Animal Selection and Evaluation

1. Animal Selection and Evaluation Carcass Evaluation

2. 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.

3. Pork Carcass Evaluation and Grading

4. Evaluation/Determination of Class • Even though no class distinction is made for grading barrow or gilt carcasses, one should learn to recognize the differences and be able to identify carcass class. • The classes of slaughter hogs and distinguishing characteristics are as follows:

5. Evaluation/Determination of Class Con’t. • Barrow Carcasses • Identified by the presence of a small pizzle eye (severed attachment of the penis) located dorsally from the aitch bone. • The exposed gracilis muscle ventral to the aitch bone is relatively small in size and partially covered with fat.

6. Evaluation/Determination of Class Con’t. • Gilt Carcasses • Identified by the absence of the pizzle eye. • The exposed gracilis muscle is considerably larger, bean shaped, and has very little fat covering compared to that of barrows. • No mammary development.

7. Evaluation/Determination of Class Con’t. • Sow Carcasses • Identified as same characteristics as those for gilts. • Distinguished from gilts by their developed mammary tissue associated with lactation or advanced stages of pregnancy. • Sow carcasses are usually heavier than gilts.

8. Evaluation/Determination of Class Con’t. • Stag or Boar Carcasses • Identified by same characteristics as those for barrows. • The pizzle of stags and boars is larger and more prominent than in barrows because of sexual maturity. • The shoulders of stags and boars are heavier muscled with larger bones and joints, and the skin over the shoulders is somewhat thicker and the color of lean is darker compared to boars.

9. Evaluation/Determination of Class Con’t. • Stags and boar carcasses are usually heavier and more mature in appearance than barrows.

10. Illustration of a Pizzle Eye on a Barrow and Gilt Carcass

11. Weight • Hot carcass weight is almost always obtained on pork carcasses just prior to chilling. • Hot carcass weight is shrunk 1.5% to obtain chilled carcass weight • Hot carcass wt. x .985 = chilled carcass wt. • If chilled carcasses are weighed, they are weighed just prior to cutting the wholesale cuts. • Chilled carcass weight is used to calculate dressing percentage of hogs by dividing by the live weight and multiplying by 100.

12. Length • Carcass length is measured with a metal tape or may be estimated on the hanging carcass from the cranial edge of the first rib adjacent to the backbone to the cranial edge of the aitch bone (pubic symphysis.) • Usually only one side of each carcass is measured, but both sides may be measured and then averaged.

13. Illustration of Carcass Length Measurement

14. Backfat Thickness • Thickness of backfat is estimated or measured primarily at two different locations. • The first measurement is taken at the last rib to determine pork carcass U.S.D.A. grade. • The second measurement is taken at the 10th rib which is used to calculate percent muscle in pork carcasses. • Backfat measurements are generally taken with a metal ruler and the measurement is made to the nearest .1 in.

15. Illustration Showing Locations of Backfat Measurement

16. Ribbing Pork Carcasses • Pork carcasses are frequently ribbed at the 10th rib interface to expose the loin eye muscle and backfat for educational purposes. • Pork carcasses are seldom ribbed (cut between the 10th and 11th rib to expose the loin eye muscle and 10th rib backfat) in commercial practice because of devaluation of the wholesale loin and belly. • The pork carcass grade standards are designed for use on unribbed carcasses.

17. 10th Rib Backfat Thickness • The depth of subcutaneous fat, including skin, is estimated or measured in tenths of inches at the 10th rib interface. • The 10th rib backfat is a more accurate measurement of subcutaneous fat than average backfat thickness because it is not influenced by variation in carcass splitting and trimming.

18. Illustration Showing Procedure for Backfat Measurement at the 10th Rib

19. Loin Eye Area • Area of the longissimus (eye) muscle is either estimated or measured in square inches on the cross section of the muscle at the 10th rib interface. • Area is determined either with a plastic grid (most frequently used) or from a tracing of the eye muscle with a compensating polar planimeter.

20. Illustration Showing: A. The Outline of a Loineye MuscleB. A Large LoineyeC. A Small Loineye • A. B. C.

21. Pork Carcass Grading • Grades for barrow and gilt carcasses are based on two general considerations: • Quality indicating characteristics of the lean and fat. • Expected yield of the four lean cuts (ham, lion, picnic shoulder, and Boston shoulder).

22. Illustration of Four Lean Cuts

23. Pork Carcass Grading Con’t. • Quality • Two levels of quality are considered: Carcasses with characteristics that indicate the lean has acceptable quality, and carcasses with unacceptable quality of lean. • Quality of lean is usually evaluated in the eye muscle at the 10th rib interface either on ribbed carcasses or on the wholesale loin. • Three factors are used to evaluate quality: 1)     Degree of marbling 2)     Color 3)    Firmness of lean in the eye muscle at the 10th rib Each of these factors is scored on a numerical basis from 1 to 5.

24. Pork Carcass Grading Con’t. • Yield of Lean Cuts • Four grades, U.S. No. 1, U.S. No. 2, U.S. No. 3, and U.S. NO. 4 are provided for carcasses that have indications of an acceptable lean quality and acceptable belly thickness. • These grades are based entirely on the expected carcass yield of lean cuts: GradeYield of Lean Cuts U.S. No. 1 60.4% and over U.S. No. 2 57.4% to 60.3% U.S. No. 3 54.5% to 57.3% U.S. No. 4 Less than 54.4%

25. Pork Carcass Grading Con’t. • Yield of Lean Cuts Con’t. • Pork carcasses differ in lean cut yield because of differences in backfat thickness and in degree of muscling. • Backfat thickness is most highly related to yield of lean cuts. As the amount of external fat increases, the yield of lean cuts decreases. • The degree of muscling is determined by a subjective evaluation of the thickness of muscling in relation to skeletal size. Fatness must also be considered when degree of muscling is evaluated.

26. Illustration Showing Degrees and Scores of Pork Carcass Muscling • A. Thick, 3.0 • B. Average, 2.0 • C. Thin, 1.0

27. 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.

28. 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.

29. 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.

30. 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.

31. 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.

32. 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.

33. 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).

34. 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.

35. 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.

36. 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.

37. 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.

38. 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.

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

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

41. 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

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

43. 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.

44. Illustration Showing Site of the 12th Rib Fat Thickness Measurement

45. 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.

46. 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).

47. 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

48. 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.

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

50. 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.