Estimates of subprimal yields from beef carcasses as affected by USDA grades, subcutaneous fat trim level, and carcass sex class and type.

One hundred beef carcasses were selected to represent the mix of cattle slaughtered across the United States. Selection criteria included breed type (60% British/continental European, 20% Bos indicus, and 20% dairy carcasses), sex class (beef and Bos indicus: 67% steers, 33% heifers; dairy: 100% steers), USDA quality grade (4% Prime, 53% Choice, and 43% Select), USDA yield grade (10% YG 1, 43% YG 2, 40% YG 3, and 7% YG 4), and carcass weight (steers: 272.2 to 385.6 kg, heifers: 226.8 to 340.2 kg). One side of each carcass was fabricated into boneless subprimals and minor cuts following Institutional Meat Purchase Specifications. After fabrication, subprimals were trimmed progressively of fat in .64-cm increments beginning with a maximum of 2.54 cm and ending with .64 cm. Linear regression models were developed for each individual cut, including fabrication byproduct items (bone, fat trim) to estimate the percentage yield of those cuts reported by USDA Market News. Strip loin, top sirloin butt, and gooseneck rounds from heifers tended to have a higher percentage yield at the same USDA yield grade than the same cuts from steers, possibly resulting from increased fat deposition on heifers. Percentage of fat trimmed from dairy steers was 2 to 3% lower than that from other sex-class/carcass types; however, due to increased percentage of bone and less muscle, dairy steers were lower-yielding. Fat trimmed from carcasses ranged from 7.9 to 15.6% as the maximum trim level decreased from 2.54 to .64 cm.     

Effect of frame size, muscle score, and external fatness on live and carcass value of beef cattle.

Commercial slaughter steers (n = 329) and heifers (n = 335) were selected to vary in slaughter frame size and muscle thickness score, as well as adjusted 12th rib fat thickness. After USDA carcass grade data collection, one side of each carcass was fabricated into boneless primals/subprimals and minor tissue components. Cuts were trimmed to 2.54, 1.27, and .64 cm of external fat, except for the bottom sirloin butt, tritip, and tenderloin, which were trimmed of all fat. Four-variable regression equations were used to predict the percentage (chilled carcass weight basis) yield of boneless subprimals at different fat trim levels (.64, 1.27, and 2.54 cm) as influenced by sex class, frame size, muscle score, and adjusted 12th rib fat thickness. Carcass component values, total carcass value, carcass value per 45.36 kg of carcass weight, and live value per 45.36 kg of live weight were calculated for each phenotypic group and external fat trim level. Carcass fatness and muscle score had the most influence on live and carcass value (per 45.36 kg weight basis). Carcasses with .75 and 1.50 cm of fat at the 12th rib were more valuable as the trim level changed from 2.54 cm to .64 cm; however, for carcasses with 2.25 cm of fat at the 12th rib, value was highest at the 2.54 cm trim level. Value was maximized when leaner cattle were closely trimmed. There was no economic incentive for trimming light-muscled or excessively fat carcasses to .64 cm of external fat.     

Beef carcass composition of slaughter cattle differing in frame size, muscle score, and external fatness.

Commercial slaughter steers (n = 329) and heifers (n = 335) were selected to vary in slaughter frame size and muscle thickness score, as well as carcass adjusted 12th-rib fat thickness. After collection of USDA carcass grade data, one side of each carcass was fabricated into boneless primals, subprimals, and minor tissue components. Cuts were trimmed to 2.54, 1.27, and .64 cm of external fat, except for the knuckle, tri-tip, and tenderloin, which were trimmed of all fat. Forced four-variable regression equations were used to predict the percentage (chilled carcass weight basis) yield of boneless subprimals at the three fat trim levels as influenced by sex class, frame size, muscle score, and adjusted 12th-rib fat thickness. Independent variables that had the most influence on percentage yield of primals and boneless subprimals were adjusted 12th-rib fat thickness and sex class. Within the same phenotypic group, percentage of trimmable fat increased by 2.32% as 12th-rib fat thickness increased by .75 cm. Estimated percentage yield of the major subprimals from the loin and round tended to be higher or relatively equal for heifer carcasses at all trim levels compared with those subprimals from steer carcasses. Holding frame size, sex class, and fat thickness constant, there was a higher percentage yield of chuck roll, rib eye roll, and strip loin for carcasses from thick-muscled cattle than for those from average- and thin-muscled cattle. Frame size had little effect on percentage yield of boneless subprimals.     

