Impact of dietary myo-inositol supplements on immune cell distribution and cytokine expression in laying hens of two different strains.

Myo-inositol (MI) is involved in the regulation of key immune cell activities, including signaling pathways and cellular processes. Although immune cell distribution and cytokine expression are key determinants of immune competence in laying hens, the potential role of MI in regulating these parameters is largely unexplored. Thus, this study investigated the effects of dietary MI on the immune system of laying hens. At the age of 26 wk, corresponding to the peak laying period, 40 Lohmann Brown-Classic (LB) and 40 Lohmann LSL-Classic (LSL) hens received a maize-soybean meal-based diet either without (MI0) or with 1 (MI1), 2 (MI2) or 3 (MI3) g supplemented MI/kg feed for 4 wk, resulting in a 2 × 4 factorial design. We measured numbers of various leukocytes in blood, spleen and cecal tonsils, lymphocyte functionality and gene expression of pro- and anti-inflammatory cytokines. Dietary MI supplementation resulted in cell type-, strain- and concentration-specific effects, including increased circulating B cells in LSL hens fed with MI2, reduced splenic B cells in LB hens with MI1 and MI2 and lower CD4+CD25high cells in the cecal tonsils of both strains with MI2. Strain-specific modulation of foxp3 and IL-12 gene expression was also observed. However, neither diet × strain interaction nor dietary MI revealed a clear dose-response relationship. On the contrary, immunological differences between the two strains, irrespective of MI supplementation, were highly prominent and are consistent with previous studies, with a generally higher innate immune response in LB hens, and a more specific and cellular immune response in LSL hens. Overall, our findings indicate that dietary MI supplementation does not broadly alter immune responses in laying hens but can modulate specific immune parameters in a strain-dependent manner. Despite the limited impact, dietary MI may still represent a potential approach to support more balanced immune responses. The results further emphasize immunological, physiological and metabolic variations between the two strains and the importance of genetic background when evaluating nutritional strategies for immune modulation.