Freezing and thawing or freezing, thawing, and aging effects on beef tenderness.

The objective of this study was to determine the effect of freezing and thawing or freezing and thawing with an additional aging period after frozen storage on the tenderness of longissimus lumborum (LL) and semitendinosus (ST) steaks relative to aged, fresh steaks. Left-side LL and ST (n = 35 each) were obtained from U.S. Select carcasses classified at the grading stand by the U.S. Meat Animal Research Center visible and near-infrared spectroscopy tenderness system to have predicted slice shear force greater than 16.5 kg at 14 d postmortem. At 2 d postmortem, 2.54 cm thick steaks were cut from each muscle and assigned to 1 of the following treatments: 2 d fresh (2FRESH), 2 d freeze + thaw (2FREEZE), 2 d freeze + thaw + 12 d age (2FREEZE+12AGE), 14 d fresh (14FRESH), 14 d freeze + thaw (14FREEZE), 14 d freeze + thaw + 14 d age (14FREEZE+14AGE), and 28 d fresh (28FRESH). Steaks assigned to a freezing treatment were frozen at -26°C for 30 d before thawing/cooking or thawing with an additional aging period at 2°C. Slice shear force for LL and ST was lower (P < 0.01) for 2FREEZE (27.4 and 24.5 kg) and 14FREEZE (22.4 and 22.4 kg) compared to 2FRESH (33.0 and 29.2 kg) and 14FRESH (25.3 and 25.5 kg), respectively. Slice shear force for LL and ST was lower (P < 0.01) for 2FREEZE+12AGE (17.8 and 20.8 kg) and 14FREEZE+14AGE (14.6 and 19.0 kg) compared to 14FRESH (25.3 and 25.5 kg) and 28FRESH (18.7 and 21.7 kg), respectively. Desmin degradation for LL was not different (P > 0.05) between 2FREEZE (21.0%) and 2FRESH (14.6%) or between 14FREEZE (40.4%) and 14FRESH (38.4%); however, desmin degradation was higher (P < 0.06) in 2FREEZE+12AGE (46.7%) and 14FREEZE+14AGE (71.1%) when compared to 14FRESH (38.4%) and 28FRESH (60.5%), respectively. Cooking loss for LL was higher (P < 0.01) in 2FREEZE+12AGE (15.2%) compared to 14FRESH (14.0%) but was not different (P > 0.05) between 14FREEZE+14AGE (15.0%) and 28FRESH (14.3%). Freezing and thawing or a combination of freezing, thawing, and aging resulted in increased tenderness for LL and ST steaks when compared to fresh steaks with the same aging time. These results indicate freezing could be incorporated into normal commercial product distribution processes to improve the consistency of meat tenderness. Researchers who freeze steaks before tenderness assessment should be aware and acknowledge that freezing affects tenderness data.

Relationship between the numbers of Escherichia coli and the prevalence of Escherichia coli O157:H7 on hides of carcasses at a large beef packing plant.

Due to the expense of monitoring multiple serotypes of Escherichia coli at slaughter, a study was conducted at a beef abattoir in southern Alberta to determine relationships between E. coli and E. coli O157:H7 on hides. Swab samples were collected from carcasses immediately prior to hide removal over 8 weeks in summer (n = 591) and winter (n = 686). Detection of E. coli was highest in summer (P < 0.05), although detection of E. coli O157:H7 did not differ by season. Numbers of E. coli did not vary by season, but were affected by slaughter plant hygiene schedules. E. coli O157:H7 was more likely (P < 0.001) to be detected on hides of carcasses with the most E. coli (>3.5 log CFU/50 cm²). For E. coli < 3.5 log CFU/50 cm², the likelihood of detecting E. coli O157:H7 did not differ. Consequently, for 83% of carcasses, there was no relationship between numbers of E. coli and detection of E. coli O157:H7 on hides.

The effects of Capn1 gene inactivation on skeletal muscle growth, development, and atrophy, and the compensatory role of other proteolytic systems.

