Finishing Beef Steers Research Articles

Evaluation of Guanidinoacetic Acid Supplementation on Finishing Beef Steer Growth Performance, Skeletal Muscle Cellular Response, and Carcass Characteristics.

This study elucidated the effects of dosage-dependent guanidinoacetic acid (GAA) supplementation on growth performance, muscle responses, and carcass characteristics in finishing beef steers. Thirty crossbred Red Angus beef steers (395 ± 28.09kg) were randomly assigned one of three treatments during a 146-day feedlot study: basal diet without GAA supplementation (CONTROL), 1g of GAA per 100kg of BW daily (LOWGAA), and 2g of GAA per 100kg of BW daily (HIGHGAA). Individual feed intake was monitored daily, growth performance parameters were collected every 28 days, and longissimus muscle (LM) biopsies occurred every 56 days. In biopsied LM, greater (P = 0.048) mRNA expression of IGF-1 was observed in LOWGAA steers on d 112 compared to the CONTROL group. LOWGAA steers also exhibited greater expression of myosin heavy chain (MHC) I compared to CONTROL steers (P < 0.05) and MHC IIA compared to both CONTROL and HIGHGAA treatment groups (P < 0.01) on d 112. GAA supplementation resulted in no change in carcass characteristics, serum and LM tissue metabolites, LM composition, and Warner-Bratzler shear force (WBSF) values (P > 0.05). Data collected from this study demonstrate the influence of GAA supplementation on the gene expression of MHC isoforms and their role in skeletal muscle growth, differentiation, and muscle fiber-typing.

PSIII-7 Effects of Saccharomyces cerevisiae fermentation product on total tract digestibility, ruminal fermentation, and plasma metabolome of beef steers fed a finishing diet

Abstract Saccharomyces cerevisiae fermentation product (SCFP) has been widely studied; however, its mode of action on high-concentrate diets has not been fully elucidated. This study evaluated the impact of SCFP on total tract digestibility, fecal excretions of N, P, Zn, and Cu, rumen fermentation, and plasma metabolome of finishing beef steers. Ruminally cannulated Holstein steers [n = 8; body weight (BW) = 580 ± 29.2 kg] were enrolled in a crossover design study with 25-d treatment periods and a 24-d washout period. Steers were fed ad libitum a finishing diet consisting of 20% corn silage and 80% concentrate (on DM basis). Steers were blocked based on initial BW and randomly assigned to two treatments in period 1 and switched to the other treatment in period 2. The treatments were CON (Control, basal diet only) and SCFP (basal diet top-dressed with 12 gּ steer-1ּ ּ d-1 SCFP, NaturSafe, Diamond V, Cedar Rapids, IA). Feed and fecal samples were collected during d 22 to 24 for determination of digestibility. Blood was collected before morning feeding on d 25. Plasma samples were analyzed for metabolome with liquid chromatography-mass spectrometry (LC-MS). Rumen fluid was collected via the rumen cannula at 0, 4, 8, and 12 h post-morning feeding on d 25 and analyzed for pH, volatile fatty acids (VFA), and NH3-N. Performance and ruminal fermentation characteristics data were analyzed using the GLIMMIX procedure of SAS 9.4. Metabolomic data analysis was conducted with Metaboanalyst 6.0. Supplementing steers with SCFP reduced DMI (10.6 vs. 11.4 kg/d, P = 0.05) without affecting (P &amp;gt; 0.05) average daily gain, feed efficiency, and digestibility of organic matter, crude protein, and neutral detergent fiber. Treatment did not affect (P &amp;gt; 0.10) fecal excretions of N, P, Cu, and Zn. Feeding SCFP increased ruminal pH (6.29 vs. 6.01, P = 0.01), numerically reduced concentrations of NH3-N (5.01 vs 6.25 mM, P = 0.16), and total VFA (96.8 vs. 102.5 mM, P = 0.15). SCFP also reduced the ruminal molar proportion of butyrate (11.2 vs. 12.8 molar %, P = 0.01) and tended to increase those of isobutyrate (1.03 vs. 0.90, molar %, P = 0.06) and isovalerate (2.62 vs. 2.29, molar %, P = 0.10). Supplementation of SCFP enriched (P ≤ 0.05) purine metabolism, amino sugar and nucleotide sugar metabolism, and lysine degradation pathways in the plasma. Additionally, tryptophan metabolism and pyrimidine metabolism pathways tended to be enriched (0.05 &amp;lt; P ≤ 0.10) by SCFP. Our findings indicate that feeding SCFP improved the ruminal pH of finishing cattle, which may be beneficial for preventing subacute ruminal acidosis in feedlot cattle. Additionally, SCFP enriched several important plasma nitrogen metabolism pathways, potentially associated with microbial nitrogen metabolism in the rumen, warranting further research.

