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Genetic marker effects and type of inheritance are estimated with poor precision when minor marker allele frequencies are low. A stable composite population (MARC III) was subjected to marker-assisted selection for multiple years to equalize specific marker frequencies to 1) estimate effect size and mode of inheritance for previously reported SNP on targeted beef carcass quality traits (n= 254), 2) estimate pleiotropic effects of previously reported SNP on nontarget performance traits (n= 542 or 254), and 3) evaluate tenderness SNP specific residual variance for LM tenderness. Three haplotypes within μ-calpain(CAPN1), a SNP in calpastatin(CAST), and a dinucleotide substitution in diacylglycerol O-acyltransferase 1(DGAT1) were successfully selected to equalize their frequencies. Traits evaluated were birth BW, weaning BW, yearling BW, final BW, dressing percent, HCW, fat thickness, LM area, USDA marbling score, yield grade, LM slice shear force (SSF), and visible and near-infrared (VISNIR)-predicted SSF. While the CAPN1genotype effect on SSF was not significant (P= 0.12), the direction and size of CAPN1contrasts were consistent with previous research. Effects on SSF between divergent CAPN1haplotypes (1.153 kg) and the additive effect of CAST(0.902 kg) were large, and animals homozygous for tender alleles at both CAPN1and CASTwould have 4.11 kg lower SSF (27.5% of the mean) than animals homozygous tough for both markers. Furthermore, the interaction between CAPN1and CASTfor SSF was not significant (P= 0.40). There were significant effects for DGAT1on adjusted fat thickness (P= 0.02) and VISNIR-predicted SSF (P< 0.001) with additive and dominance modes of inheritance (P< 0.05) for both traits. Furthermore, CASTgenotype specific residual variance models fit significantly better (P< 0.001) than single residual variance models for SSF, with the tougher genotypes having progressively larger residual (and hence phenotypic) variances. Therefore, risk of a tough steak from the undesired CASTgenotype is increased through both an increase in mean and an increase in variation. This work is supportive of the importance of CAPN1and CASTfor mean tenderness in beef, confirms an effect of CASTon beef LM tenderness variation, and identifies an effect of DGAT1on subcutaneous fat thickness.

Zilpaterol hydrochloride (ZH) has been approved for use since 2006; however, there is no research on any interactions between ZH and coproducts. Additionally, there is no published information on the potential effects of ZH on heat stress in feedlot cattle. Therefore, an experiment was conducted to determine the effects of feeding dry-rolled corn (DRC)-based diets with and without wet distillers grains with solubles (WDGS) and ZH on performance, carcass characteristics, and heat stress in feedlot cattle. Four hundred thirty-eight steers were used in a randomized complete block design with a 2 × 2 factorial arrangement of treatments in 16 pens with 26 to 28 steers in each pen. Factors consisted of inclusion of 0 or 30% (on a DM basis) WDGS and inclusion of ZH at 0 or 84 mg/steer daily for 21 d at the end of the finishing period. Therefore, cattle were blocked by BW and randomly assigned to 1 of the resulting 4 treatment combinations: 1) DRC-based diet with 0% WDGS and 84 mg/steer ZH, 2) DRC-based diet with 0% WDGS and no ZH, 3) DRC-based diet with 30% WDGS and 84 mg/steer of ZH, and 4) DRC-based diet with 30% WDGS and no ZH. Final live BW, carcass-adjusted BW, ADG, and G:F were greater for cattle fed ZH than non-ZH-fed cattle (P< 0.01). Additionally, cattle fed ZH consumed 7.4% less DM than cattle not fed ZH (P< 0.01). Cattle fed ZH for 21 d also had a 2.9% greater HCW (P< 0.01), a 1.1% greater dressing percentage (P< 0.01), 7.3% greater LM area (P< 0.01), and an 8.4% improvement in yield grade (P< 0.01) than cattle not fed ZH. For the main effect of WDGS inclusion, ADG was greater for cattle fed 0 vs. 30% WDGS (P= 0.04) and G:F also tended to be greater for cattle fed 0 vs. 30% WDGS (P= 0.07) for the 21-d ZH feeding period. However, when evaluated over the entire experiment, cattle fed 30 vs. 0% WDGS had a greater ADG and G:F (P< 0.01). Furthermore, cattle fed 30 vs. 0% WDGS had a greater dressing percentage and tended to have a greater amount of 12th rib fat (P< 0.07). Heat stress measurements were collected during the time cattle were fed ZH, from May 31 to July 12, 2013. The slopes for change in respiration rate and panting score per day were positive but were not different across dietary treatments (P> 0.71); in addition, the slopes for change in respiration rate and panting score when accounting for environmental conditions were positive but were not different across dietary treatments (P> 0.32).

