Minor differences in perceived sheepmeat eating quality scores of Australian, Chinese and American consumers.

Understanding consumer sensory perceptions of sheepmeat is essential for consumer satisfaction post-purchase. Meat Standards Australia (MSA) sensory protocols have been effectively utilised in beef for international consumers however, to date sheepmeat testing is largely limited to Australian consumers. This study measured the sensory responses (liking of odour, tenderness, juiciness, liking of flavour, and overall liking) of 2160 untrained American, Australian and Chinese consumers to grilled longissimus lumborum (LL) and semimembranosus (SM) muscles from 164 lambs and 168 yearlings. Across countries there was no difference in juiciness or overall liking sensory scores. American consumers scored tenderness, flavour and odour slightly higher than Australian consumers, and Chinese consumer scores were lowest. Consistently for all countries, sensory scores were greatest in the LL muscle, in lambs compared to yearlings particularly for the LL, and Merino sired and female lambs. These results indicate that cultural background has minimal impact on sensory perceptions of sheepmeat, and provides valuable information for future eating quality prediction models.

Strategies to predict and improve eating quality of cooked beef using carcass and meat composition traits in Angus cattle.

Product quality is a high priority for the beef industry because of its importance as a major driver of consumer demand for beef and the ability of the industry to improve it. A 2-prong approach based on implementation of a genetic program to improve eating quality and a system to communicate eating quality and increase the probability that consumers' eating quality expectations are met is outlined. The objectives of this study were 1) to identify the best carcass and meat composition traits to be used in a selection program to improve eating quality and 2) to develop a relatively small number of classes that reflect real and perceptible differences in eating quality that can be communicated to consumers and identify a subset of carcass and meat composition traits with the highest predictive accuracy across all eating quality classes. Carcass traits, meat composition, including Warner-Bratzler shear force (WBSF), intramuscular fat content (IMFC), trained sensory panel scores, and mineral composition traits of 1,666 Angus cattle were used in this study. Three eating quality indexes, EATQ1, EATQ2, and EATQ3, were generated by using different weights for the sensory traits (emphasis on tenderness, flavor, and juiciness, respectively). The best model for predicting eating quality explained 37%, 9%, and 19% of the variability of EATQ1, EATQ2, and EATQ3, and 2 traits, WBSF and IMFC, accounted for most of the variability explained by the best models. EATQ1 combines tenderness, juiciness, and flavor assessed by trained panels with 0.60, 0.15, and 0.25 weights, best describes North American consumers, and has a moderate heritability (0.18 ± 0.06). A selection index (I= -0.5[WBSF] + 0.3[IMFC]) based on phenotypic and genetic variances and covariances can be used to improve eating quality as a correlated trait. The 3 indexes (EATQ1, EATQ2, and EATQ3) were used to generate 3 equal (33.3%) low, medium, and high eating quality classes, and linear combinations of traits that best predict class membership were estimated using a predictive discriminant analysis. The best predictive model to classify new observations into low, medium, and high eating quality classes defined by the EATQ1 index included WBSF, IMFC, HCW, and marbling score and resulted in a total error rate of 47.06%, much lower than the 60.74% error rate when the prediction of class membership was based on the USDA grading system. The 2 best predictors were WBSF and IMFC, and they accounted for 97.2% of the variability explained by the best model.

Effect of vitamin D, zilpaterol hydrochloride supplementation, and postmortem aging on shear force measurements of three muscles in finishing beef steers.

Vitamin D (D3) supplementation may be used to increase tenderness in beef from cattle fed zilpaterol hydrochloride (ZH). The study was arranged as a 2 × 2 factorial with fixed effects of ZH (no ZH or ZH fed at 8.3 mg/kg DM for 20 d with a 3-d withdrawal) and D3 (no D3 or 500,000 IU D3·steer·d for 10 d prior to harvest). Cattle ( = 466) were harvested in 2 blocks on the basis of BW with subsequent collection of carcass data. Full loins and inside rounds ( = 144 of each subprimal) were collected for fabrication of 5 steaks from the longissimus lumborum (LL), gluteus medius (GM), and semimembranosus (SM), which were aged for 7, 14, 21, 28, or 35 d. Warner-Bratzler shear force (WBSF) was used to evaluate mechanical tenderness of LL, GM, and SM steaks at all aging periods. Slice shear force (SSF) analysis was conducted on only 14- and 21-d LL steaks. No interactions ( > 0.05) between ZH and D3 occurred throughout the entire study. Supplementing ZH resulted in increased HCW ( < 0.01), larger LM area ( < 0.01), and improved calculated yield grades ( < 0.01) with decreases in fat thickness ( = 0.02) and marbling scores ( = 0.05). Supplementation with D3 increased calculated yield grade ( < 0.01) and decreased ( = 0.01) rib eye area. Feeding ZH increased ( ≤ 0.05) WBSF of LL steaks at each postmortem age interval, whereas D3 had no effect ( > 0.05) on WBSF or SSF of LL steaks. Like for WBSF, ZH supplementation increased SSF values at 14 and 21 d postmortem ( < 0.01) compared with those for non-ZH steaks. There was an interaction between ZH and postmortem age ( < 0.01) for WBSF of LL steaks. At 7 d LL steaks from ZH steers sheared over 0.6 kg greater than non-ZH steaks; however, by 21 d this difference was reduced to an average of 0.2 kg. Differences in distribution between LL steaks below 3.0 kg from non-ZH and ZH-fed cattle were also notable ( ≤ 0.05) through 21 d of aging. At 35 d postmortem a high proportion of LL steaks (68.5%) from ZH-fed steers required less than 3.0 kg to shear. Supplementation with ZH and D3 had no impact ( > 0.05) on WBSF values of GM steaks. Feeding ZH did not alter WBSF of SM steaks, but at 28 d D3 increased ( = 0.04) WBSF values. Shear force in ZH steaks was not effectively reduced by feeding D3 for 10 d to steers prior to harvest. Aging, however, was an effective method of reducing initially greater shear force values in LL steaks and, to a lesser degree, GM steaks from ZH-fed cattle.