Myofibrillar protein turnover is a key component of muscle growth and degeneration, requiring proteolytic enzymes to degrade the skeletal muscle proteins. The objective of this study was to investigate the role of the calpain proteolytic system in muscle growth development using µ-calpain knockout (KO) mice in comparison with control wild-type (WT) mice, and evaluate the subsequent effects of silencing this gene on other proteolytic systems. No differences in muscle development between genotypes were observed during the early stages of growth due to the up regulation of other proteolytic systems. The KO mice showed significantly greater m-calpain protein abundance (P < 0.01) and activity (P < 0.001), and greater caspase 3/7 activity (P < 0.05). At 30 wk of age, KO mice showed increased protein:DNA (P < 0.05) and RNA:DNA ratios (P < 0.01), greater protein content (P < 0.01) at the expense of lipid deposition (P < 0.05), and an increase in size and number of fast-twitch glycolytic muscle fibers (P < 0.05), suggesting that KO mice exhibit an increased capacity to accumulate and maintain protein in their skeletal muscle. Also, expression of proteins associated with muscle regeneration (neural cell adhesion molecule and myoD) were both reduced in the mature KO mice (P < 0.05 and P < 0.01, respectively), indicating less muscle regeneration and, therefore, less muscle damage. These findings indicate the concerted action of proteolytic systems to ensure muscle protein homeostasis in vivo. Furthermore, these data contribute to the existing evidence of the importance of the calpain system's involvement in muscle growth, development, and atrophy. Collectively, these data suggest that there are opportunities to target the calpain system to promote the growth and/or restoration of skeletal muscle mass.

Associations of genetic markers in cattle receiving differing implant protocols.

The potential interaction of growth-promoting implants and genetic markers previously reported to be associated with growth, carcass traits, and tenderness was evaluated. Two implant protocols were applied to subsets of steers (n = 383) and heifers (n = 65) that were also genotyped for 47 SNP reported to be associated with variation in growth, fat thickness, LM area, marbling, or tenderness. The "mild" protocol consisted of a single terminal implant [16 mg estradiol benzoate (EB), 80 mg trenbalone acetate (TBA) or 8 mg EB, 80 mg TBA given to steers and heifers, respectively]. The "aggressive" protocol consisted of both a growing implant (8 mg EB, 40 mg TBA) for the lightest half of the animals on the aggressive protocol and 2 successive implants (28 mg EB, 200 mg TBA) given to all animals assigned to the aggressive treatment. Implant protocol had measurable impact on BW and ADG (P < 0.05), with the aggressive protocol increasing these traits before the terminal implant (relative to the mild protocol), whereas the mild protocol increased ADG after the terminal implant so that the final BW and ADG over the experimental period were similar between protocols. Animals on the aggressive protocol had significantly increased (P < 0.05) LM area (1.9 cm(2)), slice shear force (1.4 kg), and intact desmin (0.05 units), but decreased (P < 0.05) marbling score (49 units) and adjusted fat thickness (0.1 cm), and yield grade (0.15 units). Among both treatments, 8 of 9 growth-related SNP were associated with BW or ADG, and 6 of 17 tenderness-related SNP were associated with slice shear force or intact desmin. Favorable growth alleles generally were associated with increased carcass yield traits but decreased tenderness. Similarly, favorable tenderness genotypes for some markers were associated with decreased BW and ADG. Some interactions of implant protocol and genotype were noted, with some growth SNP alleles increasing the effect of the aggressive protocol. In contrast, putative beneficial effects of favorable tenderness SNP alleles were mitigated by the effects of aggressive implant. These type of antagonisms of management variables and genotypes must be accounted for in marker assisted selection (MAS) programs, and our results suggest that MAS could be used to manage, but likely will not eliminate negative impact of implants on quality.

Effects of breed of sire on carcass composition and sensory traits of lamb.

