Extreme heat events in cattle feedlots kill tens of thousands of animals annually and cause widespread subclinical heat stress that impairs immune function and wellbeing across entire feedlot populations.
Severe heat stress causes panting, drooling, reduced feed intake, and eventual collapse from hyperthermia. Animals that die from heat stress experience a prolonged process of physiological deterioration before death. Subclinical heat stress — animals above thermal neutral zone but not dying — causes immune suppression, weight loss, and chronic discomfort across large fractions of feedlot populations during summer. The welfare cost of inadequate heat mitigation is both acute in mortality events and chronic in subclinical stress.