Assessment of volatile compounds, neutral and polar lipid fatty acids of four beef muscles from USDA Choice and Select graded carcasses and their relationships with consumer palatability scores and intramuscular fat content.

Fatty acids (FA) in neutral and polar lipids (NL and PL) and volatile compounds were determined in Gluteus medius (GM), Longissimus lumborum (LL), Serratus ventralis (SV), and Semimembranosus (SM) muscles from upper 2/3 USDA Choice and Select quality grades (QG). Concentrations of NL FA (mg/g) were influenced by intramuscular fat (IMF) content being greater in upper 2/3 Choice compared with Select. The SV contained greater concentrations of NL FA; meanwhile, the SM contained the lowest quantities of NL FA. Percentages (g/100g of total FA) of NL SFA and MUFA were increased in beef with greater IMF content. Concentrations and percentages of PL FA had muscle specific differences between QG. Volatile compounds were primarily affected by muscle. Increases in SFA and MUFA were related with consumer liking, regardless of lipid fraction. Overall the influence of QG on SFA and MUFA was muscle specific. Therefore, each muscle may require specific considerations when considering FA, volatile compounds, and ultimately consumer liking.

Genetic parameters for sensory traits in longissimus muscle and their associations with tenderness, marbling score, and intramuscular fat in Angus cattle.

The objective of this study was to estimate heritabilities for sensory traits and genetic correlations among sensory traits and with marbling score (MS), Warner-Bratzler shear force (WBSF), and intramuscular fat content (IMFC). Samples of LM from 2,285 Angus cattle were obtained and fabricated into steaks for laboratory analysis and 1,720 steaks were analyzed by a trained sensory panel. Restricted maximum likelihood procedures were used to obtain estimates of variance and covariance components under a multitrait animal model. Estimates of heritability for MS, IMFC, WBSF, tenderness, juiciness, and connective tissue traits were 0.67, 0.38, 0.19, 0.18, 0.06, and 0.25, respectively. The genetic correlations of MS with tenderness, juiciness, and connective tissue were estimated to be 0.57 ± 0.14, 1.00 ± 0.17, and 0.49 ± 0.13, all positive and strong. Estimated genetic correlations of IMFC with tenderness, juiciness, and connective tissue were 0.56 ± 0.16, 1.00 ± 0.21, and 0.50 ± 0.15, respectively. The genetic correlations of WBSF with tenderness, juiciness, and connective tissue were all favorable and estimated to be -0.99 ± 0.08, -0.33 ± 0.30 and -0.99 ± 0.07, respectively. Strong and positive genetic correlations were estimated between tenderness and juiciness (0.54 ± 0.28) and between connective tissue and juiciness (0.58 ± 0.26). In general, genetic correlations were large and favorable, which indicated that strong relationships exist and similar gene and gene networks may control MS, IMFC, and juiciness or WBSF, panel tenderness, and connective tissue. The results from this study confirm that MS currently used in selection breeding programs has positive genetic correlations with tenderness and juiciness and, therefore, is an effective indicator trait for the improvement of tenderness and juiciness in beef. This study also indicated that a more objective measure, particularly WBSF, a trait not easy to improve through phenotypic selection, is an excellent candidate trait for genomic selection aimed at improving eating satisfaction.

Sensory evaluation of tender beef strip loin steaks of varying marbling levels and quality treatments.

The palatability of tender [Warner-Bratzler shear force values <33.34N (3.4kg)] beef strip loins of 10 different treatments [USDA Prime, High Choice (upper 1/3 Choice), Low Choice (lower 1/3 Choice), Select, Standard, Australian Wagyu, American Wagyu, Holstein Select, Holstein Top Choice (upper 2/3 Choice) and Grass-finished] was evaluated by consumers and a trained flavor panel. In general, tenderness, juiciness, flavor, and overall liking ratings as well as acceptability percentage for each trait, increased with increased fat levels. Moreover, overall liking was highly correlated (P<0.01) with flavor liking (r=0.96) as well as fat percentage (r=0.79). Beef flavor scores were positively associated (P<0.01) with fat-like (r=0.67) and umami (r=0.59) flavors. Fat level was the primary driver of beef flavor acceptability in all samples when no undesirable off-flavors were present.

