Introduction
Lubabegron fumarate (LUB; Experior, Elanco Animal Health, Indianapolis, Indiana), is labeled for use in beef steers and heifers fed in confinement for slaughter to reduce ammonia gas emissions per pound of live and carcass weight (US Food and Drug Administration [FDA], 2018). This approval is the first of its kind. Other β-adrenergic agonists (β-A), specifically ractopamine hydrochloride (RAC) and zilpaterol hydrochloride (ZIL), were previously approved for increased rate of weight gain, improved feed efficiency, and increased carcass leanness (FDA, 2003; FDA, 2006).
The uniqueness of LUB is its function as both a β-A and β-blocker, or β-antagonist, categorized as a β-modulator. This difference in functionality causes an agonistic response at the β3 receptor, while blocking or performing antagonistic behaviors at β1 and β2 receptors (Dilger et al., 2021). This is a vast departure from RAC or ZIL, which both functioned as β1 and β2 agonists, functions to alter the intracellular energy balance and repartition nutrients to deposit protein and limit lipogenesis, in part due to the activation of the activated protein kinase pathway (Johnson et al., 2014). Currently, the cellular mechanisms by which LUB increases growth are still relatively unknown, although they have been shown to have a limited lipolytic response (Hwang et al., 2022).
With the increased use of LUB in the industry, a better understanding of its potential impact on meat quality is necessary. Data evaluating the effects of LUB on palatability and meat quality have not been widely published. The foremost concern is that LUB can reduce marbling scores from as little as 10° to upwards of 80° of marbling, depending on dose and duration (Kube et al., 2021; Teeter et al., 2021; Vogel et al., 2023). The FDA approval for LUB cited a slight increase in Warner-Bratzler shear force, albeit this increase was “at a level unlikely to be distinguishable by consumers” (FDA, 2018). Corona et al. (2025) presented evidence of decreasing tenderness related to LUB duration for both trained sensory analysis and shear force in conventional beef steers. Moreover, Decker et al. (2026) found decreased tenderness related to LUB use in beef heifers. Additionally, both ZIL and RAC are known to negatively impact tenderness (Garmyn et al., 2010; Arp et al., 2013; Martin et al., 2014).
Holstein steers represent a unique portion of the fed cattle population. They are generally less efficient in comparison to their beef counterparts, resulting in lower average daily gain and necessitating greater days on feed (Albrecht et al., 2006). Nonetheless, these animals still represent a sizable portion of the total fed cattle population. Moreover, there is evidence indicating β-A use negatively effects tenderness in Holstein steers. Notably, Howard et al. (2014) found a decrease in instrumental tenderness by both ZIL and RAC. Martin et al. (2014) also found increases in instrumental tenderness by ZIL and RAC. These tenderness changes translated to trained sensory tenderness differences only by ZIL but not by RAC (Howard et al., 2014). Collectively, these findings demonstrate that Holstein steers may respond differently to β-A supplementation with respect to meat quality attributes, highlighting the importance of evaluating the effects of LUB specifically within dairy-type cattle populations. Therefore, the current study aimed to understand the influence of LUB supplementation on steak dimensionality and palatability traits in Holstein steers.
Materials and Methods
Sample collection and processing
Holstein steers fed LUB at a dose of 3.5 mg/kg of dry matter intake for 0 d (control [CON]), 28 d (LUB28), 56 d (LUB56), or 84 d (LUB84) were identified from Kayser et al. (2024). Cattle were harvested at a large packing plant in the northwest United States and chilled for 24 h before grading and fabrication. Strip loins (IMPS 180, NAMP 2014) from carcasses (N = 212) across 3 USDA quality grades, USDA Select (slight00–slight99, n = 5), Choice (small00–moderate99, n = 174), and USDA Prime (slightly abundant00–abundant99, n = 34), were collected across 2 harvest days and transported to the Gordon W. Davis Meat Laboratory at Texas Tech University. At 7 d postmortem, loins were fabricated into 2.54-cm steaks. Steaks were randomly assigned to an aging period of 7 d, 14 d, 21 d, 28 d, or 35 d aging and then further assigned to an assay: trained sensory or slice shear force (SSF). Once tagged with a unique 4-digit identification number, steaks were pictured for steak dimensionality and vacuum packaged (MULTIVAC, F 100; Multivac Inc., Kansas City, Missouri). Steaks assigned to 7 d of aging were frozen immediately in a single layer (−20°C), while all other steaks were stored at 2°C to 4°C for their allotted aging period and frozen in a single layer at −20°C. Only steaks within the USDA Choice category were utilized for trained sensory and fatty-acid analysis, while shear force was performed on all quality grades.
