Heat stress during summer months impairs dairy and beef cattle reproduction through physiological mechanisms that reduce conception rates, increase embryo mortality, and compromise both animal welfare and farm economics.
The welfare dimensions of heat-stress-related reproductive failure in cattle extend beyond the frustration of missed conception cycles to the physiological experience of the heat stress itself. Cows experiencing chronic THI above 80 show reduced feed intake, increased standing time, respiratory distress from panting, and elevated rectal temperatures — a cluster of welfare harms that precede and accompany reproductive failure. The embryos that fail to develop following heat-stressed conception represent a hidden welfare cost: their loss reflects an environment so physiologically stressful that developmental processes cannot proceed normally. Cooling interventions that improve reproduction also directly improve welfare by reducing heat load on individual cows. The ethical dimension of expanding heat stress seasons under climate change — where dairy and beef cattle are expected to endure progressively more difficult thermal conditions — requires both on-farm adaptation and engagement with the climate policies that determine the long-term thermal environment these animals will inhabit.