EFFECTS OF BREED OF SIRE AND AGE-SEASON OF FEEDING ON MUSCLE TENDERNESS IN THE BEEF CHUCK

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1 EFFECTS OF BREED OF SIRE AND AGE-SEASON OF FEEDING ON MUSCLE TENDERNESS IN THE BEEF CHUCK K L. Christensen, D. D. Johnson, D. D. Hargrove, R. L. West and T. T. Marshall SUMMARY Steers (n = 59) produced from the crossing of Braford, Simbrah, Senepol and Simmental bulls to Brahman-sired and Romana Redsired cows and the mating of Brahman bulls to Angus cows were used in this study to determine the effects of sire breed group and age season of feeding on muscle tenderness in the chuck. Half of the steers were placed in the feedlot immediately after weaning, and the others were stockered during the winter and placed in the feedlot as yearlings during the summer. Steers were slaughtered at a compositional equivalent endpoint (.4 in external fat) as determined by visual and with realtime ultrasound monitoring. In general, there were no muscle tenderness effects due to sire breed group or age-season of feeding with the exception of the Serratus centrals muscle, wherein muscles from the Brahman-sired and Braford-sired steers were more tender than the Simmental-sired steers, and the Supraspinahts muscle, where the muscles from yearlings were lower in shear value compared to muscles from calves. Data suggest that if these muscles are removed from the chuck intact and cut perpendicular to the muscle fiber, they would be acceptable in tenderness. INTRODUCTION During the early 1980's chuck prices averaged nearly 1.5 times the price of fed cattle. By 1988, this ratio declined to less than1.3, suggesting that the chuck has become a relatively less valuable portion of the beef animal. An estimated $400 million was lost in revenue in 1988 due to the low price received for the chuck, and a similar amount of lost revenue is anticipated during The marketing potential of the beef chuck is thought to be depressed due to variation in 1) the cut-out yield of the chuck, and 2) the palatability characteristics of the muscles in the chuck. (Johnson, et al., 1988). Unfortunately, few studies have been conducted to evaluate tenderness and determine the optimal use of muscles from the beef chuck. The diverse palatability characteristics of the muscles are further amplified by the traditional way of fabricating the chuck; in many instances muscles are cut with the fiber orientation rather than across them. Paterson and Parrish (1986) and McKeith et al. (1973) have studied several muscles from the beef chuck and have characterized them according to their palatability attributes. Results of these studies indicate that many chuck muscles are very desirable in palatability and tenderness if they are removed intact and cut in the proper muscle fiber orientation. This procedure would entail whole muscle boning and also offers the advantage of subsequently being able to remove the seam fat which is objectionable to the consumer (Meade et al., 1989). Traditionally, the chuck has been merchandized in the form of low-priced roasts and steaks. Therefore, the objective of this study was to determine the effects on tenderness when muscles from the chuck were removed intact and cut across the grain. Particularly, the influence of breed of sire and management practices (feeding weanling calves vs yearlings) were compared.

2 MATERIALS AND METHODS Fifty-nine steers calved in 1988 at the University of Florida Beef Research Unit (BRU), Gainesville, were selected for this study. The steers were produced from the crossing of Braford, Simbrah, Senepol and Simmental bulls to Brahman-sired and Romana Red-sired cows; and Brahman bulls mated to Angus cows. Approximately one half of the steers in each breed group were randomly assigned to be fed as weanling calves during the cool period of the year (November to May), while the others were assigned to a winter stocker program followed by feeding during the warm period of the year (June to October). The steers were fed a 75% dry-matter diet consisting of high moisture corn (79%), cottonseed hulls (12%), a commercial 50% protein pellet (4%), and molasses (5%). All steers were implanted with Ralgro just prior to being placed in the feedlot. Additionally, those steers still on feed 90 days later were implanted with Synovex S. External fat (subcutaneous fat) of the feedlot steers was monitored visually and ultrasonically. Upon reaching.4 inches subcutaneous fat at the 12th rib, each steer was weighed in the morning before feeding and shipped to the University of Florida Meats Laboratory. Steers were allowed overnight access to water and slaughtered the following morning. Standard slaughter procedures were followed. Carcasses were chilled for 24 h at 32 to 34 F prior to being ribbed. The carcasses were ribbed between the 12th and 13th ribs and evaluated for USDA quality and yield grade factors by University of Florida personnel. The cross cut chuck was removed between the 5th and 6th ribs perpendicular to the dorsal line of the carcass. Further dissection included the removal and separation of subcutaneous fat, intermuscular fat, major muscles, and bone. Individual muscle weights were recorded of those weighing greater than.5 lb. Samples (1 in steaks) for tenderness determination were cut across the grain of fibers from the Triceps brachii, Supraspinatus, Serratus ventralis, and Longissimus dorsi (removed from the short loin) muscles of each carcass. The remaining portions of the Triceps brachii, Serratus ventralis, and Supraspinatus muscles were ground for uniformity using a food processor. Chemical analyses were performed by oven drying and ether extraction procedures to monitor changes in intramuscular fat deposition of these muscles. The Longissimus dorsi was not available for grinding, and thus not used for chemical analyses. Steaks were vacuum packaged and allowed to age for five days at 32 to 34 F before they were frozen. Steaks were broiled on a Farberware Open-Hearth broiler until they reached an internal temperature of 158 F. Steaks were allowed to cool to room temperature and a minimum of six, 1/2 in cores were removed from each steak for shear force determination using a Warner-Bratzler shear device. Data were analyzed using the least squares, fixed model procedures of the Statistical Analysis System (SAS, 1982). Main effects of sire breed group and season of feeding, along with their interaction were included in the mathematical model used in the analysis. RESULTS AND DISCUSSION Warner-Bratzler shear force values, an objective measure of force required to shear a 1/2 in cooked muscle core, were used in determining if the breed of sire or age-season of feeding affected tenderness. As shear force numerically increases, indicating more force required to shear the cooked core, the steak is considered tougher. Shear force values of less than 10 pounds are considered tender, values ranging from pounds are intermediate in tenderness, and values greater than 12 pounds are considered tough or very chewy. The highest values obtained in this study demonstrated steaks were intermediate in tenderness (Table1). No differences were apparent with respect to