The experiment was designed to validate the use of ultrasound to evaluate body composition in mature beef cows. Both precision and accuracy of measurement were assessed. Cull cows (n= 87) selected for highly variable fatness were used. Two experienced ultrasound technicians scanned and assigned BCS to each cow on 2 consecutive days. Ultrasound traits were backfat thickness (UBFT), LM area (ULMA), body wall thickness (UBWT), rump fat depth (URFD), rump muscle depth (URMD), and intramuscular fat (UIMF; %). Cows were then harvested. Carcass traits were HCW, backfat thickness (CBFT), LM area (CLMA), body wall thickness (CBWT), and marbling score (CMS). Correlations between consecutive live measurements were greatest for subcutaneous fat (r> 0.94) and lower for BCS (r> 0.74) and URMD (r> 0.66). Repeatability bias differed from 0 for only 1 technician for URMD and UIMF (P< 0.01). Technicians differed in repeatability SE for only ULMA (P< 0.05). Correlations between live and carcass measurements were high for backfat and body wall thickness (r> 0.90) and slightly less for intramuscular fat and LM area (r= 0.74 to 0.79). Both technicians underestimated all carcass traits with ultrasound, but only CBFT and CBWT prediction bias differed from 0 (P< 0.05). Technicians had similar prediction SE for all traits (P> 0.05). Technician effects generally explained <1% of the total variation in precision. After accounting for technician, animal effects explained 50.4% of remaining variation in differences between repeated BCS (P< 0.0001) but were minimal for scan differences. When cows with mean BCS <4 or >7 were removed, the portion of remaining variation between repeated measurements defined by animal effects increased for most traits and was significant for UBFT and URFD (P= 0.03). Technician effects explained trivial variation in accuracy (P> 0.24). Animal effects explained 87.2, 75.2, and 81.7% (P< 0.0001) of variation remaining for CBFT, CLMA, and CBWT prediction error, respectively, and remained large and highly important (P< 0.0001) when only considering cows with BCS from 4 to 7. We conclude that experienced ultrasound technicians can precisely and accurately measure traits indicative of composition in mature beef cows. However, animal differences define substantial variation in scan differences and, especially, prediction errors. Implications for technician certification, carcass pricing, and genetic evaluation are discussed.

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.

Genetic marker effects and interactions are estimated with poor precision when minor marker allele frequencies are low. An Angus population was subjected to marker assisted selection for multiple years to increase divergent haplotype and minor marker allele frequencies to 1) estimate effect size and mode of inheritance for previously reported SNP on targeted beef carcass quality traits; 2) estimate effects of previously reported SNP on nontarget performance traits; and 3) evaluate tenderness SNP specific residual variance models compared to a single residual variance model for tenderness. Divergent haplotypes within µ-calpain (CAPN1), and SNP within calpastatin (CAST) and growth hormone receptor (GHR) were successfully selected to increase their frequencies. Traits evaluated were birth BW, weaning BW, final BW, fat thickness, LM area, USDA marbling score, yield grade, slice shear force (SSF), and visible and near infrared predicted slice shear force. Both CAPN1and CASTexhibited additive (P< 0.001) modes of inheritance for SSF and neither exhibited dominance (P≥ 0.19). Furthermore, the interaction between CAPN1and CASTfor SSF was not significant (P= 0.55). Estimated additive effects of CAPN1(1.049 kg) and CAST(1.257 kg) on SSF were large in this study. Animals homozygous for tender alleles at both CAPN1and CASTwould have 4.61 kg lower SSF (38.6% of the mean) than animals homozygous tough for both markers. There was also an effect of CASTon yield grade (P< 0.02). The tender CASTallele was associated with more red meat yield and less trimmable fat. There were no significant effects (P≥ 0.23) for GHRon any of the traits evaluated in this study. Furthermore, CASTspecific residual variance models were found to fit significantly better (P< 0.001) than single residual variance models for SSF, with the tougher genotypes having larger residual variance. Thus, the risk of a tough steak from the undesired CASTgenotype is increased through both an increase in mean and an increase in variation. This work confirms the importance of CAPN1and CASTfor tenderness in beef, provides a new effect of CASTon beef tenderness, and questions the utility of GHRas a selection marker for beef quality.

