Wood-derived lignans magnolol and honokiol improve nutrient utilization in broilers and regulate inflammation and epithelial repair in vitro.

Plant-derived lignans are increasingly investigated as components of feed supplements in poultry production due to their antioxidant, anti-inflammatory and intestinal barrier-supporting properties. However, direct evidence linking lignan supplementation to improved nutrient digestibility remains limited, and the individual contributions of magnolol and honokiol to the biological effects of such additives are not yet fully understood. This study therefore examined the effects of a wood-derived lignan feed supplement containing both compounds on growth performance, nutrient utilization and intestinal health in broiler chickens, alongside targeted in vitro mechanistic investigations. In a 35-day broiler feeding trial, 180 birds in 6 pens per treatment received a control diet or the lignan supplement at 0.1 g/kg feed. Supplementation increased body weight by 90.8 g and reduced feed-to-gain ratio from 1.41 to 1.32. Apparent ileal digestibility of crude protein, crude ash, calcium and phosphorus increased by 2.8 %, 3.9 %, 5.1 % and 2.2 %, respectively. Jejunal gene expression analysis revealed a significant downregulation of IL-8, while TNF-α and IL-10 remained unaffected. To further investigate underlying mechanisms, magnolol and honokiol were evaluated in intestinal epithelial and immune cell models. Transepithelial transport was documented for both lignans in the Caco-2 model, with magnolol achieving higher apparent permeability. Magnolol enhanced wound closure speed in IPEC-J2 cells, reflecting a capacity to support epithelial restitution after injury. In contrast, honokiol reduced intracellular reactive oxygen species in epithelial cells and strongly suppressed nitric oxide production in LPS-stimulated macrophages, pointing to a dominant role in redox and inflammatory signaling. Both compounds inhibited NF-κB activation, though honokiol acted more broadly across TLR4-dependent and -independent pathways. These in vitro findings provide possible explanations for the in vivo effects, although their contribution to the observed responses in broilers remains to be established. Overall, magnolol and honokiol provide complementary and mechanistically distinctive activities in vitro and their combined use in a single feed supplement may therefore represent a promising strategy for improving nutrient utilization and productive performance in poultry production.