Effects of Newcastle Disease/Infectious Bronchitis Vaccine and Feeding Yeast Products on the Innate Immune System in the Proventriculus and Ileum of Broiler Chicks

The aim of this study was to determine whether Newcastle disease/infectious bronchitis (ND/IB) vaccination and yeast product diet supplementation modulate the expression of innate immune molecules in the proventriculus and ileum of broiler chicks. One-day-old male broiler chicks were divided into four groups (V–Y– (control), V–Y+, V+Y–, and V+Y+ groups, where V and Y represent vaccination and yeast product supplementation, respectively). Chicks in the V+Y– and V+Y+ groups were immunized with the live ND/IB vaccine, whereas chicks in the V–Y– and V–Y+ groups were not. Chicks in the V–Y+ and V+Y+ groups received feed containing yeast products from day 4, whereas chicks in the V–Y– and V+Y– groups did not. The proventriculus and ileum were collected on day 7 to analyze the expression of seven Toll-like receptors (TLRs) and Dectin-1. In the proventriculus, compared with those of the V–Y– control group, the TLR7 and TLR21 expression levels were higher in the V+Y– group; however, there were no differences in the expression levels of any TLR or Dectin-1 in the ileum. There were also no differences in the expression of avian β-defensins and cathelicidin-1 in the proventriculus and ileum between the control and treatment groups. The expression of granzyme in cytotoxic cells and interleukin (IL)-1B was upregulated by ND/IB vaccination in the proventriculus. Supplementation with yeast products upregulated only granzyme expression in the ileum and downregulated IL-6 expression in the proventriculus in chicks immunized with the ND/IB vaccine. Thus, we concluded that ND/IB vaccination is effective at enhancing the innate immune system in the proventriculus of chicks, at least until day 7 post-hatching, whereas the effects of diet supplementation with yeast products may be limited, at least under the present study conditions.