3 tenderness of the Triceps brachii, Supraspinatus, and Longissimus dorsi muscles due to sire breed or age season of feeding. Steaks from Brahman-sired and Braford-sired steers had the lowest shear values for the Serratus centrals muscle, while Simmental-sired steers had the greatest. Shear values for this muscle were all below 10, which may be attributed to the high percentage of intramuscular fat (mean=8.5%) in this cut of meat. The muscles did not differ in tenderness when comparing steers fed as calves with yearlings with the exception of the Supraspinatus muscle. This muscle had greater thaw loss (P <.10) and cooking loss (P <.05) in calves than in yearlings (Table 2). The greater loss of intramuscular moisture would create a higher resistance for the shearing device to penetrate and thus possibly explain the higher shear values seen in the calves. Percentage cooking loss and thaw loss did not differ among breed groups; however, percentage cooking loss was greater in the Triceps brachii, and Supraspinatus muscles of the calves than in the yearlings (P <.05). This difference may be partially due to post-slaughter handling conditions or variation in purge loss. The Brahman-sired steers had Serratus ventralis muscles with significantly higher percentages of intramuscular fat than Brafordsired, Simbrah-sired and Simmental-sired steers (P <.05). In addition, Brahman-sired steers had Supraspinatus muscles with significantly higher percentages of intramuscular fat than did the Simbrah-sired steers, while the Braford-sired, Senepol-sired and Simmental sired steers were intermediate to both (P <.05). The general trend for a higher percentage of intramuscular fat within all three muscles in the Brahman-sired steers might be explained by higher proportions of Angus breeding in these steers compared to steers from other sire breeds. The Longissimus dorsi muscle was used in this study as a basis to compare the tenderness of the three chuck muscles to (Table 1). Furthermore, it was used as a reference since overall tenderness of the carcass is generally determined by the shearing of this muscle. The Longissimus dorsi muscle appeared to exhibit higher shear values than did the other muscles. The other muscles are normally ranked high in toughness because they are typically cut with the muscle fiber orientation rather than across them (Paterson and Parrish, 1986; McKeith et al., 1973). When cut in the proper manner, these muscles have the potential to be tender and could be marketed in a way to obtain higher monetary returns. LITERATURE CITED Johnson, R. C., C. M. Chen, T. S. Muller, W. J. Costello, J. R. Romans, and K W. Jones Characterization of the muscles within the beef forequarter. J. Food Sci. 53:1247. McKeith, F. K, D. L. De VoL R. S. Miles, P. J. Bechtel, and T. R. Carr Chemical and sensory properties of thirteen major beef muscles. J. Food Sci. 50:869. Meade, M. K, D. D. Johnson and R. L. West Evaluation of a streamlined processing procedure for beef carcasses. Florida Beef Cattle Research Report. p36. Paterson, B. C., and F. C. Parrish, Jr A sensory panel and chemical analysis of certain beef chuck muscles. J. Food Sci. 51:876. SAS SAS User's Guide Statistics. SAS Inst. Inc. Gary, N.C.

4 TABLE 1. MEANS FOR WARNER-BRATZLER SHEAR FORCE BY BREED OF SIRE AND AGE-SEASON OF FEEDING Muscle Serratus Logissimus Main effect n a Triceps brachii ventralis Supraspinatus dorsi Breed of Sire Brahman c Braford c Simbrah bc Senepol bc 9.7 Simmental b 9.9 Season-Age Calves-cool b 10.8 Yearlings-warm c a n = Dumber of steers b,c Means in same column with different superscripts differ (P <.05).

5 TABLE 2. MEANS FOR MUSCLE CHARACTERISTICS BY BREED GROUP AND AGE-SEASON OF FEEDING Main effect n a Cook loss, % Thaw loss, % Fat b, % Muscle Serr Sup Tri c Serr d Sup e Ld f Tri Serr Sup Ld Tri Breed of Sire Brahman g 4.4 g Braford h 3.5 gh Simbrah h 3.3 h Senepol gh 3.5 gh SimmeDtal h 3.7 gh Age-Season Calves-cool g 30.5 g h 5.4 g 3.9 g Yearlings-warm h 20.0 h 19.9 h g 2.1 h 2.8 h a number of steers b % Intramuscular fat. c,d,e,f Triceps brachii, Serratus ventratis, Supraspinatus and Longissimus dorsi muscles, respectively. g,h Means in same column (within main effect) with different superscripts differ (P <.05).