Technical note: validation of a model for online classification of US Select beef carcasses for longissimus tenderness using visible and near-infrared reflectance spectroscopy

The present experiment was conducted to provide a validation of a previously developed model for online classification of US Select carcasses for LM tenderness based on visible and near-infrared (VISNIR) spectroscopy and to determine if the accuracy of VISNIR-based tenderness classification could be enhanced by making measurements after postmortem aging. Spectroscopy was conducted online, during carcass grading, at a large-scale commercial fed beef-processing facility, and the strip loin was obtained from the left side of US Select carcasses (n = 467). Slice shear force (SSF) was measured on fresh steaks at 2 and 14 d postmortem. Online VISNIR tenderness classes differed in mean SSF values at both 2 d (29.4 vs. 33.6 kg) and 14 d (18.0 vs. 21.2 kg) postmortem (P < 10(-7)). Online VISNIR tenderness classes differed in both the percentage of carcasses with LM SSF values greater than 40 kg at 2 d postmortem (5.1 vs. 21.0%; P < 10(-6)) and the percentage of carcasses with LM SSF values greater than 25 kg at 14 d postmortem (6.8 vs. 23.2%; P < 10(-5)). Whereas 15.0% of the carcasses sampled for this experiment had LM SSF values greater than 25 kg at 14 d postmortem, only 6.8% of the carcasses classified as tender by VISNIR had LM SSF values greater than 25 kg. All the carcasses sampled that had LM SSF values greater than 35 kg at 14 d postmortem were accurately classified as tough by VISNIR. Before measurement of SSF on d 14, VISNIR spectroscopy was conducted on the SSF steak. Tenderness classes based on d 14 VISNIR spectra differed both in mean SSF value at 14 d postmortem (17.7 vs. 21.6 kg; P < 10(-11)) and the percentage of carcasses with LM SSF values greater than 25 kg at 14 d postmortem (7.3 vs. 22.7%; P < 10(-5)). These data support our previous work showing that VISNIR spectroscopy can be used to classify US Select carcasses noninvasively for LM tenderness, and the results establish that this technology could also be applied to aged US Select strip loins. This technology would allow packing companies and other segments of the beef marketing chain to identify US Select carcasses or strip loins that excel in LM tenderness for use in branded beef programs.     

Development of a system for classification of pork loins for tenderness using visible and near-infrared reflectance spectroscopy

Boneless pork loins (n = 901) were evaluated either on the loin boning and trimming line of large-scale commercial plants (n = 465) or at the US Meat Animal Research Center abattoir (n = 436). Exposed LM on the ventral side of boneless loins was evaluated with visible and near-infrared spectroscopy (VISNIR; 450 to 1,000 nm) using a commercial system that was developed for on-line evaluation of beef tenderness. Boneless loin sections were aged (2°C) until 14 d postmortem, and two 2.54-cm-thick chops were obtained from the 11th-rib region. Fresh (never frozen) chops were cooked (71°C) and LM slice shear force (SSF) was measured on each of the 2 chops. Those 2 values were averaged, and that value was used for all analyses. Loins were blocked by plant (n = 3), production day (n = 24), and observed SSF (mean = 13.9 kg; SD = 3.7 kg; CV = 26.8%; range 6.4 to 32.4 kg). One-half of the loins were assigned to a calibration data set, which was used to develop regression equations, and one-half of the loins were assigned to a prediction data set, which was used to validate the regression equations. A partial least-squares regression model was developed, and loins were classified as predicted tender or not predicted tender if their VISNIR-predicted SSF was <14.0 kg or ≥14.0 kg, respectively. Analysis of variance was used to determine the effect of VISNIR classification on SSF. The calibration data set and prediction data set had 61.9 and 60.9% of the loins classified as predicted tender, respectively. For both the calibration data set and the prediction data set, mean SSF was less for loins predicted tender than loins not predicted tender (P < 0.001). Relative to loins that were not predicted tender, the percentage of loins with SSF ≥20 kg was less for loins predicted tender in the calibration data set (3.6 vs. 8.1%) and prediction data set (1.8 vs. 13.6%). These results clearly indicate that the VISNIR technology could be used to noninvasively classify pork loins on-line for tenderness.     

