(3) Slaughter barrows and gilts with average muscling will be graded according to their estimated backfat thickness over the last rib. Animals with thin muscling will be graded one grade lower than indicated by the estimated backfat thickness over the last rib. Animals with thick muscling will be graded one grade higher than indicated by their estimated backfat thickness over the last rib, except that animals with an estimated 1.75 inches or greater last rib backfat thickness must remain in the U.S. No. 4 grade.

(i) The official grade standards contain a mathematical equation for calculating the grade and a table for determining a preliminary grade based on the estimated backfat thickness over the last rib. Also, the individual grade specifications describe the various combinations of muscling and last rib backfat thickness which qualify for that grade.

[49 FR 48674, Dec. 14, 1984]

§ 53.153 Specifications for official United States standards for grades of slaughter barrows and gilts.

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(a) The grade of a slaughter barrow or gilt with indications of acceptable quality is determined on the basis of the following equation: Grade X last rib backfat thickness, inches) (1.0 X muscling score). To apply this equation, muscling should be scored as follows: thin (inferior) 1, average 2, and thick (superior) = 3. Animals with thin muscling cannot grade U.S. No. 1. The grade may also be determined by calculating a preliminary grade according to the schedule shown in Table 1 and adjusting up or down one grade for superior or inferior muscling, respectively.

(b) The following descriptions provide a guide to the characteristics of slaughter barrows and gilts in each grade.

(1) U.S. No. 1. (i) Barrows and gilts in this grade are expected to have an acceptable quality of lean and belly thickness and a high expected yield (60.4 percent and over) of four lean cuts. U.S. No. 1 barrows and gilts must have less than average estimated backfat thickness over the last rib with average muscling, or average estimated backfat over the last rib coupled with thick muscling.

(ii) Barrows and gilts with average muscling may be graded U.S. No. 1 if their estimated backfat thickness over the last rib is less than 1.00 inch. Animals with thick muscling may be graded U.S. No. 1 if their estimated backfat thickness over the last rib is less than 1.25 inches. Barrows and gilts with thin muscling may not be graded U.S. No. 1.

(2) U.S. No. 2. (i) Barrows and gilts in this grade are expected to have an acceptable quality of lean and belly thickness and an average expected yield (57.4 to 60.3 percent) of four lean cuts. Animals with average estimated backfat thickness over the last rib and average muscling, less than average estimated backfat thickness over the last rib and thin muscling, or greater than average estimated backfat thickness over the last rib and thick muscling will qualify for this grade.

(ii) Barrows and gilts with average muscling will be graded U.S. No. 2 if their estimated backfat thickness over the last rib is 1.00 to 1.24 inches. Barrows and gilts with thick muscling will be graded U.S. No. 2 if their estimated backfat thickness over the last rib is 1.25 to 1.49 inches. Barrows and gilts with thin muscling must have less than 1.00 inch of estimated backfat over the last rib to be graded U.S. No. 2.

(3) U.S. No. 3. (i) Barrows and gilts in this grade are expected to have an acceptable quality of lean and belly thickness and a slightly low expected yield (54.4 to 57.3 percent) of four lean cuts. Barrows and gilts with average muscling and more than average estimated backfat thickness over last rib, thin muscling and average estimated

backfat thickness over the last rib, or thick muscling and much greater than average estimated backfat thickness over the last rib will qualify for this grade.

(ii) Barrows and gilts with average muscling will be graded U.S. No. 3 if their estimated backfat thickness over the last rib is 1.25 to 1.49 inches. Barrows and gilts with thick muscling will be graded U.S. No. 3 if their estimated backfat thickness over the last rib is 1.50 to 1.74 inches. Barrows and gilts with 1.75 inches or more of estimated backfat thickness over the last rib cannot grade U.S. No. 3. Barrows and gilts with thin muscling will be graded U.S. No. 3 if their estimated backfat thickness over the last rib is 1.00 to 1.24 inches.

(4) U.S. No. 4. (i) Barrows and gilts in this grade are expected to have an acceptable quality of lean and belly thickness and a low expected yield (less than 54.4 percent) of four lean cuts. Barrows and gilts in the U.S. No. 4 grade always have more than average estimated backfat over the last rib and thick, average, or thin muscling, depending on the degree to which the estimated backfat thickness over the last rib exceeds the average.