Pork quality has a large impact on consumer preference and perception of eating quality. A genome-wide association was performed for pork quality traits [intramuscular fat (IMF)], slice shear force (SSF), color attributes, purge, cooking loss, and pH] from 531 to 1,237 records on barrows and gilts of a Landrace-Duroc-Yorkshire population using the Illumina PorcineSNP60 BeadChip. Associations were detected using MTDFREML for all traits. Intramuscular fat had the greatest number of SNP associations, followed by pH, purge, cooking loss, shear force, and color. Two regions contained associations for multiple traits; one on SSC1 at 255 Mb near calcineurin subunit B (PPP3R2) was associated with SSF, moisture loss, and pH, and one on SSC6 from 28 to 29.5 Mb for purge and IMF containing the candidate genes glucose-6-phosphate isomerase (GPI) and KCTD15. Some of the other compelling candidate genes in regions associated with meat quality include CEBPA, SNAI1, and FAM132A for IMF, CAPN1 for SSF, GLUL for pH, and PRKAG3 and ITGB1 with cooking loss.

Distillers grains and distillers solubles are by-products of grain fermentation used to produce ethanol and contain greater concentrations of NDF and ADF, compared with other grains and concentrates they replace in feedlot diets. Typical finishing diets in the United States contain 8.3% and 9.0% roughage. Therefore, it is plausible that the dietary concentration of roughage can be altered when distillers grains are included in feedlot diets. The effects of roughage concentration in dry-rolled, corn-based diets containing wet distillers grains with solubles (WDGS) were evaluated in steers (n = 128; initial BW = 339 kg), using Calan gates. Each diet was based on dry-rolled corn and contained 25% WDGS with coarsely ground alfalfa hay (AH), replacing corn at 2% (AH-2), 6% (AH-6), 10% (AH-10), and 14% (AH-14) of DM. Feed offered was recorded daily, orts were measured weekly, and BW was measured on d 0, 1, 35, 70, 105, 140, 174, and 175. After commercial harvest and chilling, carcasses were evaluated on-line with a beef carcass grading camera to assess marbling and yield grade traits. The data were analyzed using the Mixed Procedure of SAS, in which contrast statements were used to separate linear and quadratic effects of AH inclusion. Decreasing concentrations of AH in the finishing diet resulted in a tendency for a quadratic response (P = 0.07) in final BW, where BW increased from 2 to 6% AH inclusion but then decreased from 6 to 14% inclusion. Similarly, ADG from d 0 to end responded quadratically (P < 0.01), in which ADG increased from 2 to 6% yet subsequently decreased from 6 to 14% AH inclusion. Dry matter intake from d 0 to end increased linearly (P = 0.02) as AH inclusion increased in the diet, whereas G:F increased from 2 to 6% AH inclusion and then decreased linearly (P < 0.01) from 6 to 14% AH inclusion. Concentration of AH in the finishing diet did not affect HCW, marbling score, or the proportion of cattle grading USDA choice (P ≥ 0.18). However, dressing percent and LM area did respond in a quadratic manner (P < 0.02), in which they decreased from 2 to 10% AH inclusion and increased from 10 to 14% AH in the diet. Yield grade and adjusted 12th rib fat responded quadratically (P < 0.01), in which both increased from 2 to 6% AH inclusion and decreased from 6 to 14% inclusion. Analysis of responses of G:F and ADG on AH predict the apex at 3% and 7% for G:F and ADG, respectively, when fed in diets containing 25% WDGS.

The objective this study was to evaluate the effects of incidence of bovine respiratory disease (BRD) and overall incidence of pathogenic diseases (IPD) on carcass traits. Two independent populations were used. The first population included crossbred steers (GPE7; n = 642) derived from sires of 7 Bos taurusbreeds: Angus, Charolais, Gelbvieh, Hereford, Limousin, Red Angus, and Simmental. The second population included crossbred steers (GPE8; n = 621) derived from tropically adapted Bos taurusbreeds and Bos indicus-influenced breeds: Beefmaster, Brangus, Bonsmara, and Romosinuano, as well as Hereford and Angus. Treatment records for BRD, infectious keratoconjunctivitis, and infectious pododermatitis were available for these populations. Incidence of BRD was treated as an independent effect. Incidences of the 3 microbial pathogenic diseases were pooled into a single trait to represent overall pathogenic disease incidence. Traits evaluated were HCW; KPH; LM area; marbling score; fat thickness; dressing percentage; yield grade; retail, fat, and bone yields; and meat tenderness. Both BRD and IPD were associated with differences in yield grade in GPE7 and GPE8 steers. Animals treated for BRD had decreased yield grades (P= 0.003 and P= 0.02, in GPE7 and GPE8, respectively) compared with untreated animals. Animals treated for IPD had decreased yield grades (P= 0.0006 and P= 0.004, in GPE7 and GPE8, respectively) compared with untreated animals. Incidence of BRD and IPD were associated with a reduction in fat thickness in GPE7 and GPE8 steers. Animals treated for BRD had reduced adjusted fat measurements (P= 0.0007 and P= 0.01, in GPE7 and GPE8) compared with untreated animals. Animals treated for IPD also had reduced adjusted fat measurements (P= 0.0003 and P= 0.002, in GPE7 and GPE8) compared with untreated animals. Animals treated for BRD (P< 0.007) or IPD (P< 0.02) in the GPE7 population also had decreased estimated KPH measurements compared with unaffected animals. Animals affected with BRD in GPE8 had greater (P< 0.05) shear force measurements than unaffected animals. Animals affected with IPD in GPE8 had greater HCW (P< 0.03) and fat yield (P< 0.01) measurements but lesser bone yield (P< 0.03) and retail product yield (P< 0.01) measurements than unaffected animals. The relationship between disease and carcass traits should be given consideration by future studies that aim to develop selection strategies based on specific traits.