Effect of hot-fat trimming on factors associated with the subprimal yield of beef carcasses.

Thirty-two crossbred cattle (steers = 17; heifers = 15) exhibiting an ultrasound fat thickness at the 12 to 13th rib region of at least 10 mm were selected from a slaughter shift at a commercial packing plant. After splitting, alternating sides of each carcass were trimmed of 1) subcutaneous fat in excess of 6.4 mm; 2) all kidney, pelvic, and heart fat; and 3) all cod or udder fat and fat in the flank region. Both sides of each carcass were fabricated into subprimals (final trim level of 6.4 mm) according to normal industry procedures. Effect of hot-fat trimming, yield grade (3, 4, and 5), and gender on hot-fat trim, fabrication fat trim, major subprimal, and total subprimal yield of untrimmed and trimmed carcasses were determined. Higher numerical yield grade (YG) corresponded with higher (P less than .05) percentages of hot-fat trim. Hot-fat trimming increased (P less than .05) the difference in fabrication fat trim between steers and heifers and between YG 3 and YG 5. Steers and heifers differed (P less than .05) in percentage of major subprimals and total subprimals when processed conventionally, whereas hot-fat trimming eliminated this difference (P less than .05). Untrimmed YG 3 carcasses had 3.1 and 5.0% higher major subprimal yield (P less than .05) than untrimmed YG 4 and YG 5 carcasses, respectively, whereas hot-fat trimming reduced this difference to 2.5% for YG 4 and to 3.7% for YG 5.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of sex-class, USDA yield grade and USDA quality grade on seam fat trim from the primals of beef carcasses

Beef carcasses (129 steers and 80 heifers) differing in weight, muscling, fatness and marbling score were selected to represent the full spectrum of USDA yield grades; one side was fabricated into boneless primal cuts. Primals were trimmed of all external fat and intermuscular (seam) fat and all components were weighed. Regression equations were developed to predict the percentage of seam fat on an external fat-free primal basis using USDA yield grade (YG), marbling score and a squared function of YG as the independent variables. YG (.77) and marbling score (.67) were highly correlated to seam fat. Heifers tended to have a higher predicted percentage of seam fat than did steers across all YG. Primals from USDA Choice carcasses had approximately 1.0 percentage point more predicted seam fat than did USDA Select primals at the same YG and sex-class. The YG 2.5 heifers had similar proportions of predicted seam fat from primals as YG 3.5 steers, but YG 3.5 heifers tended to have more seam fat than YG 4.5 steers. The same trend was noted between YG 4.5 heifers and YG 5.5 steers, indicating a sex-related deposition of seam fat in fed cattle.     

Retail yields from beef chuck and round subprimals from two grade groups when merchandised as single muscle cuts