(ii) Barrows and gilts with average muscling will be graded U.S. No. 4 if their estimated backfat thickness over the last rib is 1.50 inches or greater. Barrows and gilts with thick muscling will be graded U.S. No. 4 with estimated backfat thickness over the last rib of 1.75 inches or greater, and those with thin muscling will be graded U.S. No. 4 with 1.25 inches or greater estimated backfat over the last rib.

(5) U.S. Utility. All barrows and gilts with probable unacceptable quality of lean or belly thickness will be graded U.S. Utility, regardless of their muscling or estimated backfat thickness over the last rib. Also, all barrows and gilts which may produce soft and/or oily fat will be graded U.S. Utility. [49 FR 48675, Dec, 14, 1984]

§ 53.154 Application of standards for grades of slaughter sows.

(a) The standards for grades of slaughter sows are based on (1) differences in yields of lean cuts and of fat cuts and (2) differences in quality of

cuts. These characteristics vary rather consistently from one grade to another. The U.S. No. 1 grade has about the minimum degree of finish necessary to produce pork carcasses with quality characteristics indicative of acceptable palatability in the cuts. The U.S. No. 2 grade is overfinished and the U.S. No. 3 grade is decidedly overfinished in relation to the minimum finish associated with acceptable palatability. Yields of lean cuts are lower and yields of fat cuts are higher, in proportion to the degree of overfinish, in these grades than in the U.S. No. 1 grade. Medium grade sows are underfinished and produce carcasses which are soft and have indications of insufficient quality for acceptably palatable cuts. Cull grade sows are decidedly underfinished and the pork is soft and watery with little or no marbling and low palatability.

(b) The grades for slaughter sows are closely related to the grades for sow carcasses, and the desired objective in grading sows is the accurate prediction of the carcass grade that will be produced. Degree of finish is an important factor in grading, and the expected average back fat thickness of carcasses produced by each grade of slaughter sows forms a part of the standards. The results of study of carcass measurement and cutting data show that carcasses equal in fat thickness are approximately equal in yields of cuts regardless of differences in weight. Therefore, the expected back fat thickness of carcasses from each grade of slaughter sows is the same at all weights. The following table outlines the carcass fat thickness guides for each grade of slaughter sows.

quires an accurate appraisal of these live animal characteristics indicative of carcass finish and grade. No attempt is made to describe in the standards the many combinations of characteristics which may qualify an animal for a particular grade, and sound judgment is required to appropriately analyze varying combinations.

(d) Slaughter sows that have produced several litters of pigs may show considerable roughness along the underline due to extensive development of mammary tissue. In addition, sows from which pigs were weaned only a short time prior to grading may show evidence that the mammary tissue is still active in milk production and not completely dry. Since smoothness and dryness of the underline have little effect on the basic grade determining factors, no provision is made in the standards for altering the grade of slaughter sows due to differences in these characteristics. It is recognized that the value determining factors to be considered in marketing sows include dryness and smoothness as well as such other factors as weight, degree of finish, quality, and fill. However, consideration of all such factors in determining grade would require a complicated system with a great number of grades in order to make each grade sufficiently restrictive to be practical and useful. Therefore, the grades outlined in these standards identify differences in slaughter sows with respect to yields of cuts and quality. They were designed as practical aids in evaluating slaughter sows when used in conjunction with other factors such as weight, fill, smoothness, and dry

ness.

§ 53.155 Specifications for official U.S.

standards for grades of slaughter sows. (a) U.S. No. 1 grade. U.S. No. 1 grade slaughter sows have an intermediate degree of finish near the minimum required to produce pork cuts of acceptable palatability. Sows with the minimum finish for U.S. No. 1 grade are moderately long and slightly wide in relation to weight. Width of body is rather uniform from top to bottom and from front to rear. The back, from side to side, is moderately full and thick with a well-rounded appearance

and blends smoothly into the sides. The sides are moderately long and slightly thick; the flanks are slightly thick and full. Depth at the rear flank may be slightly less than depth at the fore flank. Hams are usually moderately thick and full with a slightly thick covering of fat. Jowls are usually moderately thick and full but appear trim. Sows in this grade produce U.S. No. 1 grade carcasses.