Genetic markers in casein (CSN1S1) and thyroglobulin (TG) genes have previously been associated with fat distribution in cattle. Determining the nature of these genetic associations (additive, recessive, or dominant) has been difficult, because both markers have small minor allele frequencies in most beef cattle populations. This results in few animals homozygous for the minor alleles. selection to increase the frequencies of the minor alleles for 2 SNP markers in these genes was undertaken in a composite population. The objective was to obtain better estimates of genetic effects associated with these markers and determine if there were epistatic interactions. Selection increased the frequencies of minor alleles for both SNP from <0.30 to 0.45. Bulls (n = 24) heterozygous for both SNP were used in 3 yr to produce 204 steer progeny harvested at an average age of 474 d. The combined effect of the 9 CSN1S1 × TG genotypes was associated with carcass-adjusted fat thickness (P < 0.06) and meat tenderness predicted at the abattoir by visible and near-infrared reflectance spectroscopy (P < 0.04). Genotype did not affect BW from birth through harvest, ribeye area, marbling score, slice shear force, or image-based yield grade (P > 0.10). Additive, dominance, and epistatic SNP association effects were estimated from genotypic effects for adjusted fat thickness and predicted meat tenderness. Adjusted fat thickness showed a dominance association with TG SNP (P < 0.06) and an epistatic additive CSN1S1 × additive TG association (P < 0.03). For predicted meat tenderness, heterozygous TG meat was more tender than meat from either homozygote (P < 0.002). Dominance and epistatic associations can result in different SNP allele substitution effects in populations where SNP have the same linkage disequilibrium with causal mutations but have different frequencies. Although the complex associations estimated in this study would contribute little to within-population selection response, they could be important for marker-assisted management or reciprocal selection schemes.

The 2011 National Beef Quality Audit (NBQA-2011) assessed the current status of quality and consistency of fed steers and heifers. Beef carcasses (n = 9,802), representing approximately 10% of each production lot in 28 beef processing facilities, were selected randomly for the survey. Carcass evaluation for the cooler assessment of this study revealed the following traits and frequencies: sex classes of steer (63.5%), heifer (36.4%), cow (0.1%), and bullock (0.03%); dark cutters (3.2%); blood splash (0.3%); yellow fat (0.1%); calloused rib eye (0.05%); overall maturities of A (92.8%), B (6.0%), and C or greater (1.2%); estimated breed types of native (88.3%), dairy type (9.9%), and Bos indicus(1.8%); and country of origin of United States (97.7%), Mexico (1.8%), and Canada (0.5%). Certified or marketing program frequencies were age and source verified (10.7%), ≤A40(10.0%), Certified Angus Beef (9.3%), Top Choice (4.1%), natural (0.6%), and Non-Hormone-Treated Cattle (0.5%); no organic programs were observed. Mean USDA yield grade (YG) traits were USDA YG (2.9), HCW (374.0 kg), adjusted fat thickness (1.3 cm), LM area (88.8 cm2), and KPH (2.3%). Frequencies of USDA YG distributions were YG 1, 12.4%; YG 2, 41.0%; YG 3, 36.3%; YG 4, 8.6%; and YG 5, 1.6%. Mean USDA quality grade (QG) traits were USDA quality grade (Select93), marbling score (Small40), overall maturity (A59), lean maturity (A54), and skeletal maturity (A62). Frequencies of USDA QG distributions were Prime, 2.1%; Choice, 58.9%; Select, 32.6%; and Standard or less, 6.3%. Marbling score distribution was Slightly Abundant or greater, 2.3%; Moderate, 5.0%; Modest, 17.3%; Small, 39.7%; Slight, 34.6%; and Traces or less, 1.1%. Carcasses with QG of Select or greater and YG 3 or less represented 85.1% of the sample. This is the fifth benchmark study measuring targeted carcass characteristics, and information from this survey will continue to help drive progress in the beef industry. Results will be used in extension and educational programs as teaching tools to inform beef producers and industry professionals of the current state of the U.S. beef industry.

