Utilization of aqueous distillate and solid residue fractions derived from zero-waste Hydrodistillation of Zanthoxylum myriacanthum wall. ex Hook. f. for improving broiler immunity and intestinal functions

Phytogenic feed additives derived from plant processing by-products are increasingly explored as sustainable approaches to enhance poultry health, food quality, and production efficiency, supporting food security and sustainable agriculture. This study was to evaluate the effects of dietary supplementation with aqueous distillate (AD) and solid residue (SR) derived from the hydrodistillation of Zanthoxylum myriacanthum Wall. ex Hook. f. on safety, meat quality, intestinal morphology, immune responses, and gut microbiota in broiler chickens. A total of 150 one-day-old Ross 308 broilers were randomly assigned to three dietary treatments for 35 days: a basal diet (control), a basal diet supplemented with 1,000 mg/kg AD, or a basal diet supplemented with 1,000 mg/kg SR. For supporting animal health and well-being, neither fraction induced adverse effects on serum biochemical parameters or mortality. No significant differences were observed over the entire experimental period. Both AD and SR significantly improved breast meat redness and affected thawing loss in thigh meat (p < 0.05). SR supplementation also significantly increased villus height, and upregulated GLUT2 expression (p < 0.05). Additionally, the expression of GLUT2 exhibited a significant positive correlation with villus height (r = 0.998; p = 0.035) and a strong positive association with meat redness (r = 0.913; p = 0.267). Moreover, the expression of IL-1β and TNF-α was significantly suppressed by supplementation with both fractions (p < 0.05), whereas IL-10 expression was significantly enhanced by AD supplementation (p < 0.05). For gut microbiota analysis, overall microbial diversity was not significantly altered by the supplementations, although the genera Bacteroides were significantly altered in both AD and SR groups compared with the control group (p < 0.05). These findings support the practical use of hydrodistillation by-products of Z. myriacanthum as resource-efficient and environmentally responsible feed additives that promote sustainable production systems, and further dose-response evaluation is recommended to optimize their application in broiler production.