformation adequate for that grade despite the fact that, because of a lack of fatness, they may

not have the overall degree of thickness and fullness described. The conformation of a carcass is

evaluated by averaging the conformation of its various component parts, giving consideration not

only to the proportion that each cut is of the carcass weight but also to the general desirability of

each cut as compared with other cuts. Superior conformation implies a high proportion of edible

meat to bone and a high proportion of the weight of the carcass in the more demanded cuts and is

reflected in carcasses which are very thickly muscled, very wide and thick in relation to their

length, and which have a very plump, full, and well-rounded appearance. Inferior conformation

implies a low proportion of edible meat to bone and a low proportion of the weight of the carcass

in the more demanded cuts and is reflected in carcasses which are very thinly muscled, very

narrow in relation to their length, and which have a very angular, thin, and sunken appearance. 

(3) The quality of the lean flesh is best evaluated by consideration of its texture, firmness, and

marbling, as observed in a cut surface, in relation to the apparent maturity of the animal from

which the carcass was produced. However, in grading ovine carcasses, direct observation of

these characteristics usually is not possible. Therefore, the quality of the lean is evaluated

indirectly by giving consideration to the quantity of fat streakings within and upon the inside flank

muscles in relation to the apparent evidences of maturity. Within each grade, the requirements for

flank fat streakings increase progressively with evidences of advancing maturity. To facilitate the

application of this principle, the relationship between flank fat streakings, maturity, and quality is
6

shown in Figure 1. Flank fat streakings are categorized in descending order of quantity as

follows: Abundant, moderately abundant, slightly abundant, moderate, modest, small, slight,

traces, practically devoid, and devoid. In addition, the standards specify a minimum degrees of

firmness of lean flesh and external fat for each grade and a minimum degree of external fatness for

carcasses in the Prime and Choice grades. The different degrees of firmness in descending order

of firmness are: Extremely firm, tends to be extremely firm, firm, tends to be firm, moderately

firm, tends to be moderately firm, slightly firm, tends to be slightly firm, tends to be slightly soft,

slightly soft, tends to be moderately soft, moderately soft, soft, and very soft. 

(4) The quality standards are intended to apply to all ovine carcasses without regard to the

apparent sex condition of the animal at time of slaughter. However, carcasses from males which

have thick, heavy necks and shoulders typical of uncastrated males are discounted in quality grade

in accord with the extent to which these characteristics are developed. Such discounts may vary

from less than one-half grade in carcasses from young lambs in which such characteristics are

barely noticeable to as much as two full grades in carcasses from mature rams in which such

characteristics are very pronounced. 

(c) Yield grades. (1) The yield grade of an ovine carcass is based on the amount of external fat

present. 

(2) The amount of external fat for carcasses with a normal distribution of this fat is evaluated

in terms of its actual thickness over the center of the ribeye muscle and is measured perpendicular

to the outside surface between the 12th and 13th ribs. On carcasses which do not have a normal
7

distribution of external fat, the fat thickness measurement over the ribeye may be adjusted, as

necessary, to reflect unusual amounts of fat on other parts of the carcass. In determining the

amount of this adjustment, particular attention is given to the amount of external fat on those

parts where fat is deposited at a faster-than-average rate, particularly the rump, outside of the

shoulders, breast, flank, and cod or udder. Thus, in a carcass which is fatter over these parts than

is normally associated with the actual fat thickness over the ribeye, the measurement is adjusted

upward. Conversely, in a carcass which has less fat over these parts than is normally associated

with the actual fat thickness 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 0.05 inch is not uncommon. In some carcasses a greater adjustment may be

necessary. As a guide in making these adjustments, the standards for each yield grade include an

additional related measurement -- body wall thickness, which is measured 5 inches laterally from

the middle of the backbone between the 12th and 13th ribs. As the amount of external fat

increases, the percent of retail cuts decreases -- each 0.05 inch change in adjusted fat thickness

over the ribeye changes the yield grade by one-half of a grade. 

(3) When the ribeye is exposed for grading the official grader may estimate or measure the fat

thickness, as necessary. On intact ovine carcasses, the official determination of the external fat

thickness is made by probing with an approved measuring device. Also, visual evaluations of the

fat thickness of intact carcasses may be made at the discretion of the official grader. Because

small variations in fat thickness may change the final yield grade significantly, it is essential that an

accurate fat thickness evaluation be made. Therefore, official graders are expected to take the

time necessary to make accurate measurements when visual evaluations are in doubt. Applicants

for grading can facilitate visual evaluations by cutting through the fat down to the lean over the

ribeye on at least one side of the carcass after carcasses are properly chilled. Such a cut will

greatly enhance both the speed and accuracy of yield grade evaluations. 

