Animal Selection and Evaluation Carcass Evaluation

Why Evaluate Carcasses? A complete understanding of the factors that affect carcass quality and yield grade is essential to every producer, feeder, buyer, and consumer of livestock and meat. With increased use of value based marketing systems, the ability to predict the carcass merit of market animals becomes even more imperative.

Beef Carcass Evaluation and Grading The first step in beef carcass evaluation is the determination of class or sex group. Class determination of beef carcasses is based on evidences of maturity and sex condition at the time of slaughter. In addition to class, the bovine specie is subdivided into kind.

Determination of Kind The differentiation between veal, calf, and beef carcasses is made primarily on the basis of the color of lean, although such factors as texture of lean, character of the fat, color, size, and ossification of the bone and cartilages, and the general contour of the carcass are also given consideration.

Determination of Kind Con’t Veal Veal carcasses have a grayish pink to dark grayish pink color of lean that is smooth and velvety in texture. They also have a slightly soft, pliable character of fat, and narrow and very red ribs.

Determination of Kind Con’t Calf Calf carcasses have a grayish red to moderately red color of lean, a flakier type of fat, and somewhat wider ribs with less pronounced evidences of red color.

Determination of Kind Con’t Beef Beef carcasses have evidences of more advanced maturity. Color of lean is moderately red in young beef carcasses and may be very dark red in mature beef carcasses. Fat is flaky and ribs show evidence of flatness and are slightly red in color in young beef carcasses. Cartilage shows some evidence of ossification in the sacral and lumbar regions compared to calf carcasses.

Determination of Class Since the quality grade standards and some of the qualitative properties (i.e, color, texture, etc.) of beef carcasses vary by class, identification of class is necessary in carcass evaluation. The following characteristics are used to identify and categorize beef carcasses into their respective classes.

Determination of Class Con’t. Steers Identified by the typically rough and irregular shaped fat deposit in the cod region and the presence of a relatively small pizzle eye (white disc caudal to the aitch bone; it is the severed proximal portion of the penis).

Determination of Class Con’t. Bullocks Identified by their disproportionately heavy development of rounds, noticeable crests, thickly fleshed chucks, and large prominent pizzle eyes. Bullock carcasses usually have a noticeably developed small, round muscle adjacent to the hip bone commonly referred to as the jump muscle. (May be covered with fat.) Scrotal fat is typically rough and irregular in shape like that of steers and bulls. The appearance of this fat deposit of steers, bullocks, and bulls contrasts the smooth fat deposit of the udder in heifers.

Determination of Class Con’t. Bullocks Con’t. The lean of bullocks is usually darker and coarser in texture than that of steers, but usually it is not as dark or as coarse as that from bulls. The distinction between bullock and bull carcasses is based solely on their evidences of skeletal (bone and cartilage) maturity with bullocks being the younger of these two classes.

Determination of Class Con’t. Bulls Identified by their disproportionately heavy development of rounds, noticeable crests, thickly fleshed chucks, and large prominent pizzle eyes. Noticeably developed jump muscle. (May be covered with fat.) Scrotal fat is typically rough and irregular in shape like the fat found in steers and bullocks, which contrasts the smooth udder fat of heifers. The lean is usually dark red and coarse textured. The bone characteristics of bulls show evidence of advancing skeletal maturity.

Determination of Class Con’t. Heifers Identified by smooth, uniform fat deposit in the udder region, the absence of the pizzle eye, a slightly larger pelvic cavity, and a straighter aitch bone than steers. Heifer carcasses have a large, bean-shaped bald spot (gracilis muscle) because the muscle has less fat covering it than steers. Less heavily muscled.

Determination of Class Con’t. Cows Identified by their relatively large pelvic cavity and nearly straight aitch bone (accommodates calving.) Udder is usually removed. Hips of cow carcasses usually range from slightly prominent to very prominent. Most cows are old when marketed, and in such carcasses the sacral vertebrae are fused and appear as essentially one bone. All bones are usually hard, white, and the cartilage associated with the vertebrae and aitch bone are completely ossified, except for the buttons which may not be completely ossified.