Using the near-infrared system to sort various beef middle and end muscle cuts into tenderness categories

The objectives of this study were to determine the effectiveness of a visible-near-infrared (VIS-NIR) system to predict the ultimate tenderness rating of various beef muscles and conclude if a relationship exists between predicted LM shear force and tenderness of other subprimal cuts. Carcasses (n = 768) were scanned with the VIS-NIR system in 2 commercial beef-processing facilities. Carcasses were categorized based on their predicted 14-d LM slice shear force value. After carcass scanning, 100 carcasses were randomly selected based on their tenderness classification, and subprimals (ribeye rolls, clods, knuckles, top sirloins, inside rounds, and eye of rounds) were removed, vacuum-packaged, and transported to the Oklahoma State University Food and Agricultural Products Research Center, where 2.54-cm steaks (n = 6) were fabricated and stored in refrigerated conditions (1 degrees C +/- 1) and aged for 14 d. The center steak from right-side subprimals was designated for slice shear force (LM) or Warner-Bratzler shear force (all other subprimals) analysis. The remaining steaks were categorized based on predicted tenderness taken at 2 d postmortem with the VIS-NIR spectrophotometer and used in a consumer taste study. The test population of carcasses (n = 100) scanned in-plant predicted 27 carcasses as tender, 45 carcasses as intermediate, and 28 carcasses as tough. The VIS-NIR system correctly classified 26 of the 28 (92.9% accuracy) tough carcasses. Overall consumer satisfaction was greatest (P < 0.05) for steaks classified as tender and was intermediate compared with the steaks classified as tough. It was concluded that in-plant VIS-NIR scanning can properly identify and sort carcasses into tenderness groups, which may lead to the development of certified not-tough programs.     

Online prediction of beef tenderness using a computer vision system equipped with a BeefCam module

Four experiments were conducted in two commercial packing plants to evaluate the effectiveness of a commercial online video image analysis (VIA) system (the Computer Vision System equipped with a BeefCam module [CVS BeefCam]) to predict tenderness of beef steaks using online measurements obtained at chain speeds. Longissimus muscle (LM) samples from the rib (Exp. 1, 2, and 4) or strip loin (Exp. 3) were obtained from each carcass and Warner-Bratzler shear force (WBSF) was measured after 14 d of aging. The CVS BeefCam output variable for LM area, adjusted for carcass weight (cm2/kg), was correlated (P < 0.05) with WBSF values in all experiments. The CVS BeefCam lean color measurements, a* and b*, were effective (P < 0.05) in all experiments for segregating carcasses into groups that produced LM steaks differing in WBSF values. Fat color measurements by CVS BeefCam were usually ineffective for segregating carcasses into groups differing in WBSF values; however, in Exp. 4, fat b* identified a group of carcasses that produced tough LM steaks. Quality grade factors accounted for 3, 18, 21, and 0% of the variation in WBSF among steaks in Exp. 1 (n = 399), 2 (n = 195), 3 (n = 304), and 4 (n = 184), respectively, whereas CVS BeefCam output variables accounted for 17, 30, 19, and 6% of the variation in WBSF among steaks in Exp. 1, 2, 3, and 4, respectively. A multiple linear regression equation developed with data from Exp. 2 accurately classified carcasses in Exp. 1 and 4 and thereby may be useful for decreasing the likelihood that a consumer would encounter a tough (WBSF > 4.5 kg) LM steak in a group classified as "tender" by CVS BeefCam compared with an unsorted population. Online measurements of beef carcasses by use of CVS BeefCam were useful for predicting the tenderness of beef LM steaks, and sorting carcasses using these measurements could aid in producing groups of beef carcasses with more uniform LM steak tenderness.     

Technical note: use of belt grill cookery and slice shear force for assessment of pork longissimus tenderness

The present experiments were conducted to determine whether improved beef longissimus shear force methodology could be used to assess pork longissimus tenderness. Specifically, three experiments were conducted to: 1) determine the effect of belt grill (BG) cookery on repeatability of pork longissimus Warner-Bratzler shear force (WBSF), 2) compare the correlation of WBSF and slice shear force (SSF) with trained sensory panel tenderness ratings, and 3) estimate the repeatability of pork longissimus SSF for chops cooked with a BG. In Exp. 1 and 2, the longissimus was removed from the left side of each carcass (Exp. 1, n = 25; Exp. 2, n = 23) at 1 d postmortem and immediately frozen to maximize variation in tenderness. In Exp. 1, chops were cooked with either open-hearth electric broilers (OH) or BG, and WBSF was measured. Percentage of cooking loss was lower (P < 0.001) and less variable for chops cooked with a BG (23.2%; SD = 1.7%) vs. OH (27.6%; SD = 3.0%). Estimates of the repeatability of WBSF were similar for chops cooked with OH (0.61) and BG (0.59). Although significant (P < 0.05), differences in WBSF (4.1 vs. 3.9 kg) between cooking methods accounted for less than 5% of the total variation in WBSF. In Exp. 2, the correlation of SSF (r = -0.72; P < 0.001) with trained sensory panel tenderness ratings was slightly stronger than the correlation of WBSF (r = -0.66; P < 0.001) with trained sensory panel tenderness ratings, indicating that the two methods had a similar ability to predict tenderness ratings. In Exp. 3, duplicate samples from 372 carcasses at 2 and 10 d postmortem were obtained, cooked with BG, and SSF was determined. The repeatability of SSF was 0.90, which is comparable to repeatability estimates for beef and lamb. Use of BG cookery and SSF could facilitate the collection of accurate pork longissimus tenderness data. Time and labor savings associated with BG cookery and the SSF technique should help to decrease research costs.     