78 Prolonged heat stress impact on molecular responses of skeletal muscle and growth performance in finishing beef steers

Abstract Rising temperatures significantly impact cattle production economically, reducing feed intake, efficiency, and growth, leading to substantial losses. Despite these known effects, there remains a paucity of data on the specific responses of skeletal muscle and adipose tissue to heat stress conditions. Therefore, this study aimed to elucidate the effects of prolonged heat stress on the molecular mechanisms of skeletal muscle growth and adipose tissue deposition and physiological response. Thirty-two predominantly Angus beef steers [initial average body weight (BW) = 364 ± 4.60 kg] were subject to a 28-d heat stress period. Steers were randomly allotted to one of two treatment groups (n = 16 steers/treatment) 1) Control (CON), exposed to outdoor environmental temperature-humidity index (THI) of 60; or 2) Heat Stress (HS), subject to THI of 70 to 80 for 8 h then returned to control treatment THI to simulate typical cooldown periods exhibited in instances of HS. Feed intakes were recorded daily, while BW was measured weekly prior to feed delivery. Biopsies of the skeletal muscle from the Longissimus muscle (LM) at the area of the 13th rib and adipose tissue from the subcutaneous fat of the flank region were performed on d 1, 14, and 28 for each individual steer and used for molecular analysis. For gene expression, a repeated measures ANOVA was utilized, acknowledging the individual animal as the experimental unit. The analysis of both gene expression over time and growth performance indicators was conducted using repeated measures ANOVA, with post-hoc analysis via Tukey’s test for specific comparisons. Data presentation includes the standard error of means, with an alpha (α) level set at 0.05 for determining statistical significance. Behavioral signs of heat stress, elevated respiratory rates, were observed with HS steers exhibiting a respiratory rate of 92.92 ± 24.79 breaths per minute (bpm) compared with 60.48 ± 14.94 bpm in CON steers (P &amp;lt; 0.01). Heat stress decreased average daily gain (ADG) during d 0 to 7 (49.11%) and d 15 to 21 (59.14%) compared with the control group (P &amp;lt; 0.01). Dry Matter Intake (DMI; P &amp;gt; 0.1) and feed efficiency (P &amp;gt; 0.1) were not altered in CON vs. HS steers. In skeletal muscle, on d 28 of exposure to heat stress, there was a significant overexpression of Heat Shock Protein (HSP) isoforms 20, 27, and 90 (P &amp;lt; 0.05) relative to the control group, accompanied by increased Myf5 (P &amp;lt; 0.05) gene expression. In adipose tissue, there was upregulation of PPARγ and SCD (P &amp;lt; 0.05), both of which are implicated with adipose tissue differentiation and lipid deposition process. Our findings indicated that HS modifies the expression of genes associated with skeletal muscle growth and adipose tissue deposition, concurrently impairing overall animal growth predominantly through reduced feed intake.

189 Association of the liver phosphoproteome with divergent dry matter intake in finishing beef steers

Abstract As the need for improving the sustainability of the beef industry increases, optimizing feed efficiency is of the utmost importance. The liver has a central role in nutrient metabolism, and for ruminants particularly, it is essential for providing glucose through gluconeogenesis via substrates such as propionate, lactate, and glycerol. Further, through cell signaling and vagal afferent signals, the liver acts to stimulate and inhibit dry matter intake (DMI). Thus, the objective of this study was to investigate alterations in the phosphoproteome of finishing beef steers in relation to divergent DMI to identify changes in the abundance of signaling proteins. Angus steers [n = 57; initial body weight (BW) = 518 ± 27 kg] underwent a 63-d intake trial utilizing an Insentec Roughage Intake Control System (Hokofarm Group, Emmeloord, The Netherlands). Prior to beginning the trial, liver biopsy samples were collected from all steers. Samples from steers with the greatest and least DMI (n = 8 each) were utilized for phosphoproteomic analysis. Liver protein was isolated and labeled with isobaric tandem mass tagging reagents. Samples were enriched for phosphopeptides using immobilized metal affinity chromatography and subsequently analyzed using high-performance liquid chromatography tandem mass spectrometry. Spectral data were searched in the National Center for Biotechnology Information Bos taurus protein database using MaxQuant (version 2.2.0.0; Max Planck Inst., Munich, Germany), and the data were analyzed using Perseus (version 2.0.10.0; Max Planck Inst.). Two sample t-tests were conducted to determine the difference in phosphopeptide abundance between steers with high and low DMI. A total of 16,365 phosphopeptides were identified, and 287 were differentially expressed (False Discovery Rate &amp;lt; 0.05). In addition, 2,777 phosphopeptides were differentially expressed based on an unadjusted P &amp;lt; 0.05 which were used for enrichment analysis of Gene Ontology processes and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways using the Database for Annotation, Visualization, and Integrated Discovery. The background for this analysis was all identified phosphopeptides. Gene ontology terms enriched included processes related to phosphorylation activity, intracellular signal transduction, response to insulin, kinase activity, and signaling protein binding. Enriched KEGG pathways included pathways related to insulin signaling, such as AMPK signaling, mTOR signaling, and MAPK signaling. Further, pathways related to glycolysis and gluconeogenesis, glucagon signaling, insulin resistance, carbon metabolism, and various other signaling pathways were also enriched. These results suggest a link between the liver phosphoproteome and DMI, indicating that divergent DMI is associated with alterations in signaling pathways related to nutrient uptake and metabolic processes.

