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In a previous study, the seasonal prevalence was reported for stx+ Escherichia coli O157:H7 in feces and on hides and carcasses of cattle at processing. Overall, 1,697 O157:H7 isolates have now been characterized for the incidence of (i) eae(O157), hlyA, stx1, and stx2 in the recovered isolates and (ii) presumptive rough and presumptive nonmotile isolates. Seven O157:H7 isolates (0.4%) lacked stx genes, although they carried eae and hlyA. All but one of the isolates carried both eae and hlyA. Approximately two-thirds of the isolates (64% when one isolate per sample was considered) carried both stx1 and stx2. E. coli O157:H7 cells that harbored both stx1 and stx2 were more often recovered from hides in the fall (79% of the fall hide isolates) and winter (84% of the winter hide isolates) than in the spring (53%) and summer (59%). Isolates recovered from preevisceration carcasses showed a similar but not statistically significant trend. Twenty-three of the 25 O157:H7 isolates carrying stx1 but not stx2 were recovered during summer. Fifteen presumptive rough and 117 presumptive nonmotile stx+ O157:H7 isolates were recovered. Ten (67%) of the presumptive rough isolates were recovered during summer. Ninety-five of the presumptive nonmotile isolates (81%) were recovered during fall. Forty-eight percent of the false-positive isolates (175 of 363) tentatively identified as O157:H7 were O157+ H7- and lacked eae(O157), hlyA, and stx. These data suggest that in beef processing samples (i) there are minor seasonal variations in the prevalence of stx genes among E. coli O157:H7 isolates, (ii) presumptive rough and presumptive nonmotile stx+ O157:H7 isolates are present, (iii) E. coli O157:H7 isolates lacking stx genes may be rare, and (iv) O157+ H7- isolates lacking stx genes can result in many false-positive results.

The effectiveness of current antimicrobial interventions used in reducing the prevalence or load of Escherichia coli O157 and indicator organisms on cattle hides and carcasses at two commercial beef processing plants was evaluated. Sponge sampling of beef cattle was performed at five locations from the initial entry of the animals to the slaughter floor to the exit of carcasses from the "hotbox" cooler. For each sample, E. coli O157 prevalence was determined and total aerobic bacteria, Enterobacteriaceae, and E. coli O157 were enumerated. E. coli O157 was found on 76% of animal hides coming into the plants, but no carcasses leaving the cooler were identified as contaminated with E. coli O157. A positive relationship was seen between the incidence of E. coli O157 in hide samples and that in preevisceration samples. Aerobic plate counts and Enterobacteriaceae counts averaged 7.8 and 6.2 log CFU/100 cm2, respectively, on hides, and 1.4 and 0.4 log CFU/100 cm2, respectively, on chilled carcasses. Aerobic plate counts and Enterobacteriaceae counts on preevisceration carcasses were significantly related to the respective levels on the corresponding hides; the carcasses of animals whose hides carried higher numbers of bacteria were more likely to carry higher numbers of bacteria. Implementation of the sampling protocol described here would allow processors to evaluate the efficacy of on-line antimicrobial interventions and allow industrywide benchmarking of hygienic practices.

Carcass (n = 568) and longissimus thoracis palatability (n = 460) traits from F1 steers obtained from mating Hereford (H), Angus (A), and U.S. Meat Animal Research Center (MARC) III cows to H, A, Norwegian Red (NR), Swedish Red and White (RW), Friesian (F), or Wagyu (W) sires were compared. Data were adjusted to constant age (471 d), carcass weight (356 kg), fat thickness (1.0 cm), percentage of fat trim (24%), and marbling (Small35) end points. For Warner-Bratzler shear force and trained sensory panel traits, data were obtained on longissimus thoracis steaks stored at 2 degrees C for 14 d postmortem. The following comparisons were from the age-constant end point. Carcasses from H- and A-sired steers (377 and 374 kg, respectively) were the heaviest (P < 0.05) and carcasses from W-sired steers (334 kg) were the lightest (P < 0.05). A greater (P < 0.05) percentage of carcasses from A- and W-sired steers graded USDA Choice (88 and 85%, respectively) than carcasses from other sire breeds (52 to 71%). Adjusted fat thickness for carcasses from A-sired steers (1.3 cm) was highest (P < 0.05), followed by H-sired steers (1.1 cm) and W- and F-sired steers (0.9 cm); NR- and RW-sired steers (0.8 cm) had the lowest (P < 0.05) adjusted fat thickness. Longissimus thoracis area was not different (P > 0.05) among sire breeds (mean = 80.6 cm2). Carcass yield of boneless, totally trimmed retail product was least (P < 0.05) for A-sired steers (60.1%), intermediate for H-sired steers (61.5%), and similar (P > 0.05) for all other sire breeds (62.5 to 62.8%). Longissimus thoracis steaks from carcasses of A- (3.7 kg) and W-sired (3.7 kg) steers had lower (P < 0.05) shear force values than longissimus thoracis steaks from other sire breeds (4.1 to 4.2 kg). Trained sensory panel tenderness, juiciness, or beef flavor intensity ratings for longissimus thoracis steaks did not differ (P > 0.05) among the sire breeds. Sire breed comparisons were affected by adjusting data to other end points. Heritability estimates for various carcass, yield, and palatability traits ranged from very low (h2 = 0.06 for percentage of kidney, pelvic, and heart fat) to relatively high (h2 = 0.71 for percentage of retail product yield). Relative to the other sire breeds, W-sired steers had the highest percentage of USDA Choice, Yield grade 1 and 2 carcasses, but their carcasses were the lightest.

The objective of this experiment was to test the potential of a combined water wash and cetylpyridinium chloride (CPC) treatment as a hide intervention applied to cattle in the holding pens of a processing plant immediately before stunning. Over 2 processing days, 149 control and 139 treated cattle were tested. Control cattle were processed in the normal manner. The treatment group was prewashed with water the day before harvest. Immediately before stunning, these cattle were sprayed twice with 1% CPC, first for 3 min, then for 1 min. Hides and preevisceration carcasses were sampled to determine aerobic plate counts, Enterobacteriaceae counts (EBC), and Escherichia coli O157 prevalence. The treatment reduced the prevalence of E. coli O157 on hides from 56% to 34% and the prevalence on preevisceration carcasses from 23% to 3%. The treatment decreased aerobic plate counts from 4.9 log CFU/100 cm2 to 3.4 log CFU/100 cm2 and EBC from 3.1 log CFU/100 cm2 to 2.0 log CFU/100 cm2 on preevisceration carcasses. The treatment of hides did not result in any detectable CPC contamination of the chilled carcasses. These data indicated that a 1% CPC treatment preceded by a water wash was capable of reducing hide prevalence of E. coli O157 from as high as 80% to less than 50%, resulting in preevisceration carcass prevalence of 5% or less. We conclude that water washing followed by an antimicrobial treatment, such as CPC, has great potential as an effective hide intervention step and should be further evaluated for implementation as a processing step after stunning and before hide removal.

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.

The objective of this study was to determine the extent of variation in, and relationships among, biochemical and palatability traits within and among 11 major beef muscles. Longissimus thoracis et lumborum (LD), psoas major (PM), gluteus medius (GM), semimembranosus (SM), adductor (AD), biceps femoris (BF), semitendinosus (ST), rectus femoris (RF), triceps brachii (TB), infraspinatus (IS), and supraspinatus (SS) from one side of 31 Charolais x MARC III steer carcasses were vacuum-packaged, stored at 2 degrees C until 14 d postmortem, and then frozen at -30 degrees C. The 2.54-cm-thick steaks were obtained from two or three locations within muscles in order to assess biochemical traits and Warner-Bratzler shear force, and from near the center for sensory trait evaluation. The PM was most tender and was followed by IS in both shear force and tenderness rating (P < 0.05). The other muscles were not ranked the same by shear force and tenderness rating. The BF had the lowest (P < 0.05) tenderness rating. The PM, GM, and LD had lower (P < 0.05) collagen concentration (2.7 to 4.5 mg/g muscle) than muscles from the chuck and round (5.9 to 9.0 mg/g), except for the AD (4.9 mg/g). Desmin proteolysis was highest (P < 0.05) for BF and LD (60.7 and 60.1% degraded), and was lowest (P < 0.05) for PM (20.2%). The PM, TB, IS, RF, and ST had relatively long sarcomere lengths (> 2.1 microm), whereas the GM had the shortest (P < 0.05) sarcomere length (1.7 microm). Cooking loss was lowest (P < 0.05) for BF (18.7%) and was followed by LD and IS (20.7%); it was highest (P < 0.05) for ST (27.4%). Across all muscles, tenderness rating was highly correlated (r > 0.60) with shear force, connective tissue rating, sarcomere length, and collagen content. Within a muscle, correlations among all traits were generally highest in LD and lowest in AD. Within muscle, location effects were detected (P < 0.05) for shear force (PM, ST, BF, SM, and RF), sarcomere length (PM, ST, BF, LD, SS, IS, SM, and RF), collagen concentration (PM, BF, SS, IS, SM. AD, TB, and RF), desmin degradation (PM, GM, BF, SM, AD, and, RF), and cooking loss (all muscles except SS and AD). There is a large amount of variation within and among muscles for tenderness traits and tenderness-related biochemical traits. These results increase our understanding of the sources of variation in tenderness in different muscles and provide a basis for the development of muscle-specific strategies for improving the quality and value of muscles.