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 × 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, NH3, total alcohol, L-lactate, and concentrations of generic Escherichia coli. After incubation of the samples at 22°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, NH3, H2S, 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 μ mol/g of DM) compared with the other treatment slurries (14 to 15 μ 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. colipersistence, 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 coliO157: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.

The objective of this study was to assess the association of single nucleotide polymorphisms (SNP) developed at the calpastatin(CAST) and μ-calpain(CAPN1) genes with meat tenderness and palatability traits in populations with diverse genetic backgrounds. Three populations were used in the study. One population consisted of Bos taurusthat included crossbred animals derived from Hereford, Angus, Red Angus, Limousin, Charolais, Gelbvieh, and Simmental (GPE7; n = 539). Another population consisted of Bos tauruswith Bos indicusinfluence, including crossbred animals from Hereford, Angus, Brangus, Beefmaster, Bonsmara, and Romosinuano (GPE8; n = 580). The third population was Bos indicusand consisted of purebred Brahman (STARS; n = 444). Traits evaluated were meat tenderness measured as Warner-Bratzler shear force (WBSF; kg) at 14 d postmortem, and traits evaluated by trained sensory panels that included tenderness score, juiciness, and flavor intensity. A SNP at the CASTgene had a significant (P< 0.003) effect on WBSF and tenderness score in the GPE7 and GPE8 populations. Animals inheriting the TT genotype at CASThad meat that was more tender than those inheriting the CC genotype. The marker at the CAPN1gene was significant (P< 0.03) for tenderness score in GPE7 and GPE8. Animals inheriting the CC genotype at CAPN1had meat that was more tender than those inheriting the TT genotype. Markers at the CASTand CAPN1genes were associated with flavor intensity in the GPE8 population. Animals inheriting the CC genotype at CASTand the TT genotype at CAPN1produced steaks with an intense flavor when compared with the other genotypes. An interaction between CASTand CAPN1was detected (P< 0.05) for WBSF on GPE8. The statistical significance of the interaction is questionable because of the limited number of observations in some cells. Markers developed at the CASTand CAPN1genes are suitable for use in identifying animals with the genetic potential to produce meat that is more tender.

The three objectives of this study were to 1) test for the existence of beef tenderness markers in the CAPN1gene segregating in Brahman cattle; 2) test existing CAPN1tenderness markers in indicus-influenced crossbred cattle; and 3) produce a revised marker system for use in cattle of all subspecies backgrounds. Previously, two SNP in the CAPN1gene have been described that could be used to guide selection in Bos tauruscattle (designated Markers 316 and 530), but neither marker segregates at high frequency in Brahman cattle. In this study, we examined three additional SNP in CAPN1to determine whether variation in this gene could be associated with tenderness in a large, multisire American Brahman population. One marker (termed 4751) was associated with shear force on postmortem d 7 (P< 0.01), 14 (P= 0.015), and 21 (P< 0.001) in this population, demonstrating that genetic variation important for tenderness segregates in Bos indicuscattle at or near CAPN1.Marker 4751 also was associated with shear force (P< 0.01) in the same large, multisire population of cattle of strictly Bos taurusdescent that was used to develop the previously reported SNP (referred to as the Germplasm Evaluation [GPE] Cycle 7 population), indicating the possibility that one marker could have wide applicability in cattle of all subspecies backgrounds. To test this hypothesis, Marker 4751 was tested in a third large, multisire cattle population of crossbred subspecies descent (including sire breeds of Brangus, Beefmaster, Bonsmara, Romosinuano, Hereford, and Angus referred to as the GPE Cycle 8 population). The highly significant association of Marker 4751 with shear force in this population (P< 0.001) confirms the usefulness of Marker 4751 in cattle of all subspecies backgrounds, including Bos taurus, Bos indicus,and crossbred descent. This wide applicability adds substantial value over previously released Markers 316 and 530. However, Marker 316, which had previously been shown to be associated with tenderness in the GPE Cycle 7 population, also was highly associated with shear force in the GPE Cycle 8 animals (P< 0.001). Thus, Marker 316 may continue to be useful in a variety of populations with a high percentage of Bos taurusbackgrounds. An optimal marker strategy for CAPN1in many cases will be to use both Markers 316 and 4751.

