Heat stress: an environmental challenge to immune resilience and health in dairy cows

Increasing environmental temperatures pose significant challenges to food security and animal welfare. In dairy production systems, heat stress detrimentally affects cow health, reproductive function, and immune resilience. This review summarizes the current knowledge on the impacts of heat stress in dairy cattle, emphasizing cellular targets, physiological and molecular consequences, and implications for health and productivity. Heat stress is associated with increased disease incidence in dairy cows. Elevated temperatures can increase pathogen abundance or alter host immune function, thereby compromising overall health. Both peripheral immune responses and local tissue responses are disrupted under heat stress. These effects could be mediated by various molecular mechanisms which contribute to dysregulated immune signaling. Moreover, heat stress can impair key immune pathways leading to either insufficient or excessive inflammatory responses, both of which predispose cows to disease. Effective mitigation of heat stress requires a multifaceted approach. While no single strategy fully offsets the detrimental effects of heat stress, a combination of environmental modifications (fans, shade, sprinklers), nutritional interventions (vitamins, minerals, targeted feed additives), and genetic selection for thermotolerance offer promising avenues to support cow health, immune resilience and maintain productivity in a warming climate.