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The objective was to provide an updated profile of the bovine acute-phase response to include recent advancements in technologies and expanded hematological, cytokine, and serum chemistry variables. Beef steers (n = 32; body weight [BW] = 251 ± 19.5 kg) were fitted with indwelling jugular catheters 1 d before lipopolysaccharide (LPS; 0.25 µg LPS/kg BW from Escherichia coli O111:B4) administration to facilitate serial blood collection. Rectal temperature was measured using indwelling probes, and ocular temperature was measured using infrared thermal imaging. Blood samples were collected for subsequent analysis of serum chemistry, hematology, and cytokine concentrations. Pearson correlation of rectal temperature and ocular infrared temperature was 0.61 (P

Aims Our objective was to determine how injectable antimicrobials affected populations of Salmonella enterica, Escherichia coli and Enterococcus spp. in feedlot cattle. Methods and Results Two arrival date blocks of high-risk crossbred beef cattle (n = 249; mean BW = 244 kg) were randomly assigned one of four antimicrobial treatments administered on day 0: sterile saline control (CON), tulathromycin (TUL), ceftiofur (CEF) or florfenicol (FLR). Faecal samples were collected on days 0, 28, 56, 112, 182 and study end (day 252 for block 1 and day 242 for block 2). Hide swabs and subiliac lymph nodes were collected the day before and the day of harvest. Samples were cultured for antimicrobial-resistant Salmonella, Escherichia coli and Enterococcus spp. The effect of treatment varied by day across all targeted bacterial populations (p ≤ 0.01) except total E. coli. Total E. coli counts were greatest on days 112, 182 and study end (p ≤ 0.01). Tulathromycin resulted in greater counts and prevalence of Salmonella from faeces than CON at study end (p ≤ 0.01). Tulathromycin and CEF yielded greater Salmonella hide prevalence and greater counts of 128ERYR E. coli at study end than CON (p ≤ 0.01). No faecal Salmonella resistant to tetracyclines or third-generation cephalosporins were detected. Ceftiofur was associated with greater counts of 8ERYR Enterococcus spp. at study end (p ≤ 0.03). By the day before harvest, antimicrobial use did not increase prevalence or counts for all other bacterial populations compared with CON (p ≥ 0.13). Conclusions Antimicrobial resistance (AMR) in feedlot cattle is not caused solely by using a metaphylactic antimicrobial on arrival, but more likely a multitude of environmental and management factors.

Bovine respiratory disease (BRD) is the primary animal health concern facing feedlot producers. Many antimicrobial mitigation strategies are available, but few studies have compared feedlot performance during both the receiving and finishing periods following application of different antimicrobials used as metaphylaxis at arrival. The objective of this study was to compare antimicrobial metaphylaxis methods on clinical health and growth performance across both the receiving and finishing periods. A total of 238 multiple-sourced steers in two source blocks were used in a generalized complete block design. The four treatments included: 1) a negative control, 5 mL of sterile saline injected subcutaneously (CON); 2) subcutaneous administration of florfenicol at 40 mg/kg of BW (NUF); 3) subcutaneous administration of ceftiofur in the posterior aspect of the ear at 6.6 mg/kg of BW (EXC); and 4) subcutaneous administration of tulathromycin at 2.5 mg/kg of BW (DRA). The morbidity rate for the first treatment of BRD was decreased for the DRA and EXC treatments compared to CON and NUF (P

Objective Our objective was to compare metaphylaxis with tulathromycin (META) and vaccination with a pentavalent modified-live virus respiratory vaccine (MLV) in high-risk feedlot calves and their influence on health and growth performance during a 56-d receiving period. Materials and Methods Beef bulls (n = 372) and steers (n = 106) were stratified by initial BW (234 ± 1.32 kg), health status, and sex and randomly assigned to treatments arranged in a 2 × 2 factorial: (1) no META or MLV (CON), (2) META administration on d 0 (META), (3) MLV administration on d 0 with revaccination on d 14 (MLV), and (4) META and MLV administration (META+MLV). Interactions and main effects were analyzed within a generalized complete block design using a mixed statistical model with 10 pen replicates per treatment. Body weight and feed refusals were recorded periodically to determine interim and overall (d 0 to 56) performance and feed efficiency. A subset (n = 256) was affixed with a 3-axis accelerometer ear-tag to quantify activity and rumination time. A 7-d postmetaphylactic interval was implemented for META, and bovine respiratory disease cases were determined by treatment-blinded, trained investigators. Results and Discussion The META groups had greater ADG from d 0 to 14, from d 14 to 28, and overall (P ≤ 0.01) and BW on d 56 was increased (P Implications and Applications Health and performance of high-risk feedlot cattle was improved by META but not MLV.