Steak imaging and dimensionality
Steak dimensionality was performed in the method outlined in Foraker et al. (2022). Steaks were placed on a gridded background and photographed using a digital single-lens reflex camera (Model D7100; Nikon Corp., Thailand) equipped with a fixed-zoom lens (Model DXSWMVREDIF; Nikon Corp., Thailand) and attached to a tripod directly above each steak. Each digital image was processed using an image analysis software (Fiji Image J, version 1.53t; National Institute of Health, Bethesda, Maryland). Steak area (cm2), steak length (cm), and steak widths (cm) at 25%, 50%, 75%, and 87.5% from ventral to dorsal end of each steak were measured. Length-to-width ratios were calculated using the width at 75% from the ventral edge. Each steak was numbered, with 1 representing the most anterior end of the loin, increasing to the most posterior end. Each steak was measured by 2 separate technicians and averaged among analysts for statistical analysis.
Cooking procedure
Steaks for trained sensory analysis and shear force were cooked as outlined in Decker et al. (2026). In short, steaks were thawed 24 h to 48 h at 2°C. Upon reaching an internal temperature of 0°C, steaks were cooked at 204°C, with 0% relative humidity, in a default fan speed in a combi-oven (Model SCC WE 61 E; Rational, Landberg am Lech, Germany) on a grill grate (60.73.314; Rational, Landberg am Lech, Germany). The temperature was monitored through the cooking process with an oven core temperature probe (40.04.506; Rational, Landberg am Lech, Germany). Steaks were removed from the oven to reach a peak internal temperature of 71°C using a calibrated thermometer (AccuTuff 340, model 34040; Cooper-Atkins Corporation, Middlefield, Connecticut) placed in the geometric center of each steak. Final peak temperature was recorded for all trained sensory and shear force steaks.
Trained sensory analysis
Trained sensory evaluation was performed as described in Foraker et al. (2022), using attributes adapted from Adhikari et al. (2011), located in Table 1. Steaks were subsampled for trained sensory analysis, and only samples with marbling scores small00–moderate100 were included in evaluation. All 5 aging periods were included for each of the 48 steers (n = 240). In short, panelists were trained in alignment with the American Meat Science Association guidelines for at least 20 h (Miller et al., 2026). Steaks were cooked as previously outlined, trimmed of connective tissue, cut into 1.27 cm by 1.27 cm by 2.54 cm pieces, and served to panelists under red incandescent lighting. A total of 24 panels were conducted, consisting of 6 panelists each, evaluating 10 samples, and representing a random combination of treatment and aging periods. Each panelist recorded their response for each attribute on an electronic ballot (Version 2417833; Qualtrics Software, Provo, Utah) on tablets (iPad, Apple Inc., Cupertino, California). Attributes were evaluated on a 100-point line scale, with 0 representing extremely dry/tough/not detectable and 100 representing extremely juicy/tender/intense.
Definitions and references for beef flavor attributes and intensities1
| Attribute | Definition |
|---|---|
| Beef flavor | Amount of beef flavor identity in the sample: Swanson’s beef broth |
| Fat-like | Aromatics associated with cooked animal fat, Hillshire Farms Lit’l Beef Smokies |
| Brown | A round, full aromatic generally associated with beef suet that has been broiled, caramelized, or broiled |
| Roasted | Flavor associated with beef that has been roasted or broiled beef suet |
| Metallic | The impression of slightly oxidized metal such as iron, copper, and silver spoons or Dole canned pineapple juice |
| Oxidized | Aromatic associated with oxidized fat and oils; these aromatics may include cardboard, painty, varnish, and fishy |
| Liver-like | Aromatics associated with cooked organ meat/liver, beef liver |
| Sour | Fundamental taste factor associated with citric acid or 0.050% citric acid solution |
| Umami | Flat, salty, somewhat brothy; taste of glutamate, salts of amino acids, and other molecules called nucleotides or 0.035% accent flavor enhancer solution |
Shear force measurements
SSF measurements were evaluated using procedures described by Shackelford et al. (1999). All quality grades and aging periods were included (n = 514). After cooking and recording peak internal temperature, the lateral end of the steak was blocked, and a 1 × 5-cm slice was removed parallel to muscle fibers. The slice was sheared perpendicular to the muscle fibers using an SSF machine (Tallgrass Solutions, Inc., Manhattan, Kansas) equipped with a flat, blunt-end blade (crosshead speed: 500 mm/min, load capacity: 50 kg).
Fatty-acid methyl ester analysis
Fatty-acid methyl esters (FAME) analyses were performed using methods modified from O’Fallon et al. (2007) on a subsample with a marbling score of small00–100 (n = 104). One gram of raw homogenate was weighed out and placed into a screw-cap glass vial and sealed with a polypropylene lined cap (14-962-26G; Fisherbrand, Mexico). Tridecanoic acid (0.5 mg/mL in methanol, Nu-chek, T-135; Elysian, Minnesota), which served as the internal standard, potassium hydroxide, and methanol were added to the tube before the samples were incubated in a water bath at 55°C for 1.5 h. The tubes were then cooled in an ice bath before sulfuric acid was added. The tubes were then incubated a second time following the same process above. After incubation, hexane was added, and the tubes were centrifuged for 5 min at 3,500 rpm at 21°C. Three hundred microliters of the hexane layer were transferred into autosampler vials before analysis was conducted through gas chromatography (GC). An Agilent 7890 GC instrument equipped with a flame ionization detector (FID) and an HP-88 capillary column (30 m × 0.25 mm × 0.20 μm; Agilent Technologies, Palo Alto, California) was used in the separation of FAME. One microliter of the sample was taken from the autosampler vial and injected at a split ratio of 50 to 1. The oven temperature followed the proceeding program: initial heat set at 35°C for 2 min, then increased in temperature at a rate of 3°C per minute until 200°C was reached and held for 1 min. The injector and FID were operated at 250°C. Fatty acids were identified by comparing retention times with GC reference standards (Nu-chek Prep, Inc., Elysian, Minnesota), and concentrations of each fatty acid were calculated in relation to the initial wet sample weight (mg/g).