Comparative effects of beta-adrenergic agonist supplementation on the yield and quality attributes of selected subprimals from calf-fed Holstein steers.

Mechanical portioning tests were performed on beef rib, strip loin, tenderloin, and top sirloin subprimals obtained from calf-fed Holstein steers to characterize the influence of zilpaterol hydrochloride (ZH), ractopamine hydrochloride (RH), or no ß-adrenergic agonist (ßAA; CON) on subprimal and steak yield. In addition, ßAA effects on tenderness, composition, and raw and cooked color of steaks from the aforementioned strip loin subprimals were characterized. At 14 to 15 d (ribs, tenderloins, and top sirloin) or 16 d (strip loin) postmortem, subprimals were portioned into steaks using a mechanical portioning machine. The appropriate variables were measured before and after portioning to determine ßAA influence on trimmed and untrimmed subprimal weight, subprimal length (rib only), steak weight and yield, and steak thickness (rib only). Steaks obtained from the strip loin subprimals were subjected to analysis of raw instrument color (L*, a*, b*), proximate composition, and pH. In addition, strip steaks were aged (16 or 23 d) before analysis of cooked internal color, Warner-Bratzler shear force (WBSF), and slice shear force (SSF). Briefly, ZH supplementation increased (P < 0.01) the weight of all subprimals when compared to CON. Furthermore, subprimals from CON animals consistently had fewer and lighter steaks (P ≤ 0.04) than subprimals from ZH-fed steers. Additionally, raw steaks from ZH cattle were a less vivid red (lower a* and saturation index values; P < 0.01) when compared to CON and RH steaks, which did not differ (P > 0.05). There was no interaction between ßAA treatment and postmortem aging length for WBSF or SSF (P > 0.10). However, CON steaks (3.25 kg) had lower WBSF values (P < 0.05) than ZH or RH steaks (3.68 and 3.67 kg, respectively). Regardless, aging for 23 d vs. 16 d resulted in decreased WBSF and SSF (P < 0.01) for all ßAA treatments. Although differences were numerically small, evaluations indicated the internal cooked surfaces of ZH and RH steaks were less red (P < 0.05) than CON steaks. Overall, these data reemphasize increased subprimal weights due to ßAA supplementation, particularly ZH. However, the data are not indicative of increased steak yield due to ßAA supplementation. Furthermore, the data demonstrate ßAA supplementation increases the shear force of calf-fed Holstein strip steaks regardless of postmortem aging period. However, no differences in shear force between the ßAA treatments (ZH or RH) were noted.

Comparative effects of supplementing beef steers with zilpaterol hydrochloride, ractopamine hydrochloride, or no beta agonist on strip loin composition, raw and cooked color properties, shear force, and consumer assessment of steaks aged for fourteen or twenty-one days postmortem.

Beef steers (n = 1,914) were assigned to 1 of 3 ß-adrenergic agonist (ßAA) supplementation treatments-zilpaterol hydrochloride (ZH; 8.3 mg/kg of DM for 20 d with 3-d withdrawal), ractopamine hydrochloride (RH; 308 mg·head(-1)·d(-1) for 28 d), or no ßAA (CON)-to determine the effects on consumer eating quality. Strip loins (n = 1,101; CON = 400, RH = 355, and ZH = 346) were obtained and fabricated into 2.5-cm-thick steaks for proximate, Warner-Bratzler shear force (WBSF), slice shear force (SSF), and consumer analyses; steaks were aged until 14 or 21 d postmortem. Fat and moisture contents were not affected by ßAA supplementation (P > 0.05), but strip steaks from steers fed ZH had more protein (P < 0.01) than those from steers fed CON or RH, which were similar. An interaction between ßAA and aging was observed (P < 0.01) for WBSF but not SSF. Within steaks aged 14 d, ZH steaks required the most force to shear, RH steaks were intermediate, and CON steaks had the lowest WBSF values; however, RH steaks had a stronger response to aging than CON or ZH steaks, resulting in the lowest WBSF values at 21 d. Slice shear force values were greater (P < 0.01) in steaks from steers fed ZH than in steaks from steers fed CON or RH, which did not differ. Following shear force analyses, steaks within 2 SD of each treatment mean for WBSF were selected randomly for consumer assessment of eating quality. Consumer testing (n = 400; 200/postmortem aging period) was arranged in a 3 × 3 factorial representing 3 quality grades (Select, Low Choice, and Premium Choice) and 3 treatments (ZH, RH, and CON). In steaks aged 14 d, ßAA supplementation affected (P < 0.01) tenderness, flavor, and overall liking and tenderness acceptability, resulting in lower consumer scores for ZH than CON and RH; however, juiciness, flavor, and overall acceptability were similar (P > 0.05). In steaks aged 21 d, feeding ßAA influenced (P < 0.01) only tenderness and juiciness scores. Despite these differences, ßAA did not affect (P > 0.05) acceptability. Quality grade impacted (P < 0.01) all traits and acceptability in steaks aged 14 and 21 d. In 14-d steaks, Premium Choice typically was scored higher than Low Choice or Select; however, consumers rated 21-d Low Choice and Premium Choice similarly-both receiving greater scores than Select. Consumers detected several differences in eating quality at 14 d because of ßAA supplementation. Increasing aging from 14 to 21 d mitigated differences in shear force and tenderness scores because of feeding ZH, so that tenderness and overall acceptability were similar between ZH, RH, and CON.