Illustration Showing Presence of Pizzle Eye, Udder, Cod and Scrotal Fat, Shape of Aitch Bone, Gracilis Muscle and Width of Pelvic Cavity.

Illustration Showing the Conformation of a Heifer, Steer, and Bullock Carcass.

Weight Hot carcass weight is almost always obtained on beef carcasses just before chilling, and chilled carcass weight is usually calculated from hot carcass weight. Hot carcass weight is 1 to 2% higher than chilled carcass weight. Chilled carcass weight =Hot carcass weight x .985

Dressing Percentage Chilled carcass weight is divided by live weight and multiplied by 100 to obtain dressing percentage.

Ribbing Ribbing is the process of cutting one or both sides of the carcass between the 12th and 13th rib to expose the ribeye (longissimus) muscle, marbling, and fat thickness.  Beef carcasses must be ribbed before they can be graded.

Illustration Showing Site of the 12th Rib Fat Thickness Measurement

Beef Quality Grading Beef carcass quality grade is based upon two major factors: (1) degree of marbling and (2) degree of maturity. In addition to these factors, color, texture, and firmness of lean in the ribeye muscle are considered in determining final quality grade. The beef quality grades are U.S.D.A. Prime, Choice, Select, Standard, Commercial, Utility, Cutter, and Canner.

Beef Quality Grading Con’t. Marbling Marbling is the intermingling or dispersion of fat within the lean (intramuscular fat). Marbling is estimated on the lean cut surface of the ribeye muscle at the 12th rib interface. The grade standards specify more marbling for the high grades (U.S.D.A. Prime and Choice) than in the lower grades (U.S.D.A. Select and Standard).

Beef Quality Grading Con’t. Marbling Con’t. Amount of marbling in the eye muscle is divided into ten degrees: 1.     Devoid 6.     Modest 2.     Practically devoid 7.     Moderate 3.     Traces 8.     Slightly abundant 4.     Slight 9.     Moderately abundant 5.     Small 10. Abundant

Beef Quality Grading Con’t. Marbling Con’t. Marbling is an indicator of eating quality, however, as it increases caloric content also increases. Marbling is associated with length of time on feed, type of feed, and genetic capacity for laying down this fat deposit.

Illustrations of Ribeye Muscle at the 12th Rib Showing Marbling Necessary for Quality Grades

Beef Quality Grading Con’t. Maturity Eating quality characteristics (tenderness, juiciness, and flavor) are related to animal age. Maturity refers to the physiological age of cattle rather than to the chronological age (usually unknown). Physiological indicators of maturity include bone characteristics, ossification of cartilage, and color and texture of the ribeye muscle. Cartilage ossifies (becomes bone) and bone whitens (becomes harder, flinty-like and white) with increasing age.

Beef Quality Grading Con’t. Maturity Con’t. Color of lean becomes darker due to accumulation of myoglobin and texture becomes coarser with age. There are five maturity groups and they are designated by the letters A, B, C, D, and E. A and B maturities are from young cattle and carcasses from mature cattle are designated C, D, and E. Because of ossification that has occurred in the bones and cartilage, these C, D, and E maturity carcasses are called “hard boned.”

Illustration Showing Carcass Maturity Left: A maturity carcass – bones have red color and buttons show no ossification. Right: E maturity carcass – bones are whiter and buttons (indicated by arrows) are completely ossified.

Illustration of Ribeye Muscle Showing Normal, Slightly Dark and Dark Color of Lean

Relationship of Marbling and Maturity as used in Determining Final Beef Quality Grade (Area in Black is Standard)

Beef Yield Grading Yield grade is a numerical value from 1 to 5 based upon the yield of boneless closely trimmed (approximately .3 in.), retail cuts from the round, loin, rib, and chuck. These four whole sale cuts make up about 75% of the weight, but about 90% of carcass value. The following factors have the greatest influence on carcass cutability: a. fat thickness at 12th rib b. ribeye area (measured with grid) c. hot carcass weight d. percentage kidney, pelvic, and heart fat (KPH)

Illustration of Location of Beef Primal Cuts