Statistical analysis
Data were analyzed using R statistical software version 1.4.1717 (RStudio, PBC). A value of α of less than 0.05 was considered significant for all analyses. Data for steak dimensionality were analyzed as a factorial design, with factors of steak position and LUB treatment. Data for trained sensory analysis, SSF, and fatty acids were analyzed as a split-plot design, while LUB treatment served as the main plot factor and age period as the subplot factor. Quality grade served as a random effect in SSF analysis. An analysis of variance (ANOVA) was performed for all assays. The aging period, treatment, and their interaction served as main effects. Interactions were interpreted when significant, while main effects were only interpreted if no interaction was significant. Peak temperature served as a covariate for trained sensory evaluation and SSF analysis when significant in the model. The panel was utilized as a random effect in trained sensory analysis, given not every treatment aging combination was represented in each panel. Additionally, a Tukey’s honestly significant difference adjustment was utilized to reduce the risk of type 1 error. For steak dimensionality analysis, an interaction was tested between steak position and LUB treatment. Given the interest in understanding the changes in muscle morphology across the loin, it was determined that LUB treatment be evaluated at each individual steak position. A Bonferroni’s adjustment was then utilized as a conservative adjustment to reduce comparison-wise error rate. Given the strip loins collected were from a completely controlled study in Kayser et al. (2024), and the majority of the cattle in a single cycle of the study were captured, hot-carcass weight (HCW) was not included as a covariate in analysis.
Trained sensory data were analyzed in a discriminant function analysis (DFA), using the same method described in Foraker et al. (2020). This method of analysis accounts for the multidimensional nature of sensory data, as all sensory characteristics are evaluated simultaneously, often resulting in a ‘Halo effect’ (Foraker et al., 2020). In short, data were evaluated for test assumptions and multivariate normality prior to analysis. A linear model of sensory attributes was performed to predict the sensory performance of LUB treatment, and the candisc package was used to determine the statistical significance of the discriminant functions. Loadings and standardized coefficients were extracted and utilized to determine the discriminant ability of each significant function for LUB treatment. Composite sensory scores were calculated for each sample by multiplying the standardized sensory attribute scores by their corresponding standardized canonical coefficients from each discriminant function and summing the weighted values across all attributes. This approach reduces the multidimensional sensory dataset into a single composite score that reflects the primary source of variation among samples. Positive and negative standard coefficients of individual attributes indicate the degree and direction to which each trait contributed to separation along the first discriminant function (DF1), allowing the composite score to represent the overall sensory profile rather than any single attribute independently. Given the lack of significant interaction in a univariate space, it was determined that only the main effect of LUB be focused on in a multivariate space. The model’s efficacy in distinguishing between treatments was tested using ANOVA by comparing composite sensory scores of each treatment. Pairwise comparisons between treatments were conducted using Tukey’s adjustment, with significance determined at an α value of less than 0.05.