Predicting beef tenderness using near-infrared spectroscopy

The objective of this multiple-phase study was to determine the accuracy of an on-line near-infrared (NIR) spectral reflectance system to predict 14-d-aged cooked beef tenderness. In phase I, 292 carcasses (140 US Select, 152 US Choice) were selected (d 2) from 2 commercial beef processing facilities. After carcass selection, longissimus lumborum (LL) muscle sections (ribs 9 to 12) were individually identified, vacuum-packaged, and transported to the Oklahoma State University Meats Laboratory, where a 2.54-cm-thick steak (n = 1) was fabricated and stored in refrigerated conditions (1 degrees C +/- 1). Following a 30-min oxygenation period, a NIR spectral scan was obtained on the 12th-rib LL steak. Steaks (d 3) were individually vacuum-packaged and aged at 4 degrees C for a total of 14 d before cooking slice shear force (SSF) analysis. In phases II and III, 476 carcasses (258 US Select, 218 US Choice) were immediately NIR scanned after carcass presentation to in-plant USDA grading personnel. In a similar fashion, all LL steaks were aged (1 degrees C +/- 1) for 14 d before cooking (70 degrees C) and conducting SSF. Of the phase I and II samples, 39 (6.77%) were categorized as being tough (i.e., >/= 25 kg of SSF after the 14-d postmortem aging period). Of these 39 tough samples, 20 (3.7% error rate) were correctly placed in the 90% certification level. Another 10 tough samples were placed in the 80% certification level (2.0% error rate). The overall NIR certified tender group was 1.67 kg more tender (P < 0.05) than LL samples from the noncertified samples. When the NIR predicted samples to be tough, 10% of the samples were eliminated from the phase I and II LL populations at 90% certification. The population SSF mean improved in excess of 6.5 kg. For phase III, SSF evaluation by an independent third party indicated the NIR system was able to successfully sort tough from tender LL samples to 70% certification levels. It was concluded that NIR scanning offers an in-plant opportunity to sort carcasses into tenderness outcome groups for guaranteed-tender branded beef programs.     

Consumer thresholds for establishing the value of beef tenderness.

In the present study, a national consumer evaluation was conducted for beef tenderness on USDA Select strip loin steaks of known Warner-Bratzler shear (WBS) force values, ranging from tough (> 5.7 kg) to tender (< 3.0 kg), and to assess the monetary value that consumers place on tenderness by determining the average price a consumer would pay for a steak in three tenderness categories. Three supermarkets in each of five metropolitan areas (Baltimore, MD/Washington D.C.; Chicago, IL; Dallas/Fort Worth, TX; Los Angeles, CA; and Lubbock, TX) were selected to represent a wide range of income, education, and ethnicity at each city. Five trained research teams traveled to the cities to collect data during the same 10-d period. Consumers (n = 734; minimum of 15 consumers/panel, three panels/store, three stores/city, five cities) were asked to evaluate samples from each tenderness classification (tender, intermediate, or tough) for overall and tenderness acceptability, overall quality, beef flavor, juiciness, tenderness, how much they would pay for the steak ($17.14, 14.28, or 10.98/kg), if they would pay more than current market price if guaranteed tender, and to estimate the number of meals in a 2-wk period that included beef. The consumers were 52% light beef users, consuming 0 to 8 meals containing beef in 2 wk, 41% heavy beef users (greater than 12 meals/2 wk), and 6% moderate beef users (9 to 12 meals/2 wk). Consumer tenderness acceptability increased as WBS values decreased (P < 0.05). The transition in consumer perception from tender to tough beef occurred between 4.3 and 4.9 kg of WBS based on > or = 86% consumer acceptability. Consumer acceptability for tenderness decreased from 86% at 4.3 kg for a "slightly tender" rating to 59% at 4.9 kg for a "slightly tough" rating. Data from the present study suggested that consumer WBS tenderness values of < 3.0, 3.4, 4.0, 4.3, and > 4.9 kg would result in 100, 99, 94, 86, and 25% customer satisfaction for beef tenderness, respectively. Seventy-eight percent of the consumers would purchase steaks if the retailer guaranteed them to be tender. The retail steak value differences found in this study would result in the opportunity for a premium to be paid for a guaranteed tender (< 3.0 kg WBS value) carcass of $76.26 vs the toughest (> 5.7 kg) classification. A premium of $66.96 could be paid to the tender classification carcasses vs the tough (> 4.9 kg) classification carcasses, and a premium of $36.58 could be paid for the tender classification carcasses vs the intermediate (> 3.0 to < 4.6 kg) classification carcasses. Results from the present study show that consumers can segregate differences in beef tenderness and that consumers are willing to pay more for more-tender beef.     

