Evaluation of the Immunomodulatory Capacity of the Functional Metabolites of a Saccharomyces cerevisiae Fermentation Product in Broilers

Abstract

Our lab has identified the functional metabolites of Diamond V Original XPC™ (XPC) as a potential strategy to be used by the poultry industry to enhance immune function and poultry health. Three experiments were conducted using Ross 308 birds to determine the immunomodulatory capacity of XPC in the adaptive immune system of broilers. In the first experiment (n=240), birds were randomly assigned to either a control or XPC diet. Newcastle Disease Virus (NDV)-specific humoral immune response to a live attenuated vaccine was significantly (P<0.05) higher in XPC at d42. Flow cytometry showed no significant differences in cell populations (P>0.05) between treatments on the same sampling days. In Experiment Two (n=640), birds were randomly assigned to an unvaccinated or vaccinated group and further assigned to XPC or control diets. At d1, live NDV LaSota strain vaccine was used as a primary immunization to evaluate its impact on adaptive immunity. Remarkably, no substantial NDV-specific humoral immune response was established. Body weights were significantly higher (P<0.05) in the vaccinated birds on days 4 and 7. Spleen index of the vaccinated birds was significantly (P<0.05) lower at day 28 and 35. In Experiment Three (n=180), the role of maternal antibodies on XPC’s immunomodulatory capacity was evaluated. A factorial arrangement of three vaccination protocols and two diets (XPC or Control) was used. Protocol 1 used live B1 strain as primary immunization whereas Protocol 2 used live LaSota strain. Protocol 3 used live LaSota strain after maternal antibodies had decayed. In Protocol 1, XPC birds’ NDV titers were significantly higher (P<0.001) at day 28. Protocol 3 resulted in the highest NDV-titer level during the trial; XPC birds reached a significantly (P<0.001) higher level than control birds on d35. Protocol 2 had the lowest NDV-titer. Feed conversion was significantly higher (P<0.05) in Protocol 3 compared to 1 and 2. Overall, the results indicate that XPC supplementation positively modulates the broiler immune system, allowing it to have a robust and significantly higher NDV-specific humoral immune response compared to a control diet; its immunomodulatory capacity appears to be potentiated by the level of maternal antibodies and the vaccination schedule.