22 Effects of trace mineral source and chromium propionate supplementation on rumen fermentation, growth performance, and carcass characteristics in finishing beef steers

Abstract Crossbred beef steers [n = 400; body weight (BW) = 370 ± 8 kg] were used to evaluate the effects of trace mineral (TM) source and chromium propionate (Cr) on rumen fermentation characteristics, plasma glucose and mineral concentrations, performance, and carcass characteristics in feedlot steers fed a steam-flaked corn-based finishing diet. Steers were blocked by initial BW and randomly assigned within block to 1 of 4 treatments (10 steers/pen) with 10 pens per treatment. The experimental design was a randomized complete block design with a 2 x 2 factorial arrangement of treatments. Factors included: 1) TM source [sulfate or hydroxychloride (IntelliBond] Cu, Mn, and Zn TM supplemented at 18, 40, and 90 mg/kg DM, respectively) and 2) with or without supplemental Cr (KemTRACE) at 0.0 or 0.25 mg/kg DM. Steers were individually weighed on d -1 and 0 and every 28 d throughout the experiment. Jugular blood samples and rumen contents were collected from 10 steers per treatment on d 28 and 84 of the experiment for plasma glucose and TM concentration and volatile fatty acid analysis, respectively. On d 154 of the experiment, steers were harvested at a commercial abattoir and carcass data was collected. Data were analyzed on a pen mean basis for a randomized complete block design using PROC MIXED of SAS. There was no TM source by Cr supplementation interactions for any of the response variables measured, therefore only main effects are reported. Overall ADG (P = 0.03) and gain:feed (P = 0.02) were greater in steers receiving supplemental Cr when compared with steers not supplemented with Cr. Hot carcass weight (P = 0.04), dressing percentage (P = 0.01), longissimus muscle area (P = 0.03), and USDA yield grades (P = 0.04) were greater in steers receiving hydroxychloride TM compared with steers receiving sulfate TM. Steers supplemented with Cr had a greater dressing percentage (P = 0.01) and longissimus muscle area (P = 0.04) compared with steers not supplemented with Cr. On d 28 of the experiment, ruminal acetate concentrations were lesser (P = 0.01) and ruminal propionate concentrations tended to be greater (P = 0.12) in steers receiving hydroxychloride TM compared with steers receiving sulfate TM. Steers supplemented with Cr had greater ruminal acetate concentrations (P = 0.04) and plasma glucose concentrations (P = 0.05) on d 28 of the experiment when compared with non-supplemented controls. These data indicate the Cr supplementation and TM source can influence feedlot steer performance, carcass characteristics, and rumen fermentation characteristics.

248 Impacts of sprouted barley on the performance and carcass traits in finishing Angus steers

Abstract The growing population, coupled with unpredictable weather patterns, demands that livestock producers think innovatively to improve sustainability. Producers are interested in innovative practices and technology, such as controlled environment farming to sprout cereal grains that can be fed to livestock. However, little research has determined the effects of giving these feeds to finishing beef steers. As such, Angus steers (n = 60) were stratified by body weight (BW; 385 kg ± 10.3) to receive two different diets (n = 30/diet). The control (CON) diet was a traditional finishing ration for the region, whereas the other included 20% (dry matter; DM) sprouted barley (SB) in place of corn silage. Animals were fed for 128 d in pens with Vytelle units to measure intake and feeding behavior. On d 0, 30, 60, 90, and 128 BW, ruminal fluid, and ultrasound measurements were taken. Liver score (LS) and typical carcass data were collected from a commercial harvest facility. Statistical analyses used the MIXED procedure of SAS to assess the main effect of diet for all measurements collected over time. Dry matter intake (DMI), feed efficiency (gain to feed; G:F), ruminal volatile fatty acid (VFA) composition, and feeding behavior were run as repeated measures. No differences (P = 0.37) in BW gain were found between steers receiving different diets, but steers receiving SB had decreased (P &amp;lt; 0.0001) DMI throughout the trial compared with CON. This decrease in DMI drove a diet × day effect (P = 0.004) for G:F such that SB had increased (P ≤ 0.04) G:F on d 0 and 60, but no effect (P ≥ 0.52) was observed at d 90 or 128. Steers receiving the CON diet spent more (P &amp;lt; 0.0001) time at the feed bunk than those receiving the SB diet, which supports the observation that steers receiving the CON had an increased DMI. Ruminal pH, total VFA concentration, acetate:propionate, percent propionate, and percent butyrate were each impacted by diet × day (P ≤ 0.007). The only carcass trait impacted by diet was yield grade (YG), where steers receiving the SB diet had an increased (P &amp;lt; 0.03) YG compared with CON. These results demonstrate that replacing corn silage with SB in the ration of finishing steers has some effect on ruminal VFA composition, DMI, G:F, and USDAYG. Due to decreased DMI, SB steers had increased feed efficiency which could potentially have a positive economic impact for producers. However, additional analysis is needed to further determine if these systems are economically viable in a production setting.

474 Longitudinal assessment of Salmonella enterica prevalence and concentration throughout the gastrointestinal tract of finishing beef steers with and without liver abscesses

