The Use of Probiotic Megasphaera elsdenii as a Pre-Harvest Intervention to Reduce Salmonella in Finishing Beef Cattle: An In Vitro Model

Reducing Salmonella in cattle may mitigate the risk of transmission through the food chain. Megasphaera elsdenii (ME) is a microorganism found naturally in the bovine rumen that can be administered as a probiotic to mitigate ruminal acidosis. Understanding the impact of feeding ME to Salmonella populations in cattle was the objective of this study. Bovine ruminal fluid (RF) and feces were inoculated with antibiotic susceptible or resistant Salmonella and treated with varying concentrations of ME. Salmonella was enumerated at 0, 24, 48, and 72 h using the most probable number (MPN). Volatile fatty acids (VFAs) and pH were recorded from non-inoculated samples. Treating RF with ME did not significantly impact Salmonella concentration or VFA production (p > 0.05). The pH of RF and feces decreased over time (p ≤ 0.05). Salmonella concentration declined in feces, with the largest reduction of 1.92 log MPN/g and 1.05 log MPN/g observed for antibiotic susceptible Salmonella between 0 and 72 h by the 2.5 × 10(5) CFU/g and control (0.0 CFU/g) concentration of ME, respectively. Treating RF with ME did not impact Salmonella concentration. Salmonella concentration in feces decreased, although ME must be further investigated before a conclusion regarding efficacy in vitro can be determined.