Guo Zitai, Gao Shengtao, Ouyang Jialiang, Ma Lu, Bu Dengpan
State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
College of Animal Science and Technology, Yangzhou University, Yangzhou 225009, China.
Animals (Basel). 2021 Mar 7;11(3):726. doi: 10.3390/ani11030726.
Heat stress (HS) is one of the most important factors posing harm to the economic wellbeing of dairy industries, as it reduces milk yield as well as milk protein content. Recent studies suggest that HS participates in the induction of tissue oxidative stress (OS), as elevated levels of reactive oxygen species (ROS) and mitochondrial dysfunction were observed in dairy cows exposed to hot conditions. The OS induced by HS likely contributes to the reduction in milk protein content, since insulin resistance and apoptosis are promoted by OS and are negatively associated with the synthesis of milk proteins. The apoptosis in the mammary gland directly decreases the amount of mammary epithelial cells, while the insulin resistance affects the regulation of insulin on mTOR pathways. To alleviate OS damages, strategies including antioxidants supplementation have been adopted, but caution needs to be applied as an inappropriate supplement with antioxidants can be harmful. Furthermore, the complete mechanisms by which HS induces OS and OS influences milk protein synthesis are still unclear and further investigation is needed.
热应激（HS）是对乳制品行业经济福祉造成危害的最重要因素之一，因为它会降低产奶量以及乳蛋白含量。最近的研究表明，热应激参与诱导组织氧化应激（OS），因为在暴露于炎热条件下的奶牛中观察到活性氧（ROS）水平升高和线粒体功能障碍。热应激诱导的氧化应激可能导致乳蛋白含量降低，因为氧化应激会促进胰岛素抵抗和细胞凋亡，而这与乳蛋白的合成呈负相关。乳腺中的细胞凋亡直接减少了乳腺上皮细胞的数量，而胰岛素抵抗则影响胰岛素对mTOR信号通路的调节。为了减轻氧化应激损伤，已采取了包括补充抗氧化剂在内的策略，但需要谨慎使用，因为不适当的抗氧化剂补充可能有害。此外，热应激诱导氧化应激以及氧化应激影响乳蛋白合成的完整机制仍不清楚，需要进一步研究。