In the feedlot, there can be a decrease in dry matter intake (DMI) associated with reimplanting cattle that negatively affects growth performance. This study was conducted to determine the mechanisms causing a decrease in DMI after reimplanting and identify a strategy to mitigate the decrease. Crossbred steers (n = 200; 10 pens/treatment; initial bodyweight [BW] = 386 ± 4.9 kg) were used in a randomized complete block design experiment. Cattle were implanted with Revalor-IS on day 0. Treatments included a Revalor-200 implant on day 90 before feeding with the following management practices imposed: 1) steers were returned to their home pen immediately after reimplant (PCON); 2) steers were placed in pens and restricted from feed and water for 4 h (RES); 3) steers were walked an additional 805 m after reimplant and then returned home (LOC); 4) steers were restricted from feed and water for 4 h and walked an additional 805 m (RES + LOC); 5) steers were given an oral bolus of Megasphaera elsdenii (Lactipro; MS Biotec, Wamego, KS) and were restricted from feed and water for 4 h, and then walked an additional 805 m (LACT). One hundred steers were given an ear tag to record minutes of activity (ESense Flex Tags, Allflex Livestock Intelligence, Madison, WI). As a percentage of BW, DMI was 5% greater (P = 0.01) from reimplant to end for PCON vs. RES, LOC, and RES + LOC treatments. Likewise, as a percentage of BW, DMI was 6.6% greater (P = 0.03) from reimplant to end and 4.0% greater (P = 0.05) overall for the PCON treatment vs. the LOC treatment. Overall, DMI as a percentage of BW was 3.3% greater (P = 0.02) for PCON vs. RES, LOC, and RES + LOC treatments. There was an increase in G:F from reimplant to end (P = 0.05) for RES + LOC vs. the LACT treatment. From these data, we conclude that restricting cattle from feed and water for 4 h after reimplanting did not alter subsequent DMI. Increasing locomotion had the greatest negative effect on DMI and growth performance. Management strategies to decrease locomotion associated with reimplanting would be beneficial to DMI and overall growth performance of finishing beef steers.

The study objective was to determine the effects of Bacillus subtilis PB6 and/or chromium propionate supplementation on serum chemistry, complete blood count, and fecal Salmonella spp. count in high-risk beef cattle during a 56-d feedlot receiving period and the subsequent finishing period. Four truckload blocks of crossbred beef bulls (n = 300) and steers [n = 84; total n = 384; average initial body weight (BW) = 220 ± 16.2 kg] were sourced from regional auction markets and assigned randomly to treatments arranged in a 2 × 2 factorial. Blood samples were collected from two bulls nearest to the median BW on arrival in each pen (n = 96) and fecal samples were collected from cattle in block 3 (n = 96). The generalized complete block design consisted of 12 pen replications per treatment with pen as the experimental unit. Treatments were: 1) negative control (CON); 2) 13 g per animal daily of prepared B. subtilis PB6 product (CST); 3) 450 ppb dry matter (DM) chromium propionate (CHR); and 4) 13 g per animal daily of prepared B. subtilis PB6 product and 450 ppb DM chromium propionate (CST + CHR). Treatments were top dressed in feed bunks daily using 0.45 kg per animal ground corn carrier immediately following feed delivery. Data were analyzed using mixed models with repeated measures. Day affected all serum chemistry variables (P ≤ 0.03) except total CO2 (P = 0.34) and all complete blood count variables during receiving (P ≤ 0.02) except percentage basophils (P ≥ 0.12). During the overall receiving period, serum calcium was decreased (P = 0.02) by CHR. Cattle fed CHR had greater total leukocyte count (P = 0.04) and neutrophil count (P = 0.02) during the overall receiving period. Fecal Salmonella spp. count was markedly reduced in cattle fed CST on day 28 (P = 0.01) and overall (P = 0.07). Overall, these data provide metabolic and hematologic insight into the unique challenges presented by lightweight, high-risk feeder cattle. Notably, CST was found to be effective in mitigating fecal enumeration and presumably replication of Salmonella spp. in the gastrointestinal tract.