Benchmarking carcass characteristics and muscles from commercially identified beef and dairy cull cow carcasses for Warner-Bratzler shear force and sensory attributes

The objective of this study was to benchmark carcasses and muscles from commercially identified fed (animals that were perceived to have been fed an increased plane of nutrition before slaughter) and nonfed cull beef and dairy cows and A-maturity, USDA Select steers, so that the muscles could be identified from cull cow carcasses that may be used to fill a void of intermediately priced beef steaks. Carcass characteristics were measured at 24 h postmortem for 75 carcasses from 5 populations consisting of cull beef cows commercially identified as fed (B-F, n = 15); cull beef cows commercially identified as nonfed (B-NF, n = 15); cull dairy cows commercially identified as fed (D-F, n = 15); cull dairy cows commercially identified as nonfed (D-NF, n = 15); and A-maturity, USDA Select grade steers (SEL, n = 15). Nine muscles were excised from each carcass [m. infraspinatus, m. triceps brachii (lateral and long heads), m. teres major, m. longissimus dorsi (also termed LM), m. psoas major, m. gluteus medius, m. rectus femoris, and m. tensor fasciae latae] and subjected to Warner-Bratzler shear force testing and objective sensory panel evaluation after 14 d of postmortem aging. Carcass characteristics differed (P < 0.05) among the 5 commercially identified slaughter groups for the traits of lean maturity, bone maturity, muscle score, HCW, fat color, subjective lean color, marbling, ribeye area, 12th-rib fat thickness, and preliminary yield grade. Carcasses from commercially identified, fed cull cows exhibited more (P < 0.01) weight in carcass lean than did commercially identified, nonfed cull cows. There was a group x muscle interaction (P = 0.02) for Warner-Bratzler shear force. Warner-Bratzler shear force and sensory overall tenderness values demonstrates that muscles from the SEL group were the most tender (P < 0.01), whereas muscles from the B-NF group were the least tender (P < 0.01). Sensory, beef flavor intensity was similar (P > 0.20) among cull cow carcass groups and more intense (P < 0.01) than the SEL carcass group. Muscles from the SEL group exhibited less (P < 0.01) detectable off-flavor than the cull cow carcass groups, whereas the B-NF group exhibited the most (P < 0.01) detectable off-flavor. Although carcass and muscle quality from commercially identified, fed, cull beef and dairy cows was not similar to A-maturity, USDA Select beef, they did show improvements when compared with nonfed, cull, beef and dairy cow carcasses and muscles.     

Tenderness classification of beef: II. Design and analysis of a system to measure beef longissimus shear force under commercial processing conditions.

The objectives of this study were to evaluate the efficacy of a system for classifying beef for tenderness based on a rapid, simple method of measuring cooked longissimus shear force. Longissimus steaks (2.54 cm thick) were trimmed free of s.c. fat and bone and rapidly cooked using a belt grill. A 1-cm-thick, 5-cm-long slice was removed from the cooked longissimus parallel with the muscle fibers for measurement of shear force. Slices were sheared with a flat, blunt-end blade using an electronic testing machine. The entire process was completed in less than 10 min. Therefore, in commercial application, this process could be completed during the 10- to 15-min period that carcasses are normally held to allow the ribeye to bloom for quality grading. In Exp. 1, the repeatability of slice shear force (SSF), as determined by evaluation of duplicate samples from 204 A-maturity carcasses, was .89. In Exp. 2, A-maturity carcasses (n = 483) were classified into three groups based on SSF (< 23, 23 to 40, and > 40 kg) at 3 d postmortem that differed (P < .001) in mean trained sensory panel tenderness ratings (7.3 +/- .04, 6.4 +/- .06, and 4.4 +/- .20) and the percentages (100, 91, and 28%) of samples rated "Slightly Tender" or higher at 14 d postmortem. Therefore, this tenderness classification system could be used to accurately segregate beef carcasses into expected tenderness groups. Further research is needed to test the feasibility and accuracy of this system under a variety of commercial processing conditions.     

Evaluation of sampling, cookery, and shear force protocols for objective evaluation of lamb longissimus tenderness