The objective of this study was to establish the necessary protocols and assess the efficacy of cetylpyridinium chloride (CPC) as an antimicrobial intervention on beef cattle hides. Experiments using CPC were conducted to determine (i) the methods of neutralization needed to obtain valid efficacy measurements, (ii) the effect of concentration and dwell time after treatment, (iii) the effect of CPC on hide and carcass microbial populations when cattle were treated at a feedlot and then transported to a processing facility for harvest, and (iv) the effectiveness of spray pressure and two-spray combinations of CPC and water to reduce hide microbial populations. Residual CPC in hide sponge samples prevented bacterial growth. Dey-Engley neutralization media at 7.8% and a centrifugation step were necessary to overcome this problem. All dwell times, ranging from 30 s to 4 h, after 1% CPC application to cattle hides resulted in aerobic plate counts and Enterobacteriaceae counts 1.5 log CFU/100 cm2 lower than controls. The most effective dose of CPC was 1%, which reduced aerobic plate counts and Enterobacteriaceae counts 2 and 1 log CFU/100 cm2, respectively. Low-pressure application of 1% CPC at the feedlot, transport to the processing facility, and harvest within 5 h of application resulted in no effect on Escherichia coli O157 prevalence on hides or preevisceration carcasses. Two high-pressure CPC washes lowered aerobic plate counts and Enterobacteriaceae counts by 4 log CFU/100 cm2, and two medium-pressure CPC washes were only slightly less effective. These results indicate that under the proper conditions, CPC may still be effective for reducing microbial populations on cattle hides. Further study is warranted to determine if this effect will result in reduction of hide-to-carcass contamination during processing.

The objective of this study was to determine the accuracy and repeatability of untrained laboratory consumer panelists in detecting differences in beef longissimus tenderness. At 14 d postmortem, slice shear force was measured on one steak from 192 strip loins and used to select 54 strip loins and assign 18 of the strip loins to each of three tenderness classes (tender = < 15 kg, intermediate = 15 to 27 kg, and tough = > 27 kg). Sixty-eight untrained, laboratory consumer panelists evaluated paired steaks from each tenderness class in each of two sessions (12 total observations per panelist). Mean slice shear forces for "tender," "intermediate," and "tough" were 11.1, 21.0, and 32.2 kg, respectively. Mean tenderness ratings of the untrained laboratory consumer panel were different (P < 0.05) among tenderness classes (mean of 16 panelists = 6.2, 4.9, and 3.3 for tender, intermediate, and tough, respectively), and these differences were similar regardless of how many untrained panelists were averaged to determine the panel mean (4, 8, 12, or 16). The correlations (P < 0.01) between slice shear force and the mean untrained consumer panel tenderness rating (mean of 4, r = -0.82; mean of 8, r = -0.89; mean of 12, r = -0.91; and mean of 16, r = -0.92;) were similar. Overall repeatability of the untrained consumer panel was 0.80. Repeatability of individual untrained consumer panelists for tenderness rating was highly variable: 31% were > 0.80, 36% were 0.60 to 0.79, and 33% were < 0.60. Thirty-two percent of the consumers were both accurate (correlation to slice shear force = -0.75 to -1.00, P < 0.01) and repeatable (repeatability > 0.75). There is wide variability in the ability of untrained laboratory consumer panelists to detect differences in beef tenderness. Nonetheless, untrained consumer panels can accurately and repeatedly detect differences in beef tenderness under controlled laboratory conditions. An untrained laboratory consumer panel may be able to provide as effective an evaluation of beef longissimus tenderness as a trained descriptive attribute panel.

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.

The seasonal prevalence of Escherichia coli O157:H7, Salmonella, non-O157 E. coli (STEC), and stx-harboring cells was monitored at three Midwestern fed-beef processing plants. Overall, E. coli O157:H7 was recovered from 5.9% of fecal samples, 60.6% of hide samples, and 26.7% of carcasses sampled before the preevisceration wash. This pathogen also was recovered from 1.2% (15 of 1,232) of carcasses sampled at chilling (postintervention) at approximate levels of <3.0 cells per 100 cm2. In one case, the E. coli O157:H7 concentration dropped from ca. 1,100 cells per 320 cm2 at the preevisceration stage to a level that was undetectable on ca. 2,500 cm2 at the postintervention stage. The prevalence of E. coli O157:H7 in feces peaked in the summer, whereas its prevalence on hide was high from the spring through the fall. Overall, Salmonella was recovered from 4.4, 71.0, and 12.7% of fecal, hide, and preevisceration carcass samples, respectively. Salmonella was recovered from one postintervention carcass (of 1,016 sampled). Salmonella prevalence peaked in feces in the summer and was highest on hide and preevisceration carcasses in the summer and the fall. Non-O157 STEC prevalence also appeared to vary by season, but the efficiency in the recovery of isolates from stx-positive samples ranged from 37.5 to 83.8% and could have influenced these results. Cells harboring stx genes were detected by PCR in 34.3, 92.0, 96.6, and 16.2% of fecal, hide, preevisceration carcass, and postintervention carcass samples, respectively. The approximate level of non-O157 STEC and stx-harboring cells on postintervention carcasses was > or = 3.0 cells per 100 cm2 for only 8 of 199 carcasses (4.0%). Overall, the prevalence of E. coli O157:H7, Salmonella, and non-O157 STEC varied by season, was higher on hides than in feces, and decreased dramatically, along with pathogen levels, during processing and during the application of antimicrobial interventions. These results demonstrate the effectiveness of the current interventions used by the industry and highlight the significance of hides as a major source of pathogens on beef carcasses.

The objective of this experiment was to test the hypothesis that cleaning cattle hides by removing hair and extraneous matter before hide removal would result in improved microbiological quality of carcasses in commercial beef processing plants. To test this hypothesis, we examined the effect of chemical dehairing of cattle hides on the prevalence of Escherichia coli O157:H7 and the levels of aerobic bacteria and Enterobacteriaceae on carcasses. Samples from 240 control (conventionally processed) and 240 treated (chemically dehaired before hide removal) hides (immediately after stunning but before treatment) and preevisceration carcasses (immediately after hide removal) were obtained from four visits to a commercial beef processing plant. Total aerobic plate counts (APC) and Enterobacteriaceae counts (EBC) were not (P > 0.05) different between cattle designated for chemical dehairing (8.1 and 5.9 log CFU/100 cm2 for APC and EBC, respectively) and cattle designated for conventional processing (8.0 and 5.7 log CFU/100 cm2 for APC and EBC, respectively). However, E. coli O157:H7 hide prevalence was higher (P < 0.05) for the control group than for the treated group (67% versus 88%). In contrast to hides, the bacterial levels were lower (P < 0.05) on the treated (3.5 and 1.4 log CFU/100 cm2 for APC and EBC) than the control (5.5 and 3.2 log CFU/100 cm2 for APC and EBC) preevisceration carcasses. Prevalence of E. coli O157:H7 was lower (P > 0.05) on treated than on control preevisceration carcasses (1% versus 50%). These data indicate that chemical dehairing of cattle hides is an effective intervention to reduce the incidence of hide-to-carcass contamination with pathogens. The data also imply that any effective hide intervention process incorporated into beef processing procedures would significantly reduce carcass contamination by E. coli O157:H7.

Data from 534 steers representing six sire breed groups were used to develop live animal ultrasound prediction equations for weight and percentage of retail product. Steers were ultrasonically measured for 12th-rib fat thickness (UFAT), rump fat thickness (URPFAT), longissimus muscle area (ULMA), and body wall thickness (UBDWALL) within 5 d before slaughter. Carcass measurements included in USDA yield grade (YG) and quality grade calculations were obtained. Carcasses were fabricated into boneless, totally trimmed retail products. Regression equations to predict weight and percentage of retail product were developed using either live animal or carcass traits as independent variables. Most of the variation in weight of retail product was accounted for by live weight (FWT) and carcass weight with R2 values of 0.66 and 0.69, respectively. Fat measurements accounted for the largest portion of the variation in percentage of retail product when used as single predictors (R2 = 0.54, 0.44, 0.23, and 0.54 for UFAT, URPFAT, UBDWALL, and carcass fat, respectively). Final models (P < 0.10) using live animal variables included FWT, UFAT, ULMA, and URPFAT for retail product weight (R2 = 0.84) and UFAT, URPFAT, ULMA, UBDWALL, and FWT for retail product percentage (R2 = 0.61). Comparatively, equations using YG variables resulted in R2 values of 0.86 and 0.65 for weight and percentage of retail product, respectively. Results indicate that live animal equations using ultrasound measurements are similar in accuracy to carcass measurements for predicting beef carcass composition, and alternative ultrasound measurements of rump fat and body wall thickness enhance the predictive capability of live animal-based equations for retail yield.