Consumer assessment of beef palatability from four beef muscles from USDA Choice and Select graded carcasses.

Consumer sensory analysis was conducted to determine differences in beef palatability between two quality grade categories [Upper 2/3 (Top) Choice and Select] and four muscles [longissimus lumborum (LL), gluteus medius (GM), serratus ventralis (SV), and semimembranosus (SM)]. Generally, tenderness, flavor, and overall liking scores were more desirable for Top Choice compared to Select, regardless of muscle. Consumers rated LL as more tender (P<0.05) than SV and SM, but similar to GM (P=0.52). Overall and flavor acceptability were similar (P>0.05) between LL, GM, and SV, regardless of quality grade. Consumer overall liking was most highly correlated with flavor liking (r=0.85). When tenderness was acceptable, flavor and juiciness played a major role in determining overall acceptability. Overall liking of GM and SV from Top Choice carcasses was superior to LL from Select carcasses and comparable to LL from Top Choice carcasses.

U. S. consumer perceptions of U. S. and Canadian beef quality grades.

A U.S. consumer (n = 642) study (Baltimore, MD; Phoenix, AZ; and Lubbock, TX) was conducted to compare consumer sensory scores of U.S. beef (83 USDA Choice [Choice] and 96 USDA Select [Select]) and Canadian beef (77 AAA and 82 AA) strip loins. Strip loins (n = 338) were obtained from beef processors in Canada and the United States and were wet aged until 21 d postmortem at 2°C. Marbling scores were assigned at 21 d and loins were paired according to quality grades and marbling score. Strip loins were fabricated into 2.54-cm thick steaks; steaks were vacuum packaged and frozen until further evaluations. Proximate analysis was performed to compare fat, moisture, and protein. Choice and Canadian AAA had similar marbling scores and intramuscular fat. Both Choice and Canadian AAA had greater (P < 0.05) marbling scores and intramuscular fat than Canadian AA, but Select strip loins had intermediate values that were not different from any of the other grades (P > 0.05). Consumers' opinions did not differ when comparing equivalent grades (Choice with Canadian AAA and Select with Canadian AA), but they rated Choice and Canadian AAA more palatable than Select and Canadian AA for all sensory attributes (P < 0.05). Regarding percentage of acceptability and likelihood to buy score, consumers indicated a preference and greater probability to buy (P = 0.001 and P = 0.004, respectively) strip loin steaks from higher quality grade carcasses (Choice and Canadian AAA) than lower quality grade carcasses (Select and Canada AA). Additionally, consumers gave their opinion of Canadian beef, where its quality and safety were rated as "good" to "excellent" for both attributes (76.72% and 88.36%, respectively; P < 0.05), feeling confident in beef that is imported from Canada. In the same way, consumers indicated that country-of-origin labeling was a minimal factor influencing their beef steak purchasing decisions. Results from this consumer study indicated U.S. consumers could not differentiate between U.S. and Canadian beef within comparable quality grades; however, strip loin steaks from higher quality grades were more palatable than lower quality grades according to consumer scores for eating quality traits.

MEAT SCIENCE AND MUSCLE BIOLOGY SYMPOSIUM--implant and beta agonist impacts on beef palatability.

The use of anabolic implants has a long-standing place in the cattle feeding industry, due to their positive impact on growth performance and subsequent profitability. However, implants can have adverse effects on carcass quality, shear force, and eating quality depending on the dose and frequency, or what some refer to as the aggressiveness of the implant regimen administered. Within the past decade, a new class of growth promotants, known as ß-adrenergic agonists (ßAA), has emerged in the beef feeding industry in the United States. Currently, 2 have gained U.S. Food and Drug Administration approval for use in beef finishing diets to improve performance and carcass yields. Much like anabolic implants, these repartitioning agents can have negative effects on Warner-Bratzler shear force (WBSF), but the differences do not necessarily translate directly to consumer responses for palatability and acceptance in some instances, especially when tenderness is managed through proper postmortem aging. As researchers continued to investigate the mechanisms responsible for the impact of ßAA, inevitably this led to consideration of the interaction between ßAA and anabolic implants. Early work combining zilpaterol hydrochloride (ZH) with anabolic implants improved performance, carcass yield, and meat yield with additive negative effects on WBSF. Similar results were produced when pairing ZH with anabolic steroids equipped with various release patterns. As with any tool, the key to success is proper management. Certain cattle populations may be better suited to receive growth promotants such as implants and ßAA, and postmortem management of subprimal cuts becomes vital when producers take more aggressive approaches to improve performance and yield. The objective of this review is to overview research findings related to the impact of growth promotant technologies on beef palatability, focusing specifically on the role of implants and ßAA on carcass quality, beef tenderness, and consumer responses for meat palatability.