(4) The adjusted fat thickness range for each yield grade is as follows: Yield Grade 1 -- 0.00 to

0.15 inch; Yield Grade 2 -- 0.16 to 0.25 inch; Yield Grade 3 -- 0.26 to 0.35 inch; Yield Grade 4 --

0.36 to 0.45 inch; and Yield Grade 5 -- 0.46 inch and greater. For carcass evaluation programs

and other purposes when position within a yield grade is desired, each 0.01 inch change in fatness

within these ranges would equate to a change of one-tenth of a yield grade. The following

equation may be used to convert adjusted fat thickness to yield grade: Yield Grade=0.4+(10 X

Adjusted fat thickness, inches). 

(5) The yield grade standards for each of the first four yield grades list characteristics of a

carcass with descriptions of the amount of external fat normally present on various parts of the

carcass. These descriptions are not specific requirements -- they are included only as illustrations

of carcasses which are near the borderline between grades. For example, the characteristics listed

for Yield Grade 1 represent a carcass which is near the borderline of Yield Grade 1 and Yield

Grade 2. These descriptions facilitate the visual determination of the yield grade without making

detailed measurements. 

§54.124 Specifications for official U.S. standards for grades of lamb carcasses (quality). 

(a) Prime. (1) Lamb carcasses having minimum conformation qualifications for the Prime
8

grade tend to be thickly muscled throughout, are moderately wide and thick in relation to their

length and have moderately plump and full legs, moderately wide and thick backs, and moderately

thick and full shoulders. 

(2) Minimum requirements for fat streakings within and upon the inside flank muscles are

specified for two maturity groups which cover the entire range of maturity within the lamb class. 

Typical carcasses from the younger group have moderately narrow, slightly flat rib bones;

moderately red and moist and porous break joints; and a slightly dark pink color of inside flank

muscles. The minimum degree of flank fat streakings required for such carcasses increases with

advancing maturity throughout this group from minimum small to maximum small (see Figure 1). 

(3) Typical carcasses from the more mature group have slightly wide, moderately flat rib

bones; slightly red but slightly dry and hard break joints; and a light red color of inside flank

muscles. The minimum degree of flank fat streakings required increases with advancing maturity

throughout this group from minimum modest to maximum modest (see Figure 1). 

(4) Regardless of the extent to which the conformation of a carcass may exceed the minimum

requirements for Prime, a carcass must have minimum Prime quality to be eligible for the Prime

grade. However, a development of quality which is superior to that specified as minimum for the

Prime grade may compensate, on an equal basis, for a development of conformation which is

inferior to that specified as minimum for Prime as indicated in the following example: A carcass

which has evidence of quality equivalent to the mid-point of the Prime grade (one degree of flank

fat streakings more than required as the minimum for Prime) may have conformation equivalent to

the mid-point of the Choice grade and remain eligible for Prime. However, in no instance may a

carcass be graded Prime which has a development of conformation inferior to that specified as

minimum for the Choice grade. In addition, to be eligible for Prime, the lean flesh and external fat

of lamb carcasses must be not less than tends to be moderately firm. Also, to be eligible for Prime,

a carcass must have at least a very thin covering of external fat over the top of the shoulders and

the outside of the center parts of the legs, and the back must have at least a thin covering of fat,

that is, the muscles of the back may be no more than plainly visible through the fat. 

(b) Choice. (1) Lamb carcasses having minimum conformation qualifications for the Choice

grade are slightly thick muscled throughout, they tend to be slightly wide and thick in relation to

their length and tend to have slightly plump and full legs, slightly wide and thick backs, and

slightly thick and full shoulders. 

(2) Minimum requirements for fat streakings within and upon the inside flank muscles are

specified for two maturity groups which cover the entire range of maturity within the lamb class. 

Typical carcasses from the younger group have moderately narrow, slightly flat rib bones;

moderately red and moist and porous break joints; and a moderately dark pink color of inside

flank muscles. The minimum degree of flank fat streakings required for such carcasses increases

with advancing maturity throughout this group from minimum traces to maximum traces (see

Figure 1). 

