Heat stress in dairy cattle causes significant welfare harm, reduces production, and is an increasing concern as climate change raises summer temperatures.
Heat stress causes genuine suffering in dairy cows: affected animals pant heavily, drool, stand in water if available, and show dramatically reduced appetite. Chronic heat stress over a summer season reduces immune function, increases susceptibility to mastitis and lameness, and impairs reproductive performance. The welfare impact falls disproportionately on the highest-yielding cows whose metabolic heat production is greatest. Inadequate housing ventilation, insufficient shade in outdoor areas, and absence of active cooling are structural welfare failures that are entirely preventable. As UK summers become hotter and longer, investment in cooling infrastructure is a welfare necessity that also provides economic returns through maintained production.