Our objectives were to examine the effects of prerigor excision and rapid chilling vs. conventional carcass chilling of two muscles on proteolysis and tenderness during the postmortem storage, as well as the effects of fast and slow rates of cooking on myofibrillar characteristics and tenderness. The longissimus thoracis (LT) and triceps brachii (TB), long head muscles were removed 45 min after exsanguination from the left side of 12 carcasses and chilled in an ice bath to induce cold shortening (excised, rapidly chilled). At 24 h postmortem, the corresponding muscles were removed from the right side (conventionally chilled). All muscles were cut into 2.54-cm-thick steaks and assigned to one of two postmortem times (1 or 14 d), and to raw and cooking treatments. Steaks were cooked at 260 degrees C (FAST) or 93 degrees C (SLOW) in a forced-air convection oven to an internal temperature of 70 degrees C. Cooking loss, cooking time, and Warner-Bratzler shear force (WBSF) were measured on cooked steaks. Sarcomere length (SL) and the extent of proteolysis of desmin were measured on raw and cooked steaks. As expected, the excised, rapidly chilled muscles had a much more rapid (P < 0.05) temperature decline than those that were conventionally chilled. The excised, rapidly chilled treatment resulted in shorter (P < 0.05) SL, and SL was shorter (P < 0.05) in LT than in TB steaks. Raw steaks had longer (P < 0.05) SL than cooked steaks, regardless of chilling treatment. The FAST cooking resulted in shorter (P < 0.05) SL than SLOW cooking in conventionally chilled steaks, but cooking rate had no effect (P > 0.05) on SL of rapidly chilled steaks. Generally, TB steaks required longer (P < 0.05) cooking times and had higher (P < 0.05) cooking losses than LT steaks, and FAST-cooked steaks had greater (P < 0.05) cooking losses than SLOW-cooked steaks. Rapidly chilled steaks had less (P < 0.05) degradation of desmin than conventionally chilled steaks (31 vs. 41%). Aging for 14 d increased (P < 0.05) desmin degradation. Rapid chilling of muscles resulted in much higher (P < 0.05) WBSF values, whereas aging resulted in lower (P < 0.05) WBSF values. The SLOW-cooked TB steaks were more tender (P < 0.05) than FAST-cooked TB steaks and LT steaks cooked at either rate. Excised, rapidly chilled muscles underwent proteolysis, but it occurred at a slower rate during the first 24 h postmortem than it did in conventionally chilled muscles. Cooking rate did not affect tenderness of LT steaks, but SLOW cooking resulted in more tender TB steaks.

Five hundred thirty-four steers were evaluated over a 2-yr period to determine the accuracy of ultrasonic estimates of carcass 12th-rib fat thickness (CFAT) and longissimus muscle area (CLMA). Within 5 d before slaughter, steers were ultrasonically measured for 12th-rib fat thickness (UFAT) and longissimus muscle area (ULMA) using an Aloka 500V real-time ultrasound machine equipped with a 17.2-cm, 3.5-MHz linear transducer. Overall, correlation coefficients between ultrasound and carcass fat and longissimus muscle area were 0.89 and 0.86, respectively. Correlations for UFAT with CFAT were similar between years (0.86 and 0.90), whereas the relationship between ULMA and CLMA was stronger in yr 1 (r = 0.91; n = 282) than in yr 2 (r = 0.79; n = 252). Differences between ultrasonic and carcass measurements were expressed on both an actual (FDIFF and RDIFF) and absolute (FDEV and RDEV) basis. Mean FDIFF and RDIFF indicated that ultrasound underestimated CFAT by 0.06 cm and overestimated CLMA by 0.71 cm2 across both years. Overall mean FDEV and RDEV, which are indications of the average error rate, were 0.16 cm and 3.39 cm2, respectively. Analysis of year effects revealed that FDIFF, FDEV, and RDEV were greater (P < 0.01) in magnitude in yr 1. Further analysis of FDEV indicated that leaner (CFAT < 0.51 cm) cattle were overestimated and that fatter (CFAT > 1.02 cm) cattle were underestimated with ultrasound. Similarly, steers with small CLMA (< 71.0 cm2) were overestimated, and steers with large CLMA (> 90.3 cm2) were underestimated. The thickness of CFAT had an effect (P < 0.05) on the error of UFAT and ULMA measurements, with leaner animals being more accurately evaluated for both traits. Standard errors of prediction (SEP) adjusted for bias of ultrasound measurements were 0.20 cm and 4.49 cm2 for UFAT and ULMA, respectively. Differences in SEP were observed for ULMA, but not UFAT, by year. These results indicate that ultrasound can be an accurate estimator of carcass traits in live cattle when measurements are taken by an experienced, well-trained technician, with only small differences in accuracy between years.

Five hundred thirty-four steers were evaluated over a 2-yr period to develop and validate prediction equations for estimating carcass composition from live animal ultrasound measurements and to compare these equations with those developed from carcass measurements. Within 5 d before slaughter, steers were ultrasonically measured for 12th-rib fat thickness (UFAT), longissimus area (ULMA), rump fat thickness (URPFAT), and body wall thickness (UBDWALL). Carcasses were fabricated to determine weight (KGRPRD) and percentage (PRPRD) of boneless, totally trimmed retail product. Data from steers born in Year 1 (n = 282) were used to develop prediction equations using stepwise regression. Final models using live animal variables included live weight (FWT), UFAT, ULMA, and URPFAT for KGRPRD (R2 = 0.83) and UFAT, URPFAT, ULMA, FWT, and UBDWALL for PRPRD (R2 = 0.67). Equations developed from USDA yield grade variables resulted in R2 values of 0.87 and 0.68 for KGRPRD and PRPRD, respectively. When these equations were applied to steers born in Year 2 (n = 252), correlations between values predicted from live animal models and actual carcass values were 0.92 for KGRPRD, and ranged from 0.73 to 0.76 for PRPRD. Similar correlations were found for equations developed from carcass measures (r = 0.94 for KGRPRD and 0.81 for PRPRD). Both live animal and carcass equations overestimated (P < 0.01) actual KGRPRD and PRPRD. Regression of actual values on predicted values revealed a similar fit for equations developed from live animal and carcass measures. Results indicate that composition prediction equations developed from live animal and ultrasound measurements can be useful to estimate carcass composition.

The present experiment was conducted to evaluate the ability of the U.S. Meat Animal Research Center's beef carcass image analysis system to predict calculated yield grade, longissimus muscle area, preliminary yield grade, adjusted preliminary yield grade, and marbling score under commercial beef processing conditions. In two commercial beef-processing facilities, image analysis was conducted on 800 carcasses on the beef-grading chain immediately after the conventional USDA beef quality and yield grades were applied. Carcasses were blocked by plant and observed calculated yield grade. The carcasses were then separated, with 400 carcasses assigned to a calibration data set that was used to develop regression equations, and the remaining 400 carcasses assigned to a prediction data set used to validate the regression equations. Prediction equations, which included image analysis variables and hot carcass weight, accounted for 90, 88, 90, 88, and 76% of the variation in calculated yield grade, longissimus muscle area, preliminary yield grade, adjusted preliminary yield grade, and marbling score, respectively, in the prediction data set. In comparison, the official USDA yield grade as applied by online graders accounted for 73% of the variation in calculated yield grade. The technology described herein could be used by the beef industry to more accurately determine beef yield grades; however, this system does not provide an accurate enough prediction of marbling score to be used without USDA grader interaction for USDA quality grading.

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.

Micromolar calcium activated neutral protease (CAPN1) was evaluated as a candidate gene for a quantitative trait locus (QTL) on BTA29 affecting meat tenderness by characterization of nucleotide sequence variation in the gene. Single-nucleotide polymorphisms (SNP) were identified by sequencing all 22 exons and 19 of the 21 introns in two sires (Piedmontese x Angus located at the U.S. Meat Animal Research Center in Clay Center, NE; Jersey x Limousin located at AgResearch in New Zealand) of independent resource populations previously shown to be segregating meat tenderness QTL on BTA29. The majority of the 38 SNP were found in introns or were synonymous substitutions in the coding regions, with two exceptions. Exons 14 and 9 contained SNP that were predicted to alter the protein sequence by the substitution of isoleucine for valine in Domain III of the protein, and alanine for glycine in Domain II of the protein. The resource populations were genotyped for these two SNP in addition to six intronic polymorphisms and two silent substitutions. Analysis of genotypes and shear force values in both populations revealed a difference between paternal CAPN1 alleles in which the allele encoding isoleucine at position 530 and glycine at position 316 associated with decreased meat tenderness (increased shear force values) relative to the allele encoding valine at position 530 and alanine at position 316 (P < 0.05). The association of maternal alleles with meat tenderness phenotypes is consistent with the hypothesis of CAPN1 as the gene underlying the QTL effect in two independent resource populations and presents the possibility of using these markers for selective breeding to reduce the numbers of animals with unfavorable meat tenderness traits.

Our objectives for this manuscript are to review the mechanisms of muscle growth, the biological basis of meat tenderness, and the relationship between these two processes. Muscle growth is determined by hyperplasia and hypertrophy. Muscle cell size is determined by the balance between the amount of muscle protein synthesized and the amount of muscle protein degraded. Current evidence suggests that the calpain proteolytic system is a major regulator of muscle protein degradation. Sarcomere length, connective tissue content, and proteolysis of myofibrils and associated proteins account for most, if not all, of the explainable variation in tenderness of meat after postmortem storage. The relative contribution of each of the above components is muscle dependent. The calpain proteolytic system is a key regulator of postmortem proteolysis. While changes in muscle protein degradation affect meat tenderization/tenderness, changes in muscle protein synthesis are not expected to affect meat tenderization/tenderness.

The objective of this study was to determine the effect of sampling methodology on the relationship between longissimus tenderness and measures of biochemical meat traits. Sampling methodology included measurements of sarcomere length, collagen concentration, and postmortem desmin proteolysis on raw samples and measurements of these same traits on the same cooked meat used for shear force measurement. Twenty crossbred steers and 20 crossbred barrows were used for these studies. The beef longissimus thoracis were vacuum-packaged, stored at 2 degrees C until 14 d postmortem, then frozen and stored at -30 degrees C. The pork longissimus thoracis et lumborum were vacuum-packaged, stored at 2 degrees C until 7 d postmortem, then frozen and stored at -30 degrees C. Trained sensory panel tenderness rating ranged from 3.1 to 7.6 for beef and 4.1 to 7.4 for pork. The coefficient of variation was lower for sarcomere length than for all other traits. Simple correlation coefficients between measurements on raw and cooked samples were 0.58 (beef) and 0.11 (pork) for sarcomere length, 0.66 (beef) and 0.59 (pork) for collagen, and 0.74 (beef) and 0.76 (pork) for desmin degradation. Simple correlation coefficients between biochemical traits and measures of tenderness (Warner-Bratzler shear force and trained sensory tenderness rating) were higher or not different for cooked compared to raw samples. Correlation coefficients between biochemical traits and tenderness rating were 0.38 (raw) and 0.22 (cooked) for sarcomere length, -0.12 (raw) and -0.45 (cooked) for collagen, and 0.48 (raw) and 0.80 (cooked) for desmin degradation in beef longissimus and 0.14 (raw) and 0.15 (cooked) for sarcomere length, -0.38 (raw) and -0.33 (cooked) for collagen, and 0.53 (raw) and 0.67 (cooked) for desmin degradation in pork longissimus. The coefficients of determination for explaining variation in tenderness rating using sarcomere length, collagen concentration, and desmin degradation for raw and cooked samples were 0.43 and 0.73 (beef) and 0.48 and 0.57 (pork), respectively. This study indicates that measurements of biochemical traits on the same cooked meat as used for shear force determination account for more of the variation in measures of tenderness than biochemical measurements made on a separate raw sample.