Beef subprimals from two different grade groups were obtained from two beef processors to assist in updating the Beef Computer Assisted Retail Decision Support (CARDS) program with new fabrication styles. The grade groups consisted of Top Choice (containing subprimals from carcasses with a Modest or Moderate degree of marbling) and Select (containing subprimals from carcasses with a Slight degree of marbling). Subprimals (shoulder clod; top blade, roast; arm roast; knuckle, peeled; outside round, flat) were separated into individual muscles and fabricated into retail cuts by professional retail meat cutters. Mean retail cutting yields and labor requirements were calculated from observed weights (kilograms) and processing times (seconds). Data were analyzed to determine means and standard errors of percentage yield and processing times for subprimals in each grade group, and comparisons were made between grade groups. Generally, there were few differences in processing times between Top Choice and Select subprimals, and the trimming phase required the most time to complete for each subprimal. Differences (P < 0.05) were observed in saleable yield between Top Choice and Select subprimals for the shoulder clod (Top Choice = 73.89%; Select = 78.49%), top blade, roast (Top Choice = 84.36%; Select = 86.70%), and outside round, flat (Top Choice = 85.99%; Select = 91.34%). Trimmable fat differed (P < 0.05) between Top Choice and Select subprimals: shoulder clod (Top Choice = 25.30%; Select = 20.85%), top blade, roast (Top Choice = 14.88%; Select = 12.59%), arm roast (Top Choice = 8.35%; Select = 7.47%), knuckle (Top Choice = 5.72%; Select = 2.73%), and outside round, flat (Top Choice = 13.82%; Select = 7.26%). Most of the differences in saleable yields were related to less trimmable fat for Select subprimals, which also required less trimming time than Top Choice subprimals. These data will serve to update the Beef CARDS program and will provide retailers and foodservice operators with third-party cutting yield and time allocation information.     

Dual-component video image analysis system (VIASCAN) as a predictor of beef carcass red meat yield percentage and for augmenting application of USDA yield grades

An improved ability to quantify differences in the fabrication yields of beef carcasses would facilitate the application of value-based marketing. This study was conducted to evaluate the ability of the Dual-Component Australian VIASCAN to 1) predict fabricated beef subprimal yields as a percentage of carcass weight at each of three fat-trim levels and 2) augment USDA yield grading, thereby improving accuracy of grade placement. Steer and heifer carcasses (n = 240) were evaluated using VIASCAN, as well as by USDA expert and online graders, before fabrication of carcasses to each of three fat-trim levels. Expert yield grade (YG), online YG, VIASCAN estimates, and VIASCAN estimated ribeye area used to augment actual and expert grader estimates of the remaining YG factors (adjusted fat thickness, percentage of kidney-pelvic-heart fat, and hot carcass weight), respectively, 1) accounted for 51, 37, 46, and 55% of the variation in fabricated yields of commodity-trimmed subprimals, 2) accounted for 74, 54, 66, and 75% of the variation in fabricated yields of closely trimmed subprimals, and 3) accounted for 74, 54, 71, and 75% of the variation in fabricated yields of very closely trimmed subprimals. The VIASCAN system predicted fabrication yields more accurately than current online yield grading and, when certain VIASCAN-measured traits were combined with some USDA yield grade factors in an augmentation system, the accuracy of cutability prediction was improved, at packing plant line speeds, to a level matching that of expert graders applying grades at a comfortable rate.     

Identification of quality management practices to reduce the incidence of retail beef tenderness problems: development and evaluation of a prototype quality system to produce tender beef.

A prototype quality system for ensuring beef tenderness was designed and tested. The test population of cattle was genetically diverse, but it was constrained to include youthful (14- to 17-mo-old) steers with no more than 3/8 Bos indicus inheritance. Feeding and preharvest management of the cattle were consistent with procedures recommended for production of grain-finished beef of an acceptable quality level. In addition, the target endpoint for harvest (11-mm external fat thickness over the longissimus at the 12th rib) resulted in production of mostly Select and low Choice beef carcasses; 92% of the resulting carcasses qualified for these two grade levels. Application of the prototype quality system reduced the expected rate of nonconformance to desired tenderness specifications from about one in four loin steaks (23% for top sirloins and 26% for strip loins) to approximately one in eight loin steaks (13% for top sirloins and 12% for strip loins). Tenderness comparisons among sires suggested that the rate of nonconformance for strip loin steaks might be reduced even further by control of genetic inputs into the system. Use of process control in a quality management system was demonstrated to be an effective approach for assurance of beef tenderness.     