Experiments were conducted to compare the effects of two cookery methods, two shear force procedures, and sampling location within non-callipyge and callipyge lamb LM on the magnitude, variance, and repeatability of LM shear force data. In Exp. 1, 15 non-callipyge and 15 callipyge carcasses were sampled, and Warner-Bratzler shear force (WBSF) was determined for both sides of each carcass at three locations along the length (anterior to posterior) of the LM, whereas slice shear force (SSF) was determined for both sides of each carcass at only one location. For approximately half the carcasses within each genotype, LM chops were cooked for a constant amount of time using a belt grill, and chops of the remaining carcasses were cooked to a constant endpoint temperature using open-hearth electric broilers. Regardless of cooking method and sampling location, repeatability estimates were at least 0.8 for LM WBSF and SSF. For WBSF, repeatability estimates were slightly higher at the anterior location (0.93 to 0.98) than the posterior location (0.88 to 0.90). The difference in repeatability between locations was probably a function of a greater level of variation in shear force at the anterior location. For callipyge LM, WBSF was higher (P < 0.001) at the anterior location than at the middle or posterior locations. For non-callipyge LM, WBSF was lower (P < 0.001) at the anterior location than at the middle or posterior locations. Consequently, the difference in WBSF between callipyge and non-callipyge LM was largest at the anterior location. Experiment 2 was conducted to obtain an estimate of the repeatability of SSF for lamb LM chops cooked with the belt grill using a larger number of animals (n = 87). In Exp. 2, LM chops were obtained from matching locations of both sides of 44 non-callipyge and 43 callipyge carcasses. Chops were cooked with a belt grill and SSF was measured, and repeatability was estimated to be 0.95. Repeatable estimates of lamb LM tenderness can be achieved either by cooking to a constant endpoint temperature with electric broilers or cooking for a constant amount of time with a belt grill. Likewise, repeatable estimates of lamb LM tenderness can be achieved with WBSF or SSF. However, use of belt grill cookery and the SSF technique could decrease time requirements which would decrease research costs.     

Evaluation of slice shear force as an objective method of assessing beef longissimus tenderness.

Experiments were conducted to develop an optimal protocol for measurement of slice shear force (SSF) and to evaluate SSF as an objective method of assessing beef longissimus tenderness. Whereas six cylindrical, 1.27-cm-diameter cores are typically removed from each steak for Warner-Bratzler shear force (WBSF) determination, a single 1-cm-thick, 5-cm-long slice is removed from the lateral end of each longissimus steak for SSF. For either technique, samples are removed parallel to the muscle fiber orientation and sheared across the fibers. Whereas WBSF uses a V-shaped blade, SSF uses a flat blade with the same thickness (1.016 mm) and degree of bevel (half-round) on the shearing edge. In Exp. 1, longissimus steaks were acquired from 60 beef carcasses to determine the effects of belt grill cooking rate (very rapid vs. rapid) and conditions of SSF measurement (hot vs cold) on the relationship of SSF with trained sensory panel (TSP) tenderness rating. Slice shear force was more strongly correlated with TSP tenderness rating when SSF measurement was conducted immediately after cooking (r = -.74 to -.76) than when steaks were chilled (24 h, 4 degrees C) before SSF measurement (r = -.57 to -.72). When SSF measurement was conducted immediately after cooking, the relationship of SSF with TSP tenderness rating did not differ among the belt grill cooking protocols used to cook the SSF steak. In Exp. 2, longissimus steaks were acquired from 479 beef carcasses to compare the ability of SSF and WBSF of 1.27-cm-diameter cores to predict TSP tenderness ratings. Slice shear force was more strongly correlated with sensory panel tenderness rating than was WBSF (r = -.82 vs -.77). In Exp. 3, longissimus steaks were acquired from 110 beef carcasses to evaluate the repeatability (.91) of SSF over a broad range of tenderness. Slice shear force is a more rapid, more accurate, and technically less difficult technique than WBSF. Use of the SSF technique could facilitate the collection of more accurate data and should allow the detection of treatment differences with reduced numbers of observations and reduced time requirements, thereby reducing research costs.     

Characterization of biological types of cattle (Cycle V): carcass traits and longissimus palatability

Carcass (n = 854) and longissimus thoracis palatability (n = 802) traits from F1 steers obtained from mating Hereford, Angus, and MARC III cows to Hereford or Angus (HA), Tuli (Tu), Boran (Bo), Brahman (Br), Piedmontese (Pm), or Belgian Blue (BB) sires were compared. Data were adjusted to constant age (444 d), carcass weight (333 kg), fat thickness (1.0 cm), fat trim percentage (21%), and marbling (Small00) end points. Results presented in this abstract are for age-constant data. Carcasses from BB- and HA-sired steers were heaviest (P < 0.05) and carcasses from Bo- and Tu-sired steers were lightest (P < 0.05). Adjusted fat thickness was greatest (P < 0.05) on carcasses from HA-sired steers and least (P < 0.05) on carcasses from BB- and Pm-sired steers. Numerical USDA yield grades were lowest (P < 0.05) for carcasses from Pm- and BB-sired steers and highest (P < 0.05) for carcasses from HA- and Br-sired steers. Marbling scores were highest (P < 0.05) for carcasses from HA- and Tu-sired steers and lowest (P < 0.05) for carcasses from Br-, BB-, and Pm-sired steers. Longissimus thoracis from carcasses of HA-, Pm-, and Tu-sired steers had the lowest (P < 0.05) 14-d postmortem Warner-Bratzler shear force values. Carcasses from HA-sired steers had longissimus thoracis with the highest (P < 0.05) tenderness ratings at 7 d postmortem. Longissimus thoracis from carcasses of Br- and Bo-sired steers had the highest (P < 0.05) Warner-Bratzler shear forces and the lowest (P < 0.05) tenderness ratings at 7 d postmortem. Adjustment of traits to various slaughter end points resulted in some changes in sire breed differences for carcass traits but had little effect on palatability traits. Carcasses from BB- and Pm-sired steers provided the most desirable combination of yield grade and longissimus palatability, but carcasses from HA-cross steers provided the most desirable combination of quality grade and longissimus palatability. Tuli, a breed shown to be heat-tolerant, had longissimus tenderness similar to that of the non-heat-tolerant breeds and more tender longissimus than the heat-tolerant breeds in this study.     