The study objective was to determine the effects of Bacillus subtilis PB6 and/or chromium propionate supplementation on health, growth performance, and carcass characteristics of high-risk beef cattle during a 56-d feedlot receiving period and the subsequent finishing period. Four truckload blocks of crossbred beef bulls (n = 300) and steers [n = 84; body weight (BW) = 220 ± 16.2 kg] were sourced from regional auction markets and assigned randomly to treatments arranged in a 2 × 2 factorial. The generalized complete block design consisted of 12 pen replications per treatment with pen as the experimental unit. Treatments were: 1) placebo control (CON); 2) 13 g per animal daily of B. subtilis PB6 (CST); 3) 450 ppb dry matter (DM) chromium propionate (CHR); and 4) 13 g per animal daily of B. subtilis PB6 and 450 ppb DM chromium propionate (CST + CHR). Treatments were top dressed in feed bunks daily using 0.45 kg per animal ground corn carrier immediately following feed delivery. Data were analyzed using mixed models. During the receiving period, dry matter intake (DMI) increased (P ≤ 0.03) for CST during each interim period. Overall receiving period daily DMI was 0.35 kg per animal greater for CST (P = 0.01). Cattle fed CST had greater (P ≤ 0.06) BW on days 14, 28, and 56. Likewise, average daily gain (ADG) was improved for CST from day 0 to 14 (P = 0.04) and for the overall receiving period (days 0–56; P = 0.04). From days 0 to 14, CST tended (P = 0.08) to increase gain:feed. During the finishing period, CHR reduced (P = 0.02) final BW and ADG (day 56 to final; P = 0.01) and ADG was less for CHR over the entire feeding period (day 0 to final; P = 0.03). The main effect of both CST (P = 0.02) and CHR (P = 0.03) decreased the overall treatment rate for bovine respiratory disease (BRD), and CST reduced overall antimicrobial treatment cost by $3.50 per animal compared to CON (P = 0.03). Hot carcass weight (HCW) decreased (P = 0.01) in cattle fed CHR. The percentage of edible livers tended to increase (CST × CHR; P = 0.08) in the CST treatment. Feed intake and growth performance outcomes during the receiving period were improved by CST but not CHR supplementation. However, both CST and CHR supplementation decreased the BRD morbidity rate. During the finishing period, performance and HCW were reduced in cattle supplemented with CHR.

The study objective was to determine the effects of Bacillus subtilis PB6 and/or chromium propionate supplementation on health, growth performance, and carcass characteristics of high-risk beef cattle during a 56-d feedlot receiving period and the subsequent finishing period. Four truckload blocks of crossbred beef bulls (n = 300) and steers [n = 84; body weight (BW) = 220 ± 16.2 kg] were sourced from regional auction markets and assigned randomly to treatments arranged in a 2 × 2 factorial. The generalized complete block design consisted of 12 pen replications per treatment with pen as the experimental unit. Treatments were: 1) placebo control (CON); 2) 13 g per animal daily of B. subtilis PB6 (CST); 3) 450 ppb dry matter (DM) chromium propionate (CHR); and 4) 13 g per animal daily of B. subtilis PB6 and 450 ppb DM chromium propionate (CST + CHR). Treatments were top dressed in feed bunks daily using 0.45 kg per animal ground corn carrier immediately following feed delivery. Data were analyzed using mixed models. During the receiving period, dry matter intake (DMI) increased (P ≤ 0.03) for CST during each interim period. Overall receiving period daily DMI was 0.35 kg per animal greater for CST (P = 0.01). Cattle fed CST had greater (P ≤ 0.06) BW on days 14, 28, and 56. Likewise, average daily gain (ADG) was improved for CST from day 0 to 14 (P = 0.04) and for the overall receiving period (days 0–56; P = 0.04). From days 0 to 14, CST tended (P = 0.08) to increase gain:feed. During the finishing period, CHR reduced (P = 0.02) final BW and ADG (day 56 to final; P = 0.01) and ADG was less for CHR over the entire feeding period (day 0 to final; P = 0.03). The main effect of both CST (P = 0.02) and CHR (P = 0.03) decreased the overall treatment rate for bovine respiratory disease (BRD), and CST reduced overall antimicrobial treatment cost by $3.50 per animal compared to CON (P = 0.03). Hot carcass weight (HCW) decreased (P = 0.01) in cattle fed CHR. The percentage of edible livers tended to increase (CST × CHR; P = 0.08) in the CST treatment. Feed intake and growth performance outcomes during the receiving period were improved by CST but not CHR supplementation. However, both CST and CHR supplementation decreased the BRD morbidity rate. During the finishing period, performance and HCW were reduced in cattle supplemented with CHR.