The Issue of Carcass Tenderness Expressed by Cattle Varying in Bos indicus Inheritance

This review reveals that relative to Bos taurus cattle, cattle varying in Bos indicus inheritance, especially cattle that are > 1/2 Bos indicus inheritance, lack carcass tenderness. Because consumers are willing to pay for more tender beef, it seems imperative that the commercial beef cattle industry should refrain from producing cattle that are > 1/2 Bos indicus inheritance. Because of their Superior preweaning maternal performance, F₁Bos indicus ♂ × Bos taurus 9 females and their resulting contemporary F₁steer mates will continue to be produced by the commercial beef cattle industry in the Southeast and Golf Coast areas of the U.S. Further, as progeny testing for tenderness is expensive, it is suggested that the F₁Bos indicus ♂ x Bos taurus 9 steers be identified by the commercial beef cattle industry so that the packing/ retail industries can utilize existing postmortem technology (electrical stimulation, blade tenderization, extended aging, calcium chloride injections) to partially alleviate the lack of tenderness expressed by carcasses resulting from these cattle.     

Effects of biological type of beef steers on vitamin D, calcium, and phosphorus status

Feedlot steers (n = 36) from three biological types (Bos indicus, Bos taurus-Continental, and Bos taurus-English) were used to determine the Ca, P, and vitamin D3 status of feedlot cattle. The USDA yield and quality grade traits were measured at slaughter, and the concentrations of vitamin D3 (VITD) and the metabolites 25-hydroxyvitamin D3 (25-OH D) and 1,25-dihydroxyvitamin D3 (1,25-(OH)2 D) were determined in LM, liver, kidney, and plasma. Plasma and muscle Ca and P concentrations also were determined. Biological type of cattle affected a number of carcass traits. Carcasses from Bos taurus-English cattle had more marbling, resulting in higher quality grades (P < 0.05). Carcasses from Bos taurus-Continental cattle had lower calculated yield grades (P < 0.05) than did carcasses from cattle in the other biological types. In general, differences in carcass traits resulting from biological type were consistent with other reports. Plasma and LM Ca and P concentrations were not affected (P = 0.06) by biological type of cattle, indicating that Ca and P homeostasis is a conserved trait across the different types of cattle. Plasma VITD and 25-OH D concentrations were not affected (P = 0.41) by biological type, whereas plasma 1,25-(OH)2 D concentration was lower (P < 0.05) in Bos taurus-English cattle than in Bos taurus-Continental and Bos indicus cattle. Liver VITD and 25-OH D were not affected by biological type (P = 0.76), but liver 1,25-(OH)2 D concentration was greater (P < 0.05) in Bos indicus cattle than in Bos taurus-Continental cattle. Kidney vitamin D metabolite concentrations were not affected by biological type of cattle (P = 0.21). Muscle VITD concentration was greater (P < 0.05) in Bos taurus-English cattle than in the other two biological types, and muscle 25-OH D concentrations were greater (P < 0.05) in Bos taurus-English cattle than in Bos indicus cattle. Muscle 1,25-(OH)2 D concentration was less (P < 0.05) in the Bos taurus-Continental cattle than in the other two biological types. Cooking eliminated vitamin D metabolite differences among the biological types. Our results suggest that Bos indicus cattle had greater 1,25-(OH)2 D (the biologically active form) in tissues, and greater 1,25-(OH)2 D plasma concentrations than Bos taurus cattle. Thus, the need for VITD supplementation and optimal levels of Ca and P in feedlot diets might differ between Bos indicus and Bos taurus cattle.     