(b) U.S. No. 2 grade. U.S. No. 2 grade slaughter sows have a moderately high degree of finish that is somewhat greater than the minimum required to produce pork cuts of acceptable palatability. Sows with the minimum finish for the U.S. No. 2 grade are slightly short and moderately wide in relation to weight. Width of body is often greater over the top than at the underline and tends to be slightly greater through the shoulders than through the hams. The back, from side to side, is full and thick and appears slightly flat with a noticeable break into the sides. The sides are slightly short and moderately thick; the flanks are moderately thick and full. Depth at the rear flank is nearly equal to depth at the fore flank. Hams are usually thick and full with a moderately thick covering of fat, especially over the lower part. Jowls are usually full and thick, and the neck appears rather short. Sows in this grade produce U.S. No. 2 grade carcasses.

(c) U.S. No. 3 grade. U.S. No. 3 grade slaughter sows have a high degree of finish that is considerably greater than the minimum required to produce pork cuts of acceptable palatability. Sows with the minimum finish for U.S. No. 3 grade are short and wide in relation to weight. Width of body is often somewhat greater over the top than at the underline and tends to be greater through the shoulders than through the hams. The back, from side to side, is very full and thick and appears nearly flat with a pronounced break into the sides. The sides are short and thick; the flanks are thick and full. Depth at the rear flank is equal to depth at the fore flank. Hams are usually very thick and full with a thick covering of fat especially over the lower part. Jowls are usually very full and thick, and the neck appears

short. Sows of this grade produce U.S. No. 3 grade carcasses.

(d) Medium grade. Medium grade slaughter sows have a low degree of finish which is somewhat less than the minimum required to produce pork cuts of acceptable palatability. Sows with the minimum finish for Medium grade are long and moderately narrow in relation to weight. Width of body is often less over the top than at the underline and tends to be slightly less through the shoulders than through the hams. The back, from side to side, is moderately thin and appears rather peaked at the center with a distinct slope toward the sides. The hips are moderately prominent. The sides are long and moderately thin; the flanks are thin. Depth at the rear flank is less than depth at the fore flank. Hams are usually moderately thin and flat and taper toward the shank. Jowls are usually slightly thin and flat, and the neck appears rather long. Sows in this grade produce Medium grade carcasses.

(e) Cull grade. Cull grade slaughter sows have a very low degree of finish which is considerably lower than that required to produce pork cuts of acceptable palatability. Sows with the finish typical of the Cull grade are long and narrow in relation to weight. Width of body is often somewhat less over the top than at the underline and tends to be less through the shoulders than through the hams. The back, from side to side, is thin and lacks fullness and is peaked at the center with a decided slope toward the sides. The hips are prominent. The sides are very long and thin; the flanks are very thin. Depth at the rear flank is considerably less than depth at the fore flank. Hams are usually thin and flat with a definite taper toward the shank. Jowls are usually thin and flat, and the neck appears long. Sows in this grade produce Cull grade carcasses.

§ 53.158 Application of standards for grades of feeder pigs.

(a) The grade of a feeder pig is determined by evaluating two general value-determining characteristics-its logical slaughter potential and its thriftiness.

(b) The logical slaughter potential of a thrifty feeder pig is its expected slaughter grade at a market weight of 220 pounds after a normal feeding period. In these feeder pig standards, logical slaughter potential is determined by a composite appraisal of the development of the muscular system and the skeletal system. Both of these factors have an important effect on the development of lean and fat as the animal grows and fattens, and therefore, on the expected slaughter and carcass grade.

(c) Thriftiness in a feeder pig is its apparent ability to gain weight rapidly and efficiently. Size for age, health, and other general indications of thriftiness are considered in appraising the thriftiness of feeder pigs.

(d) The standards provide for six grades of feeder pigs-U.S. No. 1, U.S. No. 2, U.S. No. 3, U.S. No. 4, U.S. Utility, and U.S. Cull. Except for the U.S. Cull grade, these names correspond to the five grade names for slaughter swine and pork carcasses. The U.S. No. 1, U.S. No. 2, U.S. No. 3, and U.S. No. 4 grades include all pigs which are thrifty. Differentiation between the U.S. No. 1, U.S. No. 2, U.S. No. 3, and U.S. No. 4 grades is based entirely on differences in logical slaughter potential. Feeder pigs in the U.S. No. 1 grade have sufficient muscling and frame to reach a market weight of 220 pounds with a minimum degree of finish. Feeder pigs in the U.S. No. 2, U.S. No. 3, and U.S. No. 4 grades usually have progressively less muscling and less frame and are expected to have progressively more finish when marketed at 220 pounds. The U.S. Utility and U.S. Cull grades include only pigs which lack thriftiness. Differentiation between the U.S. Utility and U.S. Cull grades is based entirely on differences in thriftiness.