One hundred ninety-two beef steers (BW = 332 ± 8.2 kg) were used in a randomized complete block design to evaluate the effects of differing bunk management and bulk density of steam-flaked corn (SFC) in a randomized complete block design. A factorial arrangement of treatments was used with: 1) slick bunk management (SBM) + 335 g/L SFC; 2) modified ad libitum bunk management (MAL) + 335 g/L SFC; 3) SBM + 425 g/L SFC; 4) MAL+ 425 g/L SFC. Steers were randomly assigned to treatment within BW block, with 12 pen replications per treatment. Data were analyzed using a mixed model with fixed effects of bunk management, SFC bulk density, and their interaction. Block was included as a random effect. Bunk management strategy did not affect growth performance, carcass characteristics, or liver abscess score (P > 0.10). The average daily gain (ADG) of steers fed 425 g/L SFC was greater (P = 0.05) from days 35 to 105 than those fed 335 g/L SFC; however, overall ADG did not differ (P = 0.36). The DMI of steers fed 425 g/L SFC was greater (P ≤ 0.05) than those fed 335 g/L SFC. Gain-to-feed of steers fed 425 g/L SFC tended (P = 0.10) to be lesser from days 0 to 35 but did not differ overall (P ≥ 0.12). Steers fed 425 g/L SFC tended to have greater backfat and calculated empty body fat (P ≤ 0.07) than those fed 335 g/L SFC and had a greater calculated yield grade (P = 0.05). Steers fed 425 g/L SFC had 43.51% fewer (P = 0.04) liver abscesses. Bunk management strategy did not impact growth performance or carcass characteristics; whereas, SFC processed to 425 g/L increased DMI, fat thickness, and yield grade while resulting in a decreased proportion of liver abscesses.

The objective was to determine the effects of Bacillus subtilis PB6 and/or chromium propionate supplementation on health, performance, and blood parameters in high-risk beef calves during a 56-day receiving period. Four truckload blocks of crossbred beef calves (n = 384; BW=220±16.2 kg) were assigned randomly to treatments arranged in a 2 × 2 factorial. The generalized complete block design consisted of 12 pen replications per treatment with pen as the experimental unit. Treatments were: 1) placebo control (CON); 2) 13 g/animal/d Bacillus subtilis PB6 (CLOSTAT®, Kemin Industries; CST); 3) 1 g/animal/d Cr propionate (KemTRACE® Chromium, Kemin Industries; CHR); and 4) CST+CHR. Treatments were top dressed in feed bunks daily using 0.45 kg/animal/d ground corn carrier. Blood samples were collected on days 0, 14, 28, and 56 for analysis of serum chemistry and complete blood count variables from a pen subset (n = 2/pen). Data were analyzed using MIXED and GLIMMIX procedures of SAS. The DMI was increased for CST during each interim period (P ≤ 0.03) and overall DMI was increased by 0.78 lb/animal/d for CST (P = 0.01). The CST supplemented cattle had greater BW on days 14, 28, and 56 (P ≤ 0.06). Likewise, ADG was improved for CST from day 0 to 14 (P = 0.04) and for the overall receiving period (P = 0.04). Main effects of CST (P = 0.02) and CHR (P = 0.03) decreased the percentage of calves treated for bovine respiratory disease (BRD). Morbidity was 28.0 and 39.9% for cattle with and without CST supplementation and 28.6 and 39.3% for cattle with and without CHR supplementation, respectively. Cattle fed CHR had increased (P ≤ 0.04) total leukocytes, neutrophils, serum aspartate aminotransferase and less (P = 0.02) serum calcium. Performance was improved by CST and BRD morbidity was less for CST and CHR.