C- AND G- BANDING PATTERNS AND CHROMOSOMAL MORPHOLOGY OF SOME BREEDS OF AUSTRALIAN CATTLE

A cytogenetical study using metaphase chromosomes from cultured lymphocytes, was made of 2 Banteng (Bibos banteng) steers and 218 bulls representing 13 purebreeds (Bos taurus type, Bos indicus type and Sanga) and 7 cross-breeds. Studies were made of photographic karyotypes of Giemsa stained and C-banded chromosomes of bulls of each breed and of B-banded chromosomes from 3 breeds of Bos indicus and one cross-breed Australian Friesian Sahiwal) cattle. The relative lengths of chromosomes of Bos taurus and Bos indicus bulls were compared and significant difference in relative lengths of the X chromosomes were noted between these two species. There was a differences in morphology of the Y chromosomes; Sanga, Banteng and Bos taurus type breeds had a small submetacentric Y chromosome, except for the Jersey which had a metacentric Y chromosome. All Bos indicus type bulls had an acrocentric Y chromosome but the Droughtmaster breed had two forms of the Y chromosome (submetacentric and acrocentric). The C-banding patterns of the autosomes and X chromosomes were similar for all breeds while those of the Y chromosomes of Bos indicus type cattle allowed their accurate identification. G-banding patterns of Bos indicus resembled those of Bos taurus and enabled pairing of homologous chromosomes. Centromeres of the autosomes were unstained but those of the sex chromosomes were darkly stained.     

Growth implants reduced tenderness of steaks from steers and heifers with different genetic potentials for growth and marbling

The objective of this study was to evaluate the effect of growth implants on the carcass characteristics and tenderness of steers and heifers with different genetic potentials for growth, lean meat yield production, and marbling. Two experiments were conducted. Experiment 1 evaluated Angus steers sired by bulls with high EPD for retail product yield or marbling. Implant treatment was imposed randomly within sire groups. Loins (Institutional Meat Purchasing Specifications 180) were collected from each carcass and cut into three 2.54-cm steaks aged for 7, 14 and 21 d to evaluate tenderness. The second experiment evaluated steers and heifers of British and Continental breed descent. Steers and heifers were slaughtered after 120 d on feed. Loin sections were collected, and one 2.54-cm steak aged 7 d was used for tenderness analysis. When implants were used in Angus steers, HCW and LM area increased, whereas internal fat and marbling decreased (P < 0.01). In Angus steers, sire type did not affect shear force values of steaks; however, implant use significantly increased shear force values (P < 0.01). Carcasses from cattle of Continental breed descent were significantly heavier than carcasses of British breed descent with larger LM area, slightly less fat, and a reduced yield grade (P < 0.01). Also, steer carcasses were heavier than heifer carcasses with larger LM (P < 0.05), but no effect of sex on fat depth, internal fat, yield grade or marbling was observed. No significant interactions were seen between growth implant and breed or between growth implant and sex for shear force values. Shear force values were significantly less for steaks from steers and heifers of British decent compared with steers and heifers of Continental descent (P < 0.01). Steaks from implanted steers and heifers had significantly (P < 0.01) greater shear force values than steaks from steers and heifers not implanted. Use of growth implants in growing cattle resulted in significantly heavier carcass weights, larger LM area, and reduced internal fat. However, implant use also reduced the amount of marbling along with contributing to reduced tenderness. Complicating the tenderness issue is the increased shear force values reported for heifers as well as steers of Continental breed descent. Use of implants may contribute to tenderness variability because of different animal responses to implants.     

Effects of zilpaterol hydrochloride on retail yields of subprimals from beef and calf-fed Holstein steers

Retail cutting tests were conducted on subprimals from cattle fed zilpaterol hydrochloride (ZH) to determine if the improved carcass composition and red meat yield resulting from ZH feeding would translate into increased retail yields of ready-to-cook products. As part of a 3-phase study, selection of carcasses from Holstein steers was done once (fall 2008), followed by the collection of carcasses from beef-type steers on 2 separate occasions (beef study I: summer 2009; beef study II: spring 2010). Each of the 3 groups of steers was assigned previously to 1 of 2 treatments, treated (fed 8.3 mg/kg of ZH for 20 d) or control (not fed ZH). All steers were slaughtered and carcasses were fabricated in commercial beef-processing establishments. Only those carcasses grading USDA Choice or higher were used. Five subprimals were used for both the calf-fed Holstein study (n = 546 subprimals) and beef study I (n = 576 subprimals): beef chuck, chuck roll; beef chuck, shoulder clod; beef round, sirloin tip (knuckle), peeled; beef round, top round; and beef round, outside round (flat). Seven subprimals were used in beef study II (n = 138 subprimals): beef chuck, chuck roll; beef round, sirloin tip (knuckle), peeled; beef round, top round; beef round, eye of round; beef loin, strip loin, boneless; beef loin, top sirloin butt, boneless; and beef loin, tenderloin. A simulated retail market environment was created, and 3 retail meat merchandisers prepared retail cuts from each subprimal so salable yields and processing times could be obtained. Differences in salable yields were found for the calf-fed Holstein steer chuck rolls (96.54% for ZH vs. 95.71% for control; P = 0.0045) and calf-fed Holstein steer top rounds (91.30% for ZH vs. 90.18% for control; P = 0.0469). However, other than heavier subprimals and an increased number of retail cuts obtained, total salable yields measured on a percentage basis and processing times were mostly unaffected by ZH. Cutability advantages of feeding ZH are achieved primarily in the carcass-to-subprimal conversion rather than in the subprimal-to-retail conversion.     