Two previously identified single-nucleotide polymorphism markers located within the micromolar calcium-activated neutral protease gene (CAPN1) were evaluated for their association with variation in meat tenderness using one commercial sample of Simmental × Angus crossbred calves and one multibreed, crossbred research herd. The commercial sample included 362 animals sired by 23 registered Simmental bulls bred to unregistered Angus cows and represented current industry animals in which to test the predictive merit of the markers. The second sample was a research herd including 564 steers from the Germplasm Evaluation Cycle VII population at the U.S. Meat Animal Research Center, produced with semen from popular sires of the seven Bos taurusbeef breeds with the most registrations in the United States (Angus, Charolais, Gelbvieh, Hereford, Limousin, Red Angus, and Simmental) on Angus, Hereford, and MARC III cows. These animals form a relatively outbred population that constituted a stringent test of the predictive merit of the genetic markers, although small groups were half-sibs. Warner-Bratzler shear force measurements were used to determine tenderness phenotypes for all animals. The populations were genotyped for two markers that predict variation at amino acid positions 316 and 530 of the μ-calpain polypeptide, produced by the CAPN1gene. Minor allele frequencies for markers 316 and 530 in the commercial sample were 0.17 and 0.37, respectively, and in the Cycle VII animals, were 0.20 and 0.28, respectively. Both markers showed association with shear force in the commercial sample (P= 0.04) and the Cycle VII population (P= 0.02), supporting the hypothesis that they represent potential markers to aid selection for improved meat tenderness in commercial populations of beef cattle in the United States.

Casein zymography was used to determine the effect of postmortem storage on the proteolytic activity of µ-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°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 µ-calpain activity (P< 0.05) such that after 24 and 72 h postmortem, µ-calpain had lost 42 and 95% of its activity, respectively. After 360 h postmortem, no µ-calpain activity could be detected (under the conditions used in this study). Autolysis of µ-calpain could be detected as early as 3 h postmortem. It was demonstrated that the detectable level of µ-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 µ-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 µ-calpain. These results support the widely believed conclusion that µ-calpain-mediated proteolysis of key myofibrillar and cytoskeletal proteins is responsible for postmortem tenderization. Hence, understanding the regulation of µ-calpain in postmortem muscle should be the focus of future studies.

Carcass (n = 854) and longissimus thoracis palatability (n = 802) traits from F1steers 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 objective of this study was to identify quantitative trait loci for economically important traits in two families segregating an inactive copy of the myostatin gene. Two half-sib families were developed from a Belgian Blue × MARC III (n = 246) and a Piedmontese × Angus (n = 209) sire. Traits analyzed were birth, weaning, and yearling weight (kg); preweaning average daily gain (kg/d); postweaning average daily gain (kg/d); hot carcass weight (kg); fat depth (cm); marbling score; longissimus muscle area (cm2); estimated kidney, pelvic, and heart fat (%); USDA yield grade; retail product yield (%); fat yield (%); and wholesale rib-fat yield (%). Meat tenderness was measured as Warner-Bratzler shear force at 3 and 14 d postmortem. The effect of the myostatin gene was removed using phase information from six microsatellite markers flanking the locus. Interactions of the myostatin gene with other loci throughout the genome were also evaluated: The objective was to use markers in each family, scanning the genome approximately every 25 to 30 centimorgans (cM) on 18 autosomal chromosomes, excluding 11 autosomal chromosomes previously analyzed. A total of 89 markers, informative in both families, were used to identify genomic regions potentially associated with each trait. In the family of Belgian Blue inheritance, a significant QTL (expected number of false-positives = 0.025) was identified for marbling score on chromosome 3. Suggestive QTL for the same family (expected number of false-positives = 0.5) were identified for retail product yield on chromosome 3, for hot carcass weight and postweaning average daily gain on chromosome 4, for fat depth and marbling score on chromosome 8, for 14-d Warner-Bratzler shear force on chromosome 9, and for marbling score on chromosome 10. Evidence suggesting the presence of an interaction for 3-d Warner-Bratzler shear force between the myostatin gene and a QTL on chromosome 4 was detected. In the family of Piedmontese and Angus inheritance, evidence indicates the presence of an interaction for fat depth between the myostatin gene and chromosome 8, in a similar position where the evidence suggests the presence of a QTL for fat depth in the family with Belgian Blue inheritance. Regions identified underlying QTL need to be assessed in other populations. Although the myostatin gene has a considerable effect, other loci with more subtle effects are involved in the expression of the phenotype.

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°C. At 48 h postmortem, carcasses were assigned to one of three tenderness classes (tender < 26 kg, intermediate = 26 to 42 kg, tough > 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°C, and frozen at −30°C at 14 d postmortem. Two 2.54-cm-thick steaks were obtained from each muscle, thawed to 5°C, cooked with a belt grill at 163°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.