Abstract Our objective was to longitudinally assess the presence and quantity of Salmonella enterica throughout the gastrointestinal tract of finishing beef steers with and without liver abscesses (LA). Crossbred steers [n = 225; initial body weight (BW) = 353 ± 39 kg] were used in an observational case-control design with individual steer designated as the experimental unit. Nasal, ruminal fluid, and fecal samples were collected at feedlot arrival, 1 wk after adaptation to the finishing diet, and the day before harvest at a commercial abattoir. Healthy and abscessed liver tissue samples were collected at harvest. Steers were fed a steam-flaked corn-based diet without tylosin phosphate. After harvest, LA prevalence was determined, and steers were sorted into those with and without LA. Data were analyzed using the GLIMMIX procedure of SAS. Overall, LA prevalence was 18.7% (n = 42). Nasal Salmonella prevalence was 34.4% but did not differ between steers with or without LA (P = 0.73), and nasal Salmonella concentrations did not differ between treatments (P = 0.85) or collection day (P = 0.50). Ruminal fluid Salmonella prevalence was 73.7% but did not differ between treatments (P = 0.83). From feedlot arrival to harvest, ruminal fluid Salmonella concentration and prevalence decreased (P &amp;lt; 0.01). Fecal Salmonella prevalence tended (P = 0.09) to be 6.4% greater in steers with LA. Conversely, fecal Salmonella concentration tended (P = 0.07) to be 5.9% greater in steers without LA. Fecal Salmonella prevalence was greatest after transition to the finishing diet (P &amp;lt; 0.01), whereas fecal Salmonella concentration was greatest before harvest (P &amp;lt; 0.01). Liver Salmonella prevalence was 9.8% and 6.5% for steers with and without LA, respectively, but did not differ between treatments (P = 0.47). Similarly, liver Salmonella concentrations did not differ in steers with or without LA (P = 0.18). Overall, these data suggest Salmonella concentration and prevalence were affected by time on feed, but not indicative of LA formation.

Use of a novel direct-fed microbial as an alternative for tylosin phosphate to control liver abscesses and decrease antimicrobial use in finishing beef steers*†

Use of a novel direct-fed microbial as an alternative for tylosin phosphate to control liver abscesses and decrease antimicrobial use in finishing beef steers*†

Effects of increasing the concentration of neutral detergent fiber in roughage and bulk density of steam-flaked corn on growth performance, carcass characteristics, and liver abscesses of finishing beef steers fed diets without tylosin phosphate*†

Effects of increasing the concentration of neutral detergent fiber in roughage and bulk density of steam-flaked corn on growth performance, carcass characteristics, and liver abscesses of finishing beef steers fed diets without tylosin phosphate*†

103 Effects of partial or total replacement of dried distiller’s grain with soybean meal on growth performance, carcass characteristics, sera urea nitrogen, and net energy utilization in finishing beef steers

Abstract The objective of this study was to determine if partial or complete replacement of dried distiller’s grains plus solubles (DDGS) with solvent-extracted soybean meal (SBM) influences growth performance, efficiency of dietary net energy utilization, sera urea-N (SUN) concentrations, or carcass traits in finishing beef steers. Continental × British steers [initial shrunk body weight (BW) = 382 ± 37 kg] were used in a 139-d experiment. Treatments included: DDGS fed at 20% DM (13.4% CP; DDGS), SBM replacing 50% of DDGS (14.4% CP; SBM50), and SBM replacing 100% of DDGS (15.4% CP; SBM100). Steers (n = 189) were weighed and allotted to 1 of 24 pens (n = 8 steers per pen; 8 pens per treatment) at the Ruminant Nutrition Center near Brookings, SD. Whole blood was collected and harvested as sera on d 77, 105, and 139 to determine SUN concentration. Growth and carcass data were analyzed as a randomized complete block design using the GLIMMIX procedure of SAS 9.4 with treatment and block (initial BW grouping) as fixed effects; SUN data were analyzed using repeated measures, pen was the experimental unit. Inclusion level was evaluated for linear and quadratic components by the method of orthogonal polynomials. Final BW was calculated by dividing hot carcass weight (HCW) by 0.625. No differences were noted (P ≥ 0.18) for final BW, average daily gain, dry matter intake, or feed efficiency. Dietary treatment tended to affect gain to feed ratio (G:F; quadratic; P = 0.10) and SBM increased the apparent efficiency of energy capture. Treatment had no effect (P ≥ 0.22) on HCW, rib fat, marbling score, USDA yield grade, or final BW adjusted to 28% empty body fat. Complete replacement of DDGS with SBM increased rib eye area by 1% (linear; P = 0.02), but decreased dressing percentage (linear, P = 0.03). Distribution of USDA quality or yield grades were unaffected by treatment (P ≥ 0.36). No treatment × day interaction was observed for SUN (P = 0.20). However, day (P &amp;lt; 0.01) and treatment (P &amp;lt; 0.01) effects were observed. Initial samples (d 77) differed between DDGS and SBM treatments, with the latter having greater SUN values (P &amp;lt; 0.01). On d 105, the SBM100 treatment had greater SUN than DDGS, and SBM50 was intermediate (P &amp;lt; 0.01). On d 139, steers from SBM100 had elevated increased SUN compared with SBM50 and DDGS treatments (P &amp;lt; 0.01). Net energy values calculated from animal performance for DDGS agreed closely with tabular estimates. In this experiment, replacement of DDGS with SBM increased the observed to expected ratio of dietary NE, increased muscularity and tended to decrease DP with no other observed effects on growth performance or carcass traits.