The study objective was to determine the effect of a DNA immunostimulant on recrudescence of bovine herpesvirus-1 (BHV-1) after dexamethasone challenge in beef cattle. It was hypothesized that the DNA immunostimulant would mitigate stress-induced immunosuppression; thereby, reducing the incidence of BHV-1 recrudescence. Steers (n = 10) and heifers (n = 10; initial BW = 489 kg ± 57 kg) were stratified by pre-existing BHV-1 antibody titer, sex and initial BW and randomly assigned to treatment (n = 4 pens/treatment; 2 or 3 animals/pen). All calves were administered 40 mg of dexamethasone i.v. at 0600 h from d 0 to 2, 166-d subsequent to BHV-1 challenge with 1.0 × 108 plaque-forming units per nostril. On d 1, calves were administered treatments consisting of 2 mL i.m. of DNA immunostimulant (Zelnate; ZEL) or sterile saline (CON). Once daily (0600) from d 0 to 12, a whole blood was obtained via jugular venipuncture for complete blood count (CBC) analysis and nasal swabs were collected to determine BHV-1 prevalence via virus isolation testing. A repeated measures mixed model was used to test the effect of treatment, day and their interaction for CBC variables. There was a treatment × day interaction for eosinophils (P = 0.02) and percent eosinophils (P = 0.03). Eosinophils were greater (P < 0.01) for ZEL on d 3 and 6 post-dexamethasone challenge. On d 11 and 12, eosinophils for CON rebounded such that their concentration was greater than ZEL (P < 0.01). Lymphocytes, neutrophil and monocyte concentration did not differ (P ≥ 0.44); however, a day effect (P ≤ 0.01) existed such that each variable increased transiently after dexamethasone challenge. All cattle had BHV-1 present in a nasal swab sample on at least one sample day, with prevalence of BHV-1 in nasal swab samples being greatest on d 5 (80% positive; P = 0.01). However, no treatment differences were detected for BHV-1 prevalence in this study. The DNA immunostimulant altered eosinophil concentrations but did not mitigate BHV-1 recrudesce after dexamethasone challenge

The study objective was to determine the effect of a DNA immunostimulant on recrudescence of bovine herpesvirus-1 (BHV-1) after dexamethasone challenge in beef cattle. It was hypothesized that the DNA immunostimulant would mitigate stress-induced immunosuppression; thereby, reducing the incidence of BHV-1 recrudescence. Steers (n=10) and heifers (n=10; initial BW = 489 kg ± 57 kg) were stratified by pre-existing BHV-1 antibody titer, sex and initial BW and randomly assigned to treatment (n=4 pens/treatment; 2 or 3 animals/pen). All calves were administered 40 mg of dexamethasone i.v. at 0600 h from d 0 to 2, 166-d subsequent to BHV-1 challenge with 1.0 × 108 plaque-forming units per nostril. On d 1, calves were administered treatments consisting of 2 mL i.m. of DNA immunostimulant (Zelnate; ZEL) or sterile saline (CON). Once daily (0600) from d 0 to 12, a whole blood was obtained via jugular venipuncture for complete blood count (CBC) analysis and nasal swabs were collected to determine BHV-1 prevalence via virus isolation testing. A repeated measures mixed model was used to test the effect of treatment, day and their interaction for CBC variables. There was a treatment × day interaction for eosinophils (P = 0.02) and percent eosinophils (P = 0.03). Eosinophils were greater (P < 0.01) for ZEL on d 3 and 6 post-dexamethasone challenge. On d 11 and 12, eosinophils for CON rebounded such that their concentration was greater than ZEL (P < 0.01). Lymphocytes, neutrophil and monocyte concentration did not differ (P ≥ 0.44); however, a day effect (P ≤ 0.01) existed such that each variable increased transiently after dexamethasone challenge. All cattle had BHV-1 present in a nasal swab sample on at least one sample day, with prevalence of BHV-1 in nasal swab samples being greatest on d 5 (80% positive; P = 0.01). However, no treatment differences were detected for BHV-1 prevalence in this study. The DNA immunostimulant altered eosinophil concentrations but did not mitigate BHV-1 recrudesce after dexamethasone challenge