A resource flock of 362 F2lambs 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 study was to determine the effects of dietary administration of a β-adrenergic agonist (BAA; L-644,969) and male sex condition (ram vs wether) on muscle growth and meat quality of Dorset × Romonov lambs believed to be heterozygous for the callipyge gene. At approximately 17 wk of age, lambs were blocked by weight within each sex condition and randomly assigned to BAA treatment group. The interaction of BAA and male sex condition was not significant for any of the traits measured. Rams had greater initial and final live weights, average daily gain, and hot carcass weight (P< .01). Rams did not differ (P> .05) from wethers with respect to any of the carcass traits, possibly because the wethers were so lean and heavily-muscled that there was little room for improvement. Kidney-pelvic fat weight was reduced 26% by BAA (P< .05). Knife separable lean weight and whole carcass proximate composition were not affected (P> .05) by BAA or male sex condition. Administration of BAA increased calpastatin activity at 20 d (1.1 vs 1.5 units/g), but not at 0 h (3.9 vs 4.8 units/g) postmortem, decreased myofibril fragmentation index (60.7 vs 44.9), and increased shear force (8.2 vs 10.9 kg) at 20 d postmortem (P< .05). These data suggest that muscle growth rates are near maximum in lambs expressing the callipyge gene, regardless of male sex condition or BAA treatment. Therefore, it seems that the callipyge gene exerts most, but not all, of its effect through intracellular events similar to those initiated by administering BAA.

The present experiments were conducted to determine 1) the relationship between shear force and overall tenderness of 10 major beef muscles, 2) the effect of Bos indicusinheritance on the tenderness of various beef muscles, 3) whether differences in tenderness between genotype are affected by method of cookery, and 4) the relationship between tenderness of the longissimus and tenderness of other muscles. To meet the first objective, shear force and trained sensory panel overall tenderness were determined for psoas major (PM), infraspinatus (IS), triceps brachii (TB), longissimus (LD), semitendinosus (ST), gluteus medius (GM), supraspinatus (SS), biceps femoris (BF), semimembranosus (SM), and quadriceps femoris (QF) steaks from grain-fed steer carcasses (n = 16). Shear force did not accurately reflect differences among muscles in overall tenderness. To accomplish the remaining objectives, muscles were removed from grain-fed Bos taurus× Bos taurus(n = 31) and Bos indicus× Bos taurus(n = 18) steer carcasses and aged until 14 d postmortem. Shear force of LD, TB, SS, BF, and QF steaks and QF, BF, TB, and LD roasts was higher (P< .05) for progeny of Bos indicussires than for progeny of Bos taurussires. Shear force differences among genotypes were reduced slightly by roasting. Shear force of LD was not highly related to shear force of other muscles. Thus, systems that accurately predict the tenderness of LD of a carcass will likely do little to predict the tenderness of other muscles.

The objectives of the present experiment were to examine the effects of in uteroexposure to a β-adrenergic agonist (L644,969) on prenatal and postnatal muscle growth and meat tenderness of lambs. Thirty twin-pregnant Composite IV (1/2 Finn-sheep, 1/8 Dorset, 1/8 Rambouillet, 1/8 Targhee, 1/8 Suffolk) ewe lambs were used for this experiment. All ewes were fed an alfalfa hay-corn-based diet throughout gestation and lactation. From d 25 to 95 of gestation, the diet of one-half of the ewes contained 2 ppm of L644,969on an as-fed basis. Treatment did not (P> .05) affect lamb weights at any point in the growth cycle (birth to 43 kg). Heart weights of neonatal and market lambs were increased (P< .05) by in uteroexposure to L644,969. However, weights of lamb carcass components and weights of individual muscles were not affected by treatment (P> .05). Additionally, treatment did not alter the activities of any of the components of the calpain proteolytic system in neonatal or market lambs. Concomitantly, there was no effect of treatment on myofibril fragmentation index or Warner-Bratzler shear force. Moreover, there was no effect of treatment on muscle fiber type distributions, fiber sizes, or apparent fiber number. It seems that the lack of an effect of treatment on apparent fiber number would explain the lack of an effect on muscle weight. Thus, in uteroexposure to L644,969does not seem to have promise as a method for improving lamb carcass cutability. Other methods of improving the rate and composition of lamb carcass growth while maintaining acceptable meat tenderness must be developed.

