Dietary Selenium-Enriched Bacillus subtilis Improves Feed Utilization and Modulates Selected Responses to LPS Challenge in Laying Hens

This study evaluated the effects of dietary selenium-enriched Bacillus subtilis (HBS) supplementation on laying performance, egg quality, and responses to lipopolysaccharide (LPS) challenge. A total of 120 Jinghong-1 laying hens received a basal or HBS-supplemented diet for 12 weeks. Subsequently, hens within each dietary replicate were allocated to phosphate-buffered saline (PBS)- or LPS-injected subgroups, and one hen per subgroup was sampled 12 h after injection, yielding six sampled hens per treatment combination. HBS supplementation reduced the feed-to-egg ratio (1.96 vs. 2.15, p = 0.023) and increased albumen height (7.17 vs. 6.60 mm, p = 0.003) and Haugh unit (83.01 vs. 78.65, p = 0.001). Compared with LPS, HBS+LPS showed lower serum IL-1β concentrations, higher CAT and T-SOD activities, greater jejunal villus height and villus height-to-crypt depth ratio, and higher expression of selected antioxidant- and tight-junction-related genes. Jejunal cytokine responses varied among genes. No significant differences in the measured cecal alpha-diversity indices were detected, whereas exploratory LEfSe analysis identified several treatment-associated taxa. Cecal butyrate concentration was higher in HBS than in CON, with no significant difference between HBS+LPS and LPS. Collectively, these findings indicate that HBS supplementation improved feed utilization and albumen quality and was associated with changes in selected antioxidant, inflammatory, and intestinal responses following LPS challenge. The contributions of selenium and B. subtilis could not be distinguished.