Monthly inflow and outflow data were collected from three wet detention ponds in Wilmington, North Carolina, for a 29-mo period. Two ponds drained urban areas consisting primarily of residential, mixed services, and retail usage, while the third mainly drained residential and golf course areas. One of the urban ponds achieved significant reductions in total nitrogen, nitrate, ammonium, total phosphorus, orthophosphate, and fecal coliform bacterial counts. This pond was characterized by a high length to width ratio, with most inputs directed into the upper area, and extensive coverage by a diverse community of aquatic macrophyte vegetation. The second urban pond achieved significant reductions in turbidity and fecal coliform bacterial counts, but there were no significant differences between inflowing and outflowing water nutrient concentrations. There were substantial suburban runoff inputs entering the mid- and lower-pond areas that short-circuited pollutant removal contact time. The golf course pond showed significant increases in nitrate, ammonium, total phosphorus, and orthophosphate in the outflow relative to the inflow, probably as a result of course fertilization. However, nutrient concentrations in the outflow water were low compared with discharges from a selection of other area golf courses, possibly a result of the outflow passing through a wooded wetland following pond discharge. To achieve good reduction in a variety of pollutants, wet pond design should include maximizing the contact time of inflowing water with rooted vegetation and organic sediments. This can be achieved through a physical pond design that provides a high length to width ratio, and planting of native macrophyte species.

The objective of this study was to determine the relative contributions of Piedmontese inheritance (0, 25, 50, or 75%) and myostatin genotype (+/+, mh/+, and mh/mh) to tenderness of four major muscles. Matings were made to produce animals with 0 (+/+), 1 (mh/+), or 2 (mh/mh) inactive myostatin alleles that were known to result in normal muscling, heavy muscling, and extremely heavy muscling, respectively. Over a 4-yr period, 395 steers and heifers (14 to 17 mo of age) were humanely slaughtered and the carcasses were chilled 48 h at 0 degrees C. An eight-member trained descriptive attribute panel evaluated tenderness, ease of fragmentation, connective tissue amount, juiciness, and beef flavor intensity of longissimus thoracis (LD), gluteus medius (GM), semimembranosus (SM), and biceps femoris (BF) steaks at 14 d postmortem. Data were analyzed for the main effects of group (eight combinations of myostatin genotype and percentage Piedmontese; [+/+]/0%, [+/+]/25%, [+/+]/50%, [mh/+]/25%, [mh/+]/50%, [mh/+]/75%, [mh/mh]/50%, [mh/mh]/75%) and muscle. Muscle x group interactions were not significant (P > 0.05). Within myostatin genotypes, contrasts to test the effect of percentage Piedmontese were not significant (P > 0.05). Data were reanalyzed for the main effects of myostatin genotype and muscle. Tenderness, ease of fragmentation, and amount of connective tissue ratings were higher (P < 0.05) for the mh/+ and mh/mh genotypes relative to +/+ in all muscles. In biceps femoris, mh/mh had higher (P < 0.05) tenderness, ease of fragmentation, and amount of connective tissue ratings than the mh/+ genotype. Juiciness ratings were lower (P < 0.05) for mh/mh than for mh/+ in all muscles and were lower for mh/mh than for +/+ in all muscles except gluteus medius. Beef flavor intensity ratings were lower (P < 0.05) for mh/mh than for +/+ in all muscles. Muscle ranks for tenderness within myostatin genotype were LD > GM > SM > BF, LD > GM > SM > BF, LD > GM > BF > SM, for +/+, mh/+, and mh/mh genotypes, respectively. The effects of Piedmontese inheritance on meat tenderness were all due to myostatin genotype. Piedmontese mh/mh bulls could be used as terminal sires to produce mh/+ progeny with improved carcass value due to improved tenderness in the four muscles studied.

With the recent development of technology to classify beef for tenderness, it is now possible for packers and retailers to market brands of beef known to be consistently tender. The present experiment was conducted to determine consumer impressions of Tender Select, a model beef brand comprised of cuts from tender U.S. Select carcasses. A telephone survey was conducted in metropolitan Denver, CO, to recruit consumers (n = 1,036) for this study. Consumers who met minimal limits for household income, age, and beef consumption were invited to participate in a beef shopping and usage study in a local supermarket. Point-of-purchase material was developed that described Tender Select as "the only steak guaranteed tender and lean." When shown a copy of the Tender Select concept card, 89% of participating consumers (n = 759) indicated that they would definitely or probably buy that product. Of those consumers that said they would buy the product, 35% indicated that their purchases of Tender Select would be in addition to their current fresh meat purchases. Most consumers (54.1%) indicated that if Tender Select was available at their grocery store, 1 or 2 of their next 10 purchases of beef cuts would be Tender Select. Sixty-five percent of consumers indicated that if a grocery store carried a line of beef cuts guaranteed to be tender, they would buy all of their beef at that store. Both strip loins from 104 U.S. Select beef carcasses, representing a broad range (8.7 to 43.4 kg; CV = 42%) in slice shear force (SSF) at 14 d postmortem, were used to determine the effect of SSF classification on consumer satisfaction and the correlation among trained sensory panel descriptive attribute ratings and in-home consumer ratings of beef longissimus steaks. Both trained sensory panelists and consumers rated low-SSF steaks higher than the high-SSF steaks for all traits (P < 0.001). All consumer traits (like, tenderness, juiciness, flavor like, flavor amount, and overall satisfaction) were more highly correlated with SSF and trained sensory panel tenderness ratings than with sensory panel flavor or juiciness ratings. These data show that tenderness is the primary determinant of satisfaction among consumers of U.S. Select top loin steaks and that a segment of consumers would pay a premium to purchase guaranteed-tender U.S. Select steaks.

Casein zymography was used to determine the effect of postmortem storage on the proteolytic activity of mu-calpain and m-calpain in lamb longissimus. Casein zymography assays were conducted on crude muscle extracts (only one centrifugation). Six market weight crossbred lambs were slaughtered and a portion of the longissimus lumborum was removed at death (within 15 min of exsanguination) and after 3, 6, 9, 12, 24, 72, and 360 h postmortem. Muscle samples were snap-frozen in liquid nitrogen and stored at -70 degrees C. Soluble muscle proteins were extracted from muscle samples and analyzed by in-gel casein assay to measure calpain proteolytic activity. There was a gradual decline in mu-calpain activity (P < 0.05) such that after 24 and 72 h postmortem, mu-calpain had lost 42 and 95% of its activity, respectively. After 360 h postmortem, no mu-calpain activity could be detected (under the conditions used in this study). Autolysis of mu-calpain could be detected as early as 3 h postmortem. It was demonstrated that the detectable level of mu-calpain activity is a function of the amount of muscle protein electrophoresed. Hence, the activity data reported are in relative terms, rather than absolute values. Furthermore, it was demonstrated that the activity data also are a function of the assay methods used. Different methods have different lower detection limits. Of the three assays examined, 14C-labeled casein was the most sensitive, then the in-gel casein assay, and the least-sensitive method was the standard casein assay. Unlike mu-calpain, postmortem storage had no effect on m-calpain (P > 0.05). When the calcium concentration of a muscle extract was increased to the level that induces m-calpain autolysis, m-calpain was autolyzed and its autolysis was readily detected by the in-gel casein assay. Collectively, these results demonstrate that calcium concentration in postmortem muscle is only high enough to activate mu-calpain. These results support the widely believed conclusion that mu-calpain-mediated proteolysis of key myofibrillar and cytoskeletal proteins is responsible for postmortem tenderization. Hence, understanding the regulation of mu-calpain in postmortem muscle should be the focus of future studies.

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.

The myofibril fragmentation index (MFI) is strongly associated with indices of meat tenderness, such as Warner-Bratzler shear force and sensory tenderness. The MFI is normally determined on fresh muscle. It is not known whether this index can be determined on frozen muscle. The objective of this experiment was, therefore, to determine whether there is a difference between MFI values of fresh and frozen lamb and pork longissimus. To compare the effect of freezing on MFI, longissimus samples were obtained from eight lamb carcasses at 1, 3, and 15 d postmortem and longissimus samples were obtained from 12 pork carcasses at 3 d postmortem. For each sample, MFI was conducted on both fresh muscle and snap-frozen muscle (frozen in liquid nitrogen and stored 23 to 26 d at -70 degrees C). The R2 between MFI of fresh and frozen muscle was 0.94 and 0.92 for lamb and pork longissimus, respectively. The differences between fresh and frozen MFI were not significant for either species (P > 0.05). These results indicate that it is not necessary to determine MFI on fresh muscle.