This experiment was conducted to compare meat quality and carcass composition of a diverse sampling of sheep breeds. Finnsheep, Romanov, Dorper, White Dorper, Katahdin, Rambouillet, Suffolk, Texel, Dorset, and Composite (½ Columbia rams to 1/4; Hampshire × 1/4; Suffolk) rams were mated to mature Composite ewes. Lambs (n = 804) were reared intensively, grain finished, and serially harvested over a 63-d period. Average harvest age was 216 d and average HCW was 30.7 kg. At a common harvest age, progeny of Suffolk sires were heavier than progeny of all other breeds (P < 0.05) and their carcasses were heavier (P < 0.05) than progeny of all other breeds, except White Dorper and Dorper. Progeny of Finnsheep and Romanov sires had lighter (P < 0.05) carcasses than progeny of all other breeds. Progeny of Texel, Suffolk, White Dorper, and Dorper sires had larger (P < 0.05) LM area than all other breeds. Progeny of Finnsheep and Romanov sires had smaller (P < 0.05) LM area than all other breeds. Fat thickness at the 12th rib was greater (P < 0.05) for progeny of Dorper sires than those of all other breeds, except White Dorper and Katahdin. Fat thickness at the 4th sacral vertebrae was greater (P < 0.05) for progeny of White Dorper and Dorper sires than those of all other breeds. On a carcass weight-constant basis, progeny of Suffolk sires had a lesser (P < 0.05) percentage of ether-extractable carcass fat than progeny of all other breeds, except Texel. Regardless of harvest endpoint (age-constant or HCW-constant), LM of progeny of Finnsheep and Romanov sires contained a greater (P < 0.05) percentage of intramuscular fat and received greater (P < 0.05) marbling scores than Rambouillet, Suffolk, Texel, Dorset, or Composite. Regardless of harvest endpoint, progeny of Finnsheep, Romanov, and Katahdin sires had smaller LM slice shear force values and greater trained sensory panel tenderness ratings at 7 d postmortem than did progeny of Composite, Suffolk, and Dorset sires (P < 0.05). At an age-constant basis, small differences (P < 0.05) were observed among breeds for lamb flavor intensity scores; however, when means were adjusted to a carcass weight-constant basis, breed of sire did not affect flavor intensity or off-flavor scores. These results document that each breed has relative strengths and weaknesses across traits, and that no single breed excels for all growth, carcass, and sensory traits.

Field testing of a system for online classification of beef carcasses for longissimus tenderness using visible and near-infrared reflectance spectroscopy.

The present experiments were conducted to field test a system optimized for online prediction of beef LM tenderness based on visible and near-infrared (VISNIR) spectroscopy and to develop and validate a model for prediction of tenderness that would be unbiased by normal variation in bloom time before application of VISNIR. For both Exp. 1 and 2, slice shear force (SSF) was measured on fresh (never frozen) steaks at 14 d postmortem. Carcasses with VISNIR-predicted SSF ≤15 kg were classified as VISNIR predicted tender and carcasses with VISNIR-predicted SSF >15 kg were classified as VISNIR not predicted tender. In Exp. 1, spectroscopy was conducted online, during carcass grading, at 3 large-scale commercial fed-beef processing facilities. Each carcass (n = 1,155) was evaluated immediately after ribbing and again when the carcass was graded. For model development and validation, carcasses were blocked by plant and observed SSF. One-half of the carcasses (n = 579) were assigned to a calibration data set, which was used to develop regression equations, and one-half of the carcasses (n = 576) were assigned to a prediction data set, which was used to validate the regression equations. Carcasses predicted tender by VISNIR spectroscopy had smaller (P < 10(-19)) mean LM SSF values at 14 d postmortem in the calibration (13.9 vs. 16.5 kg) and prediction (13.8 vs. 16.4 kg) data sets than did carcasses not predicted tender by VISNIR spectroscopy. Relative to carcasses not predicted tender by VISNIR, a decreased percentage of carcasses predicted tender by VISNIR had LM SSF >25 kg in the calibration (2.0 vs. 7.8%) and prediction (0.8 vs. 8.0%) data sets. In Exp. 2, carcasses (n = 4,204) were evaluated with VISNIR online at 6 commercial fed-beef processing facilities on 38 production days. The carcasses predicted tender by VISNIR spectroscopy had decreased mean LM SSF values at 14 d postmortem (16.3 vs. 19.9 kg; P < 10(-87)), longer sarcomere lengths (1.77 vs. 1.72 µm; P < 10(-10)), and a greater percentage of desmin degraded (42 vs. 34%; P < 10(-5)) by 14 d postmortem. Relative to carcasses not predicted tender by VISNIR, a decreased percentage of carcasses predicted tender by VISNIR had LM SSF >25 kg (4.9 vs. 21.3%). The present experiments resulted in development and independent validation of a robust method to noninvasively predict LM tenderness of grain-fed beef carcasses. This technology could facilitate tenderness-based beef merchandising systems.

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

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

Characterization of biological types of cattle (Cycle VIII): carcass, yield, and longissimus palatability traits.