Results and Discussion
Steak dimensionality
The results of the steak area analysis are presented in Table 2 and Figure 1. There were no interactions between steak position and LUB treatment (P < 0.05); therefore, the main effect of LUB treatment was interpreted. LUB28 was larger in area than CON at steak locations 1, 9, and 10 (P ≤ .04). There were no steak area differences between LUB56, LUB84, and CON at any location (P ≥ 0.07). There were no differences among all treatments for steak length at all steak positions (P ≥ 0.07). Of all 54 width measurements, only LUB28 was wider than CON for steak number 8 at 50% the width, and no other measurement was significant (P > 0.05). The lack of differences is unexpected, as LUB supplementation has been shown to increase ribeye area (REA). Kayser et al. (2024) reported increases of 3.6 cm2 to 5.7 cm2 in REA, increasing as the duration of LUB treatment increased in the entire sample of cattle in the study. Decker et al. (2026) found alterations in steak dimensionality, increasing steak area at 7 of 11 locations across the strip loin with 56 d of use in beef heifers, as well as differences in steak width at several locations. Kube et al. (2021), Teeter et al. (2021), Kayser et al. (2024), and Vogel et al. (2023) all cite a greater than 3 cm2 increase in REA, no matter the dose or duration of LUB use, similar to the area difference at steak position 1 in the current study. However, the previous studies utilized more conventional cattle, such as British and continental crossbred steers and heifers and cattle sourced from commercial feedyards, whereas the current study utilized Holstein steers. Nonetheless, there is evidence that β-A, specifically RAC, increases REA in Holstein steers (Hergenreder et al., 2021). The current study found a difference in the most anterior portion of the strip loin, closest to where an REA measurement would have been obtained but in only 2 other locations across the loin. Given HCW or strip loin weight was not controlled for in the current study, animal-to-animal variation likely contributed additional variability and may have limited the detection of statistically significant differences. Steers fed LUB at any duration had steaks with higher numerical area values across the entire striploin. Alternatively, LUB has been shown to increase HCW in finishing steers in combination with increasing REA (Kube et al., 2021; Teeter et al., 2021; Kayser et al., 2024; Vogel et al., 2023). Therefore, it would be expected that LUB supplementation would result in heavier strip loins and consequently larger steak areas, regardless of whether weight was statistically controlled. Moreover, steaks from dairy-type steers are smaller in area, more angular in shape, and are often less desirable by consumers (Thonney et al., 1991). It was hypothesized that LUB supplementation, through potential increases in muscle hypertrophy, may reduce some of the angularity commonly associated with dairy-type carcasses. However, the minimal differences observed in steak widths, particularly at 75% and 87.5% of the steak width, along with the lack of changes in the length-to-width ratio, suggest that LUB supplementation did not meaningfully alter overall steak shape. Therefore, the limited differences observed in steak dimensionality suggest that the effects of LUB on strip loin muscle deposition in Holstein steers may be less pronounced or more variable than previous β-A in conventionally fed beef cattle, particularly when carcass or strip loin weights are not controlled.
Results of steak dimensionality measurements from anterior (1) to posterior (13) end of the strip loin from Holstein steers treated with lubabegron fumarate for 0 d, 28 d, 56 d, or 84 d.
Estimated marginal means of US Department of Agriculture Choice strip loin steak area (cm2)1 from Holsteins fed a control diet or supplemented lubabegron for 28 d, 56 d, or 84 d (n = 212)
| Steak Position2 | CON | LUB28 | LUB56 | LUB84 | SEM3 | P Value |
|---|---|---|---|---|---|---|
| 1 | 84.7b | 90.8a | 89.2ab | 90.1ab | 1.67 | 0.04 |
| 2 | 85.3 | 88.7 | 87.1 | 89.1 | 1.56 | 0.26 |
| 3 | 83.8 | 88.0 | 85.3 | 87.2 | 1.47 | 0.17 |
| 4 | 81.1 | 86.3 | 83.3 | 83.6 | 1.52 | 0.11 |
| 5 | 78.3 | 83.5 | 80.6 | 81.0 | 1.41 | 0.08 |
| 6 | 76.5 | 80.7 | 78.1 | 79.6 | 1.40 | 0.15 |
| 7 | 76.1 | 81.3 | 77.6 | 79.8 | 1.48 | 0.09 |
| 8 | 76.5 | 80.8 | 78.4 | 81.5 | 1.47 | 0.07 |
| 9 | 76.3b | 82.9a | 78.3ab | 81.5ab | 1.50 | <0.01 |
| 10 | 79.7ab | 85.3a | 79.2b | 84.1ab | 1.57 | <0.01 |
| 11 | 80.4 | 84.1 | 80.7 | 84.3 | 1.66 | 0.17 |
| 12 | 80.4 | 81.2 | 80.0 | 83.2 | 1.84 | 0.57 |
| 13 | 80.2 | 83.7 | 80.8 | 85.4 | 2.69 | 0.42 |
Abbreviations: CON, control; LUB, lubabegron fumarate; SEM, standard error measure.
Anaylzed using Fiji Image J analysis software.
Steaks were numbered beginning at the anterior end, with 1 being the most anterior steak and 11 being most posterior.
SEM (largest) of the estimated marginal means.
Trained sensory evaluation
The results of trained sensory evaluation are in Tables 3, 4, and 5. There were no interactions (P ≥ 0.17) of treatment and aging period for any sensory attribute, thus only the main effect of interest for LUB treatment is reported. CON samples were rated more tender than LUB84 samples (P < 0.05), while LUB28 and LUB56 were not different from any other treatment (Table 3; P > 0.05). Moreover, there were no differences among treatments for all other attributes evaluated (P > 0.12). Main effects of aging treatment are presented in Table 5. Twenty-eight-day and 35-d aged samples were rated greater for tenderness than 7-d aged samples (P = 0.03). Alternatively, 35-d aged samples were rated greater for liver-like and sour flavors than 7-d, 14-d, and 21-d aged samples (P < 0.01) and rated greater for oxidized flavor than 7-d aged samples (P < 0.01). There were no differences for juiciness, beef flavor, browned, roasted, fat-like, metallic, umami, and buttery attributes among aging treatments (P > 0.06). These results are similar to those found in Foraker et al. (2020), where both off-flavors and tenderness increased as samples increased in postmortem age. However, Foraker et al. (2020) provided evidence that sensory data are multidimensional, and many of these characteristics, especially flavor attributes, are highly correlated. Therefore, evaluation of these data in both a univariate and multivariate space was justified.