(3) Typical carcasses from the more mature group have slightly wide, moderately flat rib

bones; slightly red but slightly dry and hard break joints; and a moderately light red color of inside

flank muscles. The minimum degree of flank fat streakings required for such carcasses increases

with advancing maturity throughout this group from minimum slight to maximum slight (see

Figure 1). 
9

(4) A development of quality which is superior to that specified as minimum for the Choice

grade may compensate, on an equal basis, for a development of conformation which is inferior to

that specified as minimum for Choice as indicated in the following example: A carcass which has

evidence of quality equivalent to the mid-point of the Choice grade may have conformation

equivalent to the mid-point of the Good grade and remain eligible for Choice. However, in no

instance may a carcass be graded Choice which has a development of conformation inferior to

that specified as minimum for the Good grade. Also, a carcass which has conformation at least

one-third grade superior to that specified as minimum for the Choice grade may qualify for Choice

with a development of quality equivalent to the lower limit of the upper third of the Good grade. 

Compensation of superior conformation for inferior quality is limited to one-third grade of

deficient quality. In addition, to be eligible for Choice, the lean flesh and external fat of lamb

carcasses must be not less than tends to be slightly firm. Also, to be eligible for Choice, a carcass

must have at least a very thin covering of external fat over the top of the shoulders and the

outside of the center parts of the legs, and the back must have at least a thin covering of fat, that

is, the muscles of the back may be no more than plainly visible through the fat. 

(c) Good. (1) Lamb carcasses having minimum conformation qualifications for the Good grade

are slightly thin muscled throughout, are moderately narrow in relation to their length and have

slightly thin, tapering legs, and slightly narrow and thin backs and shoulders. 

(2) Minimum requirements for fat streakings within and upon the inside flank muscles are

specified for two maturity groups which cover the entire range of maturity within the lamb class. 

Typical carcasses from the younger group have moderately narrow, slightly flat rib bones;

moderately red and moist and porous break joints; and a dark pink color of inside flank muscles. 

The minimum degree of flank fat streakings required for such carcasses increases with advancing

maturity throughout this group from minimum practically devoid to maximum practically devoid

(see Figure 1). 

(3) Typical carcasses from the more mature group have slightly wide, moderately flat rib

bones; slightly red but slightly dry and hard break joints; and a slightly dark red color of inside

flank muscles. The minimum degree of flank fat streakings required for such carcasses increases

with advancing maturity throughout this group from minimum traces to maximum traces (see

Figure 1). 

(4) A development of quality which is superior to that specified as minimum for the Good

grade may compensate, on an equal basis, for development of conformation which is inferior to

that specified as minimum for Good as indicated in the following example: A carcass which has

evidences of quality at least one-third grade superior to that specified as minimum for the Good

grade may have conformation equivalent to the minimum for the upper one-third of the Utility

grade and remain eligible for Good. However, in no instance may a carcass be graded Good

which has a development of conformation inferior to the minimum for the upper one-third of the

Utility grade. Also, a carcass which has conformation at least one-third grade superior to that

specified as minimum for the Good grade may qualify for Good with a development of quality

equivalent to the lower limit of the upper third of the Utility grade. Compensation of superior

conformation for inferior quality is limited to one-third grade of deficient quality. In addition, to

be eligible for Good, the lean flesh and external fat of lamb carcasses must be not less than slightly

soft. 
10

(d) Utility. The Utility grade includes those lamb carcasses whose characteristics are inferior

to those specified as minimum for the Good grade. 

 

§54.125 Specifications for official U.S. standards for grades of yearling mutton carcasses

(quality). 

(a) Prime. (1) Yearling mutton carcasses having minimum conformation qualifications for the

Prime grade tend to be thickly muscled throughout, are moderately wide and thick in relation to

their length and have moderately plump and full legs, moderately wide and thick backs, and

moderately thick and full shoulders. 

(2) Minimum requirements for fat streakings within and upon the inside flank muscles are

specified for one maturity group which covers the entire range of maturity within the yearling

mutton class. Typical yearling mutton carcasses have moderately wide rib bones which tend to be

flat; and a slightly dark red color of inside flank muscles. The minimum degree of flank fat

streakings required for such carcasses increases with advancing maturity throughout this group

from minimum moderate to maximum moderate (see Figure 1). 