The objective of this experiment was to evaluate alternative sources of tropically adapted cattle germplasm and compare them with Angus- (AN) and Hereford- (HE) sired steers. Carcass, yield, and longissimus thoracis palatability traits from F(1) steers (n = 621) obtained from mating AN and MARC III cows to HE, AN, Brangus (BR), Beefmaster (BM), Bonsmara (BO), or Romosinuano (RO) sires were compared. Data were adjusted to constant age (426 d), carcass weight (340 kg), fat thickness (1.0 cm), fat trim percentage (25%), and marbling (Small(00)) endpoints. For Warner-Bratzler and slice shear force and trained and untrained sensory panel traits, data were obtained on LM from ribeye steaks stored at 2 degrees C for 14 or 15 d postmortem. The following comparisons were from the age-constant endpoint. Carcasses from BM-, AN-, and BR-sired steers (358, 355, and 351 kg, respectively) were heavier (P < 0.05) than carcasses from steers from HE (343 kg) and BO (331 kg) sires; RO-sired steers (318 kg) had the lightest (P < 0.05) carcasses. Adjusted fat thicknesses for AN- and BM-sired steers (1.3 and 1.2 cm, respectively) were greater (P < 0.05) than for steers from BR (1.0 cm) and BO (0.9 cm) sires; RO-sired steers (0.8 cm) had the least fat thickness. Longissimus areas were larger (P < 0.05) for BO- and BR-sired steers (84.4 and 84.1 cm(2), respectively) than for BM- and HE-sired steers (80.8 and 80.2 cm(2), respectively). A greater (P < 0.05) percentage of carcasses from AN-sired steers graded USDA Choice (69%) than other sire breeds (17 to 47%) except HE (52%). Carcass yield of boneless, totally trimmed retail product was least (P < 0.05) for AN-sired steers (60.1%) and greatest (P < 0.05) for RO- and BO-sired steers (64.4 to 63.5%). Considering all measurements, AN LM tended to be more tender and BM LM tended to be least tender. American composite breeds BM and BR were heavier, fatter, lesser yielding, with similar marbling scores but less tender LM than BO and RO. Angus carcasses were similar in size, fatter, lesser yielding, with more marbling and more tender LM compared with BM and BR. Bonsmara and RO provide tropically adapted germplasm and produce carcasses that are lighter, leaner, greater yielding, with similar marbling and LM that tend to be more tender than carcasses from BM and BR.

Prevalence and level of Escherichia coli O157:H7 in feces and on hides of feedlot steers fed diets with or without wet distillers grains with solubles.

The objective of this study was to determine if wet distillers grains with solubles (WDGS) from corn in diets affected Escherichia coli O157:H7 in growing and finishing cattle; steers (n = 603) were randomly assigned to diets with or without WDGS. Hide and fecal samples were collected monthly (October through June) from each animal for enumeration and enrichment of E. coli O157:H7. In the growing phase (0 or 13.9% WDGS diets), fecal prevalence for E. coli O157:H7 in steers fed a diet with WDGS was twice that of the prevalence in control steers (P < 0.001). In the finishing phase (0 or 40% WDGS diets), the average prevalence in feces (P < 0.001) and on hides (P < 0.001) was higher for cattle fed WDGS. The average percentage of fecal E. coli O157:H7 enumerable samples during the finishing phase for cattle fed WDGS was 2.7% compared with 0.1% for control steers (P < 0.001). The average percentage of E. coli O157:H7 enumerable hide samples was not different between diets, but the cattle fed WDGS had higher levels (P < 0.05) of the pathogen. Animals fed WDGS had higher levels of E. coli (P < 0.001), higher pH values (P < 0.001), and lower concentrations of L-lactate (P < 0.001) in feces than those values of the control steers. These results indicate that feeding 40% WDGS could increase the level and prevalence of E. coli O157:H7 in and on feedlot cattle when E. coli O157:H7 is seasonally low.

Prevalence of Mycobacterium avium subsp. paratuberculosis in ileocecal lymph nodes and on hides and carcasses from cull cows and fed cattle at commercial beef processing plants in the United States.

Clinical associations between Crohn's disease in humans and Mycobacterium avium subsp. paratuberculosis (MAP) have been suggested but not confirmed. Cattle could be sources for MAP, but little information on MAP prevalence with beef has been reported. Samples of ileocecal lymph nodes and swabs of hides and carcasses from 343 animals at cull cattle slaughtering facilities and 243 animals at fed cattle slaughtering facilities across the United States were analyzed for the presence of MAP. Amplification of genetic sequences detected MAP DNA predominantly on hides and in lymph nodes of samples taken at both types of processing facilities. More than 34% of the cattle at cull cow slaughtering facilities had ileocecal lymph nodes that tested positive for MAP DNA. From these same cattle, hide prevalence was more than twofold greater than the prevalence in ileocecal lymph nodes, suggesting that cross-contamination could be occurring during transport and lairage. The prevalence of MAP DNA decreased during processing, and less than 11% of the carcasses tested positive after interventions in the cull cow processing facilities. Using standard double-decontamination and culture techniques, less than 1% of the postintervention carcasses tested positive for viable MAP at cull cow facilities. In samples from the facilities processing only fed cattle, MAP prevalence of 1% or less was detected for ileocecal lymph node, hide, and carcass samples, and viable MAP was not detected. Based on this study, fed cattle carcasses are unlikely sources of MAP, and carcasses at cull cow plants have only a slight risk for transmitting viable MAP, due to current interventions.