Genome-wide association study of concentrations of iron and other minerals in longissimus muscle of Angus cattle.

The objective of this study was to characterize variation and identify SNP and chromosomal regions associated with mineral concentrations in LM of Angus beef cattle. Samples of LM from 2,285 Angus cattle were obtained, and concentrations of 7 minerals, including iron, magnesium, manganese, phosphorus, potassium, sodium, and zinc, were quantified. Genomic DNA extracted from the ground beef sample used for mineral composition was genotyped with the Bovine SNP50 Infinium II BeadChip, and effects of SNP on each trait were estimated using the Bayes-Cπ module of GenSel software. Pedigree-based estimates of heritabilities and corresponding genetic variances indicate iron was the only mineral concentration that could be considered a good candidate for manipulation by genomic selection. The amount of variation that could be accounted for by SNP genotypes was concordant with pedigree-based heritabilities and varied from very low for potassium and sodium (<0.09) to medium high (0.37) for iron. Although significant chromosomal regions were identified for all minerals analyzed in this study, further study focused on iron. Seven regions on 6 chromosomes (1, 2, 7, 10, 15, and 28) were identified to have a major effect on the iron content of LM in Angus cattle. The accuracy of direct genomic values (DGV) for iron concentration was estimated using a 5-fold cross-validation strategy. The accuracy of DGV estimated as the genetic correlation between DGV and the phenotype (iron concentration) adjusted for contemporary groups was 0.59. A bivariate animal model was used to estimate genetic correlations between iron concentrations and a reduced set of economically important carcass traits: HCW, rib eye area, calculated USDA yield grade, percent KPH, and marbling score. The genetic correlations between iron concentration and HCW, percentage KPH, marbling score, and rib eye area were small (-0.19 to 0.15) and nonsignificant. Although still weak (0.22), a positive significant genetic correlation was identified between iron content and USDA calculated yield grade. Beef is a major contributor of iron and zinc in the human diet, and this study found that iron content might be effectively manipulated through marker-assisted selection programs, without compromising other carcass and palatability traits.

Effect of rate of body weight gain in steers during the stocker phase. I. Growth, partitioning of fat among depots, and carcass characteristics of growing-finishing beef cattle.

Two experiments were conducted to examine the effect of growth rate to similar age or BW on fat deposition in stocker cattle grazing dormant native range (DNR) or winter wheat pasture (WP). In each experiment, fall-weaned Angus steers were randomly allotted to 1 of 4 stocker production programs: 1) control, 1.02 kg/d of a 40% CP cottonseed meal-based supplement during grazing of DNR (CON); 2) corn/soybean meal-based supplement fed at 1% of BW during grazing of DNR (CORN); 3) grazing WP at a high stocking rate to achieve a low rate of BW gain (LGWP); and 4) grazing WP at a low stocking rate to achieve a high rate of BW gain (HGWP). In Exp. 1, a subset of steers (3 steers per treatment) was harvested after winter grazing (138 d) at similar age. The remaining WP steers were transitioned into the finishing phase, whereas DNR steers were allowed to graze the same native range pastures for another 115 d without supplementation before entering the feedyard. In Exp. 2, steers grazed their respective pastures until each treatment reached an estimated HCW of 200 kg (262, 180, 142, and 74 d, respectively, for the CON, CORN, LGWP, and HGWP treatments), at which time a subset of steers (4 steers per treatment) were selected for intermediate harvest before finishing. In both experiments, the remaining steers were fed a finishing diet to a common 12th-rib fat thickness of 1.27 cm. In Exp. 1, winter grazing ADG was 0.19, 0.52, 0.68, and 1.37 ± 0.03 kg/d; and in Exp. 2, winter/summer grazing ADG was 0.46, 0.61, 0.83, and 1.29 ± 0.02 kg/d, respectively for CON, CORN, LGWP, and HGWP treatments. At intermediate harvest in Exp. 1, HGWP steers had greater (P < 0.01) 12th-rib fat thickness and marbling scores, compared with the other treatments. However, in Exp. 2, LGWP steers had greater (P < 0.01) marbling scores compared with HGWP steers, which were greater than DNR steers. At final harvest in Exp. 1, LGWP steers had greater (P < 0.01) 12th-rib fat thickness and smaller LM area, compared with the other treatments; however, there were no differences (P = 0.99) in final marbling scores. In Exp. 2, CON steers had lower (P < 0.05) 12th-rib fat thickness and tended (P = 0.10) to have greater marbling scores, compared with the other treatments. These data suggest that changes in the partitioning of fat among depots during the stocker phase may not be reflected after finishing when steers are fed to a common 12th-rib fat thickness.

