THE EFFECT OF BREED GROUP AND AGE AT FEEDING ON BEEF CARCASS COMPOSITION

Transcription

1 THE EFFECT OF BREED GROUP AND AGE AT FEEDING ON BEEF CARCASS COMPOSITION D. D. Johnson, R. D. Huffman, S. E. Williams and D. D. Hargrove SUMMARY Steers of known percentages of Brahman (B) and Angus (A) breeding were used to study the effects of breed group (A, 3/4A: U4B, 1/2A: 1/2B and 1/4A:3t4B) and age at feeding (calves versus yearling) on carcass composition when fed to similar levels of outside fat thickness. Breed group had no effect on total boneless closely trimmed retail yield and percentage kidney, pelvic and heart fat (KPH). Sides from the 1/4 Brahman carcasses had more fat trim in excess of 3 inch than did the sides from the 3/4 Brahman carcasses. Fat trim percentages from the Angus and 1/2 Brahman carcasses were intermediate to the other two breed groups. Sides from steers fed as yearlings had greater boneless closely trimmed retail product yield, lower total fat and bone trim and less KPH fat, although fed to similar outside levels of fatness. INTRODUCTION The use of Brahman or Brahman derivative breeds has become an integral part of crossbreeding programs in the Gulf Coast region of the United States, especially Florida. The Brahman influence adds to the adaptability and growth needed for the warm, humid climate encountered in this area. A1though many cow-calf producers find Brahman influence essential to their breeding program, when these calves are marketed to other segments of the industry (feeders, packers etc.) they are often discriminated against in price, especially during periods of high supply. Some of this price discrimination is apparently justified. Reports by Huffman et al. (1988) showed that 1/2 and 3/4 Brahman steers had smaller ribeye areas per 100 lb hot carcass and lower marbling scores than the 1/4 Brahman and Angus steers. Also, the 1/2 and 3/4 Brahman steers produced a lower percentage of Choice carcasses and a higher percentage of Select and Standard carcasses than the Angus and 1/4 Brahman steers, when all groups were slaughtered at similar levels of outside fat. Johnson et al. (1989) also noted that Warner-Bratzler shear force increased and sensory panel tenderness decreased as percentage Brahman breeding increased, giving further justification for price discrimination. Packers have voiced concerns about the smaller ribeye area per hundred pounds of carcass weight of Brahman blooded cattle, as reported by Huffman et al. (1988), and have indicated that boxed-beef yields of heavy percentage Brahman cattle were lower than that of other breed types. Researchers have noted that, even though British and European breeds appear to have a more desirable conformation, Brahman and Brahman crossbreds have been comparable or often times superior in percentage of muscle yield from certain carcass locations. The objectives of this study were to compare retail yield of carcasses from varying percentages of Brahman breeding when slaughtered at similar levels of outside fatness, and to see if feeding calves versus feeding yearlings influences the percentage retail yield, when all animals are slaughtered at comparable levels of outside fatness.

2 MATERIALS AND METHODS A total of 125 steers of known percentages of Angus (A) and Brahman (B) breeding (A = 31, 3/4A: 1/4B= 32, 1/2A: 1/2B= 31, and1/4a:3/4b = 31) were purchased at weaning in 1985 and 1986 and transported to the Beef Research Unit, Gainesville. Each year half of the steers in each breed group were randomly assigned to be fed as calves during the cool period of the year (November to May), and the other half assigned to a winter stocker program followed by feeding during the warm period of the year (June to October). Steers placed in the feedlot were fed a high concentrate diet until they reached a randomly assigned slaughter end point of.4 or.6 inch estimated outside fat thickness, which was monitored with real time ultrasound measurements and visual evaluation. All steers were implanted with Ralgro TM at the beginning of the feedlot period, and those still on feed 90 days later were implanted with Synovex-S. When each steer reached its designated slaughter end point, it was weighed in the morning prior to feeding and shipped to the University of Florida Meat Laboratory, for slaughter and collection of carcass data. Carcasses were chilled to 32 to 34 F for 24 hours, ribbed, and graded for USDA quality and yield factors. These data were discussed by Huffman et al. (1988). The right side of each carcass was weighed, fabricated into wholesale cuts and weighed. The wholesale cuts were further fabricated into typical industry boneless subprimals except they were trimmed to.3 in fat. The closely trimmed boneless subprimals, fat, lean trim and bone were weighed and recorded. The fat in the lean trim was removed to a visual 25% fat content and mixed with other lean trim from the side and chemically analyzed for fat content. The actual fat percentage was used to adjust all lean trim to 25% fat and the lean trim from each cut was adjusted proportionally to its contribution to total lean trim. Retail product was considered to be the boneless, closely trimmed subprimals and any lean trim suitable for ground beef production. Also, data in this study was statistically adjusted to a common outside fat thickness by the use of analysis of covariance. Data from year 1 steers (n= 64) have been presented and discussed by Williams et al. (1988). RESULTS AND DISCUSSION Breed group effects on percentage wholesale cuts, retail product, fat trim and bone is shown in Table 1. Side weights from Angus and 1/4 Brahman carcasses were lighter (P<.01) at the same level of outside fatness than side weights of the 1/2 and 3/4 Brahman carcasses. Breed group did not effect (P >.05) any wholesale cut percentages or retail product yield of primal or subprimal cuts derived from the carcass. Breed group did influence fat trim in excess of.3 inch removed from the rib and plate region of the carcass. Fat trim removed from the 3/4 Brahman sides was less (P <.01) than the percentage fat trim removed from the other breed groups in a similar fashion, percentage fat trim removed from the plate decreased (P =.02) as percentage Brahman breeding increased. Also, 1/2 and 3/4 Brahman sides had a greater (P<.01) percentage bone in the chuck than did the Angus or 1/4 Brahman sides. Age of feeding appeared to have a greater influence on carcass composition than did breed type of the animal as seen in Table 2. At the same level of outside fatness, sides from steers fed as yearlings were 25 pounds heavier than were sides of steers fed as calves. Sides from steers fed as yearlings had higher percentages of chuck, rib and plate which would result in a greater percentage forequarter. Retail product yield from the calves fed as yearlings was significantly higher (P<.03) for all primal and subprimal cuts except for the rib, plate and foreshank than steers fed as calves. Furthermore, steers fed as

