Impacts of Nicotinamide Adenine Dinucleotide Supplementation on Longevity, Egg Quality, and Immunity in Laying Hens

The productivity and health of laying hens are major challenges for the global poultry industry, especially as flocks age and egg production declines. The present study aimed to evaluate the effects of nicotinamide riboside chloride (NRCl), a bioavailable precursor of nicotinamide adenine dinucleotide (NAD⁺), on longevity, egg quality, and immune performance in laying hens. A total of 180 Hy-Line Brown hens, 24-week-old, were randomly assigned to three dietary groups for 24 weeks, including a control group receiving standard layer feed, a low-dose NRCl group receiving 25 mg NR/kg feed, and a high-dose NRCl group receiving 50 mg NR/kg feed. The present study assessed survival rate, daily egg production, egg weight, shell strength, yolk nutrient composition, and immune parameters, including white blood cell (WBC) count, immunoglobulins (IgA and IgG), and cytokines (IL-6 and IFN-γ). The present findings indicated that supplementation with NRCl significantly increased the survival rate, resulting in 100% survival in the high-dose group compared to 93.3% in the control group. Egg production and feed conversion ratio were also enhanced in NRCl groups, indicating improved physiological resilience. The NRCl groups demonstrated significant improvements in egg quality, including stronger, thicker shells and enhanced nutritional content such as higher yolk protein, vitamin D3, and omega-3 fatty acid levels. Furthermore, immune markers were markedly elevated, reflecting enhanced immune modulation and potential disease resistance. The NRCl supplementation effectively supported metabolic efficiency, immune competence, and egg quality in laying hens. The current findings highlighted the potential of NAD⁺ precursor supplementation as a nutritional strategy to prolong the productive lifespan of commercial layers while promoting sustainable poultry production. Keywords: Egg quality, Immune response, Laying hens, Longevity, Nicotinamide adenine dinucleotide supplementation, Poultry feed