Dietary zilpaterol hydrochloride. II. Carcass composition and meat palatability of beef cattle

Experiments were conducted at 3 US locations (California, Idaho, and Texas) to determine the effects of dietary zilpaterol hydrochloride and duration of zilpaterol feeding on carcass composition and beef palatability. At each site, 160 steers and 160 heifers were stratified within sex by initial BW (study d -1) and assigned randomly within BW strata to 1 of 4 treatments in a randomized complete block design (4 blocks/treatment for each sex). The 4 treatments were arranged in a 2 (no zilpaterol vs. zilpaterol) x 2 (20- or 40-d duration of zilpaterol feeding) factorial. When included in the diet, zilpaterol was supplemented at 8.3 mg/kg (DM basis). Each pen consisted of 10 animals. After slaughter 2 carcasses per pen (n=64 per trial site) were selected. The entire right side of the selected carcasses was collected for dissection and chemical analysis of the soft tissue. Additionally, the left strip loin was collected for Warner-Bratzler shear force determinations and aged to 28 d postmortem. Sensory analysis was conducted on the Idaho trial site samples only. All data were pooled for analyses. Feeding zilpaterol hydrochloride increased carcass muscle deposition (P<0.01) of both steer and heifer carcasses. However, carcass percentage fat of steers and heifers was not affected (P>0.11) by the zilpaterol treatment. In heifer carcasses, carcass moisture percentage was increased (P=0.04) and bone percentage was decreased (P=0.02), whereas in steer carcasses, carcass moisture and bone percentage were not affected (P>0.10). In heifer carcasses, carcass ash percentage was not affected (P=0.61) by zilpaterol, whereas in steer carcasses, carcass ash percentage tended (P=0.07) to be increased. The protein-to-bone ratio was increased (P<0.001) by zilpaterol hydrochloride treatment in both steers and heifers, whereas the protein-to-fat ratio was not affected (P=0.10). Cooking loss of the LM was not affected (P=0.41) by zilpaterol treatment of steers or heifers. However, LM Warner-Bratzler shear force was increased (P=0.003) on average (3.3 vs. 4.0 kg) due to zilpaterol hydrochloride treatment of both steers and heifers. In both steers and heifers, LM sensory panel scores of overall juiciness (6.2 vs. 6.0), tenderness (6.2 vs. 6.0), and flavor intensity (6.2 vs. 6.0) tended (P=0.06) to be decreased in cattle supplemented with zilpaterol. Zilpaterol hydrochloride is a repartitioning agent that seems to affect carcass composition primarily through protein deposition. However, zilpaterol treatment can adversely affect tenderness and other palatability traits.     

Evaluation of the Tendertec beef grading instrument to predict the tenderness of steaks from beef carcasses

Four experiments were conducted, using carcasses from cattle identified for anticipated variability in tenderness (Exp. 1, 2, and 3) and carcasses selected for variability in physiological maturity and marbling score (Exp. 4), to evaluate the ability of the Tendertec Mark III Beef Grading Probe (Tendertec) to predict tenderness of steaks from beef carcasses. In Exp. 1, 2, and 3, longissimus steaks were aged for different periods of time, cooked to a medium degree of doneness (70 degrees C), and evaluated for Warner-Bratzler shear force (WBS) and trained sensory panel ratings. In Exp. 4, longissimus steaks were aged 14 d and cooked to 60, 65, 70, 75, or 80 degrees C for WBS tests and to 65 or 75 degrees C for sensory panel evaluations. Tendertec output variables were not correlated with 1) 24-h calpastatin activity, steak WBS (following 1, 4, 7, 14, 21, or 35 d of aging), or d-14 sensory panel tenderness ratings in Exp. 1 (n = 467 carcasses) or 2) 14-d WBS in Exp. 2 (n = 202 carcasses). However, in Exp. 3 (n = 29 carcasses), Tendertec output variables were correlated (P < 0.05) with tenderness of steaks aged 1, 21, 28, or 35 d, and we were able to separate carcasses into groups yielding tough, acceptable, and tender steaks. In Exp. 4 (n = 70), Tendertec output variables were correlated (P < 0.05) with steak WBS at 60 degrees C and with steak ratings for muscle fiber tenderness, connective tissue amount, and overall tenderness at 65 degrees C, but these relationships weakened (P > 0.05) as degree of doneness increased. Consequently, Tendertec output variables only were effective for stratifying carcasses according to tenderness when steaks from those carcasses in Exp. 4 were cooked to a rare or medium-rare degree of doneness. Although Tendertec was able to sort carcasses of older, mature cattle based on tenderness of steaks at some cooked end points, it failed to detect tenderness differences in steaks derived from youthful carcasses consistently, and was thus of limited value as an instrument for use in improving the quality, consistency, and uniformity of the U.S. fed-beef supply.     