The heritabilities, phenotypic correlations, and genetic correlations of lean color and palatability measures from longissimus muscle in beef cattle.

Data from a study conducted over 5 yr were analyzed to determine heritability estimates of LM lean color, as measured by subjective scoring and Hunter Colorimeter readings, and palatability, as measured by trained sensory panelists and Warner-Bratzler shear force (WBSF). Phenotypic and genetic correlations were determined between each of the measures of palatability and color. There were 1,066 cattle representing 12 different breeds in the study. Subjective lean color and a* (redness) and b* (yellowness) values were moderately heritable, 0.34 ± 0.122, 0.29 ± 0.115 and 0.28 ± 0.120, respectively, whereas the L* (lightness) was lowly heritable, 0.09 ± 0.087. The heritability of WBSF was moderately heritable ranging from 0.23 ± 0.114 (3 d) to 0.42 ± 0.148 (21 d). Sustained tenderness, as measured by sensory panelists, was found to be moderately heritable ranging from 0.16 ± 0.108 (21 d) to 0.33 ± 0.135 (14 d). Sustained juiciness and beef flavor, as measured by sensory panelists, were found to be lowly to moderately heritable ranging from 0.00 ± 0.089 (21 d) to 0.18 ± 0.105 (14 d) and 0.00 ± 0.080 (7 d) to 0.18 ± 0.110 (21 d), respectively. The significant phenotypic correlations were those between WBSF and subjective lean color, L* value, and a* value; both initial and sustained tenderness as well as beef flavor were correlated with subjective lean color and L* value. Flavor intensity and overall mouthfeel were associated with subjective lean color, L* value, a* value, and b* value. Both a* and b* values were highly correlated genetically with WBSF, -0.71 and -0.72, respectively, and subjective lean color was moderately correlated with WBSF, -0.46. The genetic correlation between subjective lean color and initial tenderness was also high, 0.56, whereas that between a* value and initial tenderness was 0.43, which was similar to that found between b* value and initial tenderness, 0.44. The genetic correlations between subjective lean color, a* value, and b* value with sustained tenderness were all high at 0.58, 0.70, and 0.58, respectively. The genetic correlations between a* value and b* value with beef flavor were low to moderate at 0.12 and 0.19, respectively, whereas that between subjective lean color and beef flavor was high, 0.64. The genetic correlations between a* value, b* value, and lean color with sustained juiciness were all moderate correlations at -0.35, -0.23, and -0.45, respectively. The genetic correlations between a* value and b* value with overall mouthfeel were high at 0.80 and 0.79, respectively, whereas that between subjective lean color and overall mouthfeel was moderate, 0.46. In conclusion, regardless of measurement technique of lean color, it was not only heritable but was also moderately to highly correlated with measurements of palatability in beef from LM.

Comparison of gene expression and fatty acid profiles in concentrate and forage finished beef.

Fatty acid profiles and intramuscular expression of genes involved in fatty acid metabolism were characterized in concentrate- (CO) and forage- (FO) based finishing systems. Intramuscular samples from the adductor were taken at slaughter from 99 heifers finished on a CO diet and 58 heifers finished on a FO diet. Strip loins were obtained at fabrication to evaluate fatty acid profiles of LM muscle for all 157 heifers by using gas chromatography fatty acid methyl ester analysis. Composition was analyzed for differences by using the General Linear Model (GLM) procedure in SAS. Differences in fatty acid profile included a greater atherogenic index, greater percentage total MUFA, decreased omega-3 to omega-6 ratio, decreased percentage total PUFA, and decreased percentage omega-3 fatty acids in CO- compared with FO-finished heifers (P<0.05). Fatty acid profiles from intramuscular samples were ranked by the atherogenic index, and 20 heifers with either a high (HAI; n=10) or low (LAI; n=10) atherogenic index were selected for gene expression analysis using real-time PCR (RT-PCR). Gene expression data for the 20 individuals were analyzed as a 2 by 2 factorial arrangement of treatments using the GLM procedure in SAS. There was no significant diet × atherogenic index interaction identified for any gene (P>0.05). Upregulation was observed for PPARγ, fatty acid synthase (FASN), and fatty acid binding protein 4 (FABP4) in FO-finished compared with CO-finished heifers in both atherogenic index categories (P<0.05). Upregulation of diglyceride acyl transferase 2 (DGAT2) was observed in FO-finished heifers with a HAI (P<0.05). Expression of steroyl Co-A desaturase (SCD) was upregulated in CO-finished heifers with a LAI, and downregulated in FO-finished heifers with a HAI (P<0.05). Expression of adiponectin (ADIPOQ) was significantly downregulated in CO-finished heifers with a HAI compared with all other categories (P<0.05). The genes identified in this study which exhibit differential regulation in response to diet or in animals with extreme fatty acid profiles may provide genetic markers for selecting desirable fatty acid profiles in future selection programs.