The caspase proteolytic system in callipyge and normal lambs in longissimus, semimembranosus, and infraspinatus muscles during postmortem storage.

The objective of this experiment was to determine whether the caspase proteolytic system has a role in postmortem tenderization. Six ewes and 6 wethers that were noncarriers and 6 ewes and 6 wethers that were expressing the callipyge gene were used for this study. Caspase activities were determined in LM at 7 different time points during the postmortem storage period: 0 h, 4 h, 8 h, 24 h, 2 d, 7 d, and 21 d and in semimembranosus (SM) and infraspinatus (IS) muscles at 0 h, 8 h, 24 h, and 7 d from callipyge and noncallipyge (normal) lambs. Calpastatin activity was determined at 0 h, 2 d, 7 d, and 21 d and slice shear force measured at 2, 7, and 21 d in the LM. Calpastatin activity and slice shear force were greater in LM from callipyge lambs than normal lambs at each time point (P < 0.001 and P < 0.0001, respectively). Caspases 3 and 7 are executioner caspases, and their combined activity was found to decrease during the postmortem storage period in LM, SM, and IS muscles from callipyge and normal lambs. Similarly, activity of the initiator caspase (caspase 9) decreased (P < 0.05) in all 3 muscles across the postmortem storage period in callipyge and normal lambs, and its decrease in activity preceded that of the executioner caspases 3/7. A positive relationship also was detected between caspase 9 and caspase 3/7 in LM, SM, and IS muscles (P < 0.0001, r = 0.85, r = 0.86, r = 0.84, respectively), which is consistent with caspase 9 being responsible for the cleavage and activation of the executioner caspases (caspase 3/7) downstream. Caspase 3/7 and caspase 9 activities at 8 h in SM were greater in normal lamb than callipyge lamb (P < 0.05), with a trend for caspase 3/7 activity to be greater at 24 h postmortem (P = 0.0841). There also was a trend for caspase 3/7 activity to be greater in LM at 21 d in normal lamb than in callipyge lamb (P = 0.053), although there were no differences detected in caspase activities between genotypes in the IS muscle, which is not affected by the callipyge gene. A negative relationship also was detected between peak caspase 3/7 activity at 8 h in LM from normal lambs and calpastatin activity at 0 and 2 d (r = -0.65, r = -0.68, respectively, P < 0.05). This relationship was not observed in LM from callipyge lambs, suggesting that caspase 3/7 may be cleaving calpastatin in normal lambs but the level of calpastatin in callipyge lambs is such that caspase 3/7 cannot degrade it sufficiently to overcome the increased content of calpastatin, and thus, calpastatin activity is the overriding factor in postmortem proteolysis in these animals. There was no direct evidence from this study that caspases have a significant role in postmortem tenderization, but they may have some role through calpastatin degradation.

Relationships among calpastatin single nucleotide polymorphisms, calpastatin expression and tenderness in pork longissimus.

Genome scans in the pig have identified a region on chromosome 2 (SSC2) associated with tenderness. Calpastatin is a likely positional candidate gene in this region because of its inhibitory role in the calpain system that is involved in postmortem tenderization. Novel single nucleotide polymorphisms (SNP) in calpastatin were identified and used to genotype a population (n = 1042) of Duroc-Landrace-Yorkshire swine for association with longissimus lumborum slice shear force (SSF) measured at days 7 and 14 postmortem. Three genetic markers residing in the calpastatin gene were significantly associated with SSF (P < 0.0005). Haplotypes constructed from markers in the calpastatin gene were significantly associated with SSF (F-ratio = 3.93; P-value = 0.002). The levels of normalized mRNA expression of calpastatin in the longissimus lumborum of 162 animals also were evaluated by real-time RT-PCR and were associated with the genotype of the most significant marker for SSF (P < 0.02). This evidence suggests that the causative variation alters expression of calpastatin, thus affecting tenderness. In summary, these data provide evidence of several significant, publicly available SNP markers associated with SSF that may be useful to the swine industry for marker assisted selection of animals that have more tender meat.