The study objective was to explore the feasibility of an alternative injection site, ischiorectal fossa (IRF), for modified-live virus (MLV) vaccination in Jersey steers. We hypothesized administration of MLV in the IRF would not cause injection site lesions and result in similar antibody response against bovine viral diarrhea virus (BVDV) compared to the neck. Jersey steers (n = 28; BW=517 ± 116 kg) were stratified by a previously assigned growth implant treatment and day-35 BVDV antibody titer and randomly assigned to 1 of 2 treatments with injection treatment equivalently represented in each of 2 pens. Treatments consisted of: 1) 2 mL MLV vaccine administered s.c. in the neck (NECK); or 2) 2 mL MLV vaccine administered s.c. in the IRF. Blood was collected on days -35, 0, 35, 70, and 105 to determine BVDV-specific antibody titers using the virus neutralization assay and BW was recorded on the same days to determine gain performance. Steers were harvested on day 106 and examined for lesions respective to injection site. Antibody titers and performance variables were statistically analyzed via a mixed model with animal as the experimental unit. Concentration of BVDV antibody increased (P = 0.05) with time, but there was no treatment difference (P = 0.94) or treatment × day interaction (P = 0.70). There was no treatment difference for BW on any day (P ≥ 0.78). There was also no treatment difference in ADG (P ≥ 0.45). However, there was a period effect, where ADG was reduced markedly (P < 0.0001) for the day 0 to 35 interim period immediately following MLV vaccination compared to day -35 to 0 (0.79 vs. 0.18 kg/d). No injection site lesions were observed during harvest and results from BVDV antibody titers and performance indicate IRF as a potential alternative route of administration for MLV vaccines.

Transition of newly received feedlot cattle from a forage- to grain-based diet remains a complicated challenge and the appropriate roughage level in receiving diets is controversial. Nutritionists must consider the paradox of dietary transition and roughage level to mitigate ruminal acidosis, yet concomitantly low DMI presents difficulty in meeting nutrient requirements when metabolic demand is increased due to stress and infectious challenges. Classic research conducted by Lofgreen et al. (1975) confronted this paradox through evaluation of increasing energy density of receiving diets (0.84, 1.01, or 1.10 Mcal NE(g) /kg) offered to newly received beef cattle. Overall, a linear increase in both performance and morbidity was observed as energy level of the diet increased. More recently, Berry et al. (2004) evaluated factors of energy concentration and starch level in receiving diets. There was no interaction or main effect on performance outcomes; however, morbidity was numerically increased for cattle consuming high starch diets. The clinical signs of bovine respiratory disease (BRD) and acute acidosis are analogous; therefore, it is likely that acidotic cattle are incorrectly diagnosed with BRD in both research and production settings. Additional research efforts have attempted to elucidate alterations in rumen microbial population and digestion (Fluharty and Loerch, 1994), physiological response to inflammatory challenge (Reuter et al., 2008), and immunological response to infectious bovine rhinotracheitis virus challenge (Schwertner et al., 2011) in cattle consuming diets with various roughage levels. Furthermore, our understanding of the rumen and intestinal microbiome is improving rapidly with culture-independent assays, products such as probiotics and exogenous lactate utilizing bacteria are available, and increased availability and use of fibrous by-product ingredients require further attention. The objectives of the current symposia are to summarize performance and health implications related to roughage level in receiving diets and present new ideas for nutritional management of newly received beef cattle.