Energy and protein requirements for growth and maintenance of F1 Nellore x Red Angus bulls, steers, and heifers

A comparative slaughter trial was conducted with 36 F1 Nellore x Red Angus calves (12 steers, 12 bulls, and 12 heifers), averaging 274 kg of BW, to assess the net requirements of protein and energy for growth and maintenance. Three cattle from each group (i.e., steers, bulls, and heifers) were slaughtered at the beginning of the trial to determine the initial body composition. The remaining calves were randomly assigned to 1 of 3 treatments: maintenance (diet containing 70% of DM as corn silage fed at 1.2% of BW daily) or concentrate at 0.75 or 1.5% of BW daily with corn silage available for ad libitum consumption. The diets were isonitrogenous (2% N, DM basis). The experimental design provided ranges in ME intake, BW, and ADG for the development of regression equations to predict the maintenance requirements for NE and net protein (MRNE and MRNP, respectively) and the growth requirement for NE and net protein (GRNE and GRNP, respectively). After 84 d of growth, the cattle were slaughtered. The cleaned gastrointestinal tracts, organs, carcasses, heads, hides, tails, feet, blood, and tissues were weighed to measure empty BW (EBW). These parts were ground separately and subsampled for chemical analyses. For each animal within a period, DMI was measured daily and samples of feces were collected to determine diet digestibility. There were no differences in MRNE (P = 0.06) among groups. The combined data indicated a MRNE of 71.2 kcal x kg(-0.75) of EBW x d(-1), with a partial efficiency of use of ME to NE(m) of 0.71. The partial efficiency of use of ME to NE for growth was 0.54 for bulls, 0.47 for steers, and 0.54 for heifers. The GRNE for steers and heifers were similar (P = 0.15) but were 18.7% greater (P = 0.03) for steers and heifers than for bulls. The MRNP did not differ among groups and averaged 2.53 g of CP x kg(-0.75) of EBW x d(-1). Likewise, GRNP was not different among groups. The percentage of retained energy deposited as protein (RE(p)) increased as the content of retained energy in the gain (RE(c), Mcal/kg of empty body gain) decreased. The RE(p) equation of the pooled data was 46.5 x e(-0.2463 x RE(c)). We conclude that the energy requirement of crossbred Bos indicus x Bos taurus for maintenance might be less than that of purebred Bos taurus and that RE(p) is nonlinearly, negatively correlated with RE(c). The GRNE was less for bulls than for steers and heifers. However, we found no differences in MRNE, MRNP, and GRNP for bulls, steers, and heifers of Nellore x Red Angus crossbreds.     

Effect of breed of cattle on innate resistance to infection with Anaplasma marginale transmitted by Boophilus microplus