Effects of zilpaterol hydrochloride and days on the finishing diet on feedlot performance, carcass characteristics, and tenderness in beef heifers

British × Continental heifers (n = 3,382; initial BW = 307 kg) were serially slaughtered to determine if increasing days on the finishing diet (DOF) mitigates negative consequences of zilpaterol HCl (ZH) on quality grade and tenderness of beef. A 2 × 3 factorial arrangement of treatments in a completely randomized block design (36 pens; 6 pens/treatment) was used. Zilpaterol HCl (8.33 mg/kg DM) was fed 0 and 20 to 22 d before slaughter plus a 3 to 5 d withdrawal to heifers spending 127, 148, and 167 DOF. Feedlot and carcass performance data were analyzed with pen as the experimental unit. Three hundred sixty carcasses (60 carcasses/treatment) were randomly subsampled, and strip loin steaks were aged for 7, 14, and 21 d for assessment of Warner-Bratzler shear force (WBSF) and slice shear force (SSF) with carcass serving as the experimental unit for analysis. No relevant ZH × DOF interactions were detected (P > 0.05). Feeding ZH during the treatment period increased ADG by 9.5%, G:F by 12.5%, carcass ADG by 33.6%, carcass G:F by 35.9%, carcass ADG:live ADG by 15.6%, HCW by 3.2% (345 vs. 356 kg), dressing percent by 1.5%, and LM area by 6.5% and decreased 12th-rib fat by 5.2% and yield grade (YG) by 0.27 units (P < 0.01). Feeding ZH tended to decrease marbling score (437 vs. 442 units; P = 0.10) and increased WBSF at 7 (4.25 vs. 3.47 kg; P < 0.01), 14 (3.57 vs. 3.05 kg; P < 0.01), and 21 d (3.50 vs. 3.03 kg; P < 0.01). Feeding ZH decreased empty body fat percentage (EBF; 29.7% vs. 30.3%; P < 0.01) and increased 28% EBF adjusted final BW (473.4 vs. 449.8 kg; P < 0.01). Analysis of interactive means indicated that the ZH × 148 DOF group had a similar percentage of USDA Prime, Premium Choice, Low Choice, and YG 1, 2, 3, 4, and 5 carcasses (P > 0.10) and decreased percentage of Select (30.4 vs. 36.6%; P = 0.03) and Standard (0.2 vs. 0.9%; P = 0.05) carcasses compared with the control × 127 DOF group. As a result of ZH shifting body composition, extending the DOF of beef heifers is an effective feeding strategy to equalize carcass grade distributions. This can be accomplished along with sustaining the ZH mediated advantages in feedlot and carcass weight gain.     

The efficacy of three objective systems for identifying beef cuts that can be guaranteed tender

The objective of this study was to determine the accuracy of three objective systems (prototype BeefCam, colorimeter, and slice shear force) for identifying guaranteed tender beef. In Phase I, 308 carcasses (105 Top Choice, 101 Low Choice, and 102 Select) from two commercial plants were tested. In Phase II, 400 carcasses (200 rolled USDA Select and 200 rolled USDA Choice) from one commercial plant were tested. The three systems were evaluated based on progressive certification of the longissimus as "tender" in 10% increments (the best 10, 20, 30%, etc., certified as "tender" by each technology; 100% certification would mean no sorting for tenderness). In Phase I, the error (percentage of carcasses certified as tender that had Warner-Bratzler shear force of > or = 5 kg at 14 d postmortem) for 100% certification using all carcasses was 14.1%. All certification levels up to 80% (slice shear force) and up to 70% (colorimeter) had less error (P < 0.05) than 100% certification. Errors in all levels of certification by prototype BeefCam (13.8 to 9.7%) were not different (P > 0.05) from 100% certification. In Phase I, the error for 100% certification for USDA Select carcasses was 30.7%. For Select carcasses, all slice shear force certification levels up to 60% (0 to 14.8%) had less error (P < 0.05) than 100% certification. For Select carcasses, errors in all levels of certification by colorimeter (20.0 to 29.6%) and by BeefCam (27.5 to 31.4%) were not different (P > 0.05) from 100% certification. In Phase II, the error for 100% certification for all carcasses was 9.3%. For all levels of slice shear force certification less than 90% (for all carcasses) or less than 80% (Select carcasses), errors in tenderness certification were less than (P < 0.05) for 100% certification. In Phase II, for all carcasses or Select carcasses, colorimeter and prototype BeefCam certifications did not significantly reduce errors (P > 0.05) compared to 100% certification. Thus, the direct measure of tenderness provided by slice shear force results in more accurate identification of "tender" beef carcasses than either of the indirect technologies, prototype BeefCam, or colorimeter, particularly for USDA Select carcasses. As tested in this study, slice shear force, but not the prototype BeefCam or colorimeter systems, accurately identified "tender" beef.     