3 yearlings had less fat trim in excess of.3 inch from the round, rib, loin, brisket, flank and plate, as well as less (P<.03) bone trim removed from the round, rib and brisket. Table 3 summarizes the effect of breed group and age at feeding on yield of total retail product, fat trim, bone and kidney, pelvic and heart fat percentages. Breed group had no effect on total boneless closely trimmed retail yield and percentage kidney, pelvic and heart fat. Sides from the 1/4 Brahman carcass had more fat trim in excess of.3 inches than did the sides from 3/4 Brahman carcasses. Fat trim percentages from the Angus and 1/2 Brahman sides were intermediate to the other two breed groups previously mentioned. Sides from steers fed as yearlings had greater (P<.01) boneless closely trimmed retail product yield, lower (P<.02) total fat and bone trim and less kidney, pelvic and heart fat. In summary, it appears that when steers are fed to similar levels of outside fatness that breed group or type had only minor influences on carcass composition. These compositional differences were in lower fat trim as percentage Brahman increased, which was apparently concentrated in the rib and plate region. This could be partially explained by findings of Huffman et al. (1989) who noted that as percentage Brahman increased, seam or intermuscular fat decreased. The rib and plate would be regions of high seam fat deposition. The fat trim reported in this study included both the subcutaneous (outside) fat and intermuscular (seam) fat. Although carcass characteristics reported by Huffman et al. (1989) would indicate that as percentage Brahman increased, ribeye area per 100 pounds carcass weight decreased indicating that according to USDA yield grade equations that high percentage Brahman carcass would be lower yielding. Actual cut-out data from this study did not substantiate the lower yield predicted by the USDA yield grade equations. It is also important to note that when steers were fed as yearlings compared to calves to a common outside fat thickness, heavier carcasses (about 50 pounds) that were higher yielding in retail product, lower in fat and bone trim and lower kidney pelvic and heart fat were produced. This finding has very significant implications on increasing lean beef production. LITERATURE CITED Huffman, R. D., D. D. Johnson and D. D. Hargrove Feedlot performance, carcass characteristics and palatability of Angus and Brahman X Angus aossbreds under different feeding management systems in Florida. Proceedings 37th Beef Cattle Short Course. p 50. Huffman, R. D., D. D. Johnson and D. D. Hargrove Effects of breed and subcutaneous fatness on the deposition of intermuscular fat. Florida Beef Cattle Research Report. p 5. Johnson, D. D., R. D. Huffman and D. D. Huffman Effects of percentage Brahman and Angus breeding, age-season of feeding and slaughter end point on meat palatability and muscle characteristics. Florida Beef Cattle Research Report. p 8. Williams, S. E., D. D. Johnson, D. D. Hargrove and D. L. Walceman The effect of breed, season of feeding, slaughter end point and diet on carcass composition and characteristics. Florida Beef Cattle Research Report. p 166.

4 TABLE 1. LEAST SQUARES MEANS FOR WHOLESALE CUTS, RETAIL PRODUCT, FAT TRIM AND BONE AS A PERCENTAGE OF SIDE WEIGHT BY BREED GROUP Breed group Probability Item: A 3/4A:1/4B 1/2A:1/2B 1/4A:3/4B Level Side wt., lb a a b 342.l b <.01 Chuck Retail Product Fat trim Bone 3.59 a 3.53 a 3.88 b 3.73 b.02 Round Retail product Fat trim Bone Rib Retail product Fat trim l.4l a 1.36 a l.28 a 1.08 b <.01 Bone Loin Retail product Fat trim Bone Brisket Retail product Fat trim Bone Flank Retail product Fat trim

5 Bone Plate Retail product Fat trim 2.02 a l.66 ab 1.4l b l.40 b.02 Bone Foreshank Retail product Fat trim Bone a,b Means within the same column and effect with different superscripts differ (P <.05). TABLE 2. LEAST SQUARES MEANS FOR WHOLESALE CUTS, RETAIL PRODUCT, FAT TRIM AND BONE AS A PERCENTAGE OF SIDE WEIGHT BY AGE AT FEEDING. Age Item: Calves Yearlings Probability Level Side wt., lb <.01 Chuck Retail product <.01 Fat trim Bone Round Retail product Fat trim <.01 Bone Rib <.01 Retail product Fat trim <.01 Bone <.01 Loin Retail product <.01 Fat trim <.01 Bone Brisket Retail product <.01 Fat trim <.01 Bone Flank Retail product Fat trim <.01 Bone Plate

6 Retail product Fat trim <.01 Bone Foreshank Retail product Fat trim Bone TABLE 3. LEAST SQUARES MEANS FOR TOTAL YIELD OF RETAIL PRODUCT, FAT TRIM, BONE AND KIDNEY PELVIC AND HEART FAT (KPH) BY BREED GROUP AND AGE AT FEEDING. Total Retail Effect Product,% Fat Trim,% Bone,% KHP Fat,% Breed group A ab b /4A:1/4B l4.09 a l3.58 b /2A:l/2B l2.45 ab l4.45 a /4A:3/4B ll.79 b ab 2.85 Probability level Age of feeding Calves Yearlings Probability level <.01 < <.01 ab Means in the same column with different superscripts differ (P<.05).