Dairy Cattle Welfare: Heat Stress in Zero-Grazing Systems

As climate change intensifies, heat stress in dairy cattle is emerging as a critical welfare and production concern. Zero-grazing systems confine cows year-round, reducing their ability to self-regulate temperature through behavioural means.

Key Facts

Dairy cows experience heat stress when temperature-humidity index exceeds 68
Heat-stressed cows show reduced feed intake, increased respiration rate, and lower milk yield
Heat stress during gestation impairs calf immune development and reduces birth weight
Shade, ventilation, and cooling systems can reduce heat stress by up to 80%
High-yield Holstein cows generate more metabolic heat and are more vulnerable to heat stress

Welfare Considerations

Heat stress causes measurable suffering: cows pant, stand in water sources, reduce activity, and show elevated cortisol. In zero-grazing systems, cows cannot seek shade or cooling behavioural strategies independently. Chronic heat stress suppresses immune function, increases lameness risk, and disrupts reproductive cycles. Welfare interventions include forced-air fans, sprinkler cooling systems, and evaporative cooling pads in holding areas. Adequate shade provision — at least 4 square metres per cow — is a minimum standard increasingly included in farm assurance schemes.

What You Can Do

Advocate for mandatory cooling provisions in dairy farm welfare standards
Support research into heat-tolerant breeds for warming regions
Choose dairy products from farms with certified heat stress management plans
Encourage retailers to include heat stress welfare criteria in supplier standards
Support climate adaptation funding for small-scale dairy farmers in tropical regions