To examine the effect of a β-adrenergic agonist (BAA) on muscle growth, proteinase activities, and postmortem proteolysis, 16 wether lambs were randomly assigned to receive 0 or 4 ppm of L644,969in a completely mixed high-concentrate diet for 6 wk. Weight of the biceps femoris was 18.6% heavier in treated lambs. At 0 h after slaughter, treated lambs had higher cathepsin B (35.6%), cathepsins B + L (19.1%), calpastatin (62.8%), and m-calpain (24.6%) than control lambs, but both groups had similar µ-calpain activities, In both longissimus and biceps femoris muscles, treated lambs had higher protein and RNA and lower DNA concentrations. However, total DNA was not affected, indicating that the increase in muscle mass was probably due to muscle hypertrophy rather than to hyperplasia. The pattern of postmortem proteolysis was significantly altered by BAA feeding. In treated lambs, postmortem storage had no effect on the myofibril fragmentation index and degradation of desmin and troponin-T. These results indicate that the ability of the muscle to undergo postmortem proteolysis has been dramatically reduced with BAA feeding. Similar proteolytic systems are thought to be involved in antemortem and postmortem degradation of myofibrillar proteins, so BAA-mediated protein accretion is probably due, at least in part, to reduced protein degradation. To examine whether protein synthesis was altered with BAA feeding, the level of skeletal muscle α-actin mRNA was quantified. Longissimus muscle α-actin mRNA abundance was 30% greater in BAA-fed lambs. Collectively, these results indicate that dietary administration of BAA increases muscle mass through hypertrophy and that the increase in muscle protein accretion is due to reduced degradation and possibly to increased synthesis of muscle proteins.

The present study was designed to determine the effects of supplemental fat or oil rich in oleic acid on the fatty acid profiles (FAP) and physical and sensory traits of pork carcasses. Sixty barrows and gilts were equally distributed among five dietary treatments consisting of a control diet of corn and soybean meal and four similar test diets that contained 10% animal fat (45.3 oleic), safflower oil (72.1 oleic), sunflower oil (80.9 oleic) or canola oil (57.7 oleic). The pigs were slaughtered after being fed these diets for 90 d at about 100 kg live weight. Carcass traits, FAP and sensory properties were evaluated for each treatment. First-rib fat thickness, ham muscling score and longissimus muscle areas were not different (P< .05), but last-rib fat thickness was increased (P< .05) with the supplemental dietary fat or oils. No differences existed for marbling scores, lean color, firmness or texture scores between the controls and pigs supplemented with either animal fat or safflower oil. However, pigs supplemented with sunflower or canola oil had lower marbling scores, lean color, firmness and texture scores. Fat became softer and more oily (P< .05) with the supplemental dietary safflower, sunflower and canola oils. Sensory evaluation (loin chops) showed no differences (P< .05) in sustained juiciness, tenderness or flavor intensity evaluations among treatments. However, the pigs fed canola oil had lower (P< .05) flavor quality scores or overall palatability evaluations. Chops from the pigs fed canola oil also had 46% more off-flavors than all other treatments.Canola oil proved unacceptable as a method of increasing oleic acid levels in pigs. Other oils significantly increased oleic acid and decreased palmitic acid content of lipid adipose deposits and longissimus muscle.

The objective of this study was to examine the effectiveness of CaCl2infusion in overcoming the toughness of meat associated with dietary administration of a β- adrenergic agonist (BAA) to lambs. Thirty-two crossbred (1/2 Finnsheep × 1/4 Dorset × 1/4 Rambouillet) wether lambs were randomly assigned to receive 0 or 4 ppm BAA (L644,969; Merck, Sharpe and Dohme Research Laboratories) in a completely mixed, high-concentrate diet for 6 wk. Animals were slaughtered in two groups of 16. At each slaughter time half of each group (0 or 4 ppm BAA) was randomly assigned to CaCl2infusion. Feeding the BAA decreased (P< .05) fat thickness, kidney-pelvic fat, yield grade, and marbling and increased (P< .05) dressing percentage, lean firmness, leg score, and biceps femoris weight. Weight of biceps femoris was 32.8% greater in BAA-fed lambs. Treated, but not infused, lambs were significantly less tender than control lambs after 1, 7, and 14 d of postmortem storage. At 24 h postmortem, BAA-fed lambs had higher (P< .05) cathepsin B, calcium-dependent protease-II (CDP-II), and CDP inhibitor activities. Calcium chloride infusion increased marbling, decreased lean firmness, increased lean color score, and increased dressing percentage (P< .05). Infusion of carcasses with CaCl2decreased (P< .05) shear force at all postmortem times. Infusion of carcasses with CaCl2had no effect on cathepsins B and B + L activities, but it had a significant effect on CDP-I, CDP-II, and CDP inhibitor activities.(ABSTRACT TRUNCATED AT 250 WORDS)

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°C). The R2between 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.