Effects of Oligomeric Ultrafine-Nano Hydrogen Water on Laying Performance, Egg Quality, Nutrient Composition, and Intestinal and Reproductive Responses in Late-Laying Hens

This study evaluated the effects of oligomeric ultrafine-nano hydrogen water (OUHW) on production performance, egg quality, egg nutrient deposition, systemic metabolism, intestinal barrier function, and reproductive status in late-laying hens. Unlike conventional hydrogen-rich water, which primarily delivers molecular hydrogen dissolved in water, OUHW integrates oligomeric water with ultrafine-nano-sized hydrogen bubbles, providing a distinct physicochemical form of hydrogen-water intervention. A total of 288 healthy 67-week-old Jingfen No. 8 laying hens were assigned to 2 treatments with 6 independent replicates per treatment (24 hens per replicate) and provided with either tap water or OUHW for 11 weeks. Compared with the control, OUHW reduced the feed conversion ratio and the rates of manure-spotting while increasing the laying rate, qualified egg rate, and total egg number during weeks 5–8 (p < 0.05). These productive and egg quality improvements were phase-specific effects observed in the late laying stage during the 11-week trial. At week 4, OUHW significantly increased egg weight (p < 0.05). At week 8, OUHW also improved eggshell compressive elastic deformation, eggshell thickness, albumen height, and Haugh unit (p < 0.05). At week 6, eggs from OUHW-treated hens had higher concentrations of glutamate, glycine, alanine, C18:0, C18:1n9c, C20:4n6, and C22:6n3 (p < 0.05). Serum metabolomics showed that 25 differential metabolites from the OUHW treatment group were predominantly enriched in glycerophospholipid, sphingolipid, branched-chain amino acid, histidine, and tryptophan metabolism. In the cecum, OUHW decreased p-cresol and increased isovaleric acid and acetic acid (p < 0.05). Notably, the overall community structures of the cecal and oviductal microbiota exhibited no significant treatment-related alterations, indicating limited structural changes in the microbial communities in response to the OUHW intervention. OUHW also reduced interleukin-2 and tumor necrosis factor-α, increased interleukin-10 in the jejunum and oviductal isthmus (p < 0.05), and upregulated the mRNA expression of ovarian steroidogenic acute regulatory protein and intestinal Occludin, Claudin-1, and Mucin-2 (p < 0.05). These findings indicate that OUHW improved laying performance, egg quality, and egg nutrient deposition, possibly through modulation of the metabolism, intestinal barrier function, ovarian function, and oviductal inflammation.