The identified DEGs.

Climate change increases global temperatures, which is lethal to both livestock and humans. Heat stress is known as one of the various livestock stresses, and dairy cows react sensitively to high-temperature stress. We aimed to better understand the effects of heat stress on the health of dairy cows and observing biological changes. Individual cows were divided into normal (21–22 °C, 50–60% humidity) and high temperature (31–32 °C, 80–95% humidity), respectively, for 7-days. We performed metabolomic and transcriptome analyses of the blood and gut microbiomes of feces. In the high-temperature group, nine metabolites including linoleic acid and fructose were downregulated, and 154 upregulated and 72 downregulated DEGs (Differentially Expressed Genes) were identified, and eighteen microbes including Intestinimonas and Pseudoflavonifractor in genus level were significantly different from normal group. Linoleic acid and fructose have confirmed that associated with various stresses, and functional analysis of DEG and microorganisms showing significant differences confirmed that high-temperature stress is related to the inflammatory response, immune system, cellular energy mechanism, and microbial butyrate production. These biological changes were likely to withstand high-temperature stress. Immune and inflammatory responses are known to be induced by heat stress, which has been identified to maintain homeostasis through modulation at metabolome, transcriptome and microbiome levels. In these findings, heat stress condition can trigger alteration of immune system and cellular energy metabolism, which is shown as reduced metabolites, pathway enrichment and differential microbes. As results of this study did not include direct phenotypic data, we believe that additional validation is required in the future. In conclusion, high-temperature stress contributed to the reduction of metabolites, changes in gene expression patterns and composition of gut microbiota, which are thought to support dairy cows in withstanding high-temperature stress via modulating immune-related genes, and cellular energy metabolism to maintain homeostasis.

气候变化导致全球气温升高，对家畜与人类均具有致命威胁。热应激（heat stress）是诸多家畜应激源之一，而奶牛对高温应激反应极为敏感。本研究旨在更深入地解析热应激对奶牛健康的影响，并观察其生物学变化。将受试奶牛分为两组：正常组（环境温度21~22℃，湿度50%~60%）与高温组（环境温度31~32℃，湿度80%~95%），每组饲养7天。本研究对奶牛血液开展代谢组学与转录组学分析，并对粪便样本进行肠道微生物组分析。高温组中共鉴定出9种差异代谢物（包括亚油酸与果糖）表达下调；同时发现154个上调、72个下调的差异表达基因（Differentially Expressed Genes，DEGs）；此外在属水平上，18种微生物（如Intestinimonas与Pseudoflavonifractor）的相对丰度与正常组存在显著差异。已有研究证实亚油酸与果糖与多种应激过程相关；对差异表达基因与差异微生物的功能富集分析显示，高温应激与炎症反应、免疫系统、细胞能量代谢机制以及微生物丁酸生成过程密切相关。上述生物学变化或有助于奶牛抵御高温应激。已知热应激可诱发免疫与炎症反应，且机体可通过代谢组、转录组与微生物组层面的调控维持内环境稳态。本研究结果显示，高温应激可引发免疫系统与细胞能量代谢的改变，具体表现为代谢物水平变化、通路富集异常以及微生物组成差异。由于本研究未纳入直接表型数据，我们认为后续需开展进一步验证工作。综上，高温应激可导致代谢物水平下降、基因表达模式与肠道微生物组组成发生改变；上述变化被认为通过调控免疫相关基因与细胞能量代谢，帮助奶牛抵御高温应激并维持内环境稳态。