Tissue‑specific effects of in ovo prebiotic stimulation on cytokine gene expression in broiler chickens

Abstract The modulation of the immune system during the early life of broiler chickens has been shown to have a beneficial effect on disease resistance and overall health. The present study investigated the effects of in ovo administration of xylo- and mannooligosaccharides (XOS and MOS) on cytokine gene expression in two immune-relevant tissues: the spleen and cecal tonsils. The injection of fertilized eggs was conducted on embryonic day 12, with the substances xylotriose (XOS3), xylotetraose (XOS4), mannotriose (MOS3), mannotetraose (MOS4), or saline (control) utilised for this purpose. The gene expression of cytokines representing general immune regulation (IL1β, IL2, IL10), Th1 (IL8, IL12, IFNβ, IFNγ), Th2 (IL4, IL6), and Th17 (IL17) pathways was quantified in 42-day-old birds using RT-qPCR. A significant immunomodulatory effect was observed in the spleen, where XOS3 consistently increased the expression of cytokines associated with Th1-, Th2-, and Th17-mediated responses, indicating enhanced systemic immune activation. Conversely, no statistically significant differences were detected in the cecal tonsils, although numerical variation was present. This muted mucosal response is likely to reflect the inherent heterogeneity and tolerance-oriented function of gut-associated lymphoid tissue, consistent with the concept of acquired immunotolerance to commensal microbiota. Collectively, these findings demonstrate that in ovo prebiotic stimulation exerts tissue-specific effects, promoting systemic immune readiness while maintaining mucosal homeostasis, and highlight XOS3 as a particularly effective modulator of splenic cytokine expression in broiler chickens.