Estimated marginal means1 of trained sensory ratings2 and composite sensory scores from discriminant function analysis of beef strip loin steaks from Holstein steers fed a control diet or supplemented lubabegron for 28 d, 56 d, or 84 d (n = 240)
| Variable | CON | LUB28 | LUB56 | LUB84 | SEM3 | P Value |
|---|---|---|---|---|---|---|
| Sensory analysis | ||||||
| Tenderness | 62.2a | 58.6ab | 59.4ab | 57.8b | 0.98 | 0.02 |
| Juiciness | 52.0 | 51.5 | 51.2 | 51.9 | 0.58 | 0.80 |
| Beef flavor | 54.4 | 53.5 | 54.4 | 54.0 | 0.34 | 0.16 |
| Browned | 50.0 | 49.1 | 49.9 | 50.0 | 0.51 | 0.55 |
| Roasted | 52.5 | 51.4 | 52.2 | 52.4 | 0.38 | 0.12 |
| Fat-like | 12.8 | 12.9 | 13.0 | 12.7 | 0.27 | 0.89 |
| Metallic | 5.6 | 5.6 | 5.6 | 6.4 | 0.35 | 0.47 |
| Umami | 15.2 | 15.4 | 16.2 | 15.4 | 0.31 | 0.16 |
| Buttery | 1.1 | 1.1 | 1.2 | 1.1 | 0.13 | 0.97 |
| Oxidized | 3.0 | 2.8 | 2.6 | 3.3 | 0.43 | 0.26 |
| Liver-like | 2.0 | 1.7 | 1.3 | 1.6 | 0.34 | 0.57 |
| Sour | 2.8 | 2.8 | 2.4 | 3.5 | 0.52 | 0.44 |
| Composite sensory scores4 | ||||||
| Function 1 | −0.51a | 0.02b | −0.12ab | 0.63c | 0.08 | <0.001 |
Abbreviations: CON, control; LUB, lubabegron fumarate; SEM, standard error measure.
Least-squares means in the same row without a common superscript differ (P < 0.05).
Interaction of age × lubabegron supplementation P ≥ 0.17.
Sensory scores: 0 = extremely dry/tough/none/bland; 50 = neither dry nor juicy/neither tough nor tender; 100 = extremely juicy/tender/abundant/intense.
SEM (largest) of the estimated marginal means.
Composite sensory scores represent the weighted combination of multiple trained sensory attributes condensed into a single discriminant function score used to maximize separation among treatment groups.
Loadings and standardized coefficients for sensory attributes on discriminant function 1 in the prediction of lubabegron treatment1 (n = 240)
| Sensory Attribute | Loadings | Standardized Coefficients |
|---|---|---|
| Beef flavor ID | −0.10 | −0.14 |
| Browned | 0.05 | 0.45 |
| Roasted | 0.05 | 0.24 |
| Metallic | 0.32 | 0.36 |
| Fat-like | −0.09 | 0.04 |
| Sour | 0.36 | 0.47 |
| Oxidized | 0.19 | 0.12 |
| Umami | 0.00 | 0.11 |
| Buttery | −0.06 | 0.23 |
| Liver-like | −0.19 | −0.15 |
| Tenderness | −0.63 | −1.10 |
| Juiciness | 0.06 | 0.44 |
| Canonical R2 | 0.16 | |
| Eigen value | 0.19 | |
| P value | 0.0005 | |
Loadings indicate the relationship between the variable and discriminant function, while standardized coefficients represent the contribution of the variable to a function.
Trained sensory ratings of beef strip loin steaks from Holstein steers fed lubabegron1 across 5 aging periods (n = 240)
| Variable2 | 7-D | 14-D | 21-D | 28-D | 35-D | SEM3 | P Value |
|---|---|---|---|---|---|---|---|
| Tenderness | 56.7a | 58.5ab | 59.4ab | 61.3b | 61.6b | 1.08 | 0.03 |
| Juiciness | 51.7 | 51.4 | 51.4 | 52.3 | 51.7 | 0.67 | 0.88 |
| Beef flavor | 54.1 | 54.6 | 54.2 | 54.1 | 53.2 | 0.39 | 0.10 |
| Browned | 50.0 | 49.8 | 50.3 | 49.1 | 49.6 | 0.58 | 0.63 |
| Roasted | 52.2 | 52.5 | 52.4 | 52.4 | 51.2 | 0.42 | 0.21 |
| Fat-like | 12.7 | 13.2 | 12.9 | 12.8 | 12.7 | 0.30 | 0.73 |
| Metallic | 5.4 | 5.4 | 5.4 | 6.2 | 6.2 | 0.36 | 0.10 |
| Umami | 15.1 | 16.1 | 16.0 | 15.8 | 14.8 | 0.30 | 0.06 |
| Buttery | 1.3 | 1.3 | 1.1 | 1.0 | 0.9 | 0.15 | 0.17 |
| Oxidized | 2.6a | 2.4a | 2.7ab | 3.2ab | 3.7b | 0.40 | <0.01 |
| Liver-like | 1.3a | 1.5a | 1.1a | 1.8ab | 2.7b | 0.28 | <0.01 |
| Sour | 2.6a | 1.7a | 2.5a | 3.1ab | 4.4b | 0.40 | <0.01 |
Abbreviation: D, day; SEM, standard error measure.
