Impact of Huoxiang Zhengqi oral liquid on the performance, egg quality, antioxidant capacity via reshaping gut microbiota in laying hens under acute heat stress.

Against the background of global warming, heat stress has become a critical issue endangering the health and production performance of laying hens. This study aimed to explore the protective effect of Huoxiang Zhengqi Oral Liquid (HX) on acute heat-stressed laying hens. A total of 90 laying hens were randomly divided into control (CON), model (MOD), low-dose (HX-L), medium-dose (HX-M), and high-dose (HX-H) groups, with six replicates per group and three hens per replicate. The MOD and HX groups were exposed to 34°C and 70%-80% relative humidity for 12 h/day for 5 days, with cold-water stimulation provided from days 2 to 5. During the administration period, HX was orally administered at doses of 0.15, 0.30, and 0.60 mL/hen/day to the HX-L, HX-M, and HX-H groups, respectively. Laying performance, egg quality, and antioxidant activities were decreased when the hens were exposed to a heat stress environment. After heat stress, the intestinal morphology of laying hens changed and cecal microbial homeostasis was disrupted. Following HX supplementation, laying rate, eggshell strength, Superoxide dismutase (SOD) activity, Immunoglobulin A (IgA), Immunoglobulin M (IgM), Luteinizing hormone (LH), Follicle-stimulating hormone (FSH) levels and the relative abundance of Bacteroidota are increased, whereas the feed/egg ratio and malondialdehyde (MDA) content are decreased. Interestingly, superior improvements in all above parameters are observed in HX-M and HX-H groups, while no significant differences are detected between these two groups (P > 0.05). In conclusion, HX effectively alleviates heat stress-induced intestinal damage, oxidative stress, and production decline in laying hens by reshaping gut microbiota. This may be attributed to the presence of magnolol, honokiol, and patchouli oil in HX. Considering the dose dependence and cost factors, the HX-M has been determined as the optimal dose.