Two beef finishing studies were conducted at the Texas Tech Burnett Center to evaluate a novel direct-fed microbial (DFMs) Lactobacillus Salivarius L28. The newly isolated strain of L. salivarius L28 has demonstrated pathogenic inhibition of Escherichia coli, Salmonella, and Listeria monocytogenes in-vitro. Additionally, Krehbiel et al. (2003) reported that DFMs have been shown to reduce fecal shedding of Escherichia coli O157:H7 and have minimal negative effects on growth performance and carcass traits. In the first study, single source crossbred steers (n = 144; BW = 371 ± 19 kg) were used in a randomized complete block design feedlot study to evaluate the effects of L28 on performance and carcass characteristics of finishing steers. Treatments included: no DFM, no subtherapeutic antibiotics, and no ionophore (CON), monensin sodium (Rumensin 90; Elanco; Greenfield, NJ; 33 g/ton DM basis) and tylosin phosphate (Tylan 40; Elanco; 11 g/ton DM basis) (MonTy), and monensin and L. salivarius L28 (10⁶ CFU steer/d) (MonPro). In the second study, single source crossbred steers (n = 240; BW = 319 ± 29 kg) were used in a randomized complete block design feedlot study. Treatments were the same as the first study, with the addition of tylosin phosphate (Tylan 40; Elanco; 11 g/ton DM basis) (TY) and L. salivarius L28 (10⁶ CFU steer/d) (PRO). No differences were observed for BW, ADG, or feed efficiency in either study. Cattle fed L28 consistently had a decreased DMI compared to controls in both studies. Both studies had a numerical depression in HCW and decrease in marbling scores for L28 fed cattle. Apparent total tract digestibility was not improved with the addition of L28. Further research is needed into the mechanism of action in order to determine the most appropriate use of L28 within the agriculture industry.