TERRA Teaching and Research Center, University of Liège, Gembloux Agro-Bio Tech (ULiège-GxABT), 5030 Gembloux, Belgium.
Institute of Animal Breeding and Genetics, Justus-Liebig-University of Gießen, Ludwigstraße 21B, 35390 Gießen, Germany.
J Dairy Sci. 2023 Jul;106(7):4471-4488. doi: 10.3168/jds.2022-22727. Epub 2023 May 8.
Heat stress implies unfavorable effects on primary and functional traits in dairy cattle and, in consequence, on the profitability of the whole production system. The increasing number of days with extreme hot temperatures suggests that it is imperative to detect the heat stress status of animals based on adequate measures. However, confirming the heat stress status of an individual is still challenging, and, in consequence, the identification of novel heat stress biomarkers, including molecular biomarkers, remains a very relevant issue. Currently, it is known that heat stress seems to have unfavorable effects on immune system mechanisms, but this information is of limited use in the context of heat stress phenotyping. In addition, there is a lack of knowledge addressing the molecular mechanisms linking the relevant genes to the observed phenotype. In this review, we explored the potential molecular mechanisms explaining how heat stress affects the immune system and, therefore, increases the occurrence of immune-related diseases in cattle. In this regard, 2 relatively opposite hypotheses are under focus: the immunosuppressive action of cortisol, and the proinflammatory effect of heat stress. In both hypotheses, the modulation of the immune response during heat stress is highlighted. Moreover, it is possible to link candidate genes to these potential mechanisms. In this context, immune markers are very valuable indicators for the detection of heat stress in dairy cattle, broadening the portfolio of potential biomarkers for heat stress.
热应激意味着对奶牛的主要和功能特性产生不利影响，因此会对整个生产系统的盈利能力产生影响。极端高温天数的增加表明，基于适当的措施来检测动物的热应激状态势在必行。然而，确认动物的热应激状态仍然具有挑战性，因此，包括分子生物标志物在内的新型热应激生物标志物的鉴定仍然是一个非常重要的问题。目前已知，热应激似乎对免疫系统机制产生不利影响，但这些信息在热应激表型方面的用途有限。此外，在将相关基因与观察到的表型联系起来的分子机制方面，知识还存在不足。在这篇综述中，我们探讨了潜在的分子机制，这些机制解释了热应激如何影响免疫系统，从而增加了牛群中与免疫相关疾病的发生。在这方面，有两个相对的假设受到关注：皮质醇的免疫抑制作用，以及热应激的促炎作用。在这两个假设中，都强调了热应激期间免疫反应的调节。此外，还可以将候选基因与这些潜在机制联系起来。在这种情况下，免疫标志物是检测奶牛热应激的非常有价值的指标，拓宽了热应激潜在生物标志物的组合。