Effect of blade tenderization, aging time, and aging temperature on tenderness of beef longissimus lumborum and gluteus medius.

Purveyors are concerned about the potential food safety risk of nonintact meat products and are seeking strategies to ensure adequate meat tenderness without blade tenderization. This study was conducted to determine the effects of blade tenderization and time and temperature of aging on beef longissimus lumborum (LL) and gluteus medius (GM) tenderness. Beef strip loins (n = 300) and top sirloin butts (n = 300) were assigned to storage at -0.5 or 3.3 degrees C for 12, 26, or 40 d. Cuts were blade tenderized (BT) or not blade tenderized (NBT) before steak cutting. One 2.54-cm steak from each subprimal was used for slice shear force determination and Western blotting of desmin. Desmin degradation was less (P < 0.05) in LL stored at -0.5 degrees C than LL stored at 3.3 degrees C (57 and 65%, respectively). Aging from 12 to 26 d increased (P < 0.05) proteolysis (50 to 65%) in LL. Regardless of aging time, BT reduced (P < 0.05) LL slice shear force values. Aging time did not affect (P > 0.05) slice shear force values of BT LL steaks (10.4, 9.9, and 9.4 kg for 12, 26, and 40 d aging, respectively), but reduced (P < 0.05) NBT steak slice shear force values (15.1, 13.8, and 12.3 kg for 12, 26, and 40 d aging, respectively). Greater temperature did not affect (P > 0.05) slice shear force values of BT LL steaks (10.2 and 9.6 kg for steaks aged at -0.5 and 3.3 degrees C, respectively), but improved (P < 0.05) slice shear force of NBT LL steaks (15.1 and 12.4, respectively). Aging at 3.3 degrees C increased (P < 0.05) proteolysis in GM steaks (43 and 54% for -0.5 and 3.3 degrees C, respectively). Longer aging times increased (P < 0.05) proteolysis (40, 46, and 60% for 12, 26, and 40 d aging, respectively) in GM steaks. Blade-tenderized GM steaks had dramatically less (P < 0.05) slice shear force values than NBT steaks (13.7 and 19.9 kg, respectively). Raising aging temperature from -0.5 to 3.3 degrees C reduced (17.6 vs. 16.0 kg; P < 0.05) and increasing aging time from 12 d to 40 d improved (17.9 vs. 15.2 kg; P < 0.05) slice shear force values of GM steaks. Blade tenderization and increased aging time and temperature all improved tenderness of beef LL and GM steaks, though blade tenderization provided greater improvements than increased aging time and temperature. Longer aging could potentially be used to replace blade tenderization for LL steaks, but not in GM steaks.

Comparison of palatability characteristics of beef gluteus medius and triceps brachii muscles.

The objective of this experiment was to evaluate triceps brachii steaks as a substitute for gluteus medius steaks in foodservice and retail applications, including the effect of aging time and USDA quality grade on the palatability of both muscles. Top sirloin butts (n = 600) and shoulder clod arm roasts (n = 600) representing US Choice and US Select quality grades were selected at 48 h postmortem and aged for 7, 14, 21, 28, 35, or 42 d. Steaks were evaluated using a trained sensory panel, slice shear force, sarcomere length, and Western blotting of desmin measurements. Sarcomere length was measured only on steaks at 14 and 42 d. Triceps brachii and gluteus medius steaks were similar in tenderness rating at 7 and 14 d, but triceps brachii steaks aged longer were more tender (P < 0.05) than were gluteus medius steaks. Triceps brachii steaks reached ultimate tenderness values by 21 d. Gluteus medius steak tenderness ratings improved through 35 d, and at 42 d were similar to those given to triceps brachii steaks at 21 d. Sarcomere lengths were longer (P < 0.05) in triceps brachii than in gluteus medius (2.09 and 1.58 mum, respectively). Significant increases in desmin degradation were detected through 42 d in both muscles (30.9, 46.3, 50.6, 51.0, 57.6, and 64.1% at d 7, 14, 21, 28, 35, and 42 for gluteus medius and 28.9, 40.8, 49.3, 59.2, 61.8, and 71.9% at d 7, 14, 21, 28, 35, and 42 for triceps brachii). At 14 d, gluteus medius had more (P < 0.05) desmin degraded than triceps brachii, but by 28 d, desmin degradation was greater (P < 0.05) in triceps brachii. Quality grade had minimal effects on palatability traits. Desmin degradation contributed to gluteus medius tenderness variation (r = 0.36) across all aging times, but not at individual aging times. Sarcomere length contributed to variation in slice shear force values of gluteus medius at 14 and 42 d (r = -0.59 and -0.48, respectively). Sarcomere length contributed to triceps brachii tenderness variation at 14 d, but not 42 d (r = 0.44 and -0.12, respectively). Desmin degradation was strongly correlated (r = 0.55) to triceps brachii tenderness ratings pooled across aging times but not at individual aging times. These data indicate that triceps brachii steaks could provide the same or improved palatability as gluteus medius steaks at the same or slightly shorter aging times.