58 Evaluation of a phytogenic blend on growth performance, health, carcass traits, and efficiency of dietary net energy utilization in finishing beef steers

Abstract The objective of this study was to determine if a formulated blend of capsicum oleoresin, clove essential oil, and garlic essential oil (CCG; Fytera Advance - Selko USA, Indianapolis IN) influences measures of cattle growth, efficiency, health, or carcass traits, during the finishing phase in steers fed a concentrate-based diet. Charolais × Angus steers [n = 96; initial shrunk body weight (BW) = 391 ± 34.0 kg] were used in a 144-d finishing experiment at the Ruminant Nutrition Center in Brookings, SD. Steers were individually weighed and allotted to one of 14 pens (n = 6 to 7 steers; 7 pens/treatment) in a randomized complete block design and randomly assigned to 1 of 2 treatments: control diet without the test product (CON) or a diet including CCG at 500 mg/steer daily (CCG). The average nutrient content of the finishing diet was: 13.5% CP; 18.7% NDF; 2.06 Mcal/kg NEm; and 1.39 Mcal/kg NEg; monensin sodium was included in the diet at 30 g/907 kg. Steers were fed twice daily, and bunks were managed according to a slick bunk system. There were no differences (P ≥ 0.10) in any growth performance outcome from d 1 to 35, 36 to 70, or 71 to 98. The within pen standard deviation for average daily gain (ADG) from d 71 to 98 tended to be reduced (P = 0.10) for CCG steers compared with CON. From d 99 to 144 steers supplemented CCG had 5% greater dietary energy utilization (P = 0.01), tended to have 5% greater ADG (P = 0.09), and 8% improved feed efficiency (P = 0.01). Experimental periods when improved pen gain uniformity and feed efficiency were observed coincided with increased summertime temperatures. No differences (P ≥ 0.15) were noted for cumulative growth performance. No differences were noted for any carcass measurements or categorical carcass outcomes, nor lung or liver health outcomes (P ≥ 0.15). Use of CCG had no appreciable influence on any cumulative growth performance responses. However, the use of CCG decreased within pen variation in ADG indicating more uniform nutrient intake among cattle and increased feed efficiency during summertime heat events.

65 Effect of two different implant programs on growth performance and carcass characteristics in beef steers fed to three differing harvest endpoints

Abstract Two implant programs (Merck Animal Health, DeSoto, KS and Zoetis, Parsippany, NJ) and 3 d on feed (DOF) endpoints were used to evaluate growth performance and carcass characteristics of finishing beef steers. Beef steers [n = 480; initial body weight (BW) = 402; SEM = 2.4 kg] were assigned to treatment pens (10 steers/pen) with pen (n = 48 pens total) as the experimental unit. Treatments were arranged as a 2 x 3 factorial including implant program: 1) a single Revalor-XS (200 mg trenbolone acetate and 40 mg estradiol-17β total) on d 0 (XS) compared with 2) Synovex-Choice (100 mg trenbolone acetate and 14 mg estradiol benzoate) on d 0 and re-implanted with a Synovex-ONE Feedlot (200 mg trenbolone acetate and 28 mg estradiol benzoate) 70 d later (CHSOF) and harvest endpoint: 1) 162 DOF, 2) 183 DOF, or 3) 204 DOF. Both implant groups were removed from their pens on the day of reimplantation. Data were analyzed as a RCBD. Final BW was calculated as HCW/0.625. An implant × DOF (P ≤ 0.04) interaction was noted for gain to feed ratio (G:F), REA, final BW adjusted to 28% estimated empty body fatness (AFBW), and USDA quality grade distribution, a tendency for an interaction was observed for final BW, average daily gain (ADG), HCW, and dressing percentage (P ≤ 0.09), no other interactions were noted for any traits evaluated (P ≥ 0.17). Steers from CHSOF/162 had increased G:F by 4.1 to 6.5% compared with others (P ≤ 0.05). Steers from XS/204 had greater REA by 3% to 10% (P ≤ 0.05) compared with all other treatments and greater AFBW by 3% to 7% (P ≤ 0.05), compared with all other treatments except CHSOF/204. Steers from XS had a greater proportion of carcasses grading USDA Prime at 162 and 183 DOF compared with CHSOF. As a result of increased DOF, the XS/204 and CHSOF/204 steers had greater final BW and HCW compared with all other treatments (P ≤ 0.05), steers from XS/183 had greater HCW than XS/162 and CHSOF/162; however, CHSOF/183 did not differ from CHSOF/162 (P ≤ 0.05). Steers from CHSOF/162 had greater ADG by 5.8% compared with CHSOF/183 (P = 0.05), while all others were intermediate. Dressing percentage was the greatest for XS/204 and least for CHSOF/183 (P ≤ 0.05). Cattle from XS had increased (P &amp;lt; 0.01) DMI by 2.6%. As DOF increased, carcass-adjusted final BW increased while ADG decreased (linear; P = 0.05). As DOF increased, REA and AFBW increased (P &amp;lt; 0.01). Increasing DOF, increased (P &amp;lt; 0.01) USDA yield grade 4 and 5 carcasses and decreased yield grade 2 and 3 carcasses. Implant strategy had a marginal influence on growth performance and carcass characteristics; however, as DOF increased carcass weights, rib fat, and ribeye area increased.

Influence of BOVAMINE DEFEND Plus on growth performance, carcass characteristics, estimated dry matter digestibility, rumen fermentation characteristics, and immune function in finishing beef steers.

