Research note: Effects of Eucommia ulmoides seed meal on egg quality, antioxidant capacity, and intestinal health in laying hens.

The source of protein feed is a critical factor influencing egg quality. This study aimed to evaluate the effects of Eucommia ulmoides seed meal (EUSM), as a novel protein feed ingredient, on egg quality, antioxidant capacity, and intestinal health in laying hens. Four hundred and fifty 50-week-old Hy-Line Brown laying hens were randomly assigned to five dietary treatments: a control diet (0% replacement) and diets in which 10%, 20%, 30%, or 40% of soybean meal protein was replaced with EUSM. Results showed that EUSM supplementation linearly decreased yolk color (P < 0.001). Eggshell strength was significantly improved at 10 - 30% replacement, exhibiting a quadratic response (P < 0.001). Serum superoxide dismutase activity and calcium concentration increased, with significant quadratic trends (P < 0.001). Regarding intestinal health, replacement at 10% increased villus height in the duodenum and upregulated the expression of Claudin, ZO1, and Occludin in the duodenum and jejunum (P < 0.05). However, replacement at ≥ 20% progressively reduced villus height in all intestinal segments (P < 0.001) and decreased tight junction protein expression in proximal segments, although ileal ZO1 and Occludin remained elevated at 20% replacement. In conclusion, replacing 10% of soybean meal protein with EUSM improves eggshell strength, antioxidant status, and intestinal barrier function, making it a promising alternative protein source for laying hen diets. Higher inclusion levels (≥20%) compromise intestinal morphology and should be avoided. These findings support the potential of EUSM to reduce soybean meal dependency in the layer industry.