(3) Regardless of the extent to which the conformation of a carcass may exceed the minimum

requirements for Prime, a carcass must have minimum Prime quality to be eligible for the Prime

grade. However, a development of quality which is superior to that specified as minimum for the

Prime grade may compensate, on an equal basis, for a development of conformation which is

inferior to that specified as minimum for Prime as indicated in the following example: A carcass

which has evidence of quality equivalent to the mid-point of the Prime grade (one degree of flank

fat streakings more than required as the minimum for Prime) may have conformation equivalent to

the mid-point of the Choice grade and remain eligible for Prime. However, in no instance may a

carcass be graded Prime which has a development of conformation inferior to that specified as

minimum for the Choice grade. In addition, to be eligible for Prime, the lean flesh and external fat

must be not less than tends to be moderately firm. Also, to be eligible for Prime, a carcass must

have at least a very thin covering of external fat over the top of the shoulders and the outside of

the center parts of the legs, and the back must have at least a thin covering of fat, that is, the

muscles of the back may be no more than plainly visible through the fat. 

(b) Choice. (1) Yearling mutton carcasses having minimum conformation qualifications for the

Choice grade are slightly thick muscled throughout, they tend to be slightly wide and thick in

relation to their length and tend to have slightly plump and full legs, slightly wide and thick backs,

and slightly thick and full shoulders. 

(2) Minimum requirements for fat streakings within and upon the inside flank muscles are

specified for one maturity group which covers the entire range of maturity within the yearling

mutton class. Typical yearling mutton carcasses have moderately wide rib bones which tend to be

flat; and a color of inside flank muscles which tends to be moderately dark red. The minimum

degree of flank fat streakings required for such carcasses increases with advancing maturity

throughout this group from minimum small to maximum small (see Figure 1). 

(3) A development of quality which is superior to that specified as minimum for the Choice

grade may compensate, on an equal basis, for a development of conformation which is inferior to

the specified as minimum for Choice as indicated in the following example: A carcass which has
11

evidence of quality equivalent to the mid-point of the Choice grade may have conformation

equivalent to the mid-point of the Good grade and remain eligible for Choice. However, in no

instance may a carcass be graded Choice which has a development of conformation inferior to

that specified as minimum for the Good grade. Also, a carcass which has a development of

conformation at least one-third grade superior to that specified as minimum for the Choice grade

may qualify for Choice with a development of quality equivalent to the lower limit of the upper

third of the Good grade. Compensation of superior conformation for inferior quality is limited to

one-third grade of deficient quality. In addition, to be eligible for Choice, the lean flesh and

external fat must be not less than tends to be slightly firm. Also, to be eligible for Choice, a

carcass must have at least a very thin covering of external fat over the top of the shoulders and the

outside of the center parts of the legs, and the back must have at least a thin covering of fat, that

is, the muscles of the back may be no more than plainly visible through the fat. 

(c) Good. (1) Yearling mutton carcasses having minimum conformation qualifications for the

Good grade are slightly thin muscled throughout, are moderately narrow in relation to their length

and have slightly thin, tapering legs, and slightly narrow and thin backs and shoulders. 

(2) Minimum requirements for fat streakings within and upon the inside flank muscles are

specified for one maturity group which covers the entire range of maturity within the yearling

mutton class. Typical yearling mutton carcasses have moderately wide rib bones which tend to be

flat; and a moderately dark red color of inside flank muscles. The minimum degree of flank fat

streakings required for such carcasses increases with advancing maturity throughout this group

from minimum slight to maximum slight (see Figure 1). 

(3) A development of quality which is superior to that specified as minimum for the Good

grade may compensate, on an equal basis, for a development of conformation which is inferior to

that specified as minimum for Good as indicated in the following example: A carcass which has

evidence of quality at least one-third grade superior to that specified as minimum for the Good

grade may have conformation equivalent to the minimum for the upper one-third of the Utility

grade and remain eligible for Good. However, in no instance may a carcass be graded Good

which has a development of conformation inferior to the minimum for the upper one-third of the

Utility grade. Also, a carcass which has conformation at least one-third grade superior to that

specified as minimum for the Good grade may qualify for Good with a development of quality

equivalent to the lower limit of the upper third of the Utility grade. Compensation of superior

conformation for inferior quality is limited to one-third grade of deficient quality. In addition, to

be eligible for Good, the lean flesh and external fat must be not less than slightly soft. 