Consumer acceptance and steak cutting yields of beef top sirloin and knuckle subprimals.

Beef knuckles (n=150) and center-cut top sirloin butts (n=150) were used to determine portion-controlled steak cutting yields, palatability characteristics, and consumer acceptance of rectus femoris (RF), vastus lateralis (VL), and gluteus medius (GM) steaks. Steak yields were higher (P<0.05) for top sirloins than knuckles. Trained sensory panel ratings for overall tenderness, juiciness, and flavor were similar between RF and GM. Consumer panel ratings for tenderness and juiciness were higher (P<0.05) for GM than RF; however, consumer perceptions of overall like and flavor were similar for GM and RF. Vastus lateralis received lower (P<0.05) trained panel and consumer ratings for all traits than either RF or GM. Palatability of VL will need improvement to be a viable foodservice offering. Yet, these data suggest that RF would amply substitute for GM in foodservice settings, and that knuckle steak yields would be adequate for foodservice applications.

Evaluation of biochemical parameters and genetic markers for association with meat tenderness in South African feedlot cattle.

A large proportion of South African feedlot cattle are crossbreds of Brahman (BrX, Bos indicus), and Simmental (SiX, Bos taurus). A sample of 20 grain fed bulls from each of these crossbreeds was used to compare meat quality with that of the small frame indigenous Nguni (NgX, Sanga) by evaluating a variety of biochemical and genetic parameters previously shown to be associated with meat tenderness. Shear force values were generally high (5.6kg average at 14days post mortem), with SiX animals higher than BrX or NgX (P=0.051) despite higher calpastatin:calpain ratio in BrX (P<0.05). Calpain activity and cold shortening were both correlated with tenderness for all classes. The sample size was too small to accurately estimate genotypic effects of previously published markers in the CAST and CAPN1 genes, but the allele frequencies suggest that only modest progress would be possible in these South African crossbreds using these markers.

Opportunities for collaborative phenotyping for disease resistance traits in a large beef cattle resource population.

The Germplasm Evaluation (GPE) Project at the US Meat Animal Research Center (USMARC) is planned to produce about 3,000 calves per year in support of the following objectives: identification and validation of genetic polymorphisms related to economically relevant traits (ERT), estimation of breed and heterosis effects among 16 breeds for ERT, and estimation of genetic correlations among ERT and physiological indicator traits (PIT). Opportunities exist for collaboration in the development and collection of PIT phenotypes for disease resistance. Other areas of potential collaboration include detailed diagnosis (identification of disease causing organisms, etc.) of treated animals, collaborative development of epidemiological statistical models that would extract more information from the records of diagnoses and treatments, or pharmacogenetics. Concentrating a variety of different phenotypes and research approaches on the same population makes each component much more valuable than it would be individually.

Odorant production and persistence of Escherichia coli in manure slurries from cattle fed zero, twenty, forty, or sixty percent wet distillers grains with solubles.

