Effects of Ixeris polycephala meal on growth performance, antioxidant function, and immune function in broilers

This study evaluated the effects of dietary Ixeris polycephala meal (IPM) on 192 male Partridge Shank broilers (30 days old). Birds were assigned to a control diet or diets supplemented with 1%, 2%, or 3% IPM. Growth performance, intestinal morphology, serum biomarkers, and splenic gene expression were assessed. Results indicated that 3% IPM maximized final body weight and average daily gain. However, a distinct immunological trade-off was observed. From 70 to 100 days, all IPM doses significantly reduced serum inflammatory cytokines (IL-1, IL-6, TNF-α). Notably, while the 1% group achieved the lowest cytokine levels, this coincided with a return to baseline TLR expression ("Resolution"). In contrast, the 2% group maintained significantly upregulated splenic TLR2 and TLR4 mRNA expression alongside cytokine suppression, suggesting a state of 'Active Tolerance'—preserving high pathogen surveillance without systemic inflammation. The 3% group exhibited attenuated TLR2 expression relative to the 2% group. Additionally, IPM supplementation enhanced antioxidant capacity (increased GSH-Px/SOD), although malondialdehyde levels were not reduced. In conclusion, while 3% IPM optimizes growth parameters, 2% IPM establishes the optimal physiological equilibrium between pathogen defense and inflammatory resolution. Therefore, 2% IPM is recommended as the precision dietary strategy for supporting immune homeostasis in the late growth phase.