Dietary Brown Mushroom Stem Powder Modulates Ileal Morphology and Barrier-Related Gene Expression in Layer Chicks

Brown mushroom stem (BMS), a nutrient-rich by-product of the mushroom processing industry, represents a potential sustainable feed ingredient for poultry. However, its effects on intestinal morphology and barrier-related gene expression in layer chicks are not well characterized. This study evaluated the influence of dietary BMS on ileal morphology and intestinal barrier-related gene expression in layer chicks. A total of 160 Lohmann LSL Lite chicks were randomly allocated to 4 dietary treatments: a control diet and control diets containing 2%, 4%, or 6% BMS as partial replacements for soybean meal on an equivalent basis, respectively. Each treatment had 5 replicates with 8 birds per replicate, and the trial lasted 36 d. Ileal samples were collected for histomorphological evaluation and quantitative real-time PCR of barrier-associated genes, including claudin-1 (CLDN1), occludin (OCLN), tight junction protein 1 (TJP1), tight junction protein 2 (TJP2), and mucin-2 (MUC2). Data were analyzed using one-way ANOVA, and orthogonal polynomial contrasts were applied to determine linear and quadratic responses to increasing BMS inclusion levels. Villus height decreased in BMS-fed groups compared with the control (linear and quadratic effects, p < 0.001), whereas crypt depth showed a quadratic response with the lowest value at 4% BMS (p < 0.001). Expression of CLDN1 mRNA was significantly elevated at 2% BMS but declined at higher inclusion levels (quadratic effect, p = 0.001). In contrast, TJP2 mRNA expression decreased with increasing BMS inclusion (linear effect, p = 0.009). No significant differences were observed for OCLN, TJP1, or MUC2 mRNA expression (p > 0.05). A composite index of barrier-related gene expression was numerically the highest at 2% BMS supplementation but did not differ significantly among treatments. These findings suggest that low dietary inclusion of BMS may support intestinal barrier-related gene expression in layer chicks, although higher levels may alter intestinal morphology without corresponding changes in barrier-related gene expression. Optimizing BMS inclusion could support sustainable poultry production by utilizing mushroom processing by-products as an alternative feed ingredient.