One hundred and eighty crossbred beef steers (406.0 ± 2.2kg) were used to determine the impact of a novel direct-fed microbial (DFM) on growth performance, carcass characteristics, rumen fermentation characteristics, and immune response in finishing beef cattle. Steers were blocked by body weight (BW) and randomly assigned, within block, to 1 of 2 treatments (3 replicates/treatment: 30 steers/replicate). Treatments included: (1) no DFM (control) and (2) DFM supplementation at 50 mg ∙ animal-1 ∙ d-1 (BOVAMINE DEFEND Plus). All steers were fed a high-concentrate finishing diet and individual feed intake was recorded daily via the GrowSafe system. BWs were collected every 28 d. On day 55, 10 steers per pen were injected with ovalbumin (OVA). Jugular blood samples were collected from each steer on days 0, 7, 14, and 21 post injection. On day 112, the same steers were injected again with OVA and intramuscularly with a pig red blood cell solution. Jugular blood samples were collected from each steer on days 0, 7, 14, and 21 post injection. On day 124, rumen fluid was collected from 3 steers per treatment and used to estimate in vitro rumen fermentation characteristics. Equal numbers of steers per treatment were transported to a commercial abattoir on days 145, 167, and 185 of the experiment, harvested, and carcass data were collected. Initial BW was similar across treatments. On days 28 and 55, steers receiving DFM had heavier BW (P < 0.01) compared to controls. The average daily gain was greater in DFM-supplemented steers from days 0 to 28 (P < 0.01) and days 0 to 55 (P < 0.01) of the experiment compared to controls. Overall dry matter intake (DMI) was greater (P < 0.04) and overall feed efficiency was similar in DFM-supplemented steers compared to controls. Dressing percentage (P < 0.02) was greater in steers receiving DFM compared to controls. Antibody titers to injected antigens were similar across treatments. However, red blood cell superoxide dismutase activity was greater (P < 0.05) in DFM-supplemented steers compared to controls. In vitro molar proportions of isobutyric and butyric acid were greater (P < 0.01) and dry matter (DM) digestibility tended (P < 0.07) to be greater in rumen fluid obtained from steers supplemented with DFM. These data suggest that BOVAMINE DEFEND Plus supplementation improves growth performance during the initial period of the finishing phase, increases overall DMI and dressing percentage, and may impact antioxidant status in beef cattle.

Effects of steam-flaked corn and wet distillers grains with solubles on energy metabolism of finishing beef steers*

Effects of steam-flaked corn and wet distillers grains with solubles on energy metabolism of finishing beef steers*

Recommendations on visit duration and sample number requirements for an automated head chamber system.

Automated head chamber systems (AHCS; GreenFeed, C-Lock Inc., Rapid City, SD) increasingly are being used for measuring the gas flux of unrestrained cattle. There are a wide range of recommendations for what constitutes a "good" visit (i.e., duration) to an AHCS and how many visits are required for the AHCS to quantify gas fluxes accurately and precisely. Accordingly, the purpose of this experiment was to investigate the effects of visit duration thresholds and the subsequent effects of these thresholds on the number of visits needed to provide adequate estimates of carbon dioxide (CO2) and methane (CH4) emissions, and oxygen (O2) consumption by beef cattle. This analysis utilized data from three previously published experiments with grazing beef steers and one experiment with finishing beef steers, with 103 steers total. When comparing all available visits, there was excellent agreement [Lin's concordance correlation coefficient (CCC) ≥ 0.96] between visits ≥ 3min in duration and those ≥ 2min for the three gases in all four experiments. When data from all four experiments were pooled, there was excellent agreement between visits ≥ 3min and those ≥ 2min and ≥ 1min for all gases (CCC ≥ 0.96). These results suggest that estimates from visits ≥ 2min are like those from visits ≥ 3min. Next, we investigated if including visits ≥ 2min or ≥ 1min would increase the minimal number of visits required to provide excellent agreement with the "gold-standard" (mean of all visits ≥ 3min). For this, we used only one of the experiments and randomly selected visits per animal ranging from n = 5 to 60, in increments of 5. The sole experiment was used because all animals had more than 60 visits. We then assessed the agreement between the "gold-standard" (mean of all visits ≥ 3min [144 ± 55.01 visits per steer]) estimates of CO2, O2, and CH4. The minimum number of visits required to achieve excellent agreement (CCC ≥ 0.90) to the "gold-standard" estimate for all gases was 30 visits ≥ 3min in duration, or 40 visits ≥ 2min in duration. Visits ≥ 1min in duration did not achieve excellent agreement, even when 60 were used. Based on these results, we recommend excluding visits < 3min in duration with 30 minimum visit records per animal. However, if researchers choose to implement a 2-min visit duration threshold then 40 visit records are needed per animal.

Association of glucose metabolism and insulin resistance with feed efficiency and production traits of finishing beef steers.

