Using a Dose-Response Approach on the Growth of Food–Borne Pathogens in Feces of Cattle Fed Three Different Direct-Fed Rations Reveals the Efficacy of Lactobacillus salivarius L28

In the past two decades, the use of probiotics in livestock production has significantly increased. Direct-fed microbials (DFMs) have become popular in beef cattle production due to consumer demand for more natural meat alternatives. The objectives of this study were to (1) evaluate the dose-response of L28 at concentrations of 6, 7, and 8 log CFU/mL to inhibit the growth of STEC and S. enterica in cattle manure, and (2) assess tylosin and monensin in cattle manure and the efficacy of L28 in pathogen inhibition. Fecal samples were collected from cattle fed three different rations: (1) monensin and tylosin (MONTY), (2) monensin with L28 (MONPRO), and (3) no L28, tylosin or monensin (BASE). Sterilized fecal samples were inoculated with a cocktail mixture of three Shiga toxin-producing Escherichia coli (STEC) or Salmonella enterica (S. enterica) strains to an initial concentration of 3.0-4.0 log CFU/g. To evaluate the dose-response, Lactobacillus salivarius (L. salivarius) L28 was applied at concentrations of 6, 7, and 8 log CFU/ml. For S. enterica, the (BASE) ration had a significant treatment time effect at 12 h and 24 h with L28 at a dose of 8 log CFU (p = 0.01, p = 0.03). For STECs, the (BASE) had a similar effect, however, not significant for 24 h (p = 0.7). A dose of 8 log CFU/mL reduced S. enterica growth in manure samples by 1.3-4.2 log CFU/g compared to BASE. While L. salivarius does not completely prevent bacterial growth, it effectively reduces foodborne pathogens. Using L. salivarius in beef products offers a natural alternative to antibiotics, benefiting both consumers and the beef industry.