Least-squares means in the same row without a common superscript differ (P < 0.05).
Interaction of age × lubabegron supplementation P ≥ 0.17.
Sensory scores: 0 = extremely dry/tough/none/bland; 50 = neither dry nor juicy/neither tough nor tender; 100 = extremely juicy/tender/abundant/intense.
SEM (largest) of the estimated marginal means.
A DFA was utilized to calculate linear combinations of the original variables, referred to as functions, that maximize among-group variation, while minimizing within-group variation as outlined in Foraker et al. (2020). The DFA was used to predict group membership based on the independent variable of LUB treatment utilizing 3 discriminant functions, each orthogonal to one another, accounting for 100% of total variation. The lack of interaction in a univariate space led to the decision to focus on LUB treatment alone rather than the interaction of LUB and aging period. The DF1 accounted for 58.7% of total variation in all sensory attributes (P < 0.001), while the second accounted for 27.5% (P = 0.11) and the third accounted for 13.8% of total variation (P = 0.42). Because there was only one significant function encompassing most of the variation in the data, this function was focused on for interpretation. Loadings and standardized coefficients of sensory values from DF1 are in Table 4, while composite sensory scores are presented in Table 3. Standardized coefficients of all attributes suggested that DF1 was most representative of tenderness (r = −1.10). No other sensory attribute had absolute values of standard coefficients greater than 0.44, indicating all had far less contribution to DF1 than tenderness. Figure 2 visualizes the composite sensory scores by LUB treatments. When tested for their ability to detect treatment differences, the model differentiated between LUB84, LUB28, and CON samples on DF1, while LUB56 samples were only different from LUB84 samples (P < 0.001). Given DF1 was loaded negatively by tenderness, more negative scores on DF1 indicate increases in myofibrillar tenderness, while higher composite sensory scores indicate decreases in tenderness scores, alongside other sensory attributes. Therefore, the model’s differentiating ability is driven by tenderness, which in turn drives significant differences in composite sensory scores. Tenderness is the primary driver of differences related to LUB treatment in both a multivariate and univariate space. This aligns with previous literature (Decker et al., 2026), which indicated a negative impact of LUB on tenderness and no difference in any other attribute in finishing beef heifers. Therefore, while sensory differences are nonexistent outside of tenderness, the differences in tenderness are large enough to be discriminated against in both a multivariate space. This aligns with the limited published literature, where LUB was noted to decrease tenderness in conventional steers and heifers (Corona et al., 2025; Decker et al., 2026). Moreover, other β-A have resulted in decreased tenderness of beef. Garmyn et al. (2014) found ZIL to decrease tenderness in strip steaks compared to RAC and CON samples. Similarly, Arp et al. (2013) found decreasing tenderness in ZIL and high doses of RAC (400 mg/steer/d) in comparison to CON and low doses of RAC (200 and 300 mg/head/d). In RAC- and ZIL-treated animals, the decrease in tenderness is primarily due to the increase in muscle hypertrophy and thus muscle fiber cross-sectional area (Gonzalez et al., 2007; Ebarb et al., 2016).
Composite sensory scores on discriminant function 1 of strip steaks treated with lubabegron fumarate for 0 (control), 28 d, 56 d, or 84 d, as assessed by trained panelists (n = 174). Composite sensory scores represent the weighted combination of multiple trained sensory attributes condensed into a single discriminant function score used to maximize separation among treatment groups. Abbreviation: DF1, first discriminant function.
Slice shear force
Figure 3 illustrates the interaction of lubabegron treatment × age (P < 0.01) on SSF values. At 7 d and 21 d of aging, CON steaks had lower shear force values than LUB56 and LUB84 (P < 0.01), while LUB28 was not different from all treatments (P > 0.05). Moreover, at 14 d of aging, CON resulted in lower shear force values than LUB84 (P < 0.01), while LUB28 and LUB56 were not different from the CON or LUB84 (P > 0.05). By 28 d and 35 d of aging, there were no differences among all treatments (P > 0.05). However, the differences at early aging periods are less than 4.6 kg of force (3.60 kg), which is the value at which consumers are likely to detect a significant difference (ASTM, 2011). These results closely align with Decker et al. (2026), where LUB increased SSF through 21 d of aging, although diminishing at 28 d and 35 d. Wendler et al. (2025) found no shear force differences in LUB-fed animals fed for the same duration as both CON- and RAC-treated steers at 21 d postmortem aging. The combination of univariate and multivariate analysis of sensory results and the current shear force results indicate LUB negatively impacts tenderness within Holstein steers. However, both sensory and shear force differences were associated with the lowest aging periods (<14 d) and greatest LUB feeding durations (84 d). At the time of this study, the use of LUB was limited to no greater than 63 d by the manufacturer’s user agreement, even though it is approved for use up to 91 d (FDA, 2018). Therefore, under current industry feeding practices and commercially relevant aging periods, the overall impact of LUB on eating quality appears minimal.
