Heat stress is a major welfare and production problem in dairy farming, with high-producing cows particularly vulnerable to temperature-humidity combinations that impair thermoregulation.
Heat stress causes a cluster of welfare harms in dairy cows: reduced feed intake causes malnutrition and metabolic instability; elevated core body temperature causes discomfort and physiological stress; reduced water intake causes dehydration; and the suppressed immune function that accompanies heat stress increases disease susceptibility. Behavioral indicators include seeking shade, standing in water, reduced lying time, and grouping at water troughs. These behaviors in cows without access to cooling represent unmet needs. Effective cooling — fans, water soaking, and shade — reduces physiological stress markers and significantly improves welfare. The economic case for cooling investment aligns with the welfare case, making heat stress management a priority for herd productivity and animal wellbeing.