[Objective] This study was conducted to investigate the effects of tradi- tional Chinese herbal medicines on blood biochemical indices of egg-laying hens under heat stress and to provide theoretical basis for clinical application of the medicines. [Method] One hundred of 88-day-old ISA-Brown hens were randomly di- vided into five groups. The hens in four groups were administrated with Prescription I herbal medicines, Prescription II herbal medicines, Vc and blank control under ar- tificially simulated heat stress, respectively. The last group was raised under normal temperature condition. Blood samples of the hens were collected on 1, 4, 8 and 10 d later and detected for their biochemical indices. [Result] The blood sodium （Na）, phosphorus （P）, potassium （K） and chlorine （CI） concentrations in hens under heat stress were decreased, while the activities of alanine aminotransferase （ALT）, lactate dehydrogenase （LDH） and creatine kinase （CK） were increased. These indices grad- ually returned to normal levels after the use of traditional Chinese herbal medicines. [Conclusion] The herbal medicines can relieve the adverse effects caused by heat stress to blood biochemical indices via different metabolic pathways of ions and en- zymes.