OBJECTIVE: To assess the innate resistance of and transmission in naive Bos taurus cross Bos indicus and purebred Bos indicus cattle when placed in a paddock with cattle infected with Anaplasma marginale and carrying Boophilus microplus ticks. DESIGN: A group of 49 purebred B indicus, and 48 B indicus cross B taurus (50%, F1 generation) 24-month-old steers were kept in the same paddock with cattle artificially infected with a virulent isolate of A marginale and Boophilus microplus. The cattle were seronegative for A marginale at the start of the trial but had previously been exposed to Babesia bovis and B bigemina. PROCEDURE: Cattle were inspected twice weekly for 118 days. Whole blood, blood smears and serum samples were collected from the cattle on day 37 after exposure and then at regular intervals to day 83 after exposure to measure packed-cell volumes, parasitaemias and antibody titres to A marginale. Any animals that met preset criteria were treated for anaplasmosis. On day 83 all cattle were treated with an acaricide and cattle infected with A marginale were removed from the rest of the group. RESULTS: A marginale was detected in blood smears from 14 crossbred and 9 B indicus steers between days 56 and 72 after exposure. Five and two of the infected crossbred and B indicus steers required treatment, respectively. One of the Bos indicus cattle died as a result of the A marginale infection despite treatment. Antibodies to A marginale were detected in the 23 infected cattle. The mean packed-cell volume depression was 40 and 37% in the affected crossbred and Bos indicus groups, respectively. There was no significant difference detected in susceptibility between these two groups. CONCLUSIONS: Innate resistance of purebred B indicus and crossbred cattle was not significantly different. The results confirm that purebred B indicus and crossbred cattle are sufficiently susceptible to warrant the use of vaccination against Anaplasma infections.     

Effects of feeding high-oil corn to beef steers on carcass characteristics and meat quality

To assess the effects of feeding high-oil corn on carcass characteristics and meat quality, 60 yearling steers were fed high concentrate diets containing either control corn (82% of diet), high-oil corn (82% of diet), or high-oil corn at a concentration that was isocaloric with the control diet (74% of diet). After being fed for 84 d, steers were slaughtered. At 72 h postmortem, carcass data were collected and rib sections from five steers grading U.S. Choice and five steers grading U.S. Select from each treatment were collected, vacuum packaged, and aged for 14 d. Three steaks (2.54 cm thick) were removed from each rib for Warner-Bratzler shear force measurement, sensory appraisal, and fatty acid composition analyses. Data were analyzed with treatment as the main effect for the carcass data and treatment, quality grade, and two-way interaction in the model for the longissimus data. The two-way interaction was nonsignificant (P > 0.05) for all variables tested. No differences were detected (P > 0.05) in carcass measurements except for marbling scores and quality grades, both of which were greater (P < 0.05) for carcasses from steers fed the high-oil corn. Overall, 78% of steers fed the high-oil corn graded U.S. Choice compared with 47% for the control and 67% for isocaloric group. Shear force and sensory properties of the longissimus were not different (P > 0.05) among treatments. Steaks from U.S. Choice carcasses rated higher (P < 0.05) for tenderness and tended to rate higher (P < 0.10) for juiciness. Feeding the isocaloric and high-oil diets increased (P < 0.05) linoleic acid, arachidonic acid, and the total PUFA content of lipid extracted from the longissimus. Saturated fatty acid percentage was lowest (P < 0.05) for high-oil corn and highest (P < 0.05) for control, with isocaloric being intermediate. Feeding high-oil corn increased (P < 0.05) pentadecyclic acid, margaric acid, and total odd-chain fatty acid content. Feeding high-oil corn in finishing beef cattle diets enhanced intramuscular lipid deposition and increased unsaturation of fatty acids of the longissimus.     

Predicting percentage of retail yield from carcass measurements, the yield grading equation, and closely trimmed, boxed beef weights.