Corn ethanol production removes starch and concentrates the remaining nutrients, including CP and minerals. When wet distillers grains with solubles (WDGS) are fed to cattle in place of corn, CP and minerals often exceed dietary needs. This may increase N emission, P run-off, and odor production. These variables are evaluated in this study. Crossbred steers (n = 160; 434 +/- 8 kg) were assigned in a completely randomized block design to 9 x 9 m pens with concrete floor (10 animals/pen; 4 pens/treatment). Steers were fed a finishing diet that contained 0, 20, 40, or 60% WDGS on a DM basis, and provided 13.3, 15.5, 20.6, or 24.9% CP, respectively. Two kilograms of manure slurry (14 to 23% DM) were collected from each pen monthly (Aug. 20, Sep. 24, and Oct. 22). Samples were analyzed immediately for odorants, DM, pH, NH(3), total alcohol, l-lactate, and concentrations of generic Escherichia coli. After incubation of the samples at 22 degrees C for 2, 4, 7, 10, 15, 21, and 28 d, samples were analyzed for methane production in addition to the above characteristics. Before incubation, NH(3), H(2)S, indole, phenol, isovalerate, isobutyrate, and acetate increased (P < 0.01) with increasing amounts of WDGS in the diet. Other odorants, including skatole, caproate, valerate, butyrate, and propionate, were greater (P < 0.01) in manure slurries from cattle fed 20 or 40% WDGS, compared to 0% WDGS. The l-lactate was greater (P < 0.01) in slurries from cattle fed 0% WDGS (447 mu mol/g of DM) compared with the other treatment slurries (14 to 15 mu mol/g of DM). After incubation, l-lactate contributed to lowered slurry pH (6.3, 7.1, 7.6, and 8.2, respectively, for 0, 20, 40, and 60% WDGS), which inhibited microbial fermentation, E. coli persistence, and methane production. Because of the favorable, more neutral pH in the 40 and 60% WDGS slurries, many of the odorant compounds were rapidly converted to methane during a 28-d static incubation. Escherichia coli O157:H7 inoculated into subsamples of the manure slurries exhibited behavior similar to that of naturally present generic E. coli, surviving in greater numbers longer (P < 0.05) in 20 and 40% WDGS slurries than in 0% WDGS. These data indicate feeding WDGS can increase odorants in manure slurries and extend the persistence of E. coli.

Estimates of genetic parameters for kyphosis in two crossbred swine populations.

Genetic parameters for degree of kyphosis were estimated from a Duroc-Landrace F(2) population (n = 316) and from a composite population (line C) composed of Duroc, Large White, and 2 sources of Landrace (n = 1,552). Live presentation did not indicate kyphosis in pigs or sows. Degree of kyphosis was measured by scoring the shape of the vertebral column of split carcasses on a scale from 0 (normal) to 3 (severe). Of the animals slaughtered, 75.6 and 68.9% were normal, 11.1 and 23.3% were mild, 11.1 and 6.2% were moderate, and 2.2 and 1.5% were severe in F(2) and line C, respectively. Fixed effects of age, sex, number of ribs, number of lumbar vertebrae, number of nipples, carcass length, and HCW were not significantly associated (P > 0.10) with kyphosis score when using linear models. Estimated heritabilities for kyphosis score were 0.30 and 0.32 in F(2) and line C, respectively, when using an animal model. Estimated genetic correlations between kyphosis score and number of ribs, number of lumbar vertebrae, number of nipples, carcass length, and HCW were 0.05, -0.13, 0.00, 0.05, and 0.03, respectively. Selection to decrease kyphosis should be effective and would not be expected to affect the number of ribs, lumbar vertebrae, nipples, or carcass length. In addition, selection for growth should not affect the incidence of kyphosis.

Enumeration of Salmonella from poultry carcass rinses via direct plating methods.

AIM: To evaluate direct plating methods for the estimation of Salmonella load in poultry carcass rinses. METHODS AND RESULTS: Two direct plating tools, the spiral plate count method (SPCM) and the hydrophobic grid membrane filtration (HGMF) method, were adapted to support quantification of Salmonella during poultry processing. Test samples consisted of 180 broiler carcasses from a commercial abattoir, 60 from each of three points in the processing line [pre-inside-outside bird wash (pre-IOBW), prechill and postchill]. The SPCM was used to estimate Salmonella load in pre-IOBW rinses, while HGMF was used to estimate Salmonella levels in prechill and postchill rinses. Carcass rinses were also evaluated for Salmonella prevalence by enrichment methods. Mean prevalences of Salmonella were 95%, 100% and 41.7%, and the geometric mean loads were 3.7 x 10(1), 5.6 x 10(0) and 5.0 x 10(-2) CFU ml(-1) for pre-IOBW, prechill and postchill rinses, respectively. CONCLUSIONS: The methods described are useful for estimating the concentration of viable and typical Salmonella in poultry carcass rinses. SIGNIFICANCE AND IMPACT OF THE STUDY: Direct plating enumeration methods can facilitate the monitoring of Salmonella load on poultry carcasses throughout the production process, and the evaluation of new processing intervention strategies.