The objective of this study was to determine the relationship of longissimus tenderness classes to tenderness of three other major muscles. Ninety-eight crossbred steers and heifers (14 to 17 mo of age) were humanely slaughtered over 9 wk and the carcasses were chilled 48 h at 0 degrees C. At 48 h postmortem, carcasses were assigned to one of three tenderness classes (tender < or = 26 kg, intermediate = 26 to 42 kg, tough > or = 42 kg) using slice shear force from the MARC Beef Classification System (n = 20, 67, and 11, respectively). The longissimus thoracis, gluteus medius, semimembranosus, and biceps femoris were removed, aged at 2 degrees C, and frozen at -30 degrees C at 14 d postmortem. Two 2.54-cm-thick steaks were obtained from each muscle, thawed to 5 degrees C, cooked with a belt grill at 163 degrees C for 5.5 min, and served warm to an eight-member trained descriptive attribute panel. Panelists evaluated each sample for tenderness, connective tissue amount, juiciness, and beef flavor intensity on 8-point scales. The mean 2-d longissimus slice shear force values were 20.7, 34.4, and 46.3 kg, respectively, for the "tender," "intermediate," and "tough" classes. Tenderness ratings were lowest (P < 0.05) for the "tough" class and highest (P < 0.05) for the "tender" class for all muscles except the gluteus medius, for which the "tender" and "intermediate" classes were not different (P > 0.05; longissimus, 7.7, 7.1, 6.3, and 7.1; semimembranosus, 6.4, 5.8, 5.1, and 5.8; biceps femoris, 5.9, 5.4, 4.8, and 5.4; gluteus medius, 6.8, 6.5, 5.8, and 6.5 for the "tender," "intermediate," "tough," and "unsorted" classes, respectively). The magnitude of the differences in tenderness ratings between the "tender" and "intermediate" classes and between the "intermediate" and "tough" classes was similar for all muscles. The percentages of tenderness ratings greater than 5.0 (slightly tender) for the "tender" and "unsorted" classes, respectively, were as follows: longissimus, 100 and 95%; semimembranosus, 95 and 85%; gluteus medius, 100 and 94%; and biceps femoris, 95 and 81%. The simple correlations between longissimus and the other muscles for tenderness ratings were as follows: semimembranosus, 0.58; biceps femoris, 0.43; and gluteus medius, 0.68. These data indicate that early-postmortem longissimus slice shear force could be used to classify top sirloin, top round, and bottom round cuts for tenderness.

The objectives of this experiment were to determine the extent of variation in proteolysis, sarcomere length, and collagen content among pork muscles and the association of those factors with tenderness variation among muscles at 1 d postmortem. Twenty-three white composite barrows were slaughtered and carcasses (66 kg) were chilled at 0 degrees C for 24 h. At 1 d postmortem, the longissimus lumborum, biceps femoris, semimembranosus, semitendinosus, and triceps brachii, long head were dissected from one side of each carcass and frozen. Trained sensory panelists evaluated tenderness, amount of connective tissue, juiciness, and pork flavor intensity of grilled (70 degrees C) chops on 8-point scales. Raw chops were used for total collagen content, sarcomere length, and the extent of desmin proteolysis. Tenderness ratings were highest (P < .05) for semitendinosus (7.2) and triceps brachii (7.1), followed by longissimus lumborum (6.4) and semimembranosus (5.7) and were lowest (P < .05) for biceps femorus (4.0). The simple correlations between longissimus lumborum tenderness and the tenderness of other muscles were .54 (semimembranosus), .34 (semitendinosus), .36 (triceps branchii), and .17 (biceps femorus). Total collagen was highest (P < .05) for biceps femorus (7.1 mg/g muscle), followed by triceps branchii (6.0 mg/g) and semitendinosus (5.3 mg/g), and lowest for semimembranosus (4.5 mg/g) and longissimus lumborum (4.1 mg/g). Sarcomere length was longest (P < .05) for semitendinosus (2.5 microm) and triceps branchii (2.4 microm), followed by semimembranosus (1.8 microm), longissimus lumborum (1.8 microm), and biceps femorus (1.7 microm). Proteolysis of desmin was greatest (P < .05) in longissimus lumborum (39.3%), followed by semimembranosus (21.0%) and biceps femoris (18.5%), then semitendinosus (.2%) and triceps brachii (.2%). Multiple linear regression using total collagen, sarcomere length, and proteolysis accounted for 57% of the variation in tenderness rating among all samples. Piecewise linear regression was used to account for the interaction of sarcomere length with proteolysis and collagen. This analysis accounted for 72% of the variation in tenderness rating. Variation in collagen, proteolysis, and sarcomere length and the degree of their interaction with one another determine the tenderness of individual muscles.

The objectives for this experiment were to determine the effect of the callipyge phenotype on protein kinetics. We studied callipyge and normal lambs (n = 37) at 5, 8, and 11 wk of age (n = 4 to 7/ group) to determine how protein kinetics are altered by this trait. Total protein, DNA, and RNA and calpastatin activity were measured in five skeletal muscles and in the heart, kidneys, and liver, and protein accretion rates were calculated. At 8 wk, the fractional synthesis rates of proteins in these tissues were measured in vivo using a primed, continuous 8-h infusion of [2H5]phenylalanine. Fractional rates of protein degradation were estimated by differences. At 5 wk of age, muscle weights, protein mass, protein:DNA, RNA:DNA, and calpastatin activity were higher (P < .05) for callipyge, and protein mass differences continued to increase through 11 wk. At 8 wk, fractional rates of protein synthesis and degradation were lower (P < .05) in callipyge than in normal lambs. The organs of callipyge lambs exhibited reduced growth at 11 wk. Thus, enhanced muscle growth seems to be maintained in callipyge lambs by reduced protein degradation rather than increased protein synthesis. However, we cannot exclude the possibility that the initial onset of the callipyge condition may be caused by an increase in the fractional rate of protein synthesis.

The objectives for this experiment were to determine the effects of gamma irradiation on 1) the palatability of vacuum-packaged frozen ground beef patties by trained sensory panel and 2) consumer evaluation of the taste of hamburgers made with those patties. Boxes (4.5 kg) of frozen (-28 degrees C) ground beef patties (113.4 g/patty, 19% fat) from a commercial supplier were irradiated at a commercial gamma irradiation facility at one of three levels (0, 3.0, or 4.5 kGy). All boxes were stored at 28 degrees C for 27 to 29 d after irradiation before evaluation by a trained descriptive attribute sensory panel and for 62 to 104 d after irradiation before consumer evaluation. The trained panel evaluated grilled patties for ground beef aroma intensity, off-aroma, and off-flavor on 4-point scales (4 = intense, none, and none; 1 = none, intense, and intense, respectively) and ground beef flavor intensity, tenderness, and juiciness on 8-point scales (8 = extremely intense, tender, or juicy; 1 = extremely bland, tough, or dry). Control patties had more intense (P<.05) ground beef aroma (3.1 vs 2.6), less off-aroma (3.3 vs 2.6), and more intense ground beef flavor (4.9 vs. 4.3) than irradiated patties. However, there were no differences (P>.05) in any sensory trait between frozen ground beef patties treated with 3.0 or 4.5 kGy of gamma irradiation. There were no differences (P>.05) among treatments for tenderness (6.3, 6.6, and 6.7) or juiciness ratings (5.7, 5.9, and 5.9), respectively, for 0, 3.0, and 4.5 kGy. The consumers evaluated taste of a hamburger that included their choice of condiments on a 10-point scale (10 = excellent; 1 = terrible). Hamburgers made with patties treated with 4.5 kGy were rated lower (P<.05) in taste than hamburgers made with either control patties or those treated with 3.0 kGy (6.5, 6.6, and 6.2, respectively, for 0, 3.0, and 4.5 kGy); however, all doses were rated at some level of "fair." These results imply that hamburgers made from ground beef patties irradiated under the conditions of this experiment would encounter little, if any, consumer acceptance problems at the 3.0 kGy dose and only slightly greater problems at the 4.5 kGy dose.

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.

A resource flock of 362 F2 lambs provided phenotypic and genotypic data to estimate effects of callipyge (CLPG) genotypes (NN, NC, CN, and CC) on meat quality traits. The mutant allele is represented as C, the normal allele(s) as N, and the paternal allele of a genotype is given first. Lambs of each genotype born in 1994 and 1995 were serially slaughtered in six groups at 3-wk intervals starting at 23 wk of age. Warner-Bratzler shear force and subjective evaluation of marbling were collected during both years from longissimus. Calpastatin activity was measured on longissimus from the 1994 group, and ELISA quantification of calpastatin protein was obtained from the 1995 group. Significant additive and paternal polar overdominance effects on meat quality traits were detected. This is in contrast to previous research that detected only polar overdominance effects on slaughter and carcass traits in this population. The magnitude of genotypic effects on shear force differed significantly between years; however, additive (P < .01), paternal polar overdominance (P < .001), and maternal dominance (P < .01) effects adjusted for variation in carcass weight were detected within each year. Shear force data adjusted to the mean slaughter age or carcass weight indicated that the means and variances of CN and CC genotypes were greater than values of NC and NN. Shear force values were greatest for CN and were intermediate for CC. The difference in shear force (adjusted for variation in slaughter age) between homozygous genotypes (additive effect) was supported by calpastatin activity data with 2-df F-tests of 3.66 (P < .05) and 11.84 (P < .001) at d 0 and 7 postmortem, respectively. Corresponding values for the paternal polar overdominance effects on calpastatin activity were 53.80 (P < .001) and 87.43 (P < .001). Calpastatin ELISA data (d 0, adjusted for slaughter age) exhibited a paternal polar overdominance effect exclusively with a 2-df F-test of 57.63 (P < .001). Additive and paternal polar overdominance effects on marbling adjusted for slaughter age had F-tests of 6.41 (P < .01) and 93.29 (P < .001), respectively. Consequences of increased longissimus shear force must be addressed if the advantages of CN lambs for dressing percentage and carcass composition are to be realized. Further research is needed to establish whether selection targeted at changing the background genome can mitigate the negative effects of the C allele on meat tenderness.