Over the past 3 yr, 100 carcasses (64 steers, 24 bulls, and 12 heifers) were fabricated into closely trimmed (6 mm maximum fat cover), boxed beef and further evaluated for percentage of retail yield at the Iowa State University Meat Laboratory. Hot carcass weight ranged from 235 to 399 kg with a least squares mean (LSM) and standard error across all sex classes of 318 +/- 3 kg. Additionally, fat cover ranged from .30 to 1.78 cm with an average of .91 +/- .05 cm. The LSM for longissimus muscle area (LMA) across all sex classes was 81.6 +/- 1.0 cm2. Bulls had significantly less subcutaneous fat (P less than .01) and greater LMA (P less than .01) than did either steers or heifers. Retail yield from the boxed chuck, expressed as a percentage of cold carcass weight, was 19.2 for bulls and 14.8 for steers. This difference was due primarily to a reduction of intermuscular fat. Similarly, bulls had a greater yield (P less than .01) of the boxed round than did steers. When cattle of differing frame sizes were compared, only percentage of retail yield of the boxed round was significant (P less than .01): large-framed cattle yielded 14.3 +/- .2%, compared with 12.8 +/- .2% for the small-framed cattle. When all possible regression analyses were run, sex class differences accounted for 25.7% of the variation in retail yield. The current USDA retail yield equation accounted for only 37.2% of the variation. Percentage of closely trimmed, boneless round had an R2-value of .57.(ABSTRACT TRUNCATED AT 250 WORDS)     

Predicting carcass composition of beef cattle using ultrasound technology.

We evaluated 20 slaughtered cattle with ultrasound before hide removal to predict fat thickness and ribeye area at the 12th rib for possible use in carcass composition prediction. Carcasses were fabricated into boneless subprimals that were trimmed progressively from 2.54 to 1.27 to .64 cm maximum fat trim levels. Stepwise regression was used to indicate the relative importance of variables in a model designed to estimate the percentage of boneless subprimals from the carcass at different external fat trim levels. Variables included those obtained on the slaughter floor (ultrasound fat thickness and ribeye area; estimated percentage of kidney, pelvic, and heart [KPH] fat; and warm carcass weight) and those obtained from carcasses following 24 h in the chill cooler (actual fat thickness, actual ribeye area, estimated percentage of KPH fat, warm carcass weight, and marbling score). At all different subprimal trim levels, percentage KPH was the first variable to enter the model. In the models using measures taken on the slaughter floor, ultrasound fat thickness was the only other variable to enter the model. Ultrasound fat thickness increased R2 and decreased residual standard deviation (RSD) in models predicting subprimals at 2.54-cm maximum fat trim; however, at 1.27- and .64-cm trim levels, R2 and RSD increased. Models using the same two variables (except actual fat instead of ultrasound) in the cooler were similar to those using data from the slaughter floor. However, as more cooler measurement variables entered the models, R2 increased and RSD decreased, explaining a greater amount of the variation in the equation. Ultrasonic evaluation on the slaughter floor may be of limited application compared with the greater accuracy found in chilled carcass assessment.     

Using live estimates and ultrasound measurements to predict beef carcass cutability

Commercial slaughter steers (n = 329) and heifers (n = 335) were selected to vary in frame size, muscle score, and carcass fat thickness to study the effectiveness of live evaluation and ultrasound as predictors of carcass composition. Three trained personnel evaluated cattle for frame size, muscle score, fat thickness, longissimus muscle area, and USDA quality and yield grade. Live and carcass real-time ultrasound measures for 12th-rib fat thickness and longissimus muscle area were taken on a subset of the cattle. At the time of slaughter, carcass ultrasound measures were taken at "chain speed." After USDA grade data were collected, one side of each carcass was fabricated into boneless primals/subprimals and trimmed to .64 cm of external fat. Simple correlation coefficients showed a moderately high positive relationship between 12th rib fat thickness and fat thickness measures obtained from live estimates (r = .70), live ultrasound (r = .81), and carcass ultrasound (r = .73). The association between estimates of longissimus muscle area and carcass longissimus muscle area were significant (P < .001) and were higher for live evaluation (r = .71) than for the ultrasonic measures (live ultrasound, r = .61; carcass ultrasound, r = .55). Three-variable regression equations, developed from the live ultrasound measures, explained 57% of the variation in percentage yield of boneless subprimals, followed by live estimates (R2 = .49) and carcass ultrasound (R2 = .31). Four-variable equations using frame size, muscle score, and selected fat thickness and weight measures explained from 43% to 66% of the variation for the percentage yield of boneless subprimals trimmed to .64 cm. Live ultrasound and(or) live estimates are viable options for assessing carcass composition before slaughter.