(e) Most feeder pigs are marketed when relatively young and before reaching a weight of 125 pounds. At this age, sex condition exerts little influence on the basic factors determining the feeder grade. Therefore, these standards are equally applicable for grading barrow, gilt, and boar pigs, although it is recognized that sex condition may influence the market price in some instances. It is assumed that

boar pigs will be castrated prior to developing the secondary physical characteristics of a boar. Sows, stags, and mature boars are seldom used as feeder animals, and these standards do not apply to those classes.

(f) Only one combination of muscling and skeletal characteristics is described in the standards for the U.S. No. 1, U.S. No. 2, U.S. No. 3, and U.S. No. 4 grades. However, feeder pigs qualifying for the U.S. No. 1, U.S. No. 2, U.S. No. 3 or U.S. No. 4 grades may vary with respect to the relative development of the individual grade factors. In fact, some will qualify for a particular grade although they have some characteristics more nearly typical of another grade, except that feeder pigs in the U.S. No. 1 grade must have at least moderately thick muscling. Feeder pigs with other characteristics of the U.S. No. 1 grade, but with less than moderately thick muscling would be in the U.S. No. 2 grade. Since no attempt is made to describe the numerous combinations of characteristics that may qualify a feeder pig for a specific grade, making appropriate compensations for varying combinations of characteristics requires the use of sound judgment.

§ 53.159 Specifications for official U.S. standards for grades of feeder pigs.

(a) U.S. No. 1. Feeder pigs in this grade near the borderline of the U.S. No. 2 grade are long and have thick muscling throughout. Thickness of muscling is particularly evident in thick and full hams and shoulders. The hams and shoulders are thicker than the back, which is well rounded. They usually present a well-balanced appearance. In no case may a feeder pig be graded U.S. No. 1 with less than moderately thick muscling. Feeder pigs in this grade are expected to produce U.S. No. 1 grade carcasses when slaughtered at 220 pounds.

(b) U.S. No. 2. Feeder pigs in this grade near the borderline of the U.S. No. 3 grade are moderately long and have moderately thick muscling throughout. Thickness of muscling is particularly evident in moderately thick and full hams and shoulders. The back usually appears slightly full and well-rounded. They usually

present a well-balanced appearance. This grade also includes feeder pigs which otherwise qualify for the U.S. No. 1 grade but have less than moderately thick muscling. Feeder pigs in this grade are expected to produce U.S. No. 8 grade carcasses when slaughtered at 220 pounds.

(c) U.S. No. 3. Feeder pigs in this grade near the borderline of the U.S. No. 4 grade are slightly short and have slightly thin muscling throughout. The hams and shoulders are slightly thin and flat and the back usually appears moderately full and thick. Feeder pigs in this grade are expected to produce U.S. No. 3 grade carcasses when slaughtered at 220 pounds.

(d) U.S. No. 4. Feeder pigs typical of the U.S. No. 4 grade are short and have thin muscling throughout. The hams are thin and rather flat, particularly in the lower parts toward the shanks. The back usually appears slightly flat and the width at the topline usually is greater than at the underline. Feeder pigs in this grade are expected to produce U.S. No. 4 grade carcasses when slaughtered at 220 pounds.

(e) U.S. Utility. Feeder pigs typical of this grade are small for their age and appear unthrifty. They often have a rough, unkempt appearance indicating the effects of disease or poor care. The hams and shoulders usually are thin and flat and taper toward the shanks. The back is thin and lacks fullness. Pigs in this grade near the borderline of the U.S. No. 1, U.S. No. 2, U.S. No. 3, and U.S. No. 4 grades are slightly small for their age and appear slightly unthrifty. It is recognized that U.S. Utility grade feeder pigs will produce U.S. No. 1, U.S. No. 2, U.S. No. 3, or U.S. No. 4 grade carcasses when slaughtered at 220 pounds provided their unthrifty condition is corrected. U.S. Utility grade feeder pigs whose unthrifty condition is not corrected will produce U.S. Utility grade car

casses.

(f) U.S. Cull. Feeder pigs typical of this grade are very deficient in thriftiness because of poor care or disease. They can be expected to reach a normal market weight only after an extremely long and costly feeding period, if at all.