The objective of this experiment was to determine the effect of sarcomere length on postmortem proteolysis and meat tenderness. Eighteen Dorset market-weight sheep were slaughtered conventionally. The longissimus thoracis et lumborum and psoas major from each carcass were either left intact on the carcass (control), which was chilled at 0 degrees C, or excised from the carcass and chilled in an ice slurry (0 degrees C). At 24 h, control muscles were excised, and all muscles were cut into sections and assigned to 1 or 10 d of postmortem storage at 2 degrees C. Sarcomere length was shorter (P < .01), as intended, in the shortened relative to the control treatment and in longissimus relative to psoas major (1.36 vs 1.69 microm, raw longissimus; 1.45 vs 3.03 microm, raw psoas major). Sarcomere length was not affected (P > .05) by aging time. Western blot analysis of troponin-T and desmin indicated no effect (P > .05) of the shortened treatment compared to the control on the extent of proteolysis. Regardless of aging time or treatment, troponin-T was more degraded (P < .01) in longissimus than in psoas major (38.1 vs 23.5%) and desmin tended to be more degraded (P = .08) in longissimus than in psoas major (50.4 vs 35.1%). Regardless of muscle or treatment, aging 10 d compared to 1 d increased degradation of troponin-T (46.3 vs 15.3%) and desmin (69.3 vs 16.1%). Warner-Bratzler shear force was greater (P < .01) in the shortened treatment than in control (6.9 vs 3.8 kg), greater (P < .01) in longissimus than in the psoas major (6.5 vs 4.2 kg), and greater (P < .01) with 1 d than with 10 d of aging time (6.1 vs 4.6 kg). A muscle x aging time interaction (P < .05) indicated shear force declined more in longissimus than in psoas major during aging. We conclude that sarcomere length did not affect the extent of proteolysis. However, sarcomere length may have an indirect effect on tenderization during aging due to its effect on initial tenderness.

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.

The objective of this experiment was to determine the impact of USDA quality grade on the palatability of "tender" longissimus when cooked well done. Warner-Bratzler shear force was determined on longissimus thoracis steaks aged 3 or 14 d postmortem (cooked to 70 degrees C) from carcasses of 692 steers and heifers. Steaks from 31 carcasses with Modest or Moderate marbling scores (Top Choice) and steaks from 31 carcasses with Slight00 to Slight40 marbling scores (Low Select) were selected for this experiment from carcasses identified as "tender" (shear force < 5.0 kg at 3 d postmortem). Longissimus thoracis steaks with 3 or 14 d of postmortem aging were cooked to 80 degrees C and evaluated by a trained sensory descriptive attribute panel. Top Choice steaks had higher (P < .05) juiciness (5.8 vs 5.3) and beef flavor intensity ratings (4.9 vs 4.6) than Low Select steaks. Aging of steaks for 14, rather than 3, d postmortem improved (P < .05) beef flavor intensity rating (4.8 vs 4.7) but not (P > .05) juiciness rating (5.6 vs 5.5). The interaction (P < .05) of quality grade and aging time for tenderness rating indicated that Top Choice steaks were more tender (P < .05) with 3 d of aging than steaks from Low Select carcasses (6.3 vs 5.8), but steaks from Top Choice and Low Select carcasses had similar (P > .05) tenderness ratings after 14 d of aging (7.0 and 6.8). Compared to palatability of steaks from Low Select carcasses, the palatability of steaks from Top Choice carcasses was less affected by elevated degree of doneness in "tender" longissimus thoracis, especially when steaks were aged for only 3 d. Although differences in sensory traits between Top Choice and Low Select steaks were small, the consumers who cook beef well done may benefit from implementation of tenderness classification in conjunction with USDA quality grade.

The objectives of this experiment were to determine 1) whether end point temperature interacts with tenderness to affect Warner-Bratzler shear force of beef longissimus and 2) if so, what impact that interaction would have on tenderness classification. Warner-Bratzler shear force was determined on longissimus thoracis cooked to either 60, 70, or 80 degrees C after 3 and 14 d of aging from carcasses of 100 steers and heifers. Warner-Bratzler shear force values (3- and 14-d aged steaks pooled) for steaks cooked to 70 degrees C were used to create five tenderness classes. The interaction of tenderness class and end point temperature was significant (P < .05). The increase in Warner-Bratzler shear force as end point temperature increased was greater (P < .05) for less-tender longissimus than more-tender longissimus (Tenderness Class 5 = 5.1, 7.2, and 8.5 kg and Tenderness Class 1 = 2.4, 3.1, and 3.7 kg, respectively, for 60, 70, and 80 degrees C). The slopes of the regressions of Warner-Bratzler shear force of longissimus cooked to 60 or 80 degrees C against Warner-Bratzler shear force of longissimus cooked to 70 degrees C were different (P < .05), providing additional evidence for this interaction. Correlations of Warner-Bratzler shear force of longissimus cooked to 60 or 80 degrees C with Warner-Bratzler shear force of longissimus cooked to 70 degrees C were .90 and .86, respectively. One effect of the interaction of tenderness with end point temperature on tenderness classification was to increase (P < .01) the advantage in shear force of a "Tender" class of beef over "Commodity" beef as end point temperature increased (.24 vs .42 vs .60 kg at 14 d for 60, 70, and 80 degrees C, respectively). When aged 14 d and cooked to 80 degrees C, "Commodity" steaks were six times more likely (P < .01) than "Tender" steaks to have shear force values > or = 5 kg (24 vs 4%). The end point temperature used to conduct tenderness classification did not affect classification accuracy, as long as the criterion for "Tender" was adjusted accordingly. However, cooking steaks to a greater end point temperature than was used for classification may reduce classification accuracy. The beef industry could alleviate the detrimental effects on palatability of consumers cooking beef to elevated degrees of doneness by identifying and marketing "Tender" longissimus.

The objective of this experiment was to compare the effects of belt grill and Open Hearth electric broiler cookery on palatability and cooking traits of longissimus steaks. The longissimus thoracis from carcasses of grain-fed steers or heifers was used. Duplicate measurements were made for Warner-Bratzler shear force at 3 and at 14 d after slaughter (n = 180) and trained sensory evaluation at 14 d after slaughter (n = 91) using both cooking methods. Belt grill-cooked samples had lower (P<.01) percentage of cooking losses (21.5 vs 25.8%) and higher (P<.01) shear force values (4.6 vs 4.3 kg) than electric broiler-cooked samples. Repeatability of duplicate measurements was higher for cooking losses (.58 vs .23) and shear force values (.85 vs .64) for belt grill than for electric broiler cooked samples. Belt grilled steaks had lower (P<.01) cooking losses (20.2 vs 29.8%); higher (P<.01) tenderness (7.0 vs 6.7) and juiciness (6.0 vs 5.1); and lower (P<.02) connective tissue amount (7.7 vs 7.8), beef flavor intensity (5.0 vs 5.1), and off-flavor (3.2 vs 3.3) ratings than steaks cooked with the electric broiler. Belt grill cooking increased the repeatability of duplicate sensory measurements for tenderness (.87 vs .71), connective tissue amount (.66 vs .30), and juiciness (.51 vs .08) ratings, and cooking losses (.63 vs .18) compared with cooking with the electric broiler. Belt grill cooking increased the precision for measurements of cooking, Warner-Bratzler shear force, and palatability traits of beef longissimus thoracis.

The present experiment was conducted to determine whether image analysis of the 12th-rib cross-section used for tenderness classification could accurately predict carcass cutability, longissimus area, and subprimal cut weights. The right side of crossbred steer and heifer carcasses (n=66) was fabricated, and the yield of totally trimmed retail product was determined. Following procedures that we have described for tenderness classification, a 2.54-cm-thick steak was removed from the 12th-rib region of the left side of each carcass, and image analysis was conducted using off-the-shelf technology. Image analysis accounted for more of the variation in retail product yield (RPYD; 89 vs 77%) and retail product weight (95 vs 90%) than did calculated yield grade. Also, image analysis accurately predicted longissimus area (R2=.88). For most subprimals, the combination of image analysis-predicted RPYD and hot carcass weight (HCW) accounted for more of the variation in subprimal weight than did the combination of calculated yield grade and HCW. Whereas HCW, by itself, accounted for only 30 to 34% of the variation in weights of round cuts, the combination of image analysis-predicted RPYD and HCW accounted for 78 to 82% of the variation in weights of round cuts. Hot carcass weight, the combination of calculated yield grade and HCW, and the combination of image analysis-predicted RPYD and HCW accounted for 54, 83, and 91% of the variation in the weight of 80% lean trimmings. Thus, image analysis could be used by the beef industry to more accurately predict individual subprimal weights. In turn, that information and appropriate price extensions could be used to more accurately estimate carcass value. Thus, image analysis could be used by the beef industry in combination with tenderness classification to accurately characterize beef carcasses for cutability and tenderness. These tools should help facilitate the development of value-based marketing systems.

