Heat stress in beef cattle occurs when the temperature-humidity index (THI) exceeds the animal's capacity to dissipate body heat. As climate change extends and intensifies summer heat events, heat stress is an increasingly significant welfare concern for beef cattle globally—particularly in intensive feedlot systems.
Cattle are less efficient at dissipating heat than humans—they rely primarily on panting and sweating from their muzzle. When environmental heat load exceeds cooling capacity, core body temperature rises, triggering a physiological emergency. Signs of severe heat stress include open-mouth breathing, drooling, trembling, reluctance to move, and collapse. Feedlot heat stress events can cause mass mortalities during extreme weather.
Heat-stressed cattle experience: chronic discomfort at moderate levels, reduced feed intake (leading to weight loss and poor condition), suppressed immune function and increased disease susceptibility, reproductive failure, behavioral changes (crowding at water, shade-seeking, reduced lying), and, in severe cases, death. The welfare harm is prolonged and systemic during hot periods.
Shade provision: The most cost-effective intervention. Shade reduces radiant heat load significantly. Natural or artificial shade should provide minimum 3-4 m² per animal. Water availability: Heat-stressed cattle drink 2-3x normal water intake. Adequate troughs with sufficient space to prevent competition are essential. Ventilation: In housed systems, fan systems and cross-ventilation reduce heat. Feed management: Adjusting feeding to evening hours when temperatures are lower reduces metabolic heat production at peak heat. Sprinkler systems: Wetted areas allow evaporative cooling.
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