Genetic parameters for concentrations of minerals in longissimus muscle and their associations with palatability traits in Angus cattle.

The objective of this study was to estimate genetic parameters for concentrations of minerals in LM and to evaluate their associations with beef palatability traits. Samples of LM from 2,285 Angus cattle were obtained and fabricated into steaks for analysis of mineral concentrations and for trained sensory panel assessments. Nine minerals, including calcium, copper, iron, magnesium, manganese, phosphorus, potassium, sodium, and zinc, were quantified. Restricted maximum likelihood procedures were used to obtain estimates of variance and covariance components under a multiple-trait animal model. Estimates of heritability for mineral concentrations in LM varied from 0.01 to 0.54. Iron and sodium were highly and moderately heritable, respectively, whereas the other minerals were lowly heritable except for calcium, copper, and manganese, which exhibited no genetic variation. Strong positive genetic correlations existed between iron and zinc (0.49, P < 0.05), between magnesium and phosphorus (0.88, P < 0.05), between magnesium and sodium (0.68, P < 0.05), and between phosphorus and potassium (0.69, P < 0.05). Overall tenderness assessed by trained sensory panelists was positively associated with manganese, potassium, and sodium and negatively associated with phosphorus and zinc concentrations (P < 0.05). Juiciness assessed by trained sensory panelists was negatively associated with magnesium and positively associated with manganese and sodium concentrations (P < 0.05). Livery or metallic flavor was not associated with any of the minerals (P > 0.05). Beefy flavor was positively associated with calcium, iron, and zinc and negatively associated with sodium concentration, whereas a painty or fishy flavor was positively associated with sodium and negatively associated with calcium and potassium concentrations (P < 0.05). Beef is a major contributor of iron and zinc in the human diet, and these results demonstrate sufficient genetic variation for these traits to be improved through marker-assisted selection programs without compromising beef palatability.

Validation comparing the effectiveness of a lactic acid dip with a lactic acid spray for reducing Escherichia coli O157:H7, Salmonella, and non-O157 Shiga toxigenic Escherichia coli on beef trim and ground beef.

The objective of this research was to compare the effectiveness of two application methods (dip versus spray) of 4.4% lactic acid for reducing pathogens on inoculated beef trim and in ground beef. Beef trim inoculated with cocktail mixtures of E. coli O157:H7, non-O157 Shiga toxigenic E. coli (STEC), or Salmonella (10(5) to 10(6) CFU/g) at separate times was subjected to five treatments: lactic acid spray (LS), lactic acid dip (LD), water spray (WS), water dip (WD), and untreated control (CTL). Intervention effectiveness for pathogen reduction was measured at 1 and 20 h after treatment on beef trim. Trim was then ground and intervention effectiveness was measured 1 h, 24 h, 72 h, and 7 days after grinding. The LD treatment reduced all pathogens significantly (P < 0.05); E. coli O157:H7 was reduced by 0.91 to 1.41 log CFU/g on beef trim and ground beef, non-O157 STEC by 0.48 to 0.82 log CFU/g, and Salmonella by 0.51 to 0.81 log CFU/g. No other treatment significantly reduced any pathogen, although the WD treatment noticeably reduced (P > 0.05) both E. coli O157:H7 and non-O157 STEC populations compared with the CTL. The LS treatment reduced E. coli O157:H7 and Salmonella by up to 0.5 log CFU/g on beef trim, but these reduced counts did not significantly differ (P > 0.05) from the CTL counts. Overall, the LD treatment was most effective for reducing all pathogens and is the best of these options for improving the safety of beef trim and subsequently produced ground beef.

Genetic parameters for carnitine, creatine, creatinine, carnosine, and anserine concentration in longissimus muscle and their association with palatability traits in Angus cattle.

The objective of this study was to estimate genetic parameters for carnitine, creatine, creatinine, carnosine, and anserine concentration in LM and to evaluate their associations with Warner-Bratzler shear force (WBSF) and beef palatability traits. Longissimus muscle samples from 2,285 Angus cattle were obtained and fabricated into steaks for analysis of carnitine, creatine, creatinine, carnosine, anserine, and other nutrients, and for trained sensory panel and WBSF assessments. Restricted maximum likelihood procedures were used to obtain estimates of variance and covariance components under a multiple-trait animal model. Estimates of heritability for carnitine, creatine, creatinine, carnosine, and anserine concentrations in LM from Angus cattle were 0.015, 0.434, 0.070, 0.383, and 0.531, respectively. Creatine, carnosine, and anserine were found to be moderately heritable, whereas almost no genetic variation was observed in carnitine and creatinine. Moderate positive genetic (0.25, P < 0.05) and phenotypic correlations (0.25, P < 0.05) were identified between carnosine and anserine. Medium negative genetic correlations were identified between creatine and both carnosine (-0.53, P < 0.05) and anserine (-0.46, P < 0.05). Beef and livery/metallic flavor were not associated with any of the 5 compounds analyzed (P > 0.10), and carnitine concentrations were not associated (P > 0.10) with any of the meat palatability traits analyzed. Carnosine was negatively associated with overall tenderness as assessed by trained sensory panelists. Similar negative associations with overall tenderness were identified for creatinine and anserine. Painty/fishy was the only flavor significantly and negatively associated with creatinine and carnosine. These results provide information regarding the concentration of these compounds, the amount of genetic variation, and evidence for negligible associations with beef palatability traits in LM of beef cattle.