(d) Utility. The Utility grade includes those yearling mutton carcasses whose characteristics

are inferior to those specified as minimum for the Good grade. 

§54.126 Specifications for official U.S. standards for grades of mutton carcasses (quality).

(a) Choice. (1) Mutton carcasses having minimum conformation qualifications for the Choice

grade are slightly thick muscled throughout, they tend to be slightly wide and thick in relation to

their length and tend to have slightly plump and full legs, slightly wide and thick backs, and

slightly thick and full shoulders. 

(2) Minimum requirements for fat streakings within and upon the inside flank muscles are
12

specified for one maturity group which covers the entire range of maturity within the mutton

class. Typical mutton carcasses have wide, flat rib bones; and a dark red color of inside flank

muscles. The minimum degree of flank fat streakings required for such carcasses increases with

advancing maturity throughout this group from minimum modest to maximum modest, (see

Figure 1). 

(3) A development of quality which is superior to that specified as minimum for the Choice

grade may compensate, on an equal basis, for a development of conformation which is inferior to

that specified as minimum for Choice as indicated in the following example: A carcass which has

evidence of quality equivalent to the mid-point of the Choice grade (one degree of flank fat

streakings more than required as the minimum of Choice) may have conformation equivalent to

the mid-point of the Good grade and remain eligible for Choice. However, in no instance may a

carcass be graded Choice which has a development of conformation inferior to that specified as

minimum for the Good grade. Also, a carcass which has conformation at least one-third grade

superior to that specified as minimum for the Choice grade may qualify for Choice with a

development of quality equivalent to the lower limit of the upper third of the Good grade. 

Compensation of superior conformation for inferior quality is limited to one-third grade of

deficient quality. In addition, to be eligible for Choice, the lean flesh and external fat must be not

less than tends to be slightly firm. Also, to be eligible for Choice, a carcass must have at least a

very thin covering of external fat over the top of the shoulders and the outside of the center parts

of the legs, and the back must have at least a thin covering of fat, that is, the muscles of the back

may be more than plainly visible through the fat. 

(b) Good. (1) Mutton carcasses having minimum conformation for the Good grade are slightly

thin muscled throughout, moderately narrow in relation to their length and have slightly thin,

tapering legs, and slightly narrow and thin backs and shoulders. 

(2) Minimum requirements for fat streakings within and upon the inside flank muscles are

specified for one maturity group which covers the entire range of maturity within the mutton

class. Typical mutton carcasses have wide, flat rib bones; and a dark red color of inside flank

muscles. The minimum degree of flank fat streakings required for such carcasses increases with

advancing maturity throughout this group from a minimum small amount to a maximum small

amount (see Figure 1). 

(3) A development of quality which is superior to that specified as minimum for the Good

grade may compensate, on an equal basis, for a development of conformation which is inferior to

that specified as minimum for Good as indicated in the following example: A carcass which has

evidence of quality at least one-third grade superior to that specified as minimum for the Good

grade may have conformation equivalent to the minimum for the upper one-third of the Utility

grade and remain eligible for Good. However, in no instance may a carcass be graded Good

which has a development of conformation inferior to that specified as minimum for the Utility

grade. Also, a carcass which has conformation at least one-third grade superior to that specified

as minimum for the Good grade may qualify for Good with a development of quality equivalent to

the lower limit of the upper third of the Utility grade. Compensation of superior conformation for

inferior quality is limited to one-third grade of deficient quality. In addition, to be eligible for

Good, the lean flesh and external fat must be not less than slightly soft. 

(c) Utility. (1) Mutton carcasses having minimum conformation qualifications for the Utility
13

grade are thinly muscled throughout, are very angular and very narrow in relation to their length

and have thin, slightly concave legs, very narrow and sunken backs, and narrow, sharp shoulders. 

Hips and shoulder joints are slightly visible. 

(2) Minimum requirements for fat streakings within and upon the inside flank muscles are

specified for one maturity group which covers the entire range of maturity within the mutton

class. Typical mutton carcasses have wide, flat rib bones; and a very dark red color of inside flank

muscles. The minimum degree of flank fat streakings required for such carcasses increases with

advancing maturity throughout this group from minimum practically devoid to maximum

practically devoid (see Figure 1). 