Increasing nutrient utilization efficiency is an important component of enhancing the sustainability of beef cattle production. The objective of this experiment was to determine the association of glucose metabolism and insulin resistance with dry matter intake (DMI), average daily gain (ADG), gain:feed ratio (G:F), and residual feed intake (RFI). Steers (n = 54; initial body weight = 518 ± 27.0kg) were subjected to an intravenous glucose tolerance test (IVGTT) where glucose was dosed through a jugular catheter and serial blood samples were collected. Three days after the last group's IVGTT, steers began a 63-d DMI and ADG test. Body weight was measured on days 0, 1, 21, 42, 62, and 63, and DMI was measured using an Insentec Roughage Intake Control system (Hokofarm Group, Emmeloord, the Netherlands). To examine relationships between DMI, ADG, G:F, and RFI with IVGTT measurements, Pearson correlations were calculated using Proc Corr of SAS 9.4 (SAS Inst. Inc., Cary, NC). Additionally, cattle were classified based on DMI, ADG, RFI, and G:F, where the medium classification was set as mean ± 0.5 SD, the low classification was < 0.5 SD from the mean, and the high classification was > 0.5 SD from the mean. No associations between DMI and IVGTT parameters were observed, and no differences were detected when classifying cattle as having low, medium, or high DMI. Peak insulin concentration in response to the IVGTT tended to be correlated with ADG (r = 0.28; P = 0.07), indicating cattle with greater ADG tend to have a greater insulin release in response to glucose. Glucose nadir concentrations tended to be positively correlated with ADG (r = 0.26; P = 0.10). Additionally, the glucose nadir was greater in high-ADG steers (P = 0.003). The association of greater glucose nadir with high-ADG could indicate that high-ADG steers do not clear glucose as efficiently as low-ADG steers, potentially indicating increased insulin resistance. Further, RFI was not correlated with IVGTT measurements, but low RFI steers had a greater peak glucose concentration (P = 0.040) and tended to have a greater glucose area under the curve (P = 0.09). G:F was correlated with glucose area under the curve (r = 0.33; P = 0.050), glucose nadir (r = 0.35; P = 0.011), and insulin time to peak (r = 0.39; P = 0.010). These results indicate that glucose metabolism and insulin signaling are associated with growth and efficiency, but the molecular mechanisms that drive these effects need to be elucidated.

Cattle, carcass, economic, and estimated emission impacts of feeding finishing steers lubabegron or ractopamine hydrochloride.

Lubabegron (Experior; Elanco, Greenfield, IN, USA) is the first U.S. Food and Drug Administration approved feed additive for reducing gas emissions from feedlot animals or their waste; it does not have live or carcass performance claims. Our primary objective was to determine the effect of lubabegron on feedlot performance and carcass traits in finishing beef steers compared to ractopamine hydrochloride (Optaflexx; Elanco, Greenfield, IN, USA). A commercial feedlot trial using cross-bred beef steers (n = 2,117; 373 ± 15kg initial body weight [BW]) was completed with a randomized complete block design. Treatments consisted of two feed additives: (1) OPT targeted to deliver 300mg/animal/d of ractopamine hydrochloride for 28 ± 7 d out from harvest and (2) EXP targeted to deliver 36mg/animal/d of lubabegron 56 ± 7 d out from harvest and a 4-d preslaughter withdrawal period. Twenty 70 to 142 hd pens with 10 pens per treatment were used. Cattle were weighed at arrival processing and at harvest and fed for an average of 167 d. Data were used to calculate production metrics, partial budgets, and estimated greenhouse gas emissions using published methods, and were analyzed using linear mixed models with pen as the experimental unit and block as a random intercept. A statistical significance threshold of α = 0.05 was determined a priori. There was no evidence for statistically significant differences between treatments for initial BW (P = 0.70), health-related outcomes (P values ≥ 0.43), or mobility scores (P = 0.09). Cattle-fed EXP had increased final BW, ADG, G:F, and decreased dry matter intake (P values ≤ 0.01) compared to OPT. Carcasses were 11 ± 1.76kg (hot carcass weight) heavier in EXP group (P < 0.01), and differed between treatments for both yield grades (YG) and quality grades distributions (P values ≤ 0.01). Cattle-fed EXP had a shift toward more YG 1 and 2, select and sub-select carcasses compared to OPT, which had as shift toward more YG 3, 4, 5, prime and choice carcasses. With increased beef production and efficiency compared to OPT, the estimated CO2 equivalent emissions from production were reduced by 6.2% per unit of carcass weight for EXP (P ≤ 0.01). Estimated net returns/animal shipped were $56.61 ± 9.37 more for EXP than OPT (P ≤ 0.01). In conclusion, when cattle were fed for the same total number of days, feeding EXP compared to OPT increased net returns, feedlot performance, and efficiency, but resulted in carcass yield and quality characteristics that may impact marketing programs.

PSXIII-14 Supplementation of a Phytogenic Feed Additive on Growth Performance, Feed Intake and Carcass Traits of Growing and Finishing Beef Steers

Abstract Phytogenic feed additives (PFA) have been shown to provide anti-inflammatory, anti-microbial and antioxidant properties across many species including livestock and can positively influence animal performance. The objective of this study was to evaluate the effects of feeding a PFA to growing and finishing beef steers on growth performance, feed efficiency, carcass traits, and liver abscesses. Forty-five crossbred steers (initial BW; 272 ± 20.5 kg) were housed in individual pens and used in a randomized complete block design including a 110-d growing period followed by a 120-d finishing period. The steers were blocked by BW and randomly allocated to 1 of 3 treatments: control (CON) basal diet without PFA or monensin; basal diet with a phytogenic feed additive (PFA; 500 mg· animal-1· /day-1) or basal diet with monensin (MON; 300 mg/head/d). The growing diet consisted of 60% silage and 40% concentrate, while the finishing diet consisted of 10% silage and 90% of concentrate (DM basis). In the growing period, dry matter intake (DMI) did not differ; whereas, final BW (415 vs. 403 kg; P = 0.10) and average daily gain (1.31 vs. 1.20 kg/d; P = 0.12) was numerically greater with PFA than CON, respectively, with no difference from MON. Feed efficiency (gain:feed) in the growing period was greater (P = 0.04) with MON (173 g/kg) than PFA (161 g/kg) and CON (156 g/kg). In the finishing period, growth performance, feed efficiency, carcass traits did not differ among treatments; whereas, DMI was numerically less (P = 0.11) with PFA (10.2 kg/d) than CON (10.8 kg/d), but there was no difference between PFA and MON (9.8 kg/d). The percentage of abscessed livers did not differ between PFA and CON, but the proportion of abscessed livers tended (P = 0.09) to be greater with MON compared with PFA and CON, without difference in severely abscessed livers among treatments. These results indicate that feed efficiency of growing steers was not improved by PFA to the level with MON. However, supplementation of PFA or MON resulted in similar finishing performance and feed efficiency.