Effects of postmortem calcium chloride injection on meat palatability traits of strip loin steaks from cattle supplemented with or without zilpaterol hydrochloride.

An experiment was conducted to determine the effects of zilpaterol hydrochloride mM supplementation (ZH; 8.3 mg/kg on a DM basis for 20 d) and calcium chloride injection [CaCl(2), 200 at 5% (wt/wt) at 72 h postmortem] on palatability traits of beef (Bos taurus) strip loin steaks. Select (USDA) strip loins were obtained from control (no ZH = 19) and ZH-supplemented carcasses (n = 20). Right and left sides were selected alternatively to serve as a control (no INJ) or CaCl(2)-injected (INJ) and stored at 4°C. Before injecting the subprimals (72 h postmortem), 2 steaks were cut for proximate, sarcomere length, and myofibrillar fragmentation index (MFI) analyses. At 7 d postmortem each strip loin was portioned into steaks, vacuum packaged, and aged for the appropriate period for Warner-Bratzler shear force (WBSF; 7, 14, 21, and 28 d postmortem), trained sensory analysis (14 and 21 d postmortem), purge loss (7 d), and MFI (3, 7, 14, 21, and 28 d postmortem). Results indicated steaks from both ZH supplementation and INJ had reduced WBSF values as days of postmortem aging increased. The WBSF values of ZH steaks were greater (P < 0.05) than no ZH steaks at each postmortem aging period. The INJ steaks had lower WBSF values (P < 0.05) than non-injected steaks. A greater percentage (91 vs. 71%) of steaks had WBSF values < 4.6 kg from steers with no ZH supplementation at 7 d postmortem, but the percentage did not differ (P > 0.05) due to ZH at 14, 21, or 28 d or due to INJ at any aging period. Trained panelists rated tenderness less in ZH steaks than steaks with no ZH at 14 d and 21 d. However, INJ improved (P < 0.05) the tenderness ratings and flavor intensity of the trained panelists, compared with their non-injected cohorts at 21 d. Zilpaterol hydrochloride supplementation reduced (P < 0.05) MFI values, but INJ resulted in greater (P < 0.05) MFI values compared with no INJ. Subprimals from ZH and INJ showed greater purge loss (P < 0.05). Although no interactions were found with ZH and CaCl(2), injecting USDA Select strip loins from ZH-fed cattle can help reduce the normal WBSF variation as it does in steaks from non-ZH-fed cattle.

Genetic polymorphisms in bovine transferrin receptor 2 (TFR2) and solute carrier family 40 (iron-regulated transporter), member 1 (SLC40A1) genes and their association with beef iron content.

Beef is considered to be an excellent source of dietary iron. However, little is known about the genetic control of beef iron content. We hypothesized that genetic polymorphisms in transferrin receptor 2 (TFR2) and solute carrier family 40 (iron-regulated transporter), member 1 (SLC40A1) could influence skeletal muscle iron content. The objective of this study was to use Angus cattle to identify single-nucleotide polymorphisms (SNPs) in the exons and flanking regions of the bovine TFR2 and SLC40A1 genes and to evaluate the extent to which genetic variation in them was associated with bovine longissimus dorsi muscle iron content. Ten novel SNPs were identified in TFR2, of which one SNP tended to be associated (P < 0.013) with skeletal muscle iron content. Nine novel SNPs in SLC40A1, NC007300: rs133108154, rs137140497, rs135205621, rs136600836, rs134388440, rs136347850, rs134186279, rs134621419 and rs137555693, were identified, of which SNPs rs134388440, rs136347850 and rs137555693 were significantly associated (P < 0.007) with skeletal muscle iron content. High linkage disequilibrium was observed among SLC40A1 SNPs rs134388440, rs136347850 and rs137555693 (R(2) > 0.99), from which two haplotypes, TGC and CAT, were defined. Beef from individuals that were homozygous for the TGC haplotype had significantly (P < 0.001) higher iron content than did beef from CAT homozygous or heterozygous individuals. The estimated size of effect of the identified haplotypes was 0.3% of the phenotypic variance. In conclusion, our study provides evidence for genetic control of beef iron concentration. Moreover, SNPs identified in SLC40A1, rs134388440, rs136347850 and rs137555693 might be useful markers for the selection of Angus cattle for altered iron content.