Interaction of slice shear force values of steaks from Holstein steers fed lubabegron for 0 d, 28 d, 56 d, or 84 d over 35 d postmortem aging. SEM (largest) = 0.42 (P < 0.01). Abbreviations: SEM, standard error of mean; SSFV, slice shear force value.
Fatty-acid concentration
Estimated marginal means for fatty-acid data analysis are presented in Table 6. The interaction of aging period and LUB treatment was not significant for any individual fatty acid or percentage of monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and saturated fatty acids (SFA; P > 0.07). The main effect of LUB treatment was then focused on for interpretation, given aging was not the focus of the current study. Total concentration (mg/g) of SFA did not exhibit significant differences across treatments (P = 0.10). However, specific SFA showed variations. Lauric acid (C12:0) and myristic acid (C14:0) significantly increased at LUB56 compared to other feeding durations (P < 0.01, P < 0.001). The total concentration of MUFA was not different among treatments (P = 0.06). Even so, individual MUFA, such as tridecanoic acid (C13:1) and trans-palmitoleic acid, were decreased in concentration at LUB56 (P < 0.01). Furthermore, myristoleic acid (C14:1n5) increased in LUB56 compared to CON (P < 0.001). However, total PUFA concentration varied across treatments (P = 0.02), with the highest total concentration observed at LUB56. Trans-linoleic acid (C18:2trans), linoleic acid (C18:2n6), and Ɣ-linoleic acid (C18:3n6) showed significant increases at LUB56 (P = 0.02, P = 0.01). Additionally, α-linoleic acid (C18:3n3) decreased in LUB84 samples in comparison to CON (P < 0.001). While it is understood that β-A performs repartition of energy from fat deposition to muscle deposition, there is little prior investigation on the effects of β-A, specifically LUB, on fatty-acid concentration. Johnson et al. (2014) details the depression of triglyceride deposition and increased lipolysis caused by β-A but gives no impression on the potential changes of fatty-acid profile. Moreover, the same level of research has not been done regarding LUB, considering its antagonistic behavior at β1 and β2 receptors and agonistic behavior at β3 (Dilger et al., 2021). However, intramuscular adipose tissue has more recently been shown to have little lipolytic response to β-A, no matter the subtype (Hwang et al., 2021), while LUB impact on lipogenesis is still widely unknown. The changes in PUFA profile in the current work indicate a possible change in the phospholipid fragment, specifically the change in arachidonic acid (C20:4n6; Wood et al., 2008). However, it is difficult to determine the exact alterations without separation of the polar and nonpolar lipid fragments. Therefore, these changes indicate LUB could be a result of altering the process of lipogenesis, thus the overall fatty-acid profile of LUB-treated samples.
Fatty-acid concentration (mg/g) present in strip loins from Holstein steers fed a control or supplemented lubabegron for 28 d, 56 d, or 84 d (n = 104)
| Fatty Acid | CON | LUB28 | LUB56 | LUB84 | SEM1 | P Value |
|---|---|---|---|---|---|---|
| 10:0 | 0.029 | 0.032 | 0.034 | 0.029 | 0.002 | 0.18 |
| 12:0 | 0.070ab | 0.085a | 0.088a | 0.066ab | 0.005 | 0.005 |
| 13:0 | 0.500 | 0.498 | 0.499 | 0.498 | 0.002 | 0.36 |
| 13:1 | 0.014ab | 0.015a | 0.012b | 0.013b | 0.002 | 0.002 |
| 14:0 | 1.660ab | 1.950bc | 2.42c | 1.450a | 0.140 | <0.001 |
| 14:1n5 | 0.470a | 0.675bc | 0.770bc | 0.540ab | 0.051 | <0.001 |
| 15:0 | 0.267ab | 0.264a | 0.320b | 0.230ab | 0.023 | 0.04 |
| 16:0 | 13.70 | 13.00 | 15.20 | 11.10 | 1.410 | 0.16 |
| 16:1trans | 0.137a | 0.123a | 0.197b | 0.121a | 0.014 | <0.001 |
| 16:1n7 | 1.071 | 1.273 | 0.822 | 0.821 | 0.223 | 0.29 |
| 17:0 | 0.714 | 0.648 | 0.720 | 0.545 | 0.082 | 0.28 |
| 17:1 | 0.456 | 0.519 | 0.755 | 0.466 | 0.107 | 0.12 |
| 18:0 | 6.63 | 5.98 | 6.98 | 5.11 | 0.792 | 0.26 |
