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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 < 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 < 0.01), whereas fecal Salmonella concentration was greatest before harvest (P < 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. [ABSTRACT FROM AUTHOR]

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 carcassadjusted 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. [ABSTRACT FROM AUTHOR]

Our objective was to evaluate the effects of random metaphylaxis administered on arrival to 0, 33, 66, or 100% of high-risk beef cattle on clinical health, growth performance, and complete blood cell counts during a 35-d receiving period. Crossbred beef steers (n = 216; arrival BW = 197 ± 6.4 kg) were used in a generalized complete block design consisting of 2 source blocks and 4 treatments. Experimental treatments and steers were randomly assigned to pen within source block: 1) negative control, subcutaneous injection with sterile saline (NCON); 2) 33% of steers/pen given metaphylaxis (33M); 3) 66% of steers/pen given metaphylaxis (66M); and 4) positive control; conventional metaphylaxis given to 100% of steers (CONV). Body weight and blood samples for quantification of complete blood count were collected on d 0, 14, and 35. Pen was considered the experimental unit for all analyses. Continuous data were analyzed using PROC MIXED, and categorical data were analyzed as binomial proportions using PROC GLIMMIX. Treatment was included in the model as a fixed effect and source block was a random effect. Complete blood counts were analyzed as repeated measures, where day was the repeated effect and pen within treatment was the subject. The percentage of steers treated with an antibiotic for bovine respiratory disease (BRD) once was greater (P < 0.01) for NCON and 33M than for 66M and CONV. Neither BW on d 35 nor average daily gain from d 0 to 35 differed among treatments (P > 0.65), but dry matter intake (DMI) and DMI as a percentage of BW from d 0 to 35 was greater (P < 0.03) for 66M and CONV than for NCON and 33M. No differences in hematological variables were detected among treatments (P > 0.19), whereas all complete blood count variables were affected by day (P < 0.01), except for mean corpuscular hemoglobin concentration (P = 0.81). Most notably, the neutrophil:lymphocyte ratio was greater (P < 0.01) on d 0 than on d 14 and 35. These data suggest that arrival metaphylaxis can be administered to 66% of cattle at random without increasing BRD morbidity while simultaneously increasing DMI similar to conventional metaphylaxis. Random metaphylaxis may be a viable method to decrease antibiotic use in the feedlot industry, while maintaining health outcomes and growth performance of high-risk beef cattle. [ABSTRACT FROM AUTHOR]

The objective was to investigate the influence of cattle origin and region of finishing on the prevalence of Salmonella, Escherichia coli O157:H7, and select antimicrobial resistance in E. coli populations. Yearling heifers (n = 190) were utilized in a 2 × 2 factorial arrangement. Heifers (n = 98) in the northern region were sourced from South Dakota (SD) while heifers (n = 92) in the southern region were sourced from Texas (TX). After feedlot arrival in each respective region, fecal Salmonella prevalence was determined, and heifers were sorted into 1 of 4 treatments: heifers sourced from SD and finished in SD (SD-SD); heifers sourced from SD and finished in TX (SD-TX); heifers sourced from TX and finished in SD (TX-SD); heifers sourced from TX and finished in TX (TX-TX). Transport for SD-TX and TX-SD heifers occurred on d 0. Fecal, pen, and water scum line (WSL) samples were collected longitudinally throughout the study; hide and subiliac lymph node (SLN) samples were collected at study end (d 78 for heifers finished in TX and d 90 for heifers finished in SD). A treatment × time interaction was observed (P = 0.01) for fecal Salmonella prevalence, with prevalence being greatest for TX-TX and TX-SD heifers before transport. From d 14 through study end, prevalence was greatest for TX-TX and SD-TX heifers compared with SD-SD and TX-SD heifers. The TX-SD heifers had a 72% decrease in Salmonella prevalence from d 1 to harvest, whereas the SD-TX heifers had a 2,200% increase in Salmonella prevalence from d 1 to harvest. Salmonella prevalence on hides were greater (P = 0.01) for heifers finished in TX compared with SD. Salmonella prevalence in SLN tended (P = 0.06) to be greater in TX-TX and SD-TX heifers compared with TX-SD and SD-SD. Fecal E. coli O157:H7 prevalence had a treatment × time interaction (P = 0.04), with SD-TX prevalence being greater than TX-SD on d 56 and SD-SD and TX-TX being intermediate. A treatment × time interaction was observed for fecal trimethoprim-sulfamethoxazole-resistant and cefotaxime-resistant E. coli O157:H7 prevalence (P ≤ 0.01). Overall, these data suggest region of finishing influences pathogenic bacterial shedding patterns, with the initial 14 d after feedlot arrival being critical for pathogen carriage. [ABSTRACT FROM AUTHOR]