Association of a single nucleotide polymorphism in the calpastatin gene with carcass and meat quality traits of beef cattle

Calpastatin (CAST) is a naturally occurring protein that inhibits the normal tenderization of meat as it ages postmortem. A SNP was identified in the CAST gene (a G to C substitution) and genotyped on crossbred commercially fed heifers (n = 163), steers (n = 226), and bulls (n = 61) from beef feedlots, and steers (n = 178) from a University of Guelph feeding trial. The association of the CAST SNP with carcass and meat quality traits was studied. Carcass traits included fat, lean, and bone yield; grade fat; LM area; and HCW. Meat quality traits included marbling grade; i.m. fat content of LM; tenderness evaluation of LM (Warner-Bratzler shear force) at 2, 7, 14, and 21 d of postmortem aging; and tenderness evaluation of semitendinosus muscle at 7 d of postmortem aging. The mixed model used in the analyses included fixed effects of CAST genotype, sex, slaughter group, and breed composition (linear covariate); sire was a random effect. For the analysis of shear force, i.m. fat content of LM was also included in the model as a linear covariate. Shear force measures were analyzed within days of postmortem aging and by repeated measures analysis. The CAST SNP allele C was more frequent (63%) in the crossbred population than allele G. The CAST SNP was associated with shear force across days of postmortem aging (P = 0.005); genotype CC yielded beef that was more tender than GG (-0.32 kg +/- 0.13), and CG had intermediate tenderness. The corresponding average allele substitution effect (G to C substitution) was also highly significant (-0.15 +/- 0.05 kg, P = 0.002). A lower percentage of unacceptably tough steaks (shear force > 5.7 kg) at 2 and 7 d postmortem was associated with an increasing number of C alleles (P < or = 0.05). At 7 d postmortem, the percentage of unacceptably tough steaks decreased by 24 and 35%, respectively, for animals carrying 1 and 2 copies of the C allele relative to animals with no C alleles. However, genotype CC had a greater fat yield (+1.44 +/- 0.56%; P = 0.037) than genotype GG, with a corresponding allele substitution effect of 0.67 +/- 0.27% (P = 0.015). Therefore, the CAST SNP allele C was associated with increased LM tenderness across days of postmortem aging and, importantly for the beef industry, had a significant reduction in the percentage of steaks rated unacceptably tough by consumers based on an assumed threshold level.     

Mechanical probes can predict tenderness of cooked beef longissimus using uncooked measurements

Two experiments were conducted to determine the effectiveness of using mechanical probes and objective color measurement on beef LM to predict cooked tenderness. In Exp. 1, sharp needle (SN), sharp blade (SB), blunt needle (BN), blunt blade (BB), and plumb bob (PB) probes were used to measure uncooked LM (n = 29) at 2 d postmortem in both a perpendicular and parallel orientation to the long axis of the strip loin. Additionally, instrumental color measurements were measured on uncooked muscle at 2 d postmortem. Steaks for trained sensory panel (TSP) and Warner-Bratzler shear force (WBSF) measurements were aged 14 d postmortem before cooking. Probe measurements taken perpendicular to the long axis of the LM were not correlated (P = 0.22 to 0.82) to TSP tenderness. Probe measurements (BB, BN, SN, SB, and PB) taken parallel to the long axis were correlated to TSP tenderness (r = -0.57, -0.40, -0.77, -0.52, and -0.53, respectively). A regression equation using the SN probe to predict TSP tenderness had a R2 value of 0.74. The SB probe combined with L* accounted for 45% of the variation in TSP tenderness, whereas the PB probe combined with L* accounted for 56% of the variation in TSP tenderness. A second experiment (n = 24) was conducted using the SN, SB, and PB probes on uncooked sections at 2 d and on cooked steaks at 14 d postmortem. Probe measurements on cooked steaks were not correlated to TSP tenderness. New regression equations were calculated using the probe measurements on uncooked steaks from both experiments. Prediction equations formulated with L* values and either SN, SB, or PB probes accounted for 49, 50, and 47% of the variability in TSP tenderness scores, respectively. An equation using WBSF of cooked steaks to predict TSP tenderness had an R2 of 0.58. Of the steaks predicted to be tender (predicted tenderness > 5.0) by the equations using the SN, SB, and PB probes on uncooked steaks and WBSF on cooked steaks, 85, 88, 80, and 84%, respectively, were actually tender (TSP tenderness > 5.0). Mechanical probe measurements of uncooked steaks at 2 d postmortem can potentially classify strip loins into groups based on tenderness, as well as WBSF measurements, which are more costly and time consuming.