The effect of rapid prerigor freezing and postrigor freezing and postrigor calcium chloride injection on the tenderness of callipyge longissimus was studied. Ewe and wether lambs (n = 49; 1/2 Dorset x 1/2 Romanov) were grain-fed and slaughtered at approximately 250 d of age. Based on leg conformation scores, 23 of the carcasses had the callipyge phenotype. Within each phenotype, approximately one-half of the carcasses were chilled conventionally (24 h at -2 degrees C). At approximately 17 min postmortem, the remaining carcasses were submersed in liquid nitrogen for 15 min and then held at -2 degrees C for 4 d. At 1 d postmortem for carcasses chilled conventionally and at 4 d postmortem for carcasses frozen in liquid nitrogen, the longissimus muscles from both sides were removed. The longissimus from one side of each carcass was vacuum-packaged and aged (1 degrees C) conventionally for 7 or 14 d. The remaining muscles were injected with a 2.22% solution of food-grade calcium chloride at 5% by weight, vacuum-packaged, and aged as above. Liquid nitrogen freezing was effective in limiting sarcomere shortening (1.99 vs 1.63 microm; P < .05). Warner-Bratzler shear force values of callipyge longissimus were 222 and 232% of that of normal longissimus after 7 and 14 d postmortem, respectively (P < .001). Also, trained panel tenderness rating was decreased by 49.4% in untreated callipyge longissimus after 14 d postmortem. Liquid nitrogen, calcium chloride injection and their combination did not affect d-14 longissimus shear force and sensory tenderness for normal lambs because untreated muscles were already tender. Liquid nitrogen freezing improved the shear force and sensory tenderness rating of callipyge longissimus by 30 and 86.2% after 14 d postmortem, respectively. Calcium chloride injection improved the shear force and sensory tenderness of callipyge longissimus by 36.7 and 86.2% after 14 d postmortem, respectively (P < .001). The most effective treatment for mitigating the callipyge effect on tenderness was the combination (freezing and calcium chloride injection) treatment, which improved the shear force and sensory tenderness by 51.2 and 124.2% after 14 d postmortem, respectively (P < .001). We conclude that either treatment can effectively mitigate the negative effect of callipyge phenotype on longissimus tenderness. Callipyge lamb carcasses subjected to the combination of prerigor liquid nitrogen freezing, postrigor calcium chloride injection, and 14 d postmortem storage had tenderness similar (P > .05) to that of normal, untreated carcasses after 14 d of postmortem storage.

The objectives of this study were to determine 1) the effectiveness of calcium chloride when injected later than 2 d postmortem, 2) the effect of extended postinjection aging time, and 3) the tenderness response curve in calcium chloride-treated beef. In Exp. 1, the longissimus thoracis et lumborum was injected on either d 2 or 14 postmortem with 5% by weight of a 200 mM calcium chloride solution. Samples were aged (1 degree C) either 7 or 35 d after injection. The uninjected control longissimus from the contralateral side was aged for 9, 21, 37, or 49 d. In Exp. 2, the longissimus thoracis et lumborum was injected on d 2 postmortem with 5% by weight of a 200 m x M calcium chloride solution then sampled for shear force on d 1, 2, 6, 8, 12, and 14 after injection. Calcium chloride injection, regardless of injection time or postinjection aging time, had higher (P < .05) sensory tenderness rating than control with the same total aging time (5.2, 5.5, 5.8, and 6.1 vs 4.3, 4.8, 5.1, and 5.3, respectively). Calcium chloride injection at d 14 reduced shear force (.7 kg) and increased tenderness rating (.7 units) as effectively (P > .05) as injection at d 2 (1.2 kg and .8 units, respectively). Calcium chloride-injected steaks had higher (P < .05) juiciness ratings than control steaks. Postrigor calcium chloride injection reduced (P < .05) shear force within 1 d after injection and resulted in more tender meat through 14 d after injection. Extended postinjection aging (35 d) had little effect on color display stability. Calcium activated tenderization can be applied as late as 14 d postmortem and will reduce the occurrence of tough meat if aging is limited.

Our objective was to compare measurement of Warner-Bratzler shear force of beef longissimus within and among institutions when each institution used its own protocol and when all institutions used a standardized protocol. In Exp. 1, each of five institutions (A, B, C, D, and E) received two adjacent steaks from each of 27 beef strip loins (longissimus lumborum). Warner-Bratzler shear force was measured for both steaks using the procedures normally used at each institution. In Exp. 2, each institution received two adjacent steaks from each of 45 strip loins. Shear force was measured for both steaks using a standardized protocol. In Exp. 1, Warner-Bratzler shear force was highest (P < .05) for A (4.7 kg) and lowest (P < .05) for B (2.9 kg). Repeatability of shear force was highest for A and C (.73 and .72), intermediate for D (.63), and lowest for B and E (.39 and .44). In Exp. 2, Warner-Bratzler shear force was highest (P < .05) for A (5.1 kg) and lowest (P < .05) for E (3.7 kg). Repeatability of shear force was highest for A (.87), intermediate for B, D, and E (.81, .75, and .80), and lowest for C (.67). Shear force values differed within and among institutions due to protocol, execution of the protocol, and instrument variation. Thus, comparisons of Warner-Bratzler shear force data among institutions are currently not valid. However, it is possible for institutions to obtain the same mean shear force value and have high repeatability if a standard protocol is properly executed with calibrated equipment.

The present experiment was conducted to determine 1) the repeatability of Warner-Bratzler shear force and trained sensory panel tenderness ratings in beef round cuts and 2) the effect of location within beef round cuts on shear force and tenderness ratings. Biceps femoris (BF) and semitendinosus (ST) were obtained from the carcasses of youthful (A-maturity), grain-fed, crossbred steers (n = 25) at 16 d postmortem. Steaks were removed from each muscle for determination of shear force and tenderness rating at each of three locations (A = proximal end, B = center, and C = distal end). Tenderness ratings of triplicate samples were slightly more repeatable than shear force for BF (R = .50 vs .30) and ST (R = .60 vs .56). However, all of those estimates of repeatability were much less than values we have obtained for beef longissimus using similar laboratory procedures (R = .79 to .90). Across both muscles and both methods of assessing tenderness, less than 40% of the total variance was accounted for by animal. The variance of tenderness rating among animals was less for BF (.12) and ST (.09) than values we have obtained for beef longissimus (.60). Location did not affect (P > .05) BF shear force; however, BF tenderness ratings were higher (P < .05) for location A (5.5) than for B (5.0) and C (5.2). Location accounted for a higher percentage of the total variance of ST tenderness rating and ST shear force than did animal. Shear force decreased (P < .05) from the proximal end to the distal end of ST (5.1, 4.6, and 3.9 kg for locations A, B, and C, respectively). Also, ST tenderness ratings were lower for location A (4.8) than for locations B (5.6) and C (5.7). Neither method of measuring tenderness was highly repeatable for BF or ST because there was little animal-to-animal variation in tenderness for these round muscles. Thus, there would be little opportunity for segregating round muscles into tenderness classes.

Carcass cut-out yields of 888 steers obtained from mating Hereford and Angus cows to Hereford or Angus (HA), Charolais (Ch), Gelbvieh (Gb), Pinzgauer (Pz), Shorthorn (Sh), Galloway (Gw), Longhorn (Lh), Nellore (Ne), Piedmontese (Pm), and Salers (Sa) sires were compared. Data were evaluated at constant age (426 d), carcass weight (324 kg), fat thickness (1.2 cm), fat trim percentage (23%), and marbling (Small(00)) end points. Piedmontese-sired steers excelled in total retail product and fat trim percentages at all slaughter end points except at the 23% fat trim end point. At an age end point, percentage of retail product was greater in steers sired by Continental European breeds (Gb, Ch, Sa, Pz; 63.3 to 65.5% at 0 cm trim) than in steers sired by British breeds (Sh, HA; 60.1 to 61.0%). Piedmontese-sired steers, which were expected to carry one copy of a major gene for muscle hypertrophy, had the highest (P < .05) retail product yields at an age end point (69.7%). At an age end point, although carcass weights were significantly heavier (P < .05) for Charolais-sired steers than for Piedmontese-sired steers, lean growth rate, as reflected by totally trimmed retail product at 426 d, was similar (P > .05) for Piedmontese and Charolais-sired steers. Differences among sire breeds were small for retail product percentage at marbling, fat thickness, and fat trim end points. Ranking of sire breeds for age-constant weight of retail product was as follows: Ch, Pm, Gb, Sa, Ne, Pz, HA, Sh, Gw, and Lh. Sire breed differences in wholesale and subprimal cut yields were similar to total retail product differences. Piedmontese-sired steers produced the most muscular, leanest, and highest-yielding carcasses, and HA- and Sh-sired steers produced the fattest, lowest-yielding carcasses.

The present experiments were conducted to evaluate the use of longissimus shear force at 1 or 2 d postmortem as a predictor of beef longissimus shear force at 14 d postmortem. Experiments 1 (n = 400) and 2 (n = 554) included carcasses slaughtered and processed under laboratory and commercial conditions, respectively. A carcass was classified as "tender," "intermediate," or "tough" if its longissimus shear value at 1 or 2 d postmortem was < 6 kg, 6 to 9 kg, or > 9 kg, respectively. For Exp. 1 and 2, large (P < .001) differences existed between each successive tenderness class in mean shear force at 14 d postmortem. Moreover, frequency analysis indicated that tenderness classification accurately (84.8 and 94.8% for Exp. 1 and 2, respectively) predicted whether the sample would have a "low" (< 6 kg) Warner-Bratzler shear (WBS) value at 14 d postmortem. All (100%) of the carcasses in the "tender" class had "low" WBS values at 14 d postmortem, most (81 and 85% for Exp. 1 and 2, respectively) of the carcasses in the "intermediate" class had "low" WBS values at 14 d postmortem, and most (74 and 67% for Exp. 1 and 2, respectively) of the carcasses in the "tough" class did not have "low" WBS values at 14 d postmortem. Although shear force at 2 d postmortem was only moderately correlated (r = .68) with shear force at 14 d postmortem, 68% of the carcasses sampled in Exp. 2 could be guaranteed tender with 100% accuracy based on shear force at 2 d postmortem. Thus, cooked beef longissimus shear force can be measured at 1 or 2 d postmortem and used to predict longissimus tenderness after cooler aging (14 d postmortem) with a relatively high degree of accuracy.

