Transcriptomic Regulations of Heat Stress Response in the liver of Lactating Dairy Cows

Heat stress (HS) has become a major challenge in the dairy industry around the world. Although numerous measures have been taken to alleviate the HS impact on milk production, the cellular level response to HS remains unclear in dairy cows. The objective of this study was to dissect functional alterations based on transcriptomic dynamics in the liver of cows under HS. Dairy cows exposed to HS exhibited both decreased feed intake and milk yield. Through liver transcriptomic analysis, differentially expressed genes were identified among three experimental conditions, including heat stress (HS), pair-fed (PF), and thermoneutral (TN) groups. We observed the upregulation of protein folding and inflammation-related genes in the HS group, while the mitochondrial genes were downregulated. Gene functional enrichment also revealed that mitochondria function and oxidative phosphorylation were dysregulated under HS. The liver transcriptome analysis generated a comprehensive gene expression regulation network upon HS in lactating dairy cows. Overall, this study provides novel insights into molecular and metabolic changes of cows conditioned under HS. Our results could facilitate the development of efficient biomarkers to mitigate the negative effect of HS on dairy cow health and productivity. Overall design: RNA-seq was to detect the differential expression genes across three environmental conditions: Heat stress, thermoneutrality, and pair-fed

热应激（Heat Stress, HS）现已成为全球乳业面临的核心挑战之一。尽管目前已采取多项措施以缓解热应激对奶牛产奶性能的负面影响，但奶牛机体在细胞层面对热应激的响应机制仍未明晰。
本研究旨在基于热应激状态下奶牛肝脏的转录组动态变化，解析其功能调控异常。暴露于热应激环境的奶牛均表现出采食量与产奶量下降的特征。
通过肝脏转录组分析，本研究在三个实验组中鉴定出差异表达基因，三组分别为热应激组（Heat Stress, HS）、配对饲喂组（Pair-Fed, PF）与热中性组（Thermoneutral, TN）。研究发现，热应激组的蛋白质折叠相关基因与炎症相关基因表达上调，而线粒体相关基因表达则出现下调。基因功能富集分析进一步显示，热应激条件下线粒体功能与氧化磷酸化通路均发生调控异常。
本次肝脏转录组分析构建了泌乳奶牛在热应激环境下的完整基因表达调控网络。综上，本研究为热应激条件下奶牛的分子与代谢变化提供了全新的研究视角。本研究结果可为开发高效生物标志物提供理论支撑，以缓解热应激对奶牛健康与生产性能的负面影响。
实验整体设计：采用RNA测序技术检测三种环境条件下的差异表达基因，涵盖热应激、热中性环境与配对饲喂三组。