| 18:1trans | 3.90 | 4.13 | 6.29 | 4.59 | 0.702 | 0.07 |
| 18:1n9 | 14.2 | 15.4 | 16.8 | 13.6 | 1.42 | 0.31 |
| 18:1n7 | 0.214 | 0.272 | 0.276 | 0.228 | 0.026 | 0.15 |
| 18:2trans | 0.132a | 0.137ab | 0.180b | 0.126a | 0.013 | 0.03 |
| 18:2n6 | 2.970ab | 2.700a | 3.620b | 2.930a | 0.200 | 0.01 |
| 18:3n6 | 0.091a | 0.089a | 0.126b | 0.086a | 0.009 | <0.01 |
| 18:3n3 | 0.096a | 0.089ab | 0.081ab | 0.061b | 0.007 | <0.001 |
| 19:0 | 2.540 | 2.030 | 3.050 | 2.200 | 0.280 | 0.06 |
| 19:1 | 0.037ab | 0.031a | 0.052b | 0.035ab | 0.005 | 0.04 |
| 20:0 | 0.122 | 0.113 | 0.149 | 0.115 | 0.010 | 0.08 |
| 20:1n5 | 0.118 | 0.101 | 0.136 | 0.113 | 0.010 | 0.13 |
| 20:1n8 | 0.320 | 0.347 | 0.409 | 0.328 | 0.030 | 0.15 |
| 20:1n11 | 0.253 | 0.290 | 0.331 | 0.253 | 0.034 | 0.20 |
| 20:2 | 0.073ab | 0.061a | 0.083b | 0.064a | 0.004 | 0.01 |
| 20:3n6 | 0.154 | 0.146 | 0.170 | 0.165 | 0.010 | 0.34 |
| 20:3n3 | 0.084 | 0.090 | 0.066 | 0.81 | 0.016 | 0.72 |
| 20:4n6 | 0.176ab | 0.156a | 0.206b | 0.187b | 0.009 | <0.01 |
| 20:5 | 0.038 | 0.037 | 0.039 | 0.036 | 0.002 | 0.66 |
| 22:0 | 0.040 | 0.038 | 0.038 | 0.038 | 0.002 | 0.61 |
| 22:1 | 0.102 | 0.137 | 0.059 | 0.134 | 0.40 | 0.37 |
| 22:3 | 0.003 | 0.003 | 0.002 | 0.002 | 0.001 | 0.33 |
| 22:4 | 0.054 | 0.052 | 0.064 | 0.055 | 0.003 | 0.13 |
| 22:5n3 | 0.074 | 0.064 | 0.082 | 0.072 | 0.005 | 0.09 |
| 22:6n3 | 0.020 | 0.016 | 0.012 | 0.013 | 0.003 | 0.10 |
| 24:0 | 0.036 | 0.036 | 0.041 | 0.049 | 0.007 | 0.23 |
| 24:1n9 | 0.045a | 0.043a | 0.057b | 0.048ab | 0.003 | 0.01 |
| SFA2 | 26.4 | 25.3 | 29.4 | 21.4 | 2.54 | 0.10 |
| MUFA3 | 21.4 | 23.7 | 26.9 | 21.3 | 21.4 | 0.06 |
| PUFA4 | 3.97ab | 3.69a | 4.69b | 3.85ab | 0.25 | 0.02 |
Abbreviations: CON, control; LUB, lubabegron fumarate; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; SEM, standard error measure; SFA, saturated fatty acids.
Least-squares means in the same row without a common superscript differ (P < 0.05).
SEM (largest) of the estimated marginal means.
Total SFA (mg/g).
Total MUFA (mg/g).
Total PUFA (mg/g).
Conclusion
This study indicates that LUB supplementation in Holstein steers has a measurable impact on meat quality, with a primary effect on tenderness at long feeding durations and short postmortem aging durations. However, the degree of change in trained sensory tenderness was slight, and shear force alterations were below the threshold in which consumers can likely detect a significant difference. Other sensory attributes, including juiciness and flavor, were not affected by LUB supplementation. LUB treatment did not significantly alter steak dimensionality or overall SFA or MUFA; however, total PUFA and specific fatty-acid concentrations were affected at certain supplementation durations. These results suggest that while LUB use in Holstein steers does decrease tenderness when standardized by quality grade, those differences are likely not detectable by a consumer.
Conflict of Interest
Two of the authors were employed by Elanco Animal Health, which provided funding for this study at the time this research was conducted.
Acknowledgments
This project was funded by Elanco Animal Health.
Author Contribution
Lindsey K. Decker: data curation, validation, writing—original draft, and writing—reviewing and editing; Reagan P. Wagner: data curation, methodology, and writing—original draft; Blake A. Foraker: validation and writing—reviewing and editing; Bradley J. Johnson: conceptualization and writing—reviewing and editing; Jerrad F. Legako: conceptualization and writing—reviewing and editing; Will C. Kayser: conceptualization, funding acquisition, and writing—reviewing and editing; Phillip J. Rincker: conceptualization, funding acquisition, and writing—reviewing and editing; and Dale R. Woerner: project administration, conceptualization, funding acquisition, and writing—reviewing and editing.
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