Heat stress is a great concern in the layer industry because it decreases egg production and egg quality. Orthosiphon stamineus extract (OE) has the potential to relieve heat stress, and rosmarinic acid (RA) is the main effective constituent of OE. However, the effects and mechanisms of OE and RA on heat stress in commercial laying hens remain unclear. In the current study, four hundred eighty 56 wk old hens were divided into 2 hen houses, one maintained at the low temperature and other maintained at a high temperature. Hens in each house were assigned to 3 dietary treatments (basal, basal + 0.4% OE, and basal + 0.02% RA) with 20 cages per treatment and 4 hens per cage. Performance traits were recorded, and 1 egg in 4 cages were collected randomly each day (35 eggs per treatment/wk) for egg quality assay. The excreta were collected by mixed every 5 adjacent cage at the end (28 d) of the experiment for apparent digestibility analysis, and then 1 hen from each 2 cages were sacrificed for blood and intestinal samples. The OE and RA supplementation increased the egg production rate (P < 0.05) and improved the eggshell strength and haugh unit (P < 0.05). The analysis of digestibility of basic nutrients showed OE or RA supplementation improved protein (OE: P = 0.074; RA: P = 0.037), fat, and Ca digestion (P < 0.05) in laying hens. To explore the mechanisms associated with the improvements of performance traits and egg quality, serum biochemical indices and related gene expression and intestinal villi integrity were measured. Supplementing the diet of the laying hens with OE or RA increased superoxide dismutase (P < 0.05) activities in both the serum and jejunum, decreased the malondialdehyde contents (P < 0.05), and also decreased the caspase-3 activity (P < 0.05) in jejunum of laying hens. Intestine sections showed RA supplementation improved the jejunum villus height (P = 0.007). The OE or RA supplements up-regulated nuclear factor erythroid 2-related factor 2 (Nrf2) and occludin gene expressions, and down-regulated caspase-3 gene expression in hens (P < 0.05). In conclusion, The OE and RA supplements may increase nutrient digestibility, stimulate the antioxidant defense mechanism system through the Nrf2-mediated pathway, decrease intestinal epithelial cell apoptosis, and protect the intestinal barrier. This study indicated that dietary supplementation with OE or RA is beneficial for laying hens under heat-stress conditions.

热应激在蛋鸡行业是一个很大的问题，因为它降低了鸡蛋的产量和鸡蛋的质量。拟南芥提取物（OE）具有缓解热应激的潜力，迷迭香酸（RA）是OE的主要有效成分。然而，在商业蛋鸡中OE和RA对热应激的影响和机理尚不清楚。在当前的研究中，将480头56周龄的母鸡分成2羽鸡舍，其中一只保持在低温下，另一只保持在高温下。将每个鸡舍中的母鸡分配给3种饮食疗法（基础，基础+ 0.4％OE和基础+ 0.02％RA），每种处理20笼，每笼4只母鸡。记录性能指标，每天随机收集4个笼子中的1个卵（每个处理/周35个卵）以进行卵质量测定。在实验结束（28 d）时，每5个相邻笼子混合收集粪便，以进行表观消化率分析，然后每2个笼子中的1只母鸡被献血和肠样本。补充OE和RA可以提高产卵率（P <0.05），并改善了蛋壳强度和哈氏单位（P <0.05）。基本营养物质的消化率分析显示，蛋鸡中OE或RA补充改善了蛋白质（OE：P  = 0.074; RA：P  = 0.037），脂肪和Ca的消化率（P <0.05）。为了探索与生产性能和蛋品质改善相关的机制，测定了血清生化指标以及相关基因表达和肠绒毛完整性。用OE或RA补充蛋鸡的饮食可以增加血清和空肠的超氧化物歧化酶（P <0.05）活性，降低丙二醛含量（P<0.05），并且还会降低蛋鸡空肠中的caspase-3活性（P <0.05）。肠道切片显示RA补充可改善空肠绒毛高度（P  = 0.007）。OE或RA补充母鸡的核因子红系2相关因子2（Nrf2）和occludin基因表达上调，而caspase-3基因表达下调（P <0.05）。总之，OE和RA补充剂可以增加营养物质的消化率，通过Nrf2刺激抗氧化防御机制系统介导的途径，减少肠道上皮细胞凋亡，并保护肠道屏障。这项研究表明，饮食中添加OE或RA对热应激条件下的蛋鸡有益。