We conducted three experiments to determine the effects of the callipyge phenotype on the tenderness of several major lamb muscles and to determine the effect of method of cookery on the tenderness of callipyge lamb at 7 d postmortem. In Exp. 1, chops from normal (n = 23) and callipyge (n = 16) carcasses were open-hearth-broiled. Warner-Bratzler shear force values of longissimus, gluteus medius, semimembranosus, biceps femoris, semitendinosus, adductor, and quadriceps femoris were 123, 44, 28, 26, 19, 16, and 13% greater, respectively, for callipyge (P < .05). In Exp. 2, muscles from normal (n = 18) and callipyge (n = 18) carcasses were oven-roasted. Shear force of triceps brachii was 11% greater for callipyge (P < .001); however, phenotype did not affect shear force of supraspinatus (P = .87) or psoas major (P = .64). In Exp. 3, a trained sensory panel evaluated leg roasts and open-hearth-broiled leg chops from normal (n = 60) and callipyge lamb carcasses (n = 60). Callipyge chops were less tender than normal chops (P < .05). Regardless of callipyge phenotype, muscles were more (P < .05) tender when roasted; however, the effect of method of cookery on tenderness scores was greater for callipyge muscles than for normal muscles. Callipyge roasts and normal roasts had similar tenderness (P = .58), and callipyge roasts were more tender than normal chops (P < .05). Regardless of cooking method, callipyge samples were less juicy than normal samples (P < .05). These data demonstrate that the callipyge phenotype will likely reduce consumer satisfaction due to reduced tenderness and juiciness; however, reduced tenderness in callipyge leg muscles could be prevented by ovenroasting.

We evaluated the combined use of 0 or 4 mg/d of recombinant porcine somatotropin (pST) and 0 or 2.75 ppm salbutamol in three genotypes of growing barrows (139 d old) differing in lean and lipid accretion potential. Treatments were in a 2 x 2 x 3 factorial arrangement, and the three genotypes tested were Meishan (M, n = 32, 49 kg), Duroc x White composite (D x Wc, n = 31, 62 kg), and Meishan x White composite (M x Wc, n = 31, 64 kg) pigs. Growth performance was evaluated over 28 d for individual pigs, and 20-h feed-deprived heat production was measured before slaughter (d 34). Daily pST injection increased ADG (+70 g/d) and reduced ADFI (-.61 kg/d) across genotypes (P < .05). Salbutamol increased (P < .05) ADG in M x Wc pigs (+146 g/d) but not in M pigs (-60 g/d) or D x Wc (+80 g/d) pigs. However, M pigs had the lowest ADG and ADFI, and M x Wc pigs not treated with salbutamol grew slower than D x Wc pigs (P < .05). Carcass protein and moisture accretion were additively (P < .05) increased by pST and salbutamol for D x Wc and M x Wc pigs. Meishan pigs had increased carcass protein and moisture accretion from pST, whereas only moisture accretion was increased by salbutamol (P < .05). The longissimus muscle area and semitendinosus weight increased as the percentage of M in the genotype decreased (P < .05), and both were increased by pST or salbutamol treatment (P < .001). Leaf fat was decreased more (P < .05) in M pigs than in D x Wc or M x Wc pigs with pST injection. The similar magnitude of leaf fat reduction between D x Wc and M x Wc pigs resulted in a mean genotype difference (P < .05), and salbutamol decreased leaf fat across genotypes. Oxygen consumption and heat production were increased by pST in M pigs more than in the crossbred genotypes, but CO2 production was reduced by similar magnitudes across genotypes, and salbutamol only tended to reduce CO2 production in D x Wc pigs. In general, these data indicate that pST and salbutamol result in additive increases in carcass lean composition; however, growth rate, carcass accretion, and various organ weights may vary among genotypes with salbutamol and pST treatment.

A study was conducted to determine consumer perceptions of beef top loin steaks of known shear force and to evaluate how buying trends were modified by the tenderness and price variations of these steaks. Strip loins were cut into a 2.54-cm-thick steaks, and the center steak from each strip loin was used to determine Warner-Bratzler shear force. The remaining steaks were placed into one of the following shear force categories based on that shear force and color-coded accordingly: 1) 2.27 to 3.58 kg (Red); 2) 4.08 to 5.40 kg (White); and 3) 5.90 to 7.21 kg (Blue). Randomly recruited consumers were allowed to evaluate steaks and then purchase steaks based on their findings. A $1.10/kg price difference was placed between each category. Results of the analysis indicated that consumers were able to differentiate between the three categories of tenderness (P < .05). In addition, consumers gave higher (P < .05) juiciness and flavor ratings to Red steaks than to Blue steaks. Overall satisfaction was higher (P < .05) for Red steaks than for the other two categories of steaks. The following percentages of steaks were purchased: 1) Red, 94.6%; 2) White, 3.6%; and 3) Blue, 1.8%. These results suggest that consumers could discern between categories of tenderness and were willing to pay a premium for improved tenderness.

The objective of this experiment was to test the hypothesis that meat toughening during the first 24 h postmortem results from sarcomere shortening during rigor mortis development. Eleven market-weight lambs were used to measure changes in shear force of clamped longissimus during rigor development. Within 15 min of exsanguination, while attached at both ends, each longissimus was separated from the vertebrae body and clamped between three sets of metal plates to prevent muscle shortening (six clamped sections per lamb). Five of the clamped sections were placed at -1.1 degrees C for 0, 3, 6, 12, or 24 h. After storage at their respective times at -1.1 degrees C, the samples were placed at -30 degrees C for 90 min and then at -5 degrees C for 8 d. The sixth section (168-h section) was stored at -1.1 degrees C for the first 24 h, at 4 degrees C for 144 h, and then treated the same as other sampling times. Sections were sampled for pH, sarcomere length, shear force, and Western blot analyses before and after storage at -5 degrees C. Shear force values were the same (P > .05) from 0 to 24 h (4.5 kg at 0 h to 4.9 kg at 24 h) then declined (P < .05) to 3.3 kg at 168 h postmortem. As evident by lack of statistical difference in the sarcomere lengths, we were successful in holding the muscle length constant. Western blot analyses of nebulin, vinculin, and troponin-T indicated that minimum degradation occurred through 12 h, was slightly increased by 24 h, and was relatively extensive by 168 h postmortem. Although limited proteolysis occurred during storage at -5 degrees C for 8 d, this by itself had no effect on shear force. Results indicate that shear force values do not increase during rigor development when muscle is prevented from shortening; thus, the toughening that occurs during the first 24 h of slaughter is most likely due to sarcomere shortening.

The objectives of these experiments were to determine 1) the most effective vitamin C concentration to stabilize color of beef cuts during retail display and 2) the effect on color of incorporating vitamin C into a calcium chloride (CaCl2) injection solution. Top round cuts (semimembranosus and adductor) were injected with 5% by weight of a 0, .25, .5, 1, 2, or 4% sodium ascorbate solution (Exp. 1) or a 0, .5, 1, or 1.5% sodium ascorbate solution (Exp. 2). In Exp. 1, vitamin C resulted in more (P < .05) stable lean color during 9 degrees C display, and .5, 1, and 2% vitamin C were most (P < .05) effective. In Exp. 2, all concentrations of vitamin C maintained redder (P < .05) steaks after 3, 5, and 7 d of display than control steaks and had a lower (P < .05) percentage of surface discoloration after 5 and 7 d of display at 1 degree C. Experiment 3 used beef bottom round cuts (biceps femoris) to compare control, vitamin C- (1%), CaCl2-(200 mM) and vitamin C + CaCl2-treated steaks displayed at 1 degree C. Calcium chloride-treated steaks were more (P < .05) brown and had a higher (P < .05) percentage of surface discoloration on d 5 and 7 than control steaks, whereas steaks treated with vitamin C or vitamin C + CaCl2 were more (P < .05) red and had lower (P < .05) discoloration on d 5 and 7 than control steaks. Vitamin C can be injected into beef subprimals to enhance lean color stability and extend retail display life. Vitamin C also can be used in combination with CaCl2 to offset potential color deterioration, after 5 d of display, due to salt-induced oxidation.

A series of experiments was conducted to determine the effects of various factors on Warner-Bratzler shear force measurement of cooked beef. As the extent of thawing of frozen steaks before cooking for shear force evaluation increases (-2 vs 12 degrees C), shear force decreases (P < .05; 7.34 vs 5.99 kg). Location within the longissimus thoracis et lumborum from which steaks were obtained (caudal, medial, or cranial) did not affect (P > .05) shear force (5.21, 5.15, or 5.26 kg, respectively) or any sensory trait. Mean shear force of longissimus steaks cooked to either a constant temperature of 70 degrees C (6.97 kg) or for a constant time of 30 min (6.38 kg) was not different (P = .06), but shear force repeatability was higher for steaks cooked to constant temperature (.79 vs .53). Mean shear force (6.20 vs 6.33 kg) and shear force repeatability (.74 vs .68) of longissimus steaks cooked by either electric broiler or convection oven broiler, respectively, were not different (P > .05). Meat cores obtained perpendicular to the steak surface, from one location within the muscle, had lower (P < .05) mean shear force (3.41 vs 4.17 kg) and much less repeatable shear force (.12 vs .66) than cores obtained parallel to muscle fiber orientation. Use of more than five cores per animal did not significantly increase repeatability of mean shear force. Numerous factors must be carefully controlled to ensure measurement of shear force is as accurate and repeatable as possible.