Salmonella enterica, which causes typhoid fever, is one of the most prevalent food-borne pathogens. Salmonellosis in cattle can greatly impact a producer’s income due to treatment costs, decreased productivity of the herd, and mortality due to disease. Current methods of treatment and prevention for salmonellosis consist of antibiotics and vaccinations, but neither of these options are perfect. Probiotics, categorized as antibiotic alternatives, are living microorganisms that are added to animal feeds in appropriate quantities in order to benefit health and productivity in adult and newborn livestock. The objective of this study was to demonstrate that Lactobacillus animalis and Propionibacterium freudenreichii, when used as a direct-fed microbial, was effective in reducing the adverse effects of experimentally induced Salmonella infection in beef calves. We conducted a single site efficacy study with masking using a randomized design comprising two groups of ten beef calves allocated to two treatment groups (control and probiotic). Procedures such as determining general health scores and body weight and collecting fecal samples were carried out following the experimental challenge of calves with Salmonella Typhimurium. The presence of at least one CFU of bacteria in feces was significantly higher among animals in the control than in the probiotic group, which was higher on days 0 to 7 than on days 8 to 14 (p = 0.012). Animals in the control group had a significantly higher presence of abnormal diarrhea scores than animals in the probiotic group (p < 0.001). Most notably, other health benefits in probiotic-fed group calves were obviously better than those for control calves and further substantiates the potential economic and health benefits of feeding effective probiotics.

Clostridium perfringens is a spore-forming, anaerobic bacterium which produces toxins and exoenzymes that cause disease in calves, especially necro-hemorrhagic enteritis-associated diarrhea often resulting in death. Clostridium infections are currently being treated with antibiotics, but even with the prudent administration of antibiotics, there are significant rates of recurrence. Probiotics, an alternative to antibiotics, are commonly employed to prevent clostridial infections. The objectives of our study were to demonstrate that two commercially available products, when used as daily, direct-fed microbials, are effective in reducing adverse effects of an experimentally induced C. perfringens infection in dairy calves. We conducted a single site efficacy study with masking using a randomized design comprising 10 calves allocated to 3 treatment groups (probiotic 1, probiotic 2, and control). The procedures such as general health scores, body weight, blood samples, and fecal sample collections were done followed by experimental challenge of calves with C. perfringens. Daily feeding of L. animalis LA51 and P. freudenreichii PF24 without or with Bacillus lichenformis CH200 and Bacillus subtilis CH201, before, during and after an oral challenge of C. perfringens significantly reduced the incidence and severity of diarrhea while improving general impression and appearance scores of calves. Most notably, survival of calves in the two probiotic-fed groups was significantly higher than for control calves and further substantiates the potential economic and health benefits of feeding effective probiotics.

Two experiments were conducted to evaluate the in vitro and in vivo effects of a novel direct-fed microbial (DFM) containing Lactobacillus animalis LA-51, Propionibacterium freudenreichii PF-24, Bacillus licheniformis CH-200, and Bacillus subtilis King (BOVAMINE DEFEND^® Plus) against Clostridium perfringens pathogenic strains. In Experiment 1 (in vitro), an agar diffusion assay was performed to qualitatively evaluate the in vitro inhibitory effects of the DFM against C. perfringens types A and C. Including the DFM in the tested yielded inhibition zones with greater than three ring diameters in a 96-well plate. In Experiment 2 (in vivo), twenty 1-day-old beef calves were allocated to control (n = 10) or DFM (n = 10) for 21 days. All calves were orally challenged with 1.0 × 10⁸ colony forming units of C. perfringens type A strain S-107 per head. The procedures such as general health scores, body weight, and fecal sample collections were performed following the C. perfringens challenge. Daily feeding of DFM significantly reduced the incidence of diarrhea while improving general impression and appearance scores of calves. Overall, these results highlight the ability of the DFM containing L. animalis LA-51, P. freudenreichii PF-24, B. licheniformis CH-200, and B. subtilis (BOVAMINE DEFEND^® Plus) to inhibit C. perfringens types A and C under different experimental settings.