Cattle Heat Stress Abatement and Dairy Welfare

Heat stress in dairy cattle reduces milk yield, impairs reproduction, and causes significant suffering. Effective abatement strategies including shade, fans, and sprinklers are well-evidenced and economically justified for producers in warm climates.

Key Facts

The temperature humidity index (THI) above 68 triggers measurable heat stress in lactating dairy cows, affecting feed intake and milk production
Cows experiencing heat stress produce up to 20 per cent less milk and have conception rates reduced by 30 per cent or more
Sprinkler systems combined with fans reduce body temperature more effectively than shade alone because evaporative cooling acts directly on the cow
Night-time heat stress is as damaging as daytime exposure — cooling in the holding pen before milking is critical
Late-gestation heat stress impairs immune function in the developing calf, with effects persisting into the next lactation

Welfare Considerations

Cows in heat stress pant, bunch near water sources, reduce lying time, and show elevated cortisol and core body temperature. Chronic heat stress impairs rumen function, increases lameness risk from time spent standing on hot concrete, and suppresses immune function, increasing mastitis susceptibility. Welfare-centred farms deploy proactive cooling — fans and sprinklers activated at THI 68, not 72 — provide adequate shade for all animals simultaneously, and ensure water trough space of at least 10 cm per cow. Indoor loose-housing systems with adequate ventilation offer a structural advantage over outdoor systems in extreme heat.

What You Can Do

Advocate for mandatory heat abatement requirements in national dairy cattle welfare codes of practice
Support research into cattle genetics that select for heat tolerance without compromising production
If purchasing dairy products, choose those from operations with certified welfare standards that include climate management
Encourage dairy farmers in your network to install sprinklers and fans before the summer season
Donate to animal welfare charities researching cost-effective heat abatement solutions for smallholder dairy producers in tropical regions