105 The Effects of Roughage Neutral Detergent Fiber Concentration and Bulk Density of Steam-Flaked Corn on Performance, Carcass Characteristics, and Liver Abscesses in Finishing Beef Steers

Abstract We evaluated the effects of dietary neutral detergent fiber (NDF) concentration from alfalfa hay and bulk density of steam-flaked corn (SFC) on growth performance, carcass characteristics, and liver abscesses in finishing beef steers. Crossbred beef steers (n = 214; 60 pens; 10 pens/treatment; initial BW 417 ± 11.9 kg) were blocked by BW and assigned randomly to treatments and fed an average of 112 d. The treatments were arranged as a 2 × 3 factorial and consisted of three NDF concentrations from alfalfa hay (3, 4.5, or 6%) and 335 g/L (10.9 kg/bu) or 425 g/L (14.5 kg/bu) steam-flaked corn (SFC; 33 or 69% starch availability, respectively). Steers were harvested at a commercial abattoir where carcass data and livers scores were collected. Performance and carcass data were analyzed with PROC MIXED of SAS with pen as the experimental unit. Pen quality grade distribution and liver scores were analyzed as binomial proportions using PROC GLIMMIX. No interactions between roughage NDF and bulk density of SFC were noted (P &amp;gt; 0.18); therefore, main effects are presented. Live and carcass-adjusted growth performance did not differ throughout the study (P ≥ 0.28), except for an increase in dry matter intake by steers fed 6% vs. 3 or 4.5% roughage NDF from d 70 to 105 (P = 0.02). Marbling score was greater (P = 0.05) for steers fed 3% than for 4.5 or 6% roughage NDF, and steers fed 335 g/L SFC tended to have a larger longissimus muscle area (P = 0.10) than those fed 425 g/L SFC. Presence of LA at harvest was 17.9 and 23.4% less (P &amp;lt; 0.01) in the steers fed 4.5 and 6% roughage NDF, respectively, than for those fed 3% roughage NDF. Similarly, the presence of A+ abscesses was greater (P = 0.03) in steers fed 3% roughage NDF than in those fed 4.5 or 6% roughage NDF. Liver abscesses were 11.7% less (P = 0.05) in steers fed 425 vs. 335 g/L SFC. Results suggest that increasing roughage NDF and bulk density of SFC are dietary strategies to decrease the presence of liver abscesses at harvest without negatively affecting growth performance.

106 Using a Novel Direct-Fed Microbial as an Alternative for Tylosin Phosphate to Control Liver Abscesses and Decrease Antimicrobial Use in Finishing Beef Steers

Abstract Our objective was to evaluate the use of a novel direct-fed microbial as an alternative to antimicrobials to decrease liver abscesses in feedlot cattle. Angus beef steers (n = 240; initial BW = 263 ± 18.0 kg) were used in a randomized complete block design comprised of 3 BW blocks and 3 pen replications per treatment. Experimental treatments were randomly assigned to pen within BW block and consisted of: 1) negative control, dietary supplement contained no tylosin phosphate (NCON); 2) positive control, dietary supplement contained tylosin phosphate (PCON); 3) positive control with tylosin phosphate removed the last 65 d of the feeding period (PCONW); and 4) novel direct-fed microbial fed at 1 g mixture/animal with 1 × 1011 CFU/g (DFM). By design, initial BW did not differ (P = 0.79) among treatments, and at the end of the 59-d receiving period, there were no differences in final BW (P = 0.25). From d 0 to d 30, ADG, DMI, DMI as a percentage of BW, and G:F did not differ (P ≥ 0.21). Likewise, ADG, DMI, DMI as a percentage of BW, and G:F, from d 31 to d 59, were not different (P ≥ 0.30). From d 0 to d 59, there were no differences in ADG, DMI, DMI as a percentage of BW, nor G:F (P ≥ 0.20). During the finishing period, live- and carcass-adjusted final BW did not differ (P ≥ 0.57) among treatments. During the finishing period, there were also no differences in ADG, DMI, DMI as a percentage of BW, or G:F (P ≥ 0.17). Carcass-adjusted ADG, DMI as a percentage of BW, and G:F also did not differ (P ≥ 0.16). Across treatments, no differences in HCW were noted (P = 0.84). Dressing percentage, marbling score, longissimus dorsi (LM) area, 12th-rib fat thickness, and calculated yield grade (YG) were not different among dietary treatments (P ≥ 0.32). Liver abscess incidence and severity were not affected by dietary treatments (P ≥ 0.13). The inclusion of a novel direct-fed microbial in finishing cattle diets did not affect growth performance, carcass characteristics, nor the prevalence of liver abscesses. However, the removal of tylosin phosphate 65 d before harvest numerically resulted in the lowest frequency of severe liver abscesses when compared with steers not fed tylosin phosphate.