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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]

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]