(3) A development of quality which is superior to that specified as minimum for the Utility

grade may compensate, on an equal basis, for a development of conformation which is inferior to

that specified as minimum for Utility as indicated in the following example: A carcass which has

evidence of quality at least one-third grade superior to that specified as minimum for the Utility

grade may have conformation equivalent to the minimum for the upper one-third of the Cull grade

and remain eligible for Utility. However, in no instance may a carcass be graded Utility which has

a development of conformation inferior to the minimum for the upper one-third of the Cull grade. 

Also, a carcass which has conformation at least one-third grade superior to that specified as

minimum for the Utility grade may qualify for Utility with a development of quality equivalent to

the lower limit of the upper third of the Cull grade. Compensation of superior conformation for

inferior quality is also limited to one-third grade of deficient quality. In addition, to be eligible for

Utility, the lean flesh and external fat must be not less than soft. 

(d) Cull. The Cull grade includes those mutton carcasses whose characteristics are inferior to

those specified as minimum for the Utility grade. 

 

§54.127 Specifications for official U.S. standards for grades of carcass lamb, yearling

mutton, and mutton (yield). 

(a) The yield grade of an ovine carcass or side is determined on the basis of the adjusted fat

thickness over the ribeye muscle between the 12th and 13th ribs. The adjusted fat thickness range

for each yield grade is as follows: Yield Grade 1 -- 0.00 to 0.15 inch; Yield Grade 2 -- 0.16 to

0.25 inch; Yield Grade 3 -- 0.26 to 0.35 inch; Yield Grade 4 -- 0.36 to 0.45 inch; and Yield Grade

5 -- 0.46 inch and greater. 

(b) 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. (i) A carcass in Yield Grade 1, which is near the borderline with Yield

Grade 2, usually has only a thin layer of external fat over the back and loin and slight deposits of

fat in the flanks and cod or udder. There is usually a very thin layer of fat over the top of the

shoulders and the outside of the legs. Muscles are usually plainly visible on most areas of the

carcass.

(ii) A carcass in Yield Grade 1 with the maximum amount of fat allowed would have an

adjusted fat thickness of 0.15 inch. Such a carcass with normal fat distribution and weighing 55

pounds would also have a body wall thickness of about 0.75 inch, and one weighing 75 pounds

would have a body wall thickness of about 0.85 inch. 
14

(2) Yield Grade 2. (i) A carcass in Yield Grade 2, which is near the borderline with Yield

Grade 3, usually has a slightly thin layer of fat over the back and loin and the muscles of the back

are not visible. The top of the shoulders and the outside of the legs have a thin covering of fat

and the muscles are slightly visible. There are usually small deposits of fat in the flanks and cod or

udder. 

(ii) A carcass in Yield Grade 2 with the maximum amount of fat allowed would have an

adjusted fat thickness of 0.25 inch. Such a carcass with normal fat distribution and weighing 55

pounds would also have a body wall thickness of about 0.90 inch, and one weighing 75 pounds

would have a body wall thickness of about 1.00 inch. 

(3) Yield Grade 3. (i) A carcass in Yield Grade 3, which is near the borderline with Yield

Grade 4, usually has a moderately thick covering of fat over the back. The top of the shoulders

are completely covered, and the legs are nearly completely covered, although the muscles on the

outside of the lower legs are visible. There usually are slightly large deposits of fat in the flanks

and cod or udder. 

(ii) A carcass in Yield Grade 3 with the maximum amount of fat allowed would have an

adjusted fat thickness of 0.35 inch. Such a carcass with normal fat distribution and weighing 55

pounds would also have a body wall thickness of about 1.05 inches, and one weighing 75 pounds

would have a body wall thickness of about 1.15 inches. 

(4) Yield Grade 4. (i) A carcass in Yield Grade 4, which is near the borderline with Yield

Grade 5, usually is completely covered with fat. There usually is a very thick covering of fat over

the back and a slightly thick covering over the shoulders and legs. There usually are large

deposits of fat in the flanks and cod or udder. 

(ii) A carcass in Yield Grade 4 with the maximum amount of fat allowed would have an

adjusted fat thickness of 0.45 inch. Such a carcass with normal fat distribution and weighing 55

pounds would also have a body wall thickness of about 1.20 inches, and one weighing 75 pounds

would have a body wall thickness of about 1.30 inches. 

(5) Yield Grade 5. A carcass in Yield Grade 5 has an adjusted fat thickness of more than 0.45

inch. The external fat covering on most parts of the carcass is usually greater than that described

for Yield Grade 4.