Evaluation of a prebiotic mannan-oligosaccharide on Salmonella Enteritidis cecal colonization and immune response of broiler chickens.

Salmonella causes 1.35 million cases of foodborne illness in the United States annually. We hypothesized that the administration of ActiveMOS®, a prebiotic mannan-oligosaccharide (MOS) product, would reduce Salmonella Enteritidis (SE) cecal colonization and improve immune function in young broilers. The objectives of this study were to assess the effects of MOS on SE cecal colonization, serum cytokines, lipopolysaccharide (LPS), and immunoglobulin M (IgM). This study consisted of two independent 14 d trials. Day-of-hatch broilers (n = 240/trial) were evenly distributed across eight floor pens and randomly assigned to four treatments. Treatments were as follows: control (0.0), 1.0, 1.5, and 2.0 kg of MOS/metric ton (MT) of feed. Broilers were orally gavaged with PBS for unchallenged treatments or SE for challenged treatments at 7 d of age. Birds were euthanized one week post gavage. Salmonella Enteritidis cecal colonization, serum pro-inflammatory cytokines- interferon gamma (IFNγ), interleukin-2 (IL-2), IL-6, IL-16, IL-21; anti-inflammatory/regulatory cytokines- IFNα, IL-10; chemokines- regulated on activation, normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein-1β (MIP-1β), MIP-3α; colony-stimulating factors- macrophage colony-stimulating factor (M-CSF); and growth factors- vascular endothelial growth factor (VEGF), IgM titers, and LPS concentrations were evaluated. Data were analyzed via a two-way ANOVA with an α = 0.05. In the first trial, Salmonella was significantly reduced by 1.07 and 0.84 log in the 1.5 kg/MT and 2.0 kg/MT MOS inclusions, respectively. In trial two, a significant 1.14 log reduction of SE in the 1.5 kg/MT MOS diet was observed. For unchallenged birds, all MOS treatments decreased IFNα levels. However, in the control basal diet, levels of IFNα were significantly diminished in SE challenged chicks. Decreased expression of IL-16 and MIP-1β was detected (p < 0.05) in SE challenged broilers compared to unchallenged birds. Levels of RANTES were significantly increased in 1.0 kg/MT and 2.0 kg/MT MOS inclusions compared to all other diets. No significant differences were observed with any other cytokines or LPS. The isotype IgM was reduced in all treatments compared to the control diet in both unchallenged and SE challenged birds, suggesting depressed humoral immunity when MOS was fed. Although a mechanism of action was not determined, these data suggest that MOS at the 1.5 kg/MT inclusion was efficacious in reducing SE.