Traditional Chinese medicine improves performance and intestinal health in laying hens under acute and chronic heat stress by modulating ileal metabolic functions.

Heat stress (HS) represents a significant challenge in poultry production, impairing thermoregulation, intestinal function, and productive performance. This study utilized acute (6 h) and chronic (14 d) HS models at 36°C in laying hens to characterize stage-dependent responses and evaluate the protective effects of a ten-ingredient traditional Chinese medicine (TCM) formulation. Both acute and chronic HS significantly increased rectal temperature and respiratory rate. Egg production declined by approximately 18% following acute HS and was further compromised under chronic exposure, along with reduced eggshell strength and weight. Dietary TCM supplementation (0.5%) alleviated physiological stress and partially restored laying performance, with more pronounced recovery observed under chronic HS. Serum analysis and histopathology indicated that TCM attenuated HS-induced impairment of ileal barrier function. Metabolomic profiling revealed stage-dependent responses: acute HS primarily disturbed redox balance, whereas chronic HS induced broader remodeling related to energy and nutrient utilization. TCM supplementation modulated metabolic functions to support immediate stress buffering under acute HS while stabilizing long-term energy support and intestinal capacity under chronic HS. Metagenomic analysis indicated that TCM selectively promoted microbial groups related to intestinal metabolism and nutrient utilization, aligning with metabolomic findings. Correlation analyses linked these TCM-associated microbial and metabolic signatures with improved thermoregulatory responses, oxidative status, and intestinal barrier indicators. Collectively, these results demonstrate that TCM supplementation enhances heat resilience in laying hens through stage-dependent modulation of the gut microbiota-metabolome axis, supporting its application